Impact of Illegal Mining on Surface Water, Sediment and Soil Quality in the Owerri River Basin, Asante-Akim Municipality, Ghana.

Abstract

Illegal mining operations popularly known as “galamsey” have become a topical issue in Ghana due to their devastating effects on the environment. The extent of the devastation is assuming alarming proportions and has destroyed both the environment and subsequently impacted human health. One of the most devious effects illegal mining activities has caused the environment is the pollution of water bodies with heavy metals and other contaminants. The determination of the total metal concentration in sediments has been the main subject of many studies on the heavy metal pollution in river Basins in Ghana. However, the total contents of heavy metals in the riverine sediment cannot give enough information about their mobility, bioavailability, or potential risks to the environment. This study was therefore carried out to determine the impact of illegal mining activities on surface water, sediment and soil quality in the Owerri River Basin in the Asante-Akim municipality, Ghana. Water and composite samples of sediment and agricultural soils were taken in six purposively selected communities (five artisanal and small-scale gold mining communities and one control site) for laboratory analysis using standard Methods. In all, a total of two hundred and forty (240) water samples, seventy-two (72) sediment each of sediment and agricultural soil samples were collected and analyzed. All the water analysis were determined using appropriate certified and acceptable international procedures (APHA, 2017). Soil and sediment samples were analyzed using standard methods. The data collected was analyzed using Stata software version 17. Descriptive statistics such as means ± SD, range, 95% CI were used to describe the data. Analysis of variance (ANOVA) at p<0.05 was used to test for the differences in means of the physiochemical parameters among the sampling sites. Principal Component Analysis (PCA) with Kaiser Meyer-Olkin (KMO) normalization was used for source apportionment of the heavy metals in water and sediment. The results showed that; the mean pH ranged from 5.5 to7.5; EC ranged from 128 to 562.5µS/cm; TDS (68.0 to 364.8mg/L); TSS (611to1994.1 mg/L); DO (2.9 to 13.9mg/L), BOD (4.6 to 20.7mg/L). With the exception of the control site, the pH, TSS, turbidity, DO and BOD in most illegal mining impacted sites exceeded the USEPA (2025) permissible limit for surface water. The EC, TDS and total alkalinity values, however, were all within USEPA, 2025 guideline limits. Cu, Cd, As, Cr, Ni, Pb and Hg levels in water samples at mining impacted sites exceeded the WHO and EPA (Ghana), 2022 acceptable limits. The concentrations of the following heavy metals in sediment; Fe, Hg, and As were above the NOAA ERL,1995 acceptable limit for sediment quality. Pb, Hg, Fe, As and Cd in agricultural soils exceeded the FAO (2016) guideline limit for agricultural soil. As, Cd, Cr, Pb, Ni, Cu and Fe were strongly associated with mobile fractions of the sediment specifically the exchangeable and carbonate bound fraction and the fraction bound to organic matter. This finding implies that these fractions are more susceptible to changes in pH and redox conditions, making the metals more mobile and prone to potential mobilization and remobilization into the water column. All the heavy metals studied indicated lower risk for dermal pathways for both adults and children population and poses non-cancer effect risk (HQ<1). Water pollution, loss of agricultural land, reduced food availability and access, and loss of fuelwood were the provisioning ecosystem services that were significantly affected in illegal mining impacted communities. The Principal Component Analysis results provides robust evidence that illegal gold mining activities is the principal driver of heavy metal pollution in both water and sediment in the study area, with additional contributions from the local geological substrate. The study therefore accentuates the need for the District Assembly to promote access to alternative safe water sources for the communities. The Environmental Protection Authority, Ministry of Lands and Natural Resources, Minerals Commission should strive to regulate the use of mercury by introducing mercury free technologies for sustainable mining. Lastly, it was recommended that the Government should provide complementary income generating projects or alternative livelihoods to the people in the study area as most participants asserted, they engage in illegal mining because they have no employment opportunities.