Re-biodegradation of all alkanes after chemical oxidation in soils

Abstract

This study aimed to investigate the rapid restoration of indigenous hydrocarbon degraders after chemical oxidation, in order to enhance the subsequent biodegradation of crude oil in soils. The Fe-SOM (2231 mg kg−1) and H2O2 were added into the oil-contaminated soil (total petroleum hydrocarbon (TPH): 16064 mg kg−1) for chemical oxidation. Then, the all and partial alkane re-biodegradation reagents were added for re-biodegradation experiments. Calculated and analyzed C-source (DOC and TPH) and N-source ( $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ , $$ {\mathrm{NO}}_3^{-}-\mathrm{N} $$ , $$ {\mathrm{NO}}_2^{-}-\mathrm{N} $$ ) consumption and the population of hydrocarbon degraders in each period. After chemical oxidation, the total biodegradation of all alkanes (re-biodegradation degree: 100%) with reagent for all alkane re-biodegradation in the late stage was higher than that in the early stage. Further study found that DOC was the main C-source and $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ was the main N-source in the early stage, while TPH and nitrate were the main C&N-sources in the late stage of re-biodegradation. In other words, the C&N-sources changed over to TPH and nitrate in the late stage. After re-biodegradation stage, increasing biodegradation (from 644 mg kg−1 in the 1st stage to 842 mg kg−1 in the 3rd stage) was observed. The results showed that re-biodegradation of all alkanes could recover growth of indigenous hydrocarbon degraders and continuously increase biodegradation of all alkanes after chemical oxidation. The C&N-sources changed from DOC and $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ to all alkanes and $$ {\mathrm{NO}}_3^{-}-\mathrm{N} $$ during re-biodegradation stage was the key factor.