WATER QUALITY AND ORGANOCHLORINE PESTICIDES IN FRESH WATER BODIES IN THE LOWER VOLTA BASIN: A CASE STUDY OF LAKES KASU AND NYAFIE. A THESIS PRESENTED TO THE DEPARTMENT OF CHEMISTRY IN FULFILMENT OF THE REQUIREMENT FOR THE MASTER OF PHILOSOPHY CHEMISTRY IN BY DEPARTMENT OF CHEMISTRY, UNIVERSITY OF GHANA, LEGON. AUGUST 2000 University of Ghana http://ugspace.ug.edu.gh University of Ghana http://ugspace.ug.edu.gh DECLARATION I hereby declared that this is my original work under the supervision o f Dr. D. Carboo, Dr. R. Akuamoah and Mr, W.J. Ntow, and has not been presented for a degree in this or any other university elsewhere. / Lord m innuor Bobabee I ^ S tu d en t) / Dr, D Carboo (Supervisor) Dr. R. Akuamoah (Supervisor) [r. W.J. Ntow (Supervisor) University of Ghana http://ugspace.ug.edu.gh DEDICATION This work is dedicated to my wife and the children for enduring my absence while at school and to the ever-loving memory o f my late mother, Madam Grace Afi Gedzah, who did not live to enjoy the fruits o f her labour. University of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGEMENT 1 am grateful, first and foremost to the Lord Almighty, for His Divine Love and Protection. My sincere thanks go to my supervisors, Dr, D. Carboo, Dr. R. Akuamoah and Mr. W.J. Ntow, for their patience, tolerance, suggestions and understanding during the duration of the work. I also wish to thank all lecturers and' colleagues o f the department for their suggestions and words o f encouragement when the going seemed to be tough. My thanks also go to the staff o f the Environmental Chemistry Division o f the Water Research Institute for their help, healthy criticisms and the use o f their equipment. I would also like to show my appreciation to the laboratory and office staff o f the department for their help in diverse ways. Last but not the least, I would like to thank the Headmaster and staff o f the Science Resource Centre at Ghanata Secondary School, Dodowa, for the use o f their equipment, and my bosom friend, Henry Teku Kreponi, for his kindness and generosity. University of Ghana http://ugspace.ug.edu.gh ABSTRACT The study was in two parts. The first part dealt with the determination o f water quality parameters such as pH, temperature, DO, BOD, COD, conductivity, turbidity, suspended solids, dissolved solids and total solids. Others are nutrients and ions such as nitrates, nitrites, phosphates, chlorides, calcium, magnesium, sodium and potassium. The rest were under hardness o f water such as calcium, magnesium and total hardness. O f all these parameters, only the values for turbidity i.e 80.8 NTU (Super-drain), 68.0 NTU (Kasu) and 25.2 NTU (Nyafie), were far beyond the WHO guideline limit o f 5 NTU for drinking water. The second part dealt with the qualitative and quantitative determination o f organochlorine pesticides levels in both water and sediment samlpes from lakes Kasu, Nyafie and the “super drain” The chemicals, lindane, hexachlorobenzene (H C B ) and 2,4,5- trichlorobenzene (2,4,5-TCB ), were found to be present using gas chromatography (GC): The water sample mean for HCB in lake Kasu (11.7ng/L) was greater than that found in lake Nyafie (2.3ng/L). No lindane was detected in any o f the sediment samples. The water sample mean for HCB in lake Nyafie (1.9ng/L) and that for lake Kasu (1.3ng/L) were relatively close. Again, no HCB was found in any o f the sediment samples. In the case of 2,4,5-TCB ,its water sample mean value for lake Kasu was a high o f 1114.1ng/L, while that for lake Nyafie was 822.5ng/L. O f all the pesticides detected, only 2,4,5-TCB was present in both water and sediment samples o f the two lakes. While the sediment mean value for lake Kasu was 125.1ng/L and that for lake Nyafie was 44.2ng/L. On the whole, the lakes can be said to be polluted and as such unsafe for drinking and recreational purposes as a result o f the presence o f the organochlorine pesticides found in them. University of Ghana http://ugspace.ug.edu.gh CONTENTS Declaration ■i Dedication iii Acknowledgement iv Abstract V Content vi Chapter One: Introduction 1 Chapter Two: Literature Review 5 Chapter Three: Experimental 24 Chapter Four: Results and Discussion 43 Chapter Five: Conclusion and Recommendation 85 Reference 87 Appendix 94 vi University of Ghana http://ugspace.ug.edu.gh CHAPTER ONE INTRODUCTION The Lower Volta Basin is taken to include all the areas lying below the Akosombo dam. It is made up o f parts or all o f six districts, namely, Asuogyaman in the northern part, through Manya Krobo, Dangme-West, North Tongu, South Tongu and Dangme-East in the south. The study area, located around Kasunya, containing lakes Kasu, Nyafie and others, is near Asutsuare, in the Dagme-W est district in the Greater Accra region. This area in general, lies between Akuse, in the Manya Krobo district, and Battor, in the North Tongu district. The local Ga-Adangbes and migrant Ewes from the two Tongu districts mainly populate the area. The main occupations o f the people are vegetable and rice farming, fishing and animal rearing. The people o f the study area do not have access to the Volta river, due to distance, and as such depend solely on the numerous lakes scattered in the area. They use these lakes for drinking, fishing and recreation purposes. Though, vegetable farming, fishing and animal rearing are mainly at the subsistence level, rice farming in the area since the early 70’s, have been commercialised with high level o f mechanization, intensive use o f fertilizers and pesticides as well as a well laid out irrigation system, by the Irrigation Development Authority (IDA) o f The Ministry o f Food and Agriculture (MOFA). In order to carry out the rice cultivation, water from the Volta is pumped into large irrigation canals to flood the rice fields. The excess waters from the fields mixed with fertilizers and pesticides applied, are then drained through a single large drain, termed, “Super­ drain’, into lake Kasu as the final dumping ground The catchment area o f lake Nyafie also receives runoffs from the rice fields o f the Korean Semaul Farms Limited (KSF) now known as the Bok Nam Kim Farms, but not through a well defined channel as in the case o f lake Kasu. According to the people staying along the banks o f these lakes, the quality o f the water has deteriorated, especially along lake Kasu, with regard to aesthetic parameters such as color and University of Ghana http://ugspace.ug.edu.gh taste. In addition, there has been increased siltation and growth o f aquatic flora, a possiible indication o f the effects o f fertilizers and other agrochemicals. Thus for over twenty years (1970-1999), lake Kasu in particular has been used as the dumping ground for fertilizers and pesticides, from rice fields in its catchment area. The effects o f the rice farming activities in the catchment areas o f these lakes coupled with the fact that the Volta river no longer floods these lakes since the construction o f the Akosombo dam, resulted in a lot o f environmental and socio-economic problems for the people. Some o f these problems are; • lake Kasu in particular, the largest o f these lakes, which is the sole source o f drinking water for all the villages along its banks, seems no longer wholesome for human consumption due to its “muddy” color which does not become clear even on standing for a long time. • massive aquatic floral growth, leading to difficulty in fishing as a result o f decreased depth and volume o f the lakes due to siltation. • Waning o f the fishing industry as a result o f the drastic depletion o f the desirable fish stocks due to the shallow and muddy nature o f the lakes, especially lake Kasu. However, since pesticide legislation has been non-existent in this country in the past, all sorts of pesticides were brought into the country without records of what use they were intended. It is also a fact that organochlorine pesticides, such as dichlorodiphenyltrichloroethane (DDT) ( I), was imported into the country and extensively used in malaria control and prevention, before the worldwide restriction on its use. Other organochlorines such as lindane (II) and endosulfan (III), are still been used in cocoa and cotton production, respectively, in the country. The high efficacy and the subsidized cost of both lindane and endosulfan made them attractive to other farmers outside the cocoa and cotton industries. Thus the use of these 2 University of Ghana http://ugspace.ug.edu.gh organochlorines can tend to be diffused, especially in the absence of any effective legislation by the Environmental Protection Agency (EPA), on their movements and uses in the country. The problems o f fertilizer and pesticide usage in vegetable and rice farming as well as the decrease in the aquatic productivity o f the water bodies within the lower Volta basin has been studied by Gordon and Ankrah1 They identified that, though a lot o f pesticides seem to be used especially for rice production in the basin, all o f them were carbamates and organophosphates. As no comprehensive work was done to determine the water quality and pesticide levels in these lakes, there is the need for such a study, hence this work. Aim of the study. It is therefore the aim o f this study is to determine the water quality and organochlorine pesticide burden o f the waters and sediments o f lakes Kasu and Nyafie as a result o f the intensive rice farming in their catchment areas. 3 University of Ghana http://ugspace.ug.edu.gh INSET Fig. 1 Map o f the Study Area with the Map o f Ghana Inserted. 4 0d ** ' University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO LITERATURE REVIEW 2:1 Preamble. Increased food production using modern methods, from the ever-dwindling agricultural lands, is the prime aim o f most farmers and governments, the entire world over. However, the attainment o f this food sufficiency goal, seems to carry with it a higher price, which, if not identified and checked, will eventually outweigh the desired benefits. This is because, agricultural wastes and the increasing wrong practices in the application and use o f pesticides and fertilizers, threaten the very existence and survival o f man and his environment. The dangers o f pesticide usage in particular have been highlighted in several textbooks and journals2 Man, to help mainly in increasing his agricultural yields, deliberately add fertilizers and pesticides, unlike other chemicals regarded as pollutants, to the environment. While fertilizers are formulated to provide sufficient nutrients to facilitate the rapid growth o f desirable plants, pesticides on the other hand, are devised to be lethal to undesirable organisms. The incorrect application o f the right type o f fertilizer in the correct amount, results in them being washed by runoff water, or leached, into both surface and ground water bodies. This, if not checked, especially in surface waters, results in the massive growth o f aquatic flora, eventually, leading to the eutrophication (death) o f that water body3. The unspecificity, persistence and bioaccumulation o f some pesticides, especially the organochlorines, as well as their generally uncontrolled use in this country, pose a considerable threat to the plant and animal population in particular and the environment in general. The movement o f chemicals in the aquatic ecosystem is very fast, and generally difficult to detect initially. Thus lakes can become increasingly polluted and species die out without any obvious signs at least in the early stages. For this reason, environmental monitoring has become University of Ghana http://ugspace.ug.edu.gh recognized as being vitally important in detecting where insidious pollution is occurring, the pollutants involved and the source from which they come 4. The composition o f lakes depend not only on the type o f soil surrounding the lake, which