Phytoremediation of Some Tropical Soils Contaminated with Petroleum Crude Oil
Loading...
Date
2013-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Ghana
Abstract
This study was undertaken in three phases to identify (phase 1), screen (phase 11) and
evaluate (phase 111) plants for their phytoremediation potential.
In Phase 1, 15 plant species made up of grasses and legumes namely: Paspalum. vaginatum,
Cynodon.dactylon, Pueraria. phaseoloides, Centrosema. pubescens, Panicum. maximum,
Schrankia. leptocarpa, Eclipta. alba (Linn.), Cyperus. haspen (Linn.), Melastromastrum.
capitatum, Acreceras. zizanoides Dandy, Pteridum aquilinum (Linn), Ludwigia.decurrens
Walt,Setaria longiseta P.Beauv., Physalis angulata (Linn.), and Desmodium scorpiurus
Desv.were identified on sites previously polluted by crude oil spills in the Niger Delta Area
of Nigeria. The first 6 species were used in phase 11 while the first four species were
earmarked (rolled over) for phase 111. Responses to Questionnaire indicated that majority of
residents in the selected sites/communities had lived in these areas for 10 or more years had
mainly JHS/SHS education; were self employed – mainly farmers and fishers although most
were unemployed in the public sector. Adverse effects of the operations of oil companies
particularly oil spillage on the environment and local residents include: loss of vegetation and
farmlands, soil and water body contamination, weak social and cultural institutions
(disrespect by youth for elders and institutions), militancy and hostage taking among youth
from the area. In phase 11, seeds of legumes among the six selected species were collected
from Accra, Aburi environs and Kusi in the Eastern region of Ghana; they were scarified,
cultured in growth medium and the seedlings which emerged from them were transplanted
into experimental pots, each containing 2000g of either Alajo or Toje soil series. One week
after transplanting, each pot was simulated with a corresponding serial crude oil
concentration of 0% (control) 1 % (24ml), 3% (83ml), 5.5% (130ml) and 8% (189ml) or 10%
(237ml) in three replicates. These concentrations were arrived at, using the fomular [(vol of
crude = % X wt / 0.844) ml]. Similarly, three replicates of each selected grass species were
planted vegetatively into 2000g of either Alajo or Toje soil series using known numbers of
propagules (stolons). After one week of planting, pots were treated with the above serial
crude oil concentrations using the appropriate volume indicated. Germination rates were
variable and results of percentage
plant
Survival
Difference
(PSD)
indicated
that
Paspalum vaginatum and Cynodon dactylon were highly tolerant of crude oil concentrations
at 3%, 5.5% and 8% on the Toje soil series and 3%, 5.5% and 10% on the Alajo soil series as
compared to Panicum maximum and where therefore selected as high contaminant tolerant
species for phase 111; whereas Puraria phaseoloides and Centrosema pubescens which had -
45% & ±42% and -16% & -35%respectively, as PSD for Alajo and Toje soil series as
compared to Schrankia leptocarpa, were also selected as low/poor contaminant tolerant
species (at 1% & 2% - introduced in phase 111as upper contamination limit for the poor
tolerant species) also, for the last stage (phase 111) of the study. For phase 111, C. dactylon,
P .vaginatum, P. phaseoloides and C. pubescens were evaluated for phytoremediation
potential at crude oil concentrations of 3%, 5.5% (added to determine mid-point tolerance for
high contamination tolerant species) and 8% for Toje soil series, and going up to 10% for
Alajo soil series for high contaminant tolerant species and 1% & 2% for low/poor tolerant
species respectively, using the randomized complete block design. Results of plant biomass
(fresh weight) decreased (between 0.5g/fw & 20g/fw) at low contaminant concentrations and
increased (between 14g/fw & 122g/fw) at high contaminant concentrations.Values of plant
enrichment were higher for Cynodon dactylon (0.9% & 4.49%) than for Paspalum vaginatum
(1.2% & 3.12%) respectively for Toje and Alajo soil series. Therefore, both Cynodon
dactylon and Paspalum vaginatum can be good plants species for phytoremediation having
accumulated total hydrocarbons up to 33,270mg/kg at 5.5% on Toje soil series and
40,466mg/kg at 8% on Alajo soil series.
Description
Thesis (PhD) - University of Ghana, 2013