Effects of potassium nitrate and organic fertilizer on microbial activity in hexadecane-contaminated soil
Biostimulation by adding exogenous nitrogen to the soil is a common application technology for soil organic pollution.However,the metabolic characteristics of soil microbial communities towards the contaminants during the remediation are still not clear.In this study,two stimulants,KNO3 and compost,were applied to13C-labeled hexadecane-contaminated soil for 30 days of remediation.The removal rates of hexadecane were determined using GC-MS,and the phospholipid fatty acid(PLFA)contents and the 13C incorporated into PLFA was quantified using 13C-PLFA-SIP technique.Results showed that the removal rates of hexadecane was higher in the KNO3(CN)and compost(CY)amendment soils than that in the natural attenuation(CC).After 30 days of incubations,the removal rates of hexadecane enhanced from 6.14％(CC)to 13.6％(CN)and 15.0％(CY),respectively.Although KNO3 amendment slightly decreased the total microbial biomass(the total PLFAs changed from 82.8 nmol·g-1 in CC to 79.7 nmol·g-1 in CN),the 13C-PLFA increased from 81.12 ng·g-1 to 92.84 ng·g-1.KNO3 amendment improved the hexadecane assimilation utilization by Gram-positive bacteria and fungi.In the compost treated soil(CY),the total PLFAs and 13C-PLFA increased to 99.3 nmol g-1 and 142.67 ng·g-1,respectively,and the assimilation utilization of hexadecane by Gram-positive bacteria and actinomycetes were significantly enhanced.In the different treatments,the microorganisms that can use hexadecane mainly included gram-positive bacteria i15∶0 and a15∶0,gram-negative bacteria 16∶1ω5c and 16∶1ω7c,fungus 18∶1ω9c,actinomycetes 16∶0(10Me),and unspecified bacteria 16:00.The results indicated that gram-positive bacteria were the most dominant hydrocarbon-degrading bacteria in the different treatments,and the remediation characterictics of KNO3 or compost addition toward hydrocarbon-polluted soil were different.
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