Incorporation Mechanisms of a Branched Nonylphenol Isomer in Soil-Derived Organo–Clay Complexes during a 180-Day Experiment

Bound-residue formation is a major dissipation process of most organic xenobiotics in soil. However, both the formation and nature of bound residues of tetrabromobisphenol A (TBBPA) in soil are unclear. Using a 14C-tracer, we studied the fate of TBBPA in an oxic soil during 143 days of incubation. TBBPA dissipated with a half-life of 14.7 days; at the end of incubation, 19.6% mineralized and 66.5% formed bound residues. Eight extractable metabolites were detected, including TBBPA methyl ethers, single-ring bromophenols, and their methyl ethers. Bound residues (mostly bound to humin) rapidly formed during the first 35 days. The amount of those humin-bound residues then quickly decreased, whereas total bound residues decreased slowly. By contrast, residues bound to humic acids and fulvic acids increased continuously until a plateau was reached. Ester- and ether-linked residues accounted for 9.6-27.0% of total bound residues during the incubation, with ester linkages being predominant. Residues bound via ester linkages consisted of TBBPA, TBBPA monomethyl ether, and an unknown polar compound. Our results indicated that bound-residue formation is the major pathway of TBBPA dissipation in oxic soil and provide first insights into the chemical structure of the reversibly ester-linked bound residues of TBBPA and its metabolites.

Section: Introductionmentioning

confidence: 99%

Fate of Tetrabromobisphenol A (TBBPA) and Formation of Ester- and Ether-Linked Bound Residues in an Oxic Sandy Soil

Wang

Jiang

et al. 2015

“…In a recent review, these attempts have been summarized . As a conclusion, NER can be differentiated into xenobiotic residues, either entrapped (type I NER) in the structural voids of the soil, covalently bound to humic matter (type II NER), or so-called biogenic residues (type III NER). − Carbon or nitrogen from certain pesticides can be used by metabolic or cometabolic degradation for synthesis of the cell constituents of microorganisms, for example, amino acids, fatty acids. After the death and cell lysis, these compounds are incorporated into SOM forming ultimately biogenic residues .…”

Section: Introductionmentioning

confidence: 99%

Quantitative Identification of Biogenic Nonextractable Pesticide Residues in Soil by ¹⁴C-Analysis

Poßberg

Schmidt

Nowak

et al. 2016

Self Cite

Quantification of nonextractable residues (NER) of pesticides in soil is feasible by use of radioactively labeled compounds, but structural information on these long-term stabilized residues is usually lacking. Microorganisms incorporate parts of the radiolabeled ((14)C-) carbon from contaminants into microbial biomass, which after cell death enters soil organic matter, thus forming biogenic nonextractable residues (bioNER). The formation of bioNER is not yet determinable in environmental fate studies due to a lack of methodology. This paper focuses on the development of a feasible analytical method to quantify proteinaceous carbon, since proteins make up the largest mass portion of bacterial cells. The test substance (14)C-bromoxynil after 56 days forms more than 70% of NER in soil. For further characterization of NER the amino acids were extracted, purified, and separated by two-dimensional thin-layer chromatography (TLC). Visualization of the (14)C-amino acids was performed by bioimaging, unambiguous identification by GC-MS and LC-MS/MS. Our analysis revealed that after 56 days of incubation about 14.5% of the (14)C-label of bromoxynil was incorporated in amino acids. Extrapolating this content based on the amount of proteins in the biomass (55%), in total about 26% of the NER is accounted for by bioNER and thus is not environmentally relevant.

“…The bound residues in NAS (Figure ) could have been formed by incorporation of TBBPA and the phenolic TPs into the organic matter in NAS via ether and ester bonds. These coupling mechanisms have also been suggested for both the biotic and abiotic formation of bound residues of phenolic compounds, such as nonylphenol and humus monomers, to soil organic matter. − The absence of the active bromohydroquinone (compound 3 ) in NAS can be attributed to its chemical reaction with organic matter in NAS, as in the case of hydroquinone to soil organic matter, which likewise contributed to bound-residue formation.…”

Section: Results and Discussionmentioning

confidence: 93%

Enhanced Transformation of Tetrabromobisphenol A by Nitrifiers in Nitrifying Activated Sludge

Jiang

Nastold

et al. 2015

The fate of the most commonly used brominated flame retardant, tetrabromobisphenol A (TBBPA), in wastewater treatment plants is obscure. Using a (14)C-tracer, we studied TBBPA transformation in nitrifying activated sludge (NAS). During the 31-day incubation, TBBPA transformation (half-life 10.3 days) was accompanied by mineralization (17% of initial TBBPA). Twelve metabolites, including those with single benzene ring, O-methyl TBBPA ether, and nitro compounds, were identified. When allylthiourea was added to the sludge to completely inhibit nitrification, TBBPA transformation was significantly reduced (half-life 28.9 days), formation of the polar and single-ring metabolites stopped, but O-methylation was not significantly affected. Abiotic experiments confirmed the generation of mono- and dinitro-brominated forms of bisphenol A in NAS by the abiotic nitration of TBBPA by nitrite, a product of ammonia-oxidizing microorganisms (AOMs). Three biotic (type II ipso-substitution, oxidative skeletal cleavage, and O-methylation) and one abiotic (nitro-debromination) pathways were proposed for TBBPA transformation in NAS. Apart from O-methylation, AOMs were involved in three other pathways. Our results are the first to provide information about the complex metabolism of TBBPA in NAS, and they are consistent with a determining role for nitrifiers in TBBPA degradation by initiating its cleavage into single-ring metabolites that are substrates for the growth of heterotrophic bacteria.