Degradation, transformation, and non-extractable residue formation of nitrated nonylphenol isomers in an oxic soil

Abstract

Nitrated nonylphenols (NNPs) are main metabolites of the endocrine-disrupting nonylphenols in soil, yet their fate is unknown. Here, using four NNP isomers (NNP₁₁₁, NNP₁₁₂, NNP₆₅, and NNP₃₈), the degradation pattern of NNPs was investigated in an oxic soil for 266 days. Specifically, NNP₁₁₁ was ¹⁴C-labeled to facilitate investigating its degradation, transformation, and non-extractable residue (NER) formation. NNPs degradation was isomer-specific with the decreasing order of half-life: NNP₁₁₁ (126 days) > NNP₁₁₂ (76 days) > NNP₆₅ (14 days) > NNP₃₈ (8.4 days), providing direct evidence of the greater persistence of NNPs in soil than their parent NPs. At the end of the incubation, 8.5 %, 7.3 %, and 39.9 % of ¹⁴C-NNP₁₁₁ was mineralized, transformed to 2-amino-NP₁₁₁, and formed NERs in active soil, respectively. In contrast, NERs in sterilized soils were significantly lower, amounting to 15.1 % and 17.3 % in autoclaved and γ-irradiated soil, respectively. The majority of the NERs (>70 %) were in humin fraction, in which type I NER was the predominant (>90 %) mode for NER formation. Our results provide comprehensive knowledge on the fate of NNPs in soil, demonstrating that isomer-specific behavior, transformation products of NNPs, and NER formation should be considered when evaluating environmental fate and risks of NNPs.

Keywords: (14)C tracer; 2-Amino-NP(111); Autoclave; Environmental fate; γ-irradiation.