Vertical profiles of pentachlorophenol and the microbial community in a paddy soil: influence of electron donors and acceptors.

Vertical variations of pentachlorophenol (PCP) dissipation and microbial community were investigated in a paddy soil with the addition of electron acceptors (NO3(-), SO4(2-)) and donors (crop residues). Crop residues enhanced PCP dissipation by supplying dissolved organic carbon (DOC) as an electron donor, whereas NO3(-) and SO4(2-) inhibited it. The dissipation of PCP in electron donor treatments resulted in the accumulation of 3,4,5-trichlorophenol (3,4,5-TCP) except for wheat residues. The abundance and diversity of phospholipid fatty acids (PLFAs) decreased with increasing soil depth. The succession of predominant PLFAs shifted from aerobic bacteria to anaerobic bacteria when electron acceptors were changed to electron donors. The saturated/monounsaturated fatty acids (S/M) ratio increased with soil depth, which probably implied that nutrient turnover rate declined after the accumulation of 3,4,5-TCP. The results showed that the addition of electron donors and acceptors modified the microbial communities, which then further influenced the degradation pathway of PCP.