NP₁EC Degradation Pathways Under Oxic and Microxic Conditions

Abstract

The degradation pathway of nonylphenol ethoxyacetic acid (NP1EC) and the conditions favoring dicarboxylated alklyphenol ethoxyacetic acid (CAnP1EC; where n = the number of aliphatic carbon atoms) formation were studied in oxic microcosms constructed with organic carbon-poor soil from the Mesa soil aquifer treatment (SAT) facility (Arizona) and pristine organic carbon-rich sediments from Coyote Creek (California). Results suggest that the availability of dissolved oxygen determines the dominant biodegradation pathway; ether cleavage and the formation of NP is favored by oxic conditions, while alkyl chain oxidation and the formation of CAP1ECs is favored under microxic conditions. In the Mesa microcosms, para-NP1EC was transformed to para-nonylphenol (NP) before being rapidly transformed to nonyl alcohols via ipso-hydroxylation. In the Coyote Creek microcosms, large quantities of CAP1ECs were observed. Initially, CA8P1ECs were the dominant metabolites, but as biodegradation continued, CAP1ECs became the dominant metabolites. Compared to the CAsP1ECs, the number of CA6P1ECs peaks observed was small (< 6) even though their concentrations were high. Several novel metabolites, tentatively identified as 3-alkylchroman-4-carboxylic acids (with alkyl groups ranging from C2 to C5), were formed in the Coyote Creek microcosms. These metabolites are presumably formed from ortho-CAP1ECs by intramolecular ring closure.

Environmental fate of phenolic endocrine disruptors: field and laboratory studies

“…The vertical position of a mass spectrometric group indicates the recalcitrance of its members to biodegradation by strain Bayram (group numbers-encircled numbers at the far right-are listed according to increased recalcitrance). sediments from California (Montgomery-Brown et al 2008). The results suggested that the oxygen tension determined the dominant biodegradation pathway.…”

“…Moreover, oxygen tension also seems to be an important factor in determining the reaction pathway of NPnEC. Under low oxygen tension, formation of CAPnEC is significant, whereas under high oxygen tension further metabolism via NP and subsequent ipso-substitution is favoured (Montgomery-Brown et al 2008).…”

“…However, two recent studies (Wettstein 2004;Montgomery-Brown et al 2008) gave indications that NP1EC is metabolized via NP. In one study, the authors performed aerobic and microaerobic microcosm experiments, in which they incubated NP1EC with organic carbon-poor soils from Arizona as well as with organic carbon-rich Figure 4.…”

“…Under fully aerobic conditions (Arizona soils), ether cleavage with formation and subsequent degradation of NP was favoured, while under microaerobic conditions (California sediments) alkyl chain oxidation with formation of CAPnEC was favoured. The authors clearly showed that in the microcosms with Arizona soils (high oxygen tension) para-NP1EC was transformed to para-NP, which was then quickly turned over to nonyl alcohols by ipso-hydroxylation (Montgomery-Brown et al 2008). …”

Degradation pathways of low-ethoxylated nonylphenols by isolated bacteria using an improved method

“…According to Jonkers et al (2001) and Di Corcia et al (1998), CAPECs started to accumulate after NPECs were formed during biotransformation of NPEOs. Montgomery-Brown et al (2008) has found that alkyl chain oxidation of NP 1 EC by microcosms and the formation of CAP 1 ECs is favored under microxic conditions. Thus, it may be possible that pathway 1 is favored by the microxic conditions.…”