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Using benchmarking to strengthen the assessment of persistence
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Chemical persistence is a key property for assessing chemical risk and chemical hazard. Current methods for evaluating persistence are questionable, since the relationship between conditions in the environment and conditions in the laboratory tests employed to evaluate persistence is often unclear. Chemical benchmarking opens new possibilities to measure persistence in the field. In this paper we explore how the benchmarking approach can be applied in both the laboratory and the field to deepen our understanding of chemical persistence in the environment and create a solid scientific basis for laboratory to field extrapolation of persistence test results.

Keyword [en]
benchmarking, persistence, regulations
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-116867OAI: oai:DiVA.org:su-116867DiVA: diva2:809207
Available from: 2015-04-30 Created: 2015-04-30 Last updated: 2016-01-29Bibliographically approved
In thesis
1. The measurement of chemical persistence in the field by benchmarking: Theory and Experiment
Open this publication in new window or tab >>The measurement of chemical persistence in the field by benchmarking: Theory and Experiment
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Persistence is one of the core criteria in chemical exposure and hazard assessment. It is often defined as the half-life for the removal of a chemical from a specified environment by transformation. Chemicals with long transformation half-lives may pose high risks for wildlife or humans and be subject to long-range transport to remote areas. It is challenging to measure persistence directly in the field in view of the complexity of the natural environment and spatial and temporal variability in environmental conditions that may affect degradation.

The mass balance approach is the most commonly used method for field measurement of persistence. In this thesis an alternative to the traditional mass balance approach that uses benchmarking is proposed and evaluated using models and field application. The benchmarking approach compares the relative behavior of chemicals, rather than measuring the absolute value of a property. The unknown property (persistence in this thesis) of test chemicals can be estimated by comparison against another chemical for which this property is known.

In Paper I, the potential of benchmarking to measure persistence in the field was evaluated by modeling. A framework for applying benchmarking to measure persistence in the field was developed. Lake systems with hydraulic residence times of the order of months were identified as appropriate field sites to measure the persistence of chemicals that are close to the regulatory thresholds, which are also on the scale of months. Field studies in two Swedish lakes were conducted. Both are shallow lakes, whereas Norra Bergundasjön (Paper II) has a longer residence time (four months) than Boren (one to two months; Paper III). In Paper II the benchmarking approach was tested to measure the persistence of a group of chemicals that were expected to stay in the water phase. Acesulfame K (artificial sweetener) without observable degradation in the lake was used as the benchmark chemical. The persistence of 9 pharmaceuticals and one X-ray contrast agent was measured to range from <1-2 days (ketoprofen) to 580-5700 days (carbamazepine). The results obtained using the benchmarking approach agreed well with the mass balance approach, indicating that the benchmarking approach can be a valid and useful method to measure persistence in the field. In Paper III the seasonality in chemical persistence was investigated by benchmarking. The seasonal difference in chemical persistence was found to be largest between spring and autumn. The persistence of 5 chemicals in spring were lower than in autumn, mainly attributed to lower temperature and less sunlight in autumn. The spatial variation of the persistence of chemicals was observed by comparing the persistence of chemicals in spring in the two lakes. Thus benchmarking is a useful tool to study the temporal and spatial variation of persistence in the