influences the amount o f salts washed into it, but also, on the age o f the lake, the living organism in the lake and the rate of evaporation o f the lake water. In addition to the materials that occur naturally in water bodies increasing amount of many substances are being introduced by mankind. These substances are often harmful to organisms in the water and to humans. Most o f these materials are introduced because, natural water bodies are convenient carriers or dumping sites for waste product13. Pollution problems rapidly escalate in severity when the rate o f pollutant emission exceeds the capacity o f the environment to assimilate them. Agricultural wastes are a major source o f water pollution. Substances such as fertilizers, pesticides and animal wastes are carried off into water bodies such as rivers, lakes and the oceans by surface runoff4. This, as well as the general worldwide agricultural usage o f pesticides can be expected to result in residues in foods and drinking water. According to Gordon et al2, there are pesticides for which approval for their use has been cancelled, but which may contaminate food and water because o f their persistence in the environment. To check these occurrences, regulatory systems have been introduced in most developed countries to ensure that pesticide residues do not constitute an unacceptable health risk, if their presence cannot be totally eliminated. Tolerances are therefore established for individual pesticides in specific commodities. Thus, only an efficient monitoring o f food samples from the market and water from its sources can protect the consumer from the potential hazards o f pesticide contamination. The dramatic increase in public-awareness and concern about the state o f the global and local environments, which has occurred in recent decades, has been accompanied and partly prompted by an ever growing body o f evidence on the extent to which pollution has caused severe environmental degradation. The introduction o f harmful substances into the 6 University of Ghana http://ugspace.ug.edu.gh environment, have been shown to have many adverse effects on human health, agricultural productivity and natural ecosystems4. Thus, the concern for public health is on the ascendancy with regard to the presence o f pesticide residues in food, water and aquatic biota, as a result o f the intensive and widespread use o f pesticides, resulting in the contamination throughout the environment. This concern is due to the fact that, man is at the top o f most food chains. In Ghana, the situation becomes very alarming when it is realized that, there is relatively little or no scientific information on the presence, behaviour and fate o f pesticides, especially the organochlorines, in the tropics and on a developing country like Ghana. The gradual awareness in some developing countries like Ghana, o f the potential environmental impact o f some modern agricultural technologies, therefore, makes the need for environmental protection and resource conservation policies and programs inevitable. 2:1 General Pesticide History. Ever since the dawn o f civilization, man has continually endeavored to improve his living conditions. In his effort to produce adequate supplies o f food, the ravages wrought by insect pests, weeds and crop as well as animal diseases have opposed man. The blasting mentioned in Amos 5 is the same cereal rust disease that is still responsible for enormous crop loss. Also the father o f botany, Theophratus (300BC)6 described many diseases known today, such as scorch, rot, scab and rust. The major pests inhibiting the growth of agricultural crops and animals are insects, fungi and weeds, and the idea o f combating them with chemicals (pesticides) is not new. A pesticide, according to the Food and Agriculture Organization (FAO)7 is, “any substance or mixture of substances intended for preventing, destroying or controlling any pest, including vectors of human or animal disease, unwanted species o f plants or animals causing harm during or otherwise interfering with the production, processing, storage, transport or marketing of 7 University of Ghana http://ugspace.ug.edu.gh food, agricultural commodities, wood and wood products or animal feedstuffs, or which may be administered to animals for the control o f insects, arachnids or other pests in or on their bodies.” According to this definition, the term includes substances intended for use as plant growth regulators, defoliants, desiccants or agents for thinning fruit or preventing the premature fall o f fruits, and substances applied to crops either before or after harvest, to protect the commodity from deterioration during storage and transportation. 8 University of Ghana http://ugspace.ug.edu.gh a oner ctironoiogical development o f chemicals used against pests (pesticides), across the years.8,9,6,10,11 is indicated in table 1 below. Table, 1: Chronological development o f some pesticides. Year N am e o f Chemical Tareet Orsanism , k ind o f D iscoverer and or disease or Class o f Pesticide Place/countrv- 1000BC Sulphur insecticide (fungicide) Homer (Greece) 7 9 AD Arsenic insecticide Pliny 7th century Nicotine insecticide 16th „ Arsenic compounds Chinese 1705 HgCl2 wood preservative Hamburg 1805 CuS04 smut pores Prevost 1814 lime and sulphur mixture apple scab Weighton 1818 pyrethrum insecticide Persia 1841 lime, sulphur, and tobacco mixture insecticide Foreyth 1845 HCH >> M. Faraday(USA) first made but not used. 1867 copper arsenate Colorado beetle USA 1882 Bordeaux mixture Wine mildew and potato blight Mildardet (France) 1886 HCN fumigant USA 1892 lead arsenate gypsy moths 1897 formaldehyde fumigant 1900 Paris green insecticide USA (1st regulation) 1912 calcium arsenate W.CPiver (USA) 1913 organo- mercurials fungicide 1927 rotenone (fish poison) insecticide 1930 alkyl thio-cynate 1931 salisylamide „ 1933 dinitro-o-cresol (sinox) » 1934 dithiocarbamate fungicide 1938 chloramil . 1939 DDT insecticide Dr Paul Mullre 1939 schraedan (Swizerland) systemic insecticide Dr G. Schraeder 1942 HCH insecticide 1st used 1943 DDT 1st manufactured and used Swizerland 1943 2,4-D and MCPA herbicide Templeman and 1946 Sexton (ICI) dinocap and crotonate fungicide 1947 sirvin and carbaryl insecticide Geiger & Co 1950 (Swizerland) malathion 1951 captan fungicide Kittleson (Standard 1958 Oil Co) diquat and paraquat herbicide IC I 1961 menazon aphidicide 9 University of Ghana http://ugspace.ug.edu.gh 2:2. Chlorinated Hydrocarbons. (Organochlorines). The chlorinated hydrocarbons are chemical compounds o f carbon, hydrogen and sometimes oxygen atoms but always with one or more atoms o f chlorine. These were the first synthetic chemical pesticides to be developed. Although many compounds were used as pesticides before 1945 (table 1), it was after that year when D D T (I) came into widespread use that, the era of chemical control o f pests really began. By stopping a wartime typhus outbreak in Italy, D D T proved its effectiveness and so sparked off a revolution in pesticide manufacturing and usage8. Aldrin (IV), dieldrin (V), chlordane and heptachlor are other commonly used chlorinated hydrocarbons. Cl Aldrin (IV) Dieldrin (V) Since the discovery o f the insecticidal properties o f D D T in 19429, vast quantities o f chlorinated hydrocarbons have been sprayed over the surface o f the earth in an effort to destroy insects. These efforts initially met with incredible success in ridding large areas o f the earth o f disease- carrying insects, particularly, those o f typhus and malaria10. In the course o f time, the understanding has begun to dawn on us that this prodigious use o f chlorinated hydrocarbons has not been without harmful and in some cases, tragic side effects. Chlorinated hydrocarbons, being usually highly stable compounds, are only slowly destroyed by natural processes in the environment. As a result, many organochlorine insecticides will remain in the environment for many years11,12. These highly stable pesticides are called “hard” pesticides. 1 0 University of Ghana http://ugspace.ug.edu.gh Chlorinated hydrocarbons are also fat soluble, and thus, tend to accumulate in fatty tissues of most animals. The food - chain that runs from plankta, small fish through larger fish and birds to larger animals including man, tends to magnify the concentrations o f organochlorine compounds at each trophic level. In nature, the principal decomposition product o f D D T is dichlorodiphenyldichloroethene (DDE) (VI). Estimates indicate that, nearly one billion pounds o f D D E are now spread throughout the world ecosystem10 One pronounced environmental effect o f D D E has been in its action on eggshell formation in many birds. D D E inhibits the enzyme, Carbonic anhydrase that controls the calcium supply for shell formation. As a consequence, the shells are often very fragile and do not survive until hatching time. This effect is expressed in the dramatic decrease in the population o f predator birds such as eagles, falcons and hawks6. D DE (VI) also accumulates in fatty tissues o f man. Although man appears to have a short-range tolerance to moderate DDE levels, the longer-range effects are far from certain. In 1967, the organochlorines accounted for half the total US production o f pesticides6. However, the use o f these compounds has been steadily decreasing in the US, partly because, insects have developed resistance to them and also as a result o f public concern about the large- scale application o f these slow-to-disappear chemicals. Though most o f them are now either completely banned or greatly restricted in use in the developed countries, it has been estimated that, residues o f D D T and its metabolites in the environment may have a half-life o f 20 years or more6. This is because, chlorinated hydrocarbons are not natural chemicals, in that, they are not synthesized by plants or animals. Produced by man in laboratories, these compounds present nature with a difficult disposal problem. Thus organochlorines tend to have persistence problems, resulting in environmental problems o f grave concern to man. Modern agriculture relies heavily on chemical pesticides. There is no doubt that pesticides have contributed much to improve the quality and quantity o f agricultural products on a worldwide basis. But attendant with these benefits has been certain risks, some o f which we have been 11 University of Ghana http://ugspace.ug.edu.gh slow to recognize. In the two decades immediately following World W ar II, the usage o f D D T and related organochlorines as well as cyclodienes insecticides, were extensive and effective. They were also misused and as a result, instances o f fish poisoning were documented, local populations o f attractive birds were sometimes reduced drastically, and reproductive failures in some species o f birds, especially raptors, were suspected, and in a few instances, proven to be associated with the use o f the chemicals13. According to Kenaga14, insecticides and herbicides make up the greatest bulk o f pesticides as measured by number, volume and value. The period from 1969 to the present, is one o f self- imposed constraints on the pesticides we use. Consideration for their impact on the environment as well as the human body itself, have resulted in the suspension or restriction on certain organochlorine pesticides in many countries. The introduction and clearance o f new compounds has been made much more difficult by the exertion o f stringent safety requirement9. The African continent, though not noted for the manufacture o f pesticides, nevertheless, is noted as a leading consumer of these chemicals, due to the prevalence o f pests as a result o f its climatic conditions. Due to the extensive use o f organochlorines in Africa, there is the need to monitor and assess the impact o f pesticides. This led to the first ever co-ordinated FAO/IAEA meeting, on the effects o f pesticide usage on the African environment, in Arusha15. This meeting gave birth to the recommendation for the need for scientific data on the use, dissipation and bioaccumulation o f these chemicals, which will form the basis o f policy formulation on the use o f these pesticides. Following on the heels o f the Arusha meeting, were others held in Vienna16 and Upsala17. 