Fate of a branched nonylphenol isomer in submerged paddy soils amended with nitrate

Using a 14C-labelled branched isomer of NP, the fate of NP was studied in two flooded typical paddy soils under anoxic conditions. Biodegradation of NP occurred under anoxic conditions and was accompanied by the production of polar metabolites and bound residues in alkaline soil extract and humin. The addition of nitrate (20 mM) increased the degradation of NP in both soils, especially in soil derived from silt loam deposit, which contained high amounts of organic matter. Less than 1% NP mineralization was detected as free CO2 in both soils, whereas up to 30, 21, 31% of NP residues comprised at least two polar metabolites, those extractable from humic substances and from the humin fraction, respectively. The denaturing gradient gel electrophoresis (DGGE) analysis of DNA extract of the soil microorganisms hinted differences of microbial community between soils with different degradation rates of NP. The present study provides for the first time information about the fate of a branched nonylphenol isomer in submerged soils amended with nitrate. The production of high amounts of polar metabolites under anoxic conditions suggests the necessity of also considering the fate and possible effects of the degradation products of NP in anoxic environment such as in waterlogged soil.