Comparing non-targeted chemical persistence assessed using an unspiked OECD 309 test to field measurements

Li, Zhe; McLachlan, Michael S.

doi:10.1039/c9em00595a

Cited by 8 publications

(17 citation statements)

References 29 publications

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“…This observation is consistent with previous reports of 2,4-D and other polar organic compound degradation in water/sediment systems. The lack of degradation in the water-only microcosms is likely attributable to insufficient biomass compared to sediment-water suspensions. ,,− …”

Section: Resultsmentioning

confidence: 99%

“…Understanding the environmental fate and transformation of polar organic compounds is critical for accurately assessing risk to ecosystems. Laboratory-based persistence studies are used to inform regulatory decisions for chemicals but are difficult to translate to the ecosystem scale, often resulting in wide variability in predicted persistence and environmental half-lives. − For example, photochemical degradation rates observed in laboratories may be orders of magnitude slower than rates observed in lakes or rivers due to differences in pathlength (i.e., water depth) and light intensity . Similarly, biodegradation rates observed in laboratories vary with inoculum source (i.e., sediment, water, or sludge) and target compound concentration, ,, making extrapolation to the environment challenging.…”

Section: Introductionmentioning

confidence: 99%

“…Assessing organic compound persistence and transformation pathways in the field presents other challenges. Many of these compounds are present at low concentrations with unknown input rates to lakes or rivers. , Transformation processes, such as photo- and biodegradation, occur simultaneously alongside physical processes, making it impossible to isolate individual reactions. ,, While quantification of known degradation products and genetic markers of biodegradation can provide insight into in situ transformations, information on specific pathways, transformation processes, and genetic data is needed for them to be successful. , …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Synthesizing Laboratory and Field Experiments to Quantify Dominant Transformation Mechanisms of 2,4-Dichlorophenoxyacetic Acid (2,4-D) in Aquatic Environments

White

Nault

McMahon

et al. 2022

Environ. Sci. Technol.

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Laboratory studies used to assess the environmental fate of organic chemicals such as pesticides fail to replicate environmental conditions, resulting in large errors in predicted transformation rates. We combine laboratory and field data to identify the dominant loss processes of the herbicide 2,4dichlorophenoxyacetic acid (2,4-D) in lakes for the first time. Microbial and photochemical degradation are individually assessed using laboratory-based microcosms and irradiation studies, respectively. Field campaigns are conducted in six lakes to quantify 2,4-D loss following large-scale herbicide treatments. Irradiation studies show that 2,4-D undergoes direct photodegradation, but modeling efforts demonstrated that this process is negligible under environmental conditions. Microcosms constructed using field inocula show that sediment microbial communities are responsible for degradation of 2,4-D in lakes. Attempts to quantify transformation products are unsuccessful in both laboratory and field studies, suggesting that their persistence is not a major concern. The synthesis of laboratory and field experiments is used to demonstrate best practices in designing laboratory persistence studies and in using those results to mechanistically predict contaminant fate in complex aquatic environments.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Synthesizing Laboratory and Field Experiments to Quantify Dominant Transformation Mechanisms of 2,4-Dichlorophenoxyacetic Acid (2,4-D) in Aquatic Environments

White

Nault

McMahon

et al. 2022

Environ. Sci. Technol.

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“…It is used to measure biodegradation by spiking the test chemical (concentrations of ≤10 μg L –1 are preferred) into aerobic natural waters or water–sediment systems with low suspended sediment concentrations (≤1 g of solids L –1 ) . However, chemical spiking has been shown to influence the microbial community and chemical attenuation, which creates doubts about the environmental relevance of the biodegradation test. ,− As an alternative, a nonspiked test has been suggested as it provides a better representation of biodegradation in the environment. , However, this test is constrained by the requirement for background contamination of the test chemicals in the environment of interest at quantifiable concentrations.…”

Section: Introductionmentioning

confidence: 99%

Increasing the Environmental Relevance of Biodegradation Testing by Focusing on Initial Biodegradation Kinetics and Employing Low-Level Spiking

Tian

Posselt

Fenner

et al. 2022

Environ. Sci. Technol. Lett.