2:3. Pesticide Usage in Ghana. Pesticide usage in Ghana dated from the colonial period in the early 20th century. It was primarily aimed at combating disease in the emerging cocoa industry at the time. Among the chemicals tried was kerosine , which was found to be ineffective, due to its low toxicity. 12 University of Ghana http://ugspace.ug.edu.gh Others include nicotine sulphate19, which was also abandoned as a result o f its high cost and mammalian toxicity. The use o f synthetic organochlorine pesticides started in the country when D D T was introduced into the country in 194 820, in the form o f emulsion spray in the cocoa industry, and for vector (malaria) control. D D T was closely followed in 195021 by lindane, which was tried and found to be more effective than DDT. The pesticide market was after that, invaded by other organochlorines pesticides, following the development o f resistance to lindane by some o f the cocoa diseases21 Trials with organophosphates such as baytex, diazinon, dibron,and sumithion, as well as carbamates like carbaryl, were done after 1963, with varying successes. Pesticide usage, both in tonnage and variety in the country is on the increase as is the case the world over. These increases are due partly to the commercialization o f agriculture from the subsistence level, in cash and food crops, as well as livestock productions. It was also believed to be prompted by the need to increase or maintain the yields from existing farms, especially in the cocoa, cotton and rice industries, as a result o f pest resistance22 and the emergence o f new pests23. M ost o f the pesticides used in the countiy for all the purposes o f agriculture and public health control o f pests are not produced in the country, but some are locally formulated. Table 2, shows some o f the pesticides formulated in Ghana and the industries concerned24. The UK was one o f the biggest exporters o f pesticides to W est Africa in 198025’26 with Ghana in the second position after Nigeria, as recipient, with 299.5 metric tonnes. Table: 2: Some pesticides formulated in Ghana. Pesticides C om pany Raid Johnson Wax Ltd Accra. Shelltox Shell Gh. Ltd, Accra Gammalin 20 (Lindane) Chemico Ltd, Tema Unden Abwakwa Plant, Kumasi 13 University of Ghana http://ugspace.ug.edu.gh In line with the general world ban on organochlorine pesticides as a result o f their enviromental persistence, bioaccumulation and biomagnification along the food-chain ’ ’ , Ghana has also followed and restricted the use o f pesticides such as dieldrin, aldrin, endrin and DDT* . Despite this ban, organochlorines such as lindane (gammalin 20) for cocoa and endosulphan (thiodan) for cotton, are the choice o f farmers in the production o f these crops. The efficacy o f these organochlorines in combating pests has made them attractive to vegetable and other food crop farmers, who despite advise and warnings still continue to use them. Another reason for the use o f these pesticides by food crop farmers, is the low price for these items, since they are heavily subsidized, as against the others, by the authority31. 2:4 Hazards of Pesticide usage on W ater bodies. The many ways in which water promotes the economic and general well being o f society are known as “beneficial uses” The major ones are water supply, recreation and aquatic life. The relative importance o f beneficial uses for any particular stream, lake or estuary, depends on the economy o f the area and the desires o f the people. Many applications such as public and industrial water supply are restricted within narrow ranges o f water quality. Unregulated waste disposal (domestic, industrial, mining, or agriculture), conflicts with use o f water as a potable source. Therefore, monitoring and the control o f quality is required to ensure that, the best employment o f the water is not prevented by the indiscriminate use o f water courses for disposition o f wastes. The evaluation o f the hazards o f pesticides in the environment inevitably requires the matching o f residues from pesticides with their biological effects. The public anxiety about environmental pollution has made the side effects o f pesticides, now, the principal research activities of biologists, chemists and environmentalists. This is because o f the ecological effects these chemicals have on non-target organisms in and around or remote from their area o f application. The organochlorine pesticides have given rise to the greatest amount o f investigative work12, 14 University of Ghana http://ugspace.ug.edu.gh resulting in several o f them being suspended or banned from general application in most developed countries. In a study in the US32, it came out that, the application o f agricultural chemicals on row crops is a major source o f non-point-source contamination o f surface and ground water in the Mid­ western. The study then concluded that, pesticides could be transported to streams and lakes by overland flows, through field drainage tiles or by ground water. Once contaminants are transported to a water source, dynamic surface and ground water interactions affect their storage and further distribution in the environment. Smith33 and Juracek34 found that pesticides pose a potential threat to water quality and many of these compounds have been detected in surface and ground water in the US in the last several decades. Halgreen35 and Gillion36 in related works on surface water assessment, came to the conclusion that, patterns o f pesticide detection in surface water, depends on several factors which include usage, persistence, solubility and detection levels. Pesticide usage as a human activity, has ecological effects on the value and resources o f lakes, marshes, rivers and other water sources, as productive zones o f the worlds food protein, water supply, recreation and wildlife conservation37. Many widely used insecticides such as toxaphene and D D T are highly toxic to fish, birds and bees38. In the US, it has been observed that spraying D D T to control spruce budworms on the Yellowstone river systems, severely reduced the population o f important fish food organisms. The effects were observed for a year and were responsible for widespread mortality o f brown trouts, mountain white fish and the long-nosed sucker. Similar observations were made in Zambia27 and in Botswana28 when dieldrin was used in the control o f tsetse flies. Thus, pesticide applications, though not deliberately intended for the aquatic ecosystem, in most cases, finally end up there by way o f runoffs and irrigation canals, resulting in the death o f fishes and other aquatic organisms which may be far removed from the area of application and the target organisms. 15 University of Ghana http://ugspace.ug.edu.gh Some people, especially farmers and people with criminal intentions, sometimes accidentally or deliberately release pesticides into watercourses. An example was reported in a Ghanaian daily newspaper39, in which some unscrupulous people were said to have deliberately applied chemicals suspected to be DDT, to kill fish in the Offin river for sale to the public. This action does not only put the public at a great risk o f contamination from eating the fish, but they would also concentrate the chemical from drinking the water and other uses. In addition, many non­ target organisms in the aquatic environment as well as birds and other animals dependent on the water, would also be adversely affected. A similar case of pesticide misuse resulting in the pollution of the aquatic ecosystem occurred in Zambia40 when a farmer intentionally dumped a drum of toxaphene into a river. The effects were noted 10 km downstream, involving the destruction of all forms of waterlife. The presence of pesticide residues of lindane, DDT, DDE and endosulphan, in fish oil extracted from the “sangara” (Niloticus appendiculatus), caught in Lake Victoria41, showed how pesticides from agricultural usage, especially in the catchment areas of water bodies, can find their way into these waters and their resources. Pesticide contamination o f water bodies is o f grave concern to the health o f man in particular and the environment as a whole. This is because, pesticides, especially, the organochlorines, being fat soluble, tend to bioconcentrate and bioaccumulate in organisms. These processes, viewed with regard to the complicated nature o f the aquatic food-chain, becomes alarming as bigger and larger fishes up the chain, cumulating in man himself, tend to biomagnify these concentration. Characterization o f pesticide levels by many people, in various environments is the trend in environmental analysis at the moment. In most o f these studies, as in this work, the focus is mainly on organochlorine pesticides, which tend to persist in the environment. In a study by Mansingh42 and others, to determine insecticide contamination o f the Jamaican enviroment, 16 University of Ghana http://ugspace.ug.edu.gh endosulfan a and p, lindane, DDE , endosulfan sulphate, dieldrin and diazinon, were identified. O f these, the first five were organochlorines while the last one is an organophosphate. They were found to be scattered all over the island in soils, surface water, sediments, flora and fauna, thus contaminating most o f their rivers and other water bodies. The main sources o f these pesticides were detected to be from runoffs from agricultural fields. Amounts found ranged from 0.037^ig/kg for dieldrin to 6.4|ig/kg for DDE. The average amount o f lindane was around 1.75|ag/kg. In their conclusion, they stated among other things that, the range of residue concentrations in most o f their waters, were often well above the tolerance levels o f many fish and shrimp species, and over their EPA ’s recommended levels, and that, many people who utilize raw river and well water are being exposed to risks. Wong et al43 and Reutergardh44 and others, in monitoring environmental pollution in Hong Kong and Thailand respectively, also found varying levels o f various organochlorines in their environments, especially in water, sediments and aquatic flora and fauna. 