Abstract
Biostimulation with exogenous nitrogen addition is a common strategy for remediation of petroleum-contaminated soils. However, the comprehensive effects of various dosages of exogenous nitrogen application on hydrocarbon removal, soil ecotoxicity, and microecological response are not clear. In this study, a petroleum-contaminated soil with total petroleum hydrocarbon (TPH) content of 8553 mg/kg was remediated by adding NH4Cl to adjust C/N ratio of 100/1(N1), 100/2(N2), 100/5(N3), and 100/10(N4), respectively. After 210 days of remediation, the TPH removal efficiency was the highest in the N2(32.55 %) when compared with that in the N1(28.43 %), N3(27.87 %) and N4 (22.60 %) treatments. PICRUSt2 analysis revealed that the abundances of oorA and oorB genes encoding EC 1.2.7.11 were significantly enhanced in the N1 and N2 but decreased in the N3 and N4 treatments, indicating that conversion of pyruvate to acetyl-CoA for participation in TCA cycle was enhanced due to low dosage of NH4Cl addition. The gene abundances of NxrA and NxrB encoding nitrification, nirK and nirS encoding denitrification in the N1 and N2 treatments were lower than those in the N3 and N4 treatments, suggesting low dose of NH4Cl addition reduces soil nitrogen loss and stabilizes taxonomic diversities. Acute toxicity test found that the earthworm weight inhibition rates in the N1, N2, N3, and N4 treatments were −2.48 %, 9.57 %, and 5.83 % and 60.21 %, respectively. This result revealed that NH4Cl application with C/N ratio of 100/2 contribute to TPH degradation and stabilization of soil ecological function, which were facilitated to remediation of petroleum-contaminated soil.
Published Version
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