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The environmental relevance of standard biodegradation tests such as OECD 309 has been questioned. Challenges include the interpretation of changing degradation kinetics over the 60–90 incubation days and the effects of chemical spiking on the microbial community. To ameliorate these weaknesses, we evaluated a modified OECD 309 test using water and sediment from three Swedish rivers. For each river, we had three treatments (no spiking, 0.5 μg L–1 spiking, and 5 μg L–1 spiking). The dissipation of a mixture of 56–80 spiked chemicals was followed over 14 days. Changes in dissipation kinetics during the incubation were interpreted as a departure of the microbial community from its initial (natural) state. The biodegradation kinetics were first-order throughout the incubation in the no spiking and 0.5 μg L–1 spiking treatments for almost all chemicals, but for the 5 μg L–1 treatment, more chemicals showed changes in kinetics. The rate constants in the no spiking and 0.5 μg L–1 treatments agreed within a factor of 2 for 35 of 37 cases. We conclude that the environmental relevance of OECD 309 is improved by considering only the initial biodegradation phase and that it is not compromised by spiking multiple chemicals at 0.5 μg L–1.

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“…They further demonstrated how the concept could be used to separate degradation half‐lives from dissipation processes in the field (a lake system; see Redman et al, 2021) and outlined its use more generally in chemical hazard and risk assessments, in particular, in calibrating and translating laboratory to field data. More recently, the same group demonstrated that comparable half‐life determinations between field‐derived and OECD TG 309 simulation tests were obtained if the tests were not spiked with a given test substance, but where biodegradation of substances in the natural waters was followed by targeted (Li & McLachlan, 2019) or nontargeted chemical analyses (Li & McLachlan, 2020). Such an approach is made possible by advances in analytical chemistry (see Specific analysis of chemicals ), but does not lend itself to new chemical substances yet to be released into the environment or those present at levels below quantification.…”

Section: Current and Future Options In Persistence Assessmentmentioning

confidence: 99%

Scientific concepts and methods for moving persistence assessments into the 21st century

Davenport

Curtis-Jackson

Dalkmann

et al. 2022

Integr Envir Assess & Manag

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The evaluation of a chemical substance's persistence is key to understanding its environmental fate, exposure concentration, and, ultimately, environmental risk. Traditional biodegradation test methods were developed many years ago for soluble, nonvolatile, single-constituent test substances, which do not represent the wide range of manufactured chemical substances. In addition, the Organisation for Economic Co-operation and Development (OECD) screening and simulation test methods do not fully reflect the environmental conditions into which substances are released and, therefore, estimates of chemical degradation half-lives can be very uncertain and may misrepresent real environmental processes. In this paper, we address the challenges and limitations facing current test methods and the scientific advances that are helping to both understand and provide solutions to them. Some of these advancements include the following: (1) robust methods that provide a deeper understanding of microbial composition, diversity, and abundance to ensure consistency and/or interpret variability between tests; (2) benchmarking tools and reference substances that aid in persistence evaluations through comparison against substances with well-quantified degradation profiles; (3) analytical methods that allow quantification for parent and metabolites at environmentally relevant concentrations, and inform on test substance bioavailability, biochemical pathways, rates of primary versus overall degradation, and rates of metabolite formation and decay; (4) modeling tools that predict the likelihood of microbial biotransformation, as well as biochemical pathways; and (5) modeling approaches that allow for derivation of more generally applicable biotransformation rate constants, by accounting for physical and/or chemical processes and test system design when evaluating test data. We also identify that, while such advancements could improve the certainty and accuracy of persistence assessments, the mechanisms and processes by which they are translated into regulatory practice and development of new OECD test guidelines need improving and accelerating. Where uncertainty remains, holistic weight of evidence approaches may be required to accurately assess the persistence of chemicals. Integr Environ Assess Manag 2022;1-34.

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Comparing non-targeted chemical persistence assessed using an unspiked OECD 309 test to field measurements

Abstract: Here we test the hypothesis that unspiked OECD 309 tests can quantitatively predict chemical persistence in the environment by comparing chemical half-lives assessed in the laboratory against those measured in the field.

Cited by 8 publications

References 29 publications

Synthesizing Laboratory and Field Experiments to Quantify Dominant Transformation Mechanisms of 2,4-Dichlorophenoxyacetic Acid (2,4-D) in Aquatic Environments

Synthesizing Laboratory and Field Experiments to Quantify Dominant Transformation Mechanisms of 2,4-Dichlorophenoxyacetic Acid (2,4-D) in Aquatic Environments

Increasing the Environmental Relevance of Biodegradation Testing by Focusing on Initial Biodegradation Kinetics and Employing Low-Level Spiking

Scientific concepts and methods for moving persistence assessments into the 21st century

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