2:5. ANALYTICAL METHODS USED IN PESTICIDE DETERMINATIONS. Today, most laboratories use one o f the multiple detection techniques (paper, thin layer and gas chromatography) for the determination o f chlorinated insecticide residues. Each has its advantages and disadvantages, but it is safe to state that GC has some advantages in offering reasonably rapid “semi-qualitative” and quantitative determinations o f several compounds which may be present in one sample.45 2:5:1. Gas Chromatographic Method. Gas chromatography, is the most widely used method for pesticide residue analysis due to its simplicity and selectivity. Most pesticides have been analysed using this technique46,67. Gas chromatography is an instrumental method invented in 1954 by M artin48. This method has been widely used for the analysis of pesticide residues in soils, sediments, flora and fauna 17 University of Ghana http://ugspace.ug.edu.gh tissues and in water. A gas chromatograph consists essentially o f a carrier gas, a column, a detector and a recorder. In gas chromatography, the components to be separated in a given sample are carried through the column by an inert gas such as nitrogen. The mixture is partitioned between the inert carrier gas and a non-volatile solvent distributed on a solid support, which makes up the column. The solvent selectivity retards the sample components according to their distribution coefficient until they form separate bands on the column. The components leave the column in the gas stream and are recorded as a function o f time by the detector. The various components are therefore identified by the use o f the retention times and are quantified by the use of the area o f chromatographic peaks. The separation o f the components is achieved in the column. The success or failure o f any separation will therefore depend on the choice o f column. There are two types o f columns, namely, capillary columns and packed columns. Capillary columns are open tubes o f small diameters with a thin liquid film on the wall. Packed columns consist o f an inert solid material supporting a thin film o f non-volatile liquid. The solid support, type and amount o f liquid phase, method o f packing, length and temperature o f column, are important factors in obtaining good resolutions. Capillary columns have been found to have higher efficiencies and have been widely used for pesticide residue analysis. Examples of capillary columns in use for pesticide residue analysis are SPB 5, SPB 608 and SE 30. Packed columns that have also been used for pesticide residue analysis include dimethyl silaxane polymers like DC 200 and SE 3048 Detectors indicate the presence and measure the amount o f components coming from the column. There are various types o f detectors. There are non-selective detectors such as the conductivity cell and Flame Ionization Detector (FID). There are however, other detectors, which are selective. Examples o f these include Phosphorus detector and Electron Capture Detector (ECD). They have the advantage o f selectively detecting only certain types of 18 University of Ghana http://ugspace.ug.edu.gh compounds. The ECD is used extensively for the detection o f organochlorines49 due to its high sensitivity and selectivity for them. Gas liquid chromatography serves as a means o f qualitative analysis. The quantitative determination is based on the measurement o f peak areas or peak heights. These are then correlated with the peak areas o f or heights o f standards o f known concentrations. The peak area, which is the most commonly used method, can be measured by one o f several techniques as listed below 50,51. (i). Planimetry. In this method, the peak area is traced manually with the use o f a planimeter. A planimeter is a device for measuring areas, by measuring the perimeter o f the peak (ii). Height and W idth at Half-height. Since normal peaks approximate a triangle, one could approximate the area by multiplying the peak height by the width at half-height. The normal peak base is not taken since large deviations may be observed due to tailing or adsorption. (iii). Triangulation. Under this, height is measured from the base line to intersection o f two targents. The base is taken as the intersection o f the two tangents with the base line. The area is calculated by the triangle formular; Area. = ' A b x h Where; b = base o f triangle, h = height o f triangle. 19 University of Ghana http://ugspace.ug.edu.gh (iv) Cutting and W eighing Paper. Peak areas are determined by cutting out the chromatographic peak and weighing the paper on an analytical balance. (v) Disc Integrator. This is a mechanical device in which the integrator pen is linked mechanically to the ball, which rides the rotating disc. W hen the recorder pen deflects, the ball moves away from the center of the disc and the ball begins to rotate.-The rotation o f the ball is transmitted mechanically to the integrator pen. Since the disc rotates at a rate proportional to the time base o f the recorder chart, the integrator pen traces the line, which represents the area o f the recorder pen’s travel. (vi) Electronic Digital Integrator. In this method, the chromatographic input signal is fed into a voltage to frequency converter which generates an input pulse rate proportional to the peak area. When the slope detector senses a peak, the pulses from the voltage to frequency converter are accumulated and printed out as a measure o f the peak area. The quantification is finally done by the correlation o f peak area o f standards with the concentration o f a particular component in the sample. This is done with the help o f a calibration curve o f concentration and peak areas. Either absolute method or internal standard method may do the calibration. 2:5:2. OTHER ANALYTICAL METHODS FOR PESTICIDES. Various other analytical methods have been used for pesticide analysis. These include: 2:5:2:1. Colorimetric Method. Colorimetry with ultra violet (UV) and visible radiation has been used for pesticide residue analysis. A quantitative method for from the analysis for lindane has been described by 20 University of Ghana http://ugspace.ug.edu.gh Davidow et al52. In this method, the pesticide was si ijected to alkali hydrolysis yielding 1,2,4- trichlorobenzene, which has maximum absorptic at 286nm. Other pesticides such as endosulfan, have also been analysed colorimetrically by heating in alkali medium to liberate SO2 , which combines with p-rosaniline in solution to produce a color absorbing at 570 nm3 . Colorimetric methods generally have the disadvantage of low selectivity and sensitivity. 2:5:2:2. Bioassay Methods. These methods are based on the measurement o f death, growth or other physiological responses o f animals, plants or microorganisms. Lang54 developed one such method, for the analysis o f pesticides such as lindane and DDT. Bioassay tecl niques have however declined in recent times, because o f its lack o f specificity and difl ulties in comparison with some other procedures in obtaining reproducible results. 2:5:2:3. Tracer Methods. These have been used extensively for pesticide residu analysis. I4C labeled lindane53 have been used to study the fate and persistence o f pesticides It usually involves dry combustion and measurement o f radiation emitted by the labeled subst mce using a liquid scintillation counter. 2:5:2:4. Distributed M easurem ents6. For the most part, water analysis has involved colli cting samples from designated sites and transporting them to the laboratory where determii itions are performed. I f the number of collection points and the collection frequency are moc est, this is appropriate and cost-effective. However, monitoring the water quality o f an entire 1 iparian basin, is another matter entirely, especially when a river or lake serves as water source md catchment for multiple uses including farming and drinking water. One approach for continually acquiring and processi j, the massive amount o f analytical data 2 1 University of Ghana http://ugspace.ug.edu.gh needed to support comprehensive freshwater monitoring is based on a system design known as “distributed measurement”. Here, instead o f the usual collect/ transport/ analysis scenario, a distributed measurement system uses an array o f on-line sensors, positioned at strategic sites along the river or lake basin or catchment. Analytical data collected by sensors are continually routed over data networks to a central collection point, where they are processed and integrated to provide a constantly updated quality map o f the monitored water system. At present, the fully automated on-line analytical distributed measurement network does not exist. Should such a system come into operation, it will be a great relief to analytical chemists, working on riparian environments. 2:5:2:5. Pulsed-Flame Photometer Detector (PFPD) and a Direct Sample Introduction (DSI) Device57. This method, used by Jing and Amirav, was used to analyze pesticide residues in food products. They described it as fast, sensitive and informative. It is based on sampling with a novel direct sample introduction (DSI) device, gas chromatographic analysis and pesticide detection with the pulsed-flame photometric detector (PFPD). Sampling with the DSI is based on introduction o f blended fruit or vegetable in a small glass vial that retains the harmful nonvolatile residue and is disposed o f after the analysis. The DSI- GC-PFPD combination provides several new features that were demonstrated and discussed. Though this method was originally developed for pesticide residue analysis in food products, it can be used with or without modification for the analysis o f pesticides in water and sediments. 2:5:2:6. Supercritical Fluid Extraction. (SFE)58. A supercritical fluid (SF), is defined as “a fluid that is above both its critical pressure and temperature” . Supercritical fluids possess unique properties, intermediate between those o f a gas and a liquid, that depends on the pressure, temperature and composition o f the fluid. In 22 University of Ghana http://ugspace.ug.edu.gh particular, the density (i.e. the solvent power o f the fluid), may be adjusted by correctly choosing both the pressure and the temperature. A typical SFE system consists o f a high- pressure pump that delivers the fluid o f an extraction cell containing the sample and maintained at the correct pressure and temperature. The SFE may be carried out in either a static or dynamic mode. The SFE has become a promising alternative technique in recent years for solid and semi-solid matrices, due to its advantages over classical solvent extraction, especially soxhlet extraction. 2:5:2:7 In situ Corona Reaction59. This is an apparently novel technique to aid the detection o f a variety o f inorganic and organic compounds in environmental and drinking water samples. In an attempt to combine the convenience o f an absorption measurement, the background suppression and AC modulation, characteristic o f reagent-base flow injection analysis (FIA), with more convenient reagents, Johnson investigated an apparent novel approach that uses UV absorption measurement together with a chemical reaction step induced in situ via highly reactive species generated in a high-voltage point-to-liquid. corona discharge. By processing the double signature o f absorption spectra measured before and after the contactless electroreagent corona reaction, suppression o f the background o f non-reacting species is obtained. All these are achieved by modifications to a HP 8452A diode array spectrometer to allow for the in situ corona dosing. 23 University of Ghana http://ugspace.ug.edu.gh CHAPTER THREE EXPERIMENTAL 3:1. The study area. The catchment areas o f lakes Kasu and Nyafie, and some o f the others at Kasunya, (fig. 1), are the sites o f some o f the large-scale intensive rice farmlands in the southern part o f the country. It comprises the rice-farm s.of the Irrigation Development Authority (IDA) o f the Ministry of Food and Agriculture (MOFA), which is centered on lake Kasu, and the Korean Semaul Farms Limited (KSF), situated on lake Nyafie all in the Dagme-west District o f the Greater Accra region. The establishments o f these farms were the direct efforts o f past and present governments in boosting agricultural production and to provide employment for the rural youths. This gesture is with the hope that, there would be a corresponding improvement in the financial and social lives o f the people, thereby encouraging them to stay in the area instead o f migrating to the towns and cities for non-existing jobs. Though the extent to which these socio-economic goals have been attained are outside the scope o f this study, there are some agricultural technologies employed by the farmers, which are likely to have some effects on the people and the environment in the project areas as a result o f these schemes. Lake Kasu and the others including Nyafie, are large fresh water bodies at Kasunya, near Asutsuare, in the Tettimang traditional area in the Lower Volta basin o f the Dangme-West district, within the Greater-Accra region o f Ghana. Historically, lake Kasu in particular, which was about 2 km wide and 6 km long, (fig.2), and the others, which are about 15km away on the easten flank o f the Volta river, facing north, were the sole source o f drinking water for the people staying along their banks. They were also reservoirs for fishes, resulting in a vibrant fishing industry. 