Influence of organic amendments used for benz[a]anthracene remediation in a farmland soil: pollutant distribution and bacterial changes

Abstract

Organic amendments are usually carried out at field-scale for efficient remediation of organic pollutants; however, their effects on pollutant distribution and the corresponding microbial mechanisms were rarely discussed. The main aim of this study was to compare the fate of benz[a]anthracene in soil amended by several bioremediation materials and underlying microbial mechanisms. In this study, the potential for biotransformation of polycyclic aromatic hydrocarbon in a farmland soil was investigated in microcosms spiked with 14C-benz[a]anthracene as the tracer. A series of organic amendments including lignin, straw, mushroom culture waste, and cow manure, as well as a fungal inoculum of Pleurotus ostreatus, were compared. Illumina sequencing was introduced to reveal the bacterial community in different amendments. The metagenomic function was predicted with the bioinformatics tool of phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt). From the results, the lignin-contained substrates (lignin, straw, mushroom culture waste) showed increase trend in the dissipation of benz[a]anthracene, while Pleurotus ostreatus and cow manure resulted in opposite trends. Specifically, mushroom culture waste mainly increased 14C to the formation of humin-bound residue (39.5 ± 6.8%); lignin amendment significantly (P < 0.05) enhanced the mineralization to CO2 (7.38 ± 0.89%) and humic acid–related nonextractable residue (9.77 ± 0.45%). The influence of straw on the environmental fate of benz[a]anthracene was marginal. High-throughput sequencing of 16S rRNA genes demonstrated that mushroom culture waste and lignin significantly changed bacterial community composition, leading to increases in the relative abundance of Pseudomonadaceae, Methylophilaceae, Bacillaceae, and Burkholderiaceae. Moreover, the result of PICRUSt showed that the genes-encoding bacterial cytochrome P450 enzymes were significantly increased in the lignin treatment, suggesting a possible co-metabolism between lignin degradation and PAH mineralization. These findings suggest lignin-containing organic amendments could be promising soil remediation agents of benz[a]anthracene by stimulating mineralization and sequestration of pollutants.