Impacts of experimental decreasing groundwater levels on bacterial community composition and hydrocarbon attenuation in oil-polluted soil from Northern China

Sub-surface oil-polluted soils are frequently subjected to temporal groundwater table fluctuations during which the biological and chemical properties of the soil are expected to change in response to hydrological variations. In this study, we investigated the influence of decreasing groundwater levels on soil enzymatic activities, microbial community and total hydrocarbon dynamics. The changes in enzymatic activities, hydrocarbon removal efficiencies and bacterial community structure in the petroleum polluted soil were monitored by routine collection and testing of soil samples every 20 days over a period of 80 days in a laboratory column setup. Polymerase chain reaction and high-throughput sequencing of soil microbial DNA were used to determine the compositions of microorganisms, alpha and beta diversity in the polluted soil while the soil enzymatic activities and total petroleum hydrocarbon were measured using spectrophotometry and gas chromatography–mass spectrometry, respectively. The results showed that experimental decreases in groundwater levels over 80 days led to increased soil alkalinity, modulated enzymatic activities and enhanced total petroleum hydrocarbon attenuation in sub-surface soil. The findings from this study will be very useful in designing and optimizing bioremediation strategies for petroleum polluted soils from cold temperate regions. © Islamic Azad University (IAU) 2021.