24 University of Ghana http://ugspace.ug.edu.gh I' Figure 2. Map of the Study area showing sampling points 25 University of Ghana http://ugspace.ug.edu.gh This once vibrant fishing industry, according to the people, began to decline after the construction o f the Akosombo dam. Their belief is that, the construction o f the dam prevented the Volta from flooding these lakes, leading to their fish stocks and waters not to be replenished every year, as was normally the case in the past. The problems o f the lakes and the people were compounded, when the government o f the first republic acquired a large track o f land within the catchment area o f lake Kasu, for the establishment o f the now defaunt Ghana Sugar Estates Limited (GHASEL), based at Asutsiiare. When GHASEL folded up, its assets were taken over by the IDA for the production o f paddy rice. The IDA, in developing its land area for rice production, directed all the drains from the rice fields into lake Kasu, through a single large drain, locally termed “ super-drain” . Due to the intensive mechanized nature o f the farms, large quantities o f fertilizers and pesticides were used to increase yields. To grow the rice after the land had been prepared, it is flooded with water from the Volta. It is this water together with the applied fertilizers and pesticides that were utilized by the crops, as well as a large amount o f silt, that is carried by the smaller drains into the super-drain, which takes them to lake Kasu, the final dumping ground. 3:2. Design and Administration of Questionnaire. Before the chemical analysis o f the water and sediments, a survey was conducted in the study area to gain an insight into the types o f pesticides that the farmers in the area use. A questionnaire (appendix A) was designed for this purpose to solicit information on; • agrochemicals used in the production and storage o f crops, • sources o f these chemicals, • type of crop on which chemical is used, • disposal o f damaged and/or expired chemicals, and • how these chemicals are stored when not being used, 26 University of Ghana http://ugspace.ug.edu.gh Fifty (50) farmers, made up o f 20 males and 30 females, randomly selected from the catchment areas o f the two lakes were administered the questionnaire. The contents o f the questionnaire were translated into the local languages o f Dangbe and Ewe for those who could neither understand nor read the English language. Their responses were then written down in the appropriate column on the questionaire. 3:3. Selection of Sampling Sites. Lake water, unlike a river water, is not uniform in the sense that resident time and turnover rate o f substances including the water, is very high and very low, respectively. Thus, no single sample can be taken to be representative o f the lake. In line with this, several sampling sites, as shown in fig. 2 were chosen in each lake as well as in the “super-drain” that empties into lake Kasu. Since the purpose o f the study was to identify and quantify the pesticides present in the waters and sediments o f the lakes, as well as water quality parameters, sites were selected such that the overall sample collected in each lake, would be representative o f that lake. In all, five (5) sites (K1 to K5) on lake Kasu, six (6) sites (N1 to N6) on lake Nyafie and one site (SD) on the “super-drain” were chosen as shown in fig 2. 3:4. Sampling. Sampling was done four (4) times in the year, i.e in January, February, June and July. The first - period, from January to February was for the dry season while the second period from June to July, was for the rainy season. At each sampling site, four (4) water samples and a sediment sample were collected at a time. The four (4) water samples were collected for: • dissolved oxygen (DO) • biochemical oxygen demand (BOD) 27 University of Ghana http://ugspace.ug.edu.gh • other water quality parameters, (such as conductivity, turbidity etc,) and • pesticides Thus, on each sampling trip, five samples were collected from the “super-drain, 25 samples from lake Kasu and 30 samples from lake Nyafie an overall total of 60 samples per trip. In all, 196 water samples and 48 sediment samples, totaling 220 samples were analyzed. 3:4:3. Type of sample container and conditioning. For DO, and BOD samples, 250 mL BOD glass bottles with stoppers were used while for pesticide samples for water, 1.5 L borosilicate glass bottles with teflon-lined caps were used. While wide mouth borosilicate bottles with stoppers were used for sediment, samples, one-litre polyethylene bottles with covers were used for water samples in the determination o f other water quality parameters60 The containers for water samples (for water quality), were washed with detergent then rinsed three times with tap water. They were then treated with chromic acid, rinsed three times with tap water, then once with a 1:1 nitric acid and finally, three times with distilled water. Those containers used for both water and sediment samples for pesticide determination were washed with detergent then rinsed three times with tap water and once with 5M HC1 solution. This was then followed with double distilled water (3 times), acetone (2 times) and pesticide grade hexane (2 times), after which the bottles were dried (uncapped) in hot air oven at about 360 °C for one and half hours61 3:4:4. Sample Collections. With the exception o f the samples collected in the “super-drain”, which was done by wading in the water, all the samples from the two lakes were collected while in a canoe. Below, is a step by step procedure used in taking samples for the determination o f the various parameters. 28 University of Ghana http://ugspace.ug.edu.gh (i) Samples for water quality parameters. The bottles were uncapped and dipped just below the water surface and filled with water. This water was then poured away on the other side o f the canoe, and was repeated two more times. After the third time the water filled bottle without any air bubbles was closed. Samples for DO were fixed before capping, by adding 2 m Lof manganous sulphate solution below the surface of the solution, followed by 2 mL o f alkaline-azide-iodide solution at the surface o f the solution, shaken for sometime and allowed to stand. For BOD and the other water quality parameter samples, nothing was done to them before capping. (ii) Samples for pesticides. One litre water samples specifically for pesticide determinations were collected in the same way as was done for BOD and other water quality parameters samples. For the collection o f sediment samples, divers were hired to dive and scoop up the sediments using a metal trowel. These were then put into their containers. Each sample as it was collected, was put on ice in an ice chest. After all the samples have been collected, they were then transported to the laboratory in the ice chests. 3:5. Analysis of samples. The quality o f the final result obtained in any analytical work depends on the care and type of sampling and pretreatment procedures followed as well as the type and nature o f the equipment used in the final analysis. Most of the methodologies used in the study were based on the established protocol at the chemistry laboratoiy o f the W ater Research Institute o f the CSIR, Accra, and on GEMS Water Operational Guide60 as well as APH A ’s Standard Methods for Examination o f Water and W astew ater61, with relevant modifications when necessary. 29 University of Ghana http://ugspace.ug.edu.gh 3:5:1. W ater Samples. The water samples were tested for water quality parameters as well as for pesticides. The water quality parameters analyzed for are pH, temperature, conductivity, turbidity, DO, dissolved solids (DS), suspended solids (SS) and total solids (TS) and transparency as physical parameters, BOD, chemical oxygen demand (COD) and Cl' as chemical parameters with NO3'- N, N 0 2"-N and P 0 43‘-P as nutrients and Ca2+, Mg2+, Na+ and K+ as major ions. The others are total hardness, Ca hardness and Mg hardness. 3:5:1:1. Analysis of various parameters. (i) pH and Temperature. Temperature and pH were determined directly in the field using portable battery operated digital electronic temperature and pH sensometers respectively (Phillip Harris scientific equipment). In measuring the pH, the equipment was calibrated by first dipping the sensor into a standard buffer solution o f pH 9 and then rinsed several times with distilled water before dipping it into another standard buffer solution o f pH 4 and rinsed again. It was then dipped into the water with the sensor just below the water surface and held still for some few minutes till a constant reading was obtained. It was done two more times. The average o f these readings was then taken as the pH for all the samples at that particular site, for that particular sampling operation. For the temperature measurements, the sensor o f the equipment was also dipped just below the surface o f the water and held still for some minutes till a constant reading was obtained and was repeated twice. The average o f these readings was then recorded as the temperature (°C) o f all the samples collected at that particular site for that day. 30 University of Ghana http://ugspace.ug.edu.gh (ii) Turbidity and Conductivity. Unlike temperature and pH, turbidity and conductivity were determined in the laboratory. For turbidity, a DRT 100 HF turbidity instrument was used. Turbidity measurement makes use of the presence o f particles (dissolved or suspended) in the water that scatter light passing through the solution. The extent, to which the light is scattered, is directly proportional to the amount of particles in the solution. Thus high turbidity values suggest large amount o f particles in the solution. Calibration o f the instrument for turbidity measurements was done using standard solutions provided in sealed glass bottles by the manufacturers for that purpose. With the calibration done, sample solutions after shaking, were poured into special glass bottles, capped, put into the instrument and the turbidity read in NTU (Nephelometric Turbidity Unit). The solution was then poured out, the bottle rinsed and refilled with another aliquot o f the same sample, and the reading taken again. The average o f these two readings was then recorded as the turbidity o f that sample. A Jenway 4020 conductivity meter was calibrated using a standard solution o f KC1 with a known conductivity value, in a special container into which the probe was dipped and the value read on the monitor in |iS/cm. After that, the probe was taken out, rinsed several tines with distilled water and dipped into about 50 mL o f the sample in a beaker, purposely used for conductivity measurements. The procedure was repeated with another 50 mL solution o f the same sample with the mean o f the two reading taken as the conductivity for the sample. (iii) DS, SS and TS. Gravimetric methods were used for the determination o f these parameters. Glass-fiber filter discs (Whatman GF/C grade), and evaporation dishes, specially prepared were used. The preparations were as follows. 