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Biotransformation of chemicals in water–sediment suspensions: influencing factors and implications for persistence assessment


Seller, Carolin; Honti, Mark; Singer, Heinz; Fenner, Kathrin (2020). Biotransformation of chemicals in water–sediment suspensions: influencing factors and implications for persistence assessment. Environmental science & technology letters, 7(11):854-860.

Abstract

Chemicals’ half-lives derived from biotransformation simulation studies are central metrics for persistence assessment in international regulatory frameworks. To determine the persistence of chemicals released to the aquatic environment, paradigm shifts in recent and ongoing revisions of chemical legislation assign increasing importance to OECD 309 simulation studies. OECD 309 studies were designed to target biotransformation in natural water (pelagic test) or in water amended with sediment (suspension test). Suspension tests bear several advantages over the pelagic test, most importantly, employing higher bacterial cell densities, which promote biotransformation of various chemicals at observable rates. However, experience with suspension tests is limited. In this study, we followed the fate of 43 pharmaceuticals, pesticides, and industrial chemicals in various suspension test setups and elucidated parameters influencing biotransformation kinetics and half-lives derived thereof. Besides striking intrastudy variability between replicates, we found that differences in sediment origin and bacterial cell density resulted in chemical half-lives that were different by up to 2 orders of magnitude, making persistence classification rather uncertain. However, data suggested that test systems employing bacterial cell densities close to the upper limit of what is commonly observed in natural surface waters (i.e., 107 cells mL−1) yielded increased and more uniform biotransformation of chemicals.

Abstract

Chemicals’ half-lives derived from biotransformation simulation studies are central metrics for persistence assessment in international regulatory frameworks. To determine the persistence of chemicals released to the aquatic environment, paradigm shifts in recent and ongoing revisions of chemical legislation assign increasing importance to OECD 309 simulation studies. OECD 309 studies were designed to target biotransformation in natural water (pelagic test) or in water amended with sediment (suspension test). Suspension tests bear several advantages over the pelagic test, most importantly, employing higher bacterial cell densities, which promote biotransformation of various chemicals at observable rates. However, experience with suspension tests is limited. In this study, we followed the fate of 43 pharmaceuticals, pesticides, and industrial chemicals in various suspension test setups and elucidated parameters influencing biotransformation kinetics and half-lives derived thereof. Besides striking intrastudy variability between replicates, we found that differences in sediment origin and bacterial cell density resulted in chemical half-lives that were different by up to 2 orders of magnitude, making persistence classification rather uncertain. However, data suggested that test systems employing bacterial cell densities close to the upper limit of what is commonly observed in natural surface waters (i.e., 107 cells mL−1) yielded increased and more uniform biotransformation of chemicals.

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Additional indexing

Item Type:Journal Article, not_refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > Environmental Chemistry
Physical Sciences > Ecology
Physical Sciences > Water Science and Technology
Physical Sciences > Waste Management and Disposal
Physical Sciences > Pollution
Physical Sciences > Health, Toxicology and Mutagenesis
Language:English
Date:6 October 2020
Deposited On:04 Feb 2021 16:06
Last Modified:06 Oct 2021 00:00
Publisher:American Chemical Society (ACS)
ISSN:2328-8930
Additional Information:Statement des Verlags: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental science & technology letters, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/abs/10.1021/acs.estlett.0c00725
OA Status:Green
Publisher DOI:https://doi.org/10.1021/acs.estlett.0c00725

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