Isomer-Specific Biodegradation of Nonylphenol in River Sediments and Structure-Biodegradability Relationship

Abstract

Nonylphenol (NP), a well-known environmental estrogen with numerous isomers, is frequently found in surface water and sediments. Recent studies showed that NP isomers exhibited different estrogenicity. However, at present little information is available on its isomer-specific degradation in the bed sediment, which is the primary sink of NP in surface aquatic systems. In this study, we investigated the biodegradability of 19 NP isomers in two river sediments under oxic and anoxic conditions. Under oxic conditions, the half-lives of NP isomers in an upper river sediment ranged from 0.9 to 13.2 d. Under reduced conditions, the persistence of NP isomers generally increased, with negligible dissipation under strongly reduced conditions. In the well-aerated sediment, NP isomers with short side chain and/or bulky α-substituents were found to be more recalcitrant to degradation. Moreover, when a total of 57 molecular descriptors were examined, the degree of branching as quantified by IDWbar was found to result in the best linear correlation with half-lives of NP isomers (R(2) = 0.88). These results indicated that the isomer-specificity of NP in environmental processes should be considered, and that simple molecular descriptors may be used to identify the more recalcitrant isomers, thus allowing prioritization in the evaluation of environmental fate and risks of NP isomers.

Isomer-specific biodegradation of nonylphenol in an activated sludge bioreactor and structure–biodegradability relationship

“…Hao et al (2009) considered the biodegradation of a few NP isomers in a sequencing batch reactor and observed that biodegradability followed a trend of NP 36 (75.4%) > NP 111 (42.9%) > NP 170 (40.7%) > NP 194 (36.2%), which was in agreement with that observed in the current study. In an oxic river sediment, alkyl chain length and a-substituent types were also found to greatly influence the biodegradation of NP isomers (Lu and Gan, 2014). However, in river sediments, the effect of a-substituent types appeared to be less monotonous than that in the bioreactor, while an opposite effect was observed for the alkyl chain length.…”

“…The extraction was repeated for two consecutive times. The cleanup procedure was similar to that in a previous study (Lu and Gan, 2014). Briefly, the extract was concentrated to about 1 mL and passed through a HyperSep Florisil SPE column (Thermo Scientific, Pittsburgh, PA) with a 5-g sorbent bed.…”

“…Triplicates were used for all influent, effluent and sludge samples. The methods for separation and identification of NP isomers may be found in a previous study (Lu and Gan, 2014). Briefly, an Agilent 6890 GC coupled with an Agilent 5973 mass spectrometer (Agilent, Santa Clara, CA) and an Agilent DB-5MS Ultra Inert capillary column (60 m  0.25 mm  0.25 mm) was used for the analysis.…”

“…Recent studies showed that estrogenic activity and biodegradation of NP were often isomer-specific Hao et al, 2009;Horii et al, 2010;Ikunaga et al, 2004;Katase et al, 2008;Lu and Gan, 2014;Makino et al, 2008;Shan et al, 2011). However, it is still inconclusive whether or not biodegradation during wastewater treatment process is isomer selective.…”

Microplastic–toxic chemical interaction: a review study on quantified levels, mechanism and implication

“…Another source of their presence in the environment involves the breakdown of ethoxylates (octylphenol ethoxylates; OPEs, and noylphenol ethoxylates; NPEs) as well as leaching from plastic debris [153]. OPs and NPs persist in the environment and are particularly toxic with their endocrine disrupting activities [50,106,148].…”