31 University of Ghana http://ugspace.ug.edu.gh The glass-fiber filter discs. The discs (pore size = 0.45um) were placed on the all-metal filtration unit membrane filter holder with pump attached, and the discs washed with three 200 rnL volumes o f distilled water. Almost all traces o f water were removed by continuing to apply the vacuum, and the washings discarded. They were then heated in an oven to a constant weight and then kept in a desiccator. The evaporation dishes. The dishes first were washed and rinsed with distilled water. They were then heated in a muffle furnance for one hour at 550 ± 50 °C, cooled in a desiccator and left there till required. DS and SS determinations. The filtering apparatus was assembled and the glass-fiber filter disc put in place. The sample was shaken vigorously and 100 mL was rapidly transferred to the funnel by means o f a 100 mL graduated cylinder. Suction was then applied for about three minutes to remove as much water as possible. The filtrate was carefully transferred into a pre- weighed evaporation dish and evaporated to dryness on a water- bath, for the determination o f DS. The evaporated sample was then dried for about an hour at 105±2 °C in the oven. It was allowed to cool in a desiccator and weighed. The drying and weighing was continued until a constant weight was obtained. The glass-fiber filter was gently removed and dried in an oven at 104 °C for one hour, cooled in a desiccator and weighed to determine the SS. The drying, cooling and weighing were repeated to a constant weight. The TS determination was done through calculation. It involves the addition o f the DS and SS values that were determined. See appendix on calculations. 32 University of Ghana http://ugspace.ug.edu.gh (iv) DO. DO was analyzed using W inkler's Azide Modification Method. The DO, though fixed in the field was determined in the laboratory the same day. To the fixed DO water samples were added 2 mL o f conc H2SO4 to digest the precipitates formed. The bottle was gently shaken a few time to hasten the digestion. 100 mL portions of the resulting solution was then titrated with a standard sodium thiosulphate solution, with starch as indicator. (v) BOD The samples taken for BOD analysis, on reaching the laboratory, were put in an incubator at 20 °C for 5 days. On the fifth day, the oxygen in the samples were fixed, digested and titrated with the standard sodium thiosulphate, in the same way as was done for the DO samples. For sites, whose DO values were less than 8 mg/L, BOD samples were diluted, with dilution water. In such cases, lOOmL o f the sample was taken and made up to 600mL, using 500mL o f the dilution water and put into the two BOD bottles. The DO o f one o f the diluted and aerated samples is determined on the first day and the other incubated for 5 days. The BOD determination was done on the 5 day. A blank o f the dilution w ater was also incubated for five days and analyzed. (v) COD. Chemical oxygen demand was analyzed using the dichromate method. To 5 mL o f the sample in a lOOmLconical flask was added 3 mL o f standard K2Cr2 0 7 , 7 mL o f conc. H2SO4, 7 mL of silver (I) sulphate and refluxed at 150 °C for two hours. After the two hours, the flask with its contents were cooled and diluted to 50 mL with de-ionized water. To the 50 ml solution was then added 2 drops o f ferroin (an o-phenanthroline ferrous complex) as indicator and the excess dichromate titrated with standard ferrous ammonium sulphate (FAS) solution. The COD was measured as 0 2 equivalent, proportional to the dichromate consumed during the refluxing by 33 University of Ghana http://ugspace.ug.edu.gh the organic matter present when Cr6+ ions were reduced to Cr31 ions. Daring the digestion, the reaction taking place according to Baird 68 can be represented as Cr20 72' + 14H+ + 6e ------► Cr3+ + 7H20 . The number o f moles o f O2 that the sample would have consumed equals 6/4 = 1,5 times the number o f moles o f dichromate, since the later accepts 6 electrons per ion whereas O2 accepts only 4: O2 + 4H+ + 4e‘ ----------► 2H20 (vi). Nutrients. NCb'-N, NO?- N and PC>43—P were each determined spectrophotometrically using an LK.B Biochron Ultrospec II UV/Visible spectrophotometer. In nitrate-N determination, 10 mL sample solution, I mL o f ,3M NaOH and 1 mL o f a reducing agent (amalgamated Cd/Cu) were heated for 10 minutes at 60°C, cooled and to it was added 1 mL o f the coloring agent (sulfanilamide in conc. HC1). For nitrite-N, the same procedure was followed with the exception o f the addition o f the reducing agent and the heating. In both cases, the absorbance of the resulting solutions was then measured at 540 nm spectrophotometrically, after standardization and calibration, using glass cuvettes. In the case o f phosphate-P, the molybdenum blue method was used. 50 mL each o f the samples were measured into conical flasks and to each 50 mL o f 2M-ammonium molybdate solution was added. Each mixture was swirled to mix well after which 0.5 mL o f the stannous chloride solution was added and mixed, upon which the blue color o f the heteropoly phospho-molybdate ion was produced. The absorbance was read at a wavelength of 690 nm. Prior to all these, standard phosphate solutions were passed through the same process to calibrate the machine. 34 University of Ghana http://ugspace.ug.edu.gh (vii) Chloride (Cl ) ions. The Vallard (argentrometric) method was used to determine the concentration o f chloride ions. 100 mL o f the sample solution was taken and to it was added 1 mL K2Cr0 4 as indicator and titrated against standardized silver nitrate solution to a brownish endpoint. (viii) Sodium and Potassium Sodium and potassium were determined using a Gallenkamp flame emission spectrophotometer with liquid petroleum gas as the fuel gas. The equipment was first calibrated with standard solutions o f their salts w ith the appropriate filter selected'. The reading in mg/L was direct, thus no calibration graph or calculation was required. After the calibration, the sample solutions were treated the same way and values obtained. After the determination o f each sample, the rubber tube, when removed from a solution was each time washed with de-ionized water before being used again. W hile analyzing the sample solutions, one o f the standard solutions used for the calibration was also intermittently analyzed. (ix) Calcium, M agnesium and Hardness. Calcium concentration, calcium hardness and total hardness were determined by complexometric titrations using EDTA. Magnesium concentration and magnesium hardness were calculated from the calcium values. For calcium, 50 mL o f the sample solution was transferred intd a conical flask then 2 mL o f 1M NaOH and a pinch o f murexide (ammonium purpurate) powder was added as indicator. The deep red colored solution formed was then titrated with the EDTA to a purple endpoint. Calcium concentration and calcium hardness were then calculated from the titration results. Total hardness was also determined using 50 mL o f a sample in a conical flask to which had been added 1 mL o f an NH 3 / NH4CI buffer ( pH o f 10) and a pinch o f Eriochrome Black T as indicator in this case. The resulting solution (wine colored) was titrated with EDTA solution to 35 University of Ghana http://ugspace.ug.edu.gh a sea-blue color endpoint. Total hardness was then calculated from the titration results. To obtain and magnesium hardness, the calcium hardness value was then subtracted from the value for total hardness as water hardness is usually assumed to be due to the presence o f calcium and magnesium ions. The magnesium concentration was also calculated from its hardness result. 3:5:2:2. Pesticides. Pesticide residue determinations for the water and sediment samples were carried out using a Hewlett-Packard Series II Model 5890 gas -liquid chromatography (GLC) with a 30m SP5 phase capillary column and a 63 Ni electron capture detector (ECD). Fig. 3 shows the scheme used in the analysis o f pesticide residues in both water and sediment samples. Fig. 3. Flow chart o f procedures followed in the analysis o f pesticides. Sanhpling (fetching o f water and scooping o f sediments) T Samples Extraction (liquid-liquid extraction for water and soxhlet extraction for sediments) samp Extracts Cleaning (C-18, 3ml/500 mg solid phase extraction tubes (SPE) Separation (gas-liquid chromatography (GC) Detection (electron capture detector) Analytical results.(retention times and peak areas.) 36 University of Ghana http://ugspace.ug.edu.gh (i) Extraction procedure.60 The one litre water samples specifically collected for pesticide residue analysis was extracted with dichloromethane (CH2C12) in 2L separating funnel. 50 mL o f the dichloromethane was added to the water sample in its original sample bottle and tightly closed with an aluminum foil line cap. It was then shaken manually for 30 minutes and the contents transferred into a 2L separating funnel. After allowing it to stand for 10 minutes to enable the organic and aqueous phases to separate, the organic layer, was transferred into a lL-separating funnel. The aqueous layer was returned to the sample bottle while the 2L separating funnel was rinsed twice with dichloromethane: 30 mL at first followed by 20 mL, transferring the solvent to the sample bottle after each rinsing. The shaking, separation and rinsing procedures outlined above was then repeated twice. After the third separation, the organic layer was again transferred into the 1L separating funnel and the aqueous layer was discarded. The 2L separating funnel was then rinsed as before but this time, the rinsing were added to the contents o f the 1L funnel. The 1 L-separating funnel was shaken for 2 minutes and allowed to stand for 10 minutes. About 5cm layer o f anhydrous sodium sulphate (Na2S 0 4) put in a 125mL sintered glass funnel was set upon a 500mL round-bottom flask. The flask with the funnel was then connected to a rotary evaporator (as a filtration column) for vacuum filtration. The organic layer in the 1L- separating funnel was then drained onto the filtration column. 50 mL o f dichloromethane was added to the aqueous phase remaining in the separating funnel, shaken well for 2 minutes and again allowed to stand for 10 minutes. The organic layer was drained through the Na2S 0 4 filter column and the aqueous layer was discarded. The separating funnel was rinsed twice with 25 mL dichloromethane and the solution passed through the filter column. The Na2S 0 4 column was washed with 50 mL o f CH2C12 and the vacuum applied until the Na2S 0 4 was dry. Each extract was evaporated under vacuum using the rotary evaporator at 33 °C (in a water bath) to about 5 mL. This was then transferred with 4 x 2 mL rinsing to a 25 mL graduated 37 University of Ghana http://ugspace.ug.edu.gh weighed samples were then added, one nanogram each o f the aforementioned pesticides in 5 mL o f double distilled water. They were then covered with aluminum foils and left in the laboratory to air dry. After drying, each weighed sample was then extracted, concentrated, cleaned up and analyzed on the GC 3:7. Pesticide Analysis. 3:7:1. The GLC. The GC used was a Helweltt-Packard Series II, Model 5890 with a 30 m SP5 phase capillary column and a 63Ni electron capture detector (ECD). Both carrier gas and make-up gas are nitrogen. Table 3 shows the parameters and conditions used in the determinations. Table 3. Conditions for the GC analysis. PARAMETER CONDITION Column internal diameter 0.53 mm Column length 30 m Column film thickness 1.5 nm Detector temperature 250 °C Injector operating temperature 200 °C Oven (column) temperature 200 °C Flow rate o f N2 30 nm per minute Injection volume 1 (iL l(iL of each o f the individual and / or combinations o f the standard pesticides used, (Aldrin, DDT, DDD, DDE, Lindane, HCB and 2,4,5-TCB) were injected into the GC and the retention times62,60,61 obtained. In the case o f the sample extracts and recovery samples, the same volume o f 11 iT. was taken in each case and subjected to the same treatments as the standards. 40 University of Ghana http://ugspace.ug.edu.gh and 2 mL o f double distilled water. After conditioning the SPE columns as outline for the water sample extracts, the extract was loaded on to it and treated in the same way as for water sample extracts. 3:6. Extraction and Cleanup Recoveries. Extraction and cleanup recoveries were done to determine the efficiency o f the methods used in the extraction, concentration, cleanup and analysis o f pesticides. In each case, the amount of pesticide recovered was expressed as a percentage o f the amount that was originally added.. 3:6:1. Water. To 1L of pesticide-free distilled water, was added 1 ng o f each o f the following pesticides, namely, aldrin, dieldrin, lindane, 2,4,5-TCB, HCB, DDT and DDE. The pesticide-seeded water was then taken through the same procedures as the water sample. 3:6:2. Sediment. For a pesticide free soil sample with a comparable matrix, the following was done. Some soil samples from the yard o f the W ater Research Institute (WRI) were taken from a depth o f about six inches, ground and soaked in distilled water for about ten hours. The « suspension was then agitated and filtered using a 63-|im sieve. The residue was then washed four times with the pesticide-free distilled water then three times with acetone and once with the pesticide grade dichloromethane. The soil sample was then dried in an oven at 500 °C for 24 hours. 5.0 g was then taken and subjected to the treatment for sediment samples and analyzed on the GC for the presence o f pesticides. When it was confirmed from the GC analysis that no pesticides were present in the soil samples, 5.0 g o f it were weighed in beakers that were purposely prepared for this. To the 39 University of Ghana http://ugspace.ug.edu.gh measuring cylinder. It was followed by evaporation to 3 mL, under a gentle stream o f N2 at (water bath), at atmospheric pressure. (ii) Cleanup. Pre-prepared Bonded C-18 SPE (3cc/500mg) columns also referred to as bonded elut (Varian, USA), were used for the cleaning o f both water and sediment sample extracts. The bonded columns were conditioned prior to loading o f the sample extracts, by flushing them with 2 mL of 98% pesticide grade methanol (Sigma Aldrich Chemical Company, USA) followed by 1 mL of double distilled water. 3 mL sample extracts were then loaded onto the conditioned SPE columns and washed with 2 mL o f a 30% solution o f the pesticide grade methanol, and 1 mL o f double distilled water. The column is then air dried by blowing air through it (using a compressor) for about 20 minutes to remove all traces o f water and methanol. The dried SPE column was then eluted with 4 mL o f pesticide grade hexane (M allinkcoff Special Chemicals of the USA), in four portions o f lm L each at an eluent flow rate o f about 2mL per minute. The eluted volume (4 mL) was then ready for analysis on the GC. 3:5:3. Sediment samples. Sediment samples were only analyzed for pesticides. (i) Extraction. The sediment samples were air dried in the laboratory. They were then ground and sieved through a 63pm screen. 5.0g triplicate samples of the sieved sediments, accurately weighed and transferred into single thickness cellulose extraction thimbles (33mm id x 100mm ed) were soxhlet extracted for about 5 hours, with 150ml o f the pesticide grade methanol. The extracts were allowed to cool. 20mL o f the extract was evaporated to about 3mL. This was then taken up in 1 mL methanol 38 University of Ghana http://ugspace.ug.edu.gh The retention times o f the standard samples were used to identify the possible pesticides present. Table 4 shows the retention times o f the standard pesticides used in the study. Table 4 Retention times o f Standard Pesticides Used in the Study. Standard Pesticide Retention TimefMinutes) Aldrin 12.112 HCB 2.242 Lindane 2.500 2,4,5-TCB 3.017 DDE 7647 DDD 9.965 DDT 12.717 3:8 Calculation of Pesticide Concentrations. The quantification o f the pesticides identified in the samples were computed from the peak area using the following equation.60 Psamp ■ Csamp = ---------- X Pstd where; Csamp Psamp Pstd. Vstd.inj. Vsamp inj. Vstd. Inj. Vsamp. Inj. Vext X M concentration o f sample peak area o f sample peak area o f standard volume o f standard injected volume o f sample injected 41 X Cstd University of Ghana http://ugspace.ug.edu.gh Vext. M Cstd = volume o f extract (ml) = weight (g) or Volume (L) o f sample extraction = concentration o f standard. 42 University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR RESULTS AND DISCUSSION 4:1. Results of the Survey The survey was conducted to solicit information on the type o f pesticides used by farmers in the study area. Out o f the 50 farmers randomly selected for the administration o f the questionnaire, 34 responded to it, giving a response level o f 64%. 4:1:1. Class of Pesticides. Pesticide is a generic term used to describe all chemical substances used to either kill or control undesirable organisms. There are four main categories o f pesticides in use, namely, organochlorines, carbamates, organophosphates and pyrethroids. Each o f these categories has many classes o f pesticides with regard to the kind o f pest for which the pesticide is being used. Some o f these classes are insecticides, fungicides, herbicides, acaridicides, molluscicides e t c. Table 5 shows the classes o f pesticides used by farmers in the study area. Table 5. Class o f Pesticides Used in the Study Area. Class of Pesticides Number o f Users Percentage (%) Used Insecticides 32 94 Fungicides 24 70.6 Herbicides 26 76.5 Growth Regulators 22 64.7 None 2 5.9 43 University of Ghana http://ugspace.ug.edu.gh Generally, it is clear from table 4 that, the majority o f our farmers make use o f pesticides in the control o f pests. This is evident from the table in which 32 out o f the 34 respondents constituting about 94% of the polled respondent population, make use o f a pesticide in their agricultural activities. This is also shown graphically in fig. 5. Only tw o farmers (5.9%) do not make use o f any pesticide at all. The table also shows that four main classes o f pesticides namely, insecticides, fungicides, herbicides and growth regulator are used by the farmers. It is also clear that insecticides are the most used, about 94% (fig. 5), while the others, herbicides (76.5%), fungicides (70.6%) and growth regulators (64.7%) are used to varying degrees. The most encouraging news from the survey is that, apparently, our farmers do not use organochlorine pesticides, but rather, use only carbamates, organophosphates and pyrethroids. 4:1:2. Type o f Chemical Used. Tables 6,7, 8 and 9 depict the details o f each class o f pesticides in use by the farmers. From these tables, it is clear that most o f the chemicals used belong to the carbamates, organophosphates and pyrethroids. The farmers without any suggestions on the questionnaire gave the names o f the pesticides used. In cases where the farmers w ere not able to give the name of a pesticide offhand, they were asked for the pesticide containers. The large number of the different types o f insecticides used attest to the fact that, in the humid climate o f the tropics, insects are the major pests to farm crops and animals.. Herbicides are used mostly on the rice farms. The percentages were calculated based on the number o f farmers using that class of pesticide. The most encouraging news from the survey is that, apparently, our farmers do not use organochlorine pesticides, but rather, use only carbamates, pyrethroids and organophosphates. 44 University of Ghana http://ugspace.ug.edu.gh CLASS OF PESTICIDES University of Ghana http://ugspace.ug.edu.gh -< H 100 University of Ghana http://ugspace.ug.edu.gh Table 6. Insecticides Used by the Farmers. Name of Insecticide Number of Users Percentage (%) Category Karate-25EC 24 75 Pyrethroid linden 13 40.6 Carbamate Perfekthion 20 62.5 ?> Fufadan-3G 14 43.6 „ Cymbush 29 90.6 Pyrethroid Sumithion-50EC 18 56.33 Organophosphate Kumakate 6 18.8 Others** Elocron 13 40.6 Carbamate Sumicombi-30EC 21 ■ 65.6 Others Actellic 32 100 Organophosphate :rs refer to those chemicals that can not be identified from the Pesticide Manual 69 Table 7. Herbicides Used By the Farmers. Name of Herbicide Number of Users Percentage (Vo) Category Furadane 14 53.9 Others Basta-20SL 15 57.8 Others Basagram-PL2 11 42.3 Carbamate Ronta 10 26.0 Others Dual 12 46.2 Others Rilof 13 50.0 Organophosphat Round-up 18 69.2 Organophosphat e 46 University of Ghana http://ugspace.ug.edu.gh Table 8. Fungicides Used by the Farmers, Name of Fungicide Number of Users Percentage (%) Category Cocopri 9 37.5 Others Kocide 12 50.0 Others Dithane-45 10 41.7 Carbamate Furadan Topsin-M 8 33.3 Carbamate Table 9. Growth Regulators Used by the Farmers. Name of Growth Number of Users Percentage (%) Category Regulator Biomex 18 81 Others Sampi 14 63.6 Others Biozyme-TF 22 100 Others Dithene 19 86.4 Others 4:1:3. Types of Crops Grown. The catcment area o f the lakes though noted for rice cultivation, recorded only 15 out o f the 34 respondents (table 10), i.e 44.1%, as rice growers. This picture is due to the fact that greater number of the farmers have stopped growing rice as a result o f a directive from the IDA to them to stop rice cultivation since 1994, for the restructuring o f the irrigation canals to extend them to a greater part o f the Accra-Plains. It is hoped that when the current restructuring o f the irrigation canals is complete, more farmers would go back to rice cultivation. 47 University of Ghana http://ugspace.ug.edu.gh Table 10. Types of Crops Grown by the Farmers. Type o f CroD Grown Number of Percentage (%) Growers Vegetables** 19 55.9 Rice (only) 3 8.9 Vegetables and Rice 12 35.2 ** = Vegetables include all other food crops apart from rice 4:1:4. Source o f Chemicals Out o f the 32 ( 94%) farmers who claimed to use pesticides, 25 (78.1% ), as shown in table 11, responded to purchasing their chemicals from approved sources, i.e from chemical stores and Agricultural Extension Officers. The others (21%) obtained their supply from fellow farmers. Sources o f Chemicals Bought by the Farmers. Source of Chemicals Number of Buyers Percentage (%) Chemical Shops 17 53.1 Extension Officers 8 25.0 Fellow Farmers 7 21.9 48 University of Ghana http://ugspace.ug.edu.gh It is hoped that, extension officers would intensify their education o f the farmers on the benefits and adverse effects o f pesticides, and encourage the farmers to obtain the chemicals through them. 4:1:5. S to rage o f Chemicals. From table 12, it is clear that, 71.9% o f farmers store chemicals at home with only 9 (28.1%) storing theirs on their farms. This is not a healthy development and such they should be advised by the Extension Officers to refrain from doing so. To avoid accidents from these pesticides, farmers should, through extension officers, be educated about the dangers of pesticides poisoning to them and their families if pesticides are stored at home especially within reach o f children. Table 12. Places o f Storage o f Pesticides by Farmers. Place of Storage Number of Farmers Percentage (%) At Home 23 71.9 On the Farm 9 28.1 4:1:6. Disposal of chemicals. Farmers were asked about what they did with expired or damaged pesticides. From table 13, it is clear that all farmers who use pesticides do not dispose o f expired or damaged chemicals. Some may even be buying already expired chemicals from the shops, since they do not care whether the chemicals are expired or not. Most o f them claimed to reuse the chemical and 49 University of Ghana http://ugspace.ug.edu.gh Table 13. How Chemicals are disposed off by Farmers. Tvne of Disposal Method Number of Farmers Percentage (%) Never disposes o f Chemicals 32 100 Disposes o f Chemicals 0 0 fertilizer containers for other purposes. There is therefore the need for education o f the farmers about the dangers in using expired pesticides just as is with drugs. 4:2. WATER QUALITY: PHYSICAL AND CHEM ICAL PARAMETERS For a fresh water source to be potable, it should satisfy the requirements of the World Health Organization (WHO). For monitoring and surveillance purposes, the WHO has come up with maximum levels o f some physical and chemical parameters for fresh water, beyond which the portability o f the water becomes questionable. These maximum levels are contained in the “WHO Guidelines Values for Potable W ater”64’, part o f which is shown in table 14, is what is adopted by the Ghana Water Company. For a particular water source to be termed potable, and as such to qualify for human consumption, the analysis o f its physical and chemical parameters should yield results less than or equal to the WHO guideline values. Exceptions are granted in cases where these guideline values are higher than that o f the nation or region, or where background levels do not permit the WHO guideline values to be attained within reasonable costs. 50 University of Ghana http://ugspace.ug.edu.gh Table 14. WHO Guideline Values for some Physical and Chemical parameters o f Potable Water. PARAM ETER VALUE Total Hardness (TS) as C aC 03 500 mg/L Chloride 250 „ „ Nitrate i o , „ Phosphate <0.3mg/L Turbidity 5 NTU Conductivity 700 mS cm'1 Dissolved Solids 1000 mg/L Na+ 200 „ „ K+ 30 Ca2+ 200 „ „ -•‘•cr- 150 „ „ pH 6.5 - 8.5 DO 8 mg/L BOD < 3 mg/L COD 250mg/L Tables 15, 16, 17 and 18 are the means o f the results obtained for the various parameters when the water samples were worked upon. Table 15. Mean Values of Physical Parameters measured for the Various Locations. PA RA M ETERS LOCATION nH Tem p. (OC) DO (mg/L) BOD fmg/U) COD (m s/L t “Super-drain” 7.0 ± 1.2 26.4 ± 0.1 1.2 ± 1.1 76.5 ±67 .8 20.5 ± 14.8 Lake Kasu 7.2 ± 0 .2 31,1 ± 1.4 7.0 ± 1.1 73.8 ±63.3 66.8 ± 5 5 .0 Lake Nyafie 6.9 ±0.1 31.6 ± 1.2 5.4 ±2 .5 49.7 ±37 .7 19.0 ± 12.6 51 University of Ghana http://ugspace.ug.edu.gh From tables 15, 16, 17 and 18, it can be seen that on the whole, most o f the physical and chemical parameters determined for lakes Kasu and Nyafie, used for drinking fall within the WHO limits with the exception o f turbidity and BOD. The higher turbidity values o f 68.04 NTU and 25.22 NTU for the two lakes are far above the 5 NTU WHO guideline. The mean BOD values o f 73.8mg/L for lake Kasu and 49.7mg/L for lake Nyafie, are also well beyond the WHO value o f <3.0 mg/L. Thus the waters o f the lakes can be said to be organically polluted with regard to the BOD values as compared to the WHO value. This line o f thought is reinforced by the fact that BOD values obtained are higher than COD values. The “super drain” is not o f much concern since it is not used as a source of potable water directly though it empties it’s contents into lake Kasu. But this does not mean that the waters o f these lakes especially that o f lake Kasu are totally wnoiesome ror numan consumption. This is because, lake Kasu, on which the majority o f the people depend, remains cloudy throughout the year. Especially in the dry season (Nov.-April), the water becomes very brown (high turbidity) as shown graphically in fig 6, that, its aesthetic value is lost especially on someone who is coming into contact with it for the very first time. It is only during the rainy season (May-Oct), when runoffs from the catchment areas fill it that, the color changes towards whitish. Lake Nyafie on the other hand, has a very near to normal clear water colour in the dry season which becomes rather tainted (whitish) during the rainy season leading to the high turbidity values for the lakes. Table 16. Mean Values measured for Physical parameters at the Various Locations. PARAMETERS LOCATION Conductivity Turbiditv SS (ing/L) DS TS (mg/L) (mS/cm) ('NTU') (mg/L) Super-drain 96.63 80.75 101.00 213.25 314.25 + 30.6 ±63.3 ±82.6 ±39.4 ±57 .0 Lake Kasu 159.22 68.04 118.79 315.36 434.15 ±38 .6 ± 28 .7 ±29.8 ±117.9 ± 141.0 Lake Nyafie 118.00 25.22 99,11 157.35 256.66 ± 58 .0 ± 15.7 ±96 .4 ±68.7 ±91.3 52 University of Ghana http://ugspace.ug.edu.gh Table 17. Mean values o f some Chemical parameters (Nutrients and Ions) measured at the Various Locations. PA R A M ETER S. (mg/L) LO C A TIO N N O i: NO?; P 0 4- c r C a2+ M g2+ + 1 C3| S uper-d ra in 0.187 0.083 0.203 1 . 4 5 6.43 1.75 8.86 3.20 + ± ± + + ± + ± 0.12 0.04 0.12 1 . 0 2,4 1.1 2.0 1.5 Lake K asu 0.178 0.058 0.087 1 1 . 1 1 8.62 3.71 17.40 6.61 + + + + ± + ± ± 0.11 0.02 0.04 3 . 9 5.0 0.4 4.1 1 Lake Nyafie 0.180 0.039 0.192 7.50 5.37 3.65 12.46 4.79 + ± + + ± + ± + 0.11 0.01 0.02 4.3 2.8 0.7 6.6 2.1 Table 18 Mean Values o f Hardness o f W ater measured at the Various Locations. .. ARA. fE xw . LO C A TIO N C a hardness M g hardness T otal hardness Super-drain 16.10 7.18 23.28 ± 6 .0 ± 4 .5 ± 5 .8 L ake K asu 20.19 15.23 35.42 ± 13.4 ± 1.7 ± 12.1 Lake Nyafie 13.41 15.01 28.43 + 6.9 ± 2 .8 ± 8 .8 53 University of Ghana http://ugspace.ug.edu.gh sasupE R DRAI a LAKE KASU □ LAKE NYAFI E pH Temp.( oC) DO(mg/L) BOD(mg/L) COD(mg/L) PARAMETERS Fig. 5. Mean Values o f Physical and Chemical Parameters for all the Locations PARAMETERS EJSUPBR DRAIN H LAKE KASU □ LAKE NYAFIE Fig. 6 Mean Values for Physical Parameters at all the Locations 54 University of Ghana http://ugspace.ug.edu.gh Fig. 7. M ean Values o f Nutrients and Ions at all the Locations. Fig. 8. M ean Values o f Water Hardness at all the Locations. 55 University of Ghana http://ugspace.ug.edu.gh 4:2:2. SEASONAL VARIATIONS. The results show some seasonal variations in the values for most physical and chemical parameters at all the sampling locations as shown in tables 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30. 4:2:2:1. pH The pH is an important parameter in water quality measurement, as it influences many biological and chemical processes within a water body and all processes associated with water treatment and supply. The pH o f water determines which substances would dissolve in or precipitate out o f it. The life o f the organisms in the water, such as fishes, and those that depend on it, such as man, birds and animals, is affected by the pH o f the water. From tables 19, 23 and 27, it is generally clear that, the pH in the rainy season is higher than that for the dry season at all locations. This can be attributed to the large volume o f water that came to dilute the relatively acidic conditions for the dry season (figs. 9, 10 and 11). Though rain water is expected to be acidic, it can only be acidic if it is collected as it falls, but ones it touches the ground and begins to flow, it turns to dissolve salts especially o f sodium, potassium and calcium carbonates, thereby increasing its pH. 4:2:2:2. Dissolved Oxygen. (DO) Water, which is in contact with 0 2 or with an 0 2-containing mixture o f gases, contain some dissolved O2 . When water is saturated by O2, the concentration o f O2 is called the equilibrium concentration. Its value depends on the partial pressure o f 0 2 in the gaseous phase, the temperature o f the water, and the concentration o f salts in the 56 University of Ghana http://ugspace.ug.edu.gh water. The normal equilibrium concentration o f 0 2 in drinking water, ranges from 4.5 to above 8 mg/L in most cases61. The real concentration o f 0 2 may differ from the equilibrium concentration because o f physical, chemical and biochemical conditions or activities such as sudden changes in temperature or barometric pressure, chemical oxidation o f substances contained in the water, or contacted by it, biochemical oxidation by assimilative activity o f green organisms etc. The DO concentration is important for the evaluation o f surface water quality and wastewater treatment control. From table 15, the mean DO values for the locations ranged from a low o f 1.2 mg/L for the “super-drain”, through 5.4 mg/L for lake Nyafie to a high o f 7.0 mg/L for lake Kasu. Thus the values for lakes Kasu and Nyafie all fall within the acceptable range for drinking water. Seasonally, the DO values o f the lakes decreased (7.59 to 6,45 mg/L for Kasu and 8.63 to 3.25 mg/L for Nyafie) from the dry to the rainy season as expected, with the exception o f the “super-drain”, in which the DO value increase during the dry to the rainy season as shown in tables 19, 23 and 27, and in figs. 9,10 and 11. The decrease in the DO values from the dry to the rainy season was as a result o f increased levels o f biodegradable materials carried into the lakes by the flood waters which required the DO in the water to oxidised them. The exception o f the value o f the “super-drain” and the relatively small decreases in the values for the lakes, were due to the turbulence created by the swift flood waters, thereby leading to increase dissolution of 0 2 in the waters. 57 University of Ghana http://ugspace.ug.edu.gh Table 19. M ean seasonal Values o f Physical and chemical parameters for “Super­ drain” . SEA SO N PA RA M ETERS DRY SEASON E l TemD.fOO DO BOD COD January 5.9 26.50 0.71 11.43 3.10 February 6.10 26.40 0.48 12.36 10.84 M ean 6.00 26.45 0.59 11.80 6.97 ±0.1 ±0.1 ±0.1 ±0.5 ±3.9 RAINY SEASON June 8.4 26.30 0.10 170.00 41.50 July 7.6 26.30 3.30 112.00 26.43 M ean 8.0 26.30 1.70 141.00 33.97 ±0.4 ±0.0 ±1.8 ±34.0 ±7.5 Table 20. M ean Seasonal Values o f Physical parameters in the “Super-drain” SEA SO N PA RA M ETERS DRY SEA SO N January Conductivit v (mS/crri) 102.60 Turbidity (NTU) 19.00 SS (mg/L) 40.00 DS (mg/L) 265.00 TS (mg/L) 305.00 February 153.90 16.00 32.00 238.00 270.00 M ean 123.25 17.50 36.00 251.50 287.50 ±25.7 ±1.0 ±4.0 ±13.5 ±17.5 RAINY SEA SO N June 84.20 140.00 94.00 178.00 272.00 July 45.80 148.00 238.00 172.00 410.00 M ean 65.00 144.00 166.00 175.00 341.00 ±19.2 ±4.0 ±72.0 ±3.0 ±69.0 58 University of Ghana http://ugspace.ug.edu.gh 4:2:2:2. BOD. The biological oxygen demand (BOD) is an approximate measure o f the amount o f biologically degradable organic matter present in a water sample. It is determined by the amount o f oxygen required for the aerobic microorganisms present in the sample to oxidise the organic matter to a stable inorganic form. As such, it is a very important pointer to pollution and health status o f the lakes. Generally, as BOD levels increase, DO levels drop. This was clearly shown in the results o f lakes Kasu and Nyafie in tables 19, 23 and 27 and in figs. 9,10 and 11. Considering the activities within the areas o f these lakes, it can be said that the BOD values were not as high as expected. The increased values for the biological oxygen demand at all the locations for the rainy season as compared to that for the dry season as shown in tables 19, 23 and 27, and graphically depicted in figs. 9, 10 and 11, is as a result o f the flooding o f these locations. This then leads to the rotting o f plants as well as human and animal wastes, carried by the surface runoff water. Thus all these are expected to increase available biodegradable matter, consequently increasing BOD at the expense o f DO, as noticed earlier. Thus taking the average BOD values for the lakes and the “super-drain”, it can be said that these waters are polluted, if BOD value is the sole indicator o f pollution since its values for all the locations is greater than the WHO value o f 3 mg/L for drinking water. 59 University of Ghana http://ugspace.ug.edu.gh Table 21 Mean Values for Nutrients and Ions in the “Super-drain”. SEASON PARAMETERS fmer/L) DRY SEASON NOs: NO,: PO4- c r Ca2+ Mj£ Na+ Kl January 0.038 nd nd 2.30 7.09 0.72 2.56 10.6 February 0.048 nd nd 2.60 7.58 0.58 9.82 2.05 M ean 0.043 nd nd 2.45 7.34 0.65 6.16 6.33 ± 0.01 ±0.2 ±0.3 ±0.1 ±3.6 ±3.8 RAINY SEASON June 0.306 0.083 0.146 0.50 , 8.66 2.76 9.40 5.80 July 0.358 0.082 0.200 0.40 2.40 2.92 5.50 2.40 M ean 0.332 0.083 0.173 0.45 '5.53 2.84 6.85 4.10 ±0.03 ±0.0 ±0.03 ± 0.1 ±3.1 ±0.1 ±1.5 ±1.7 Table 22 Seasonal Means o f Hardness o f W ater for the “Super-drain” SEASON PARAM ETERS (mg/L) DRY SEASON Ca hardness M g hardness Total hardness January 17.73 2.97 20.70 February 19.00 2.40 21.40 M ean (dry) 18.37±0.6 2.69±0.3 21.05±0.4 June 21.65 11.35 33.00 July 6.00 12.00 18.00 M ean (rainy) 13.50±7.8 11.63±0.4 25.50±7.5 4:2:2:3. Turbidity. Th