TITLE:
Assessing Earthworm Influence on Remediating Potentials of Soil Micro-Organisms, and Bioavailable Hydrocarbon Pollutant in the Niger Delta, Nigeria
AUTHORS:
Tambeke Nornu Gbarakoro, Victoria Oluwaseyi Koshoffa, Francis David Sikoki
KEYWORDS:
Petroleum Hydrocarbon Contamination, Bacteria Biodiversity, Soil Fauna, Total Organic Carbon, Nitrates
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.11 No.3,
March
31,
2023
ABSTRACT: In the Niger Delta region of Nigeria, oil explorations and exploitations
abound, causing environmental pollution with serious consequences on soil
ecosystem and its biodiversity. In spite of the relationship between microbes
and fauna in soil ecosystem, such that both organisms can metabolize certain
range of petroleum hydrocarbon substrates with the fauna influencing the
remediation potentials of bacteria, yet soil fauna is still not fully
considered in bioremediation. The influence of earthworm; Lumbricus terrestris on
the remediating potentials of soil bacteria in petroleum hydrocarbon
contaminated soils was investigated. Eighteen pots were filled with 700 g of
soil each, with nine treated with mixture of 3 levels crude oil and remediated
with earthworm, while the other nine had no earthworm. The total petroleum
hydrocarbon (TPH), soil physical, nutrient compositions, and TPH degrading
bacteria biodiversity were determined before contamination or commencement of
study and thirty days after. The results showed a decrease in TPH concentration
of 55.58%, 62.57% and 67.07% in 1 ml, 2 ml and 3 ml crude oil contaminated
soil, respectively. Species richness and abundance of bacteria organisms
increased with high relative abundance in soils remediated with earthworms,
hydrocarbon utilizing bacteria increased from less than 0.1 cfu/g to 0.4 cfu/g,
and total heterotrophic bacteria 1.6 cfu/g at the end of the study. Earthworms
increased rate of remediation potentials of bacteria, such that within 30 days
post remediation treatment, 34.14% of reduced concentration was achieved over
soil samples without earthworms at 3 ml, and 25.14% at 2 ml concentration.
Reduction in pH levels in remediated soils was between 6.39 to 6.17 and 6.74 to
6.72 in unremediated soils, while moisture content was 6.73% to 6.77% unremediated
and 5.85% to 6.62% in earthworm remediated soils. Total organic carbon,
nitrates in soils inoculated with earthworms were lower in concentration than
those without earthworms. Reverse was the case with potassium, phosphate and
phosphorous concentrations which were above those without earthworms. Results
indicate statistically, significant difference between reduction in TPH in earthworm
remediated soils and unremediated soils, pointing out that earthworm is a good
candidate for facilitation of bacteria remediation-petroleum hydrocarbon
contamination.