Effects and mechanisms of exogenous carbon addition on organic carbon pools in petroleum hydrocarbon contaminated soil

The problem of soil petroleum hydrocarbon pollution caused by the extensive use of petroleum and its products needs to be solved urgently. As a biostimulation, the addition of glucose can increase the number of microorganisms and improve the activity of petroleum degrading bacteria. However, there are few reports on the effects of glucose on different fractions of organic carbon in polluted soils. Low, medium and high concentrations of glucose (50 %, 100 % and 300 % soil microbial biomass carbon) were added to petroleum hydrocarbon contaminated soil. The response law and microbiological mechanism of soil organic carbon components to glucose input were revealed by the isotope tracing technique and high-throughput sequencing technology. The increase of stable soil organic carbon fractions was found due to the carbon turnover of glucose mediated by microorganisms. The addition of glucose resulted in a decrease in the particulate organic carbon pool and an increase in the mineral-associated organic carbon pool. The results of isotope tracer technique showed that glucose addition increased the δ¹³C value of soil organic carbon from −10.76 ‰ to 84.11 ‰ −858.18 ‰. High concentration of glucose addition would lead to more glucose to the stable carbon pool. Microbial communities and functions analysis showed that Bacillus was a pioneer genus activated by glucose, and the relative abundance reached 25.97 % on the 0th day in the high concentration group. Compared with other functional genes involved in carbon metabolism, the gene bglX encoding β-glucosidase had the highest abundance in the high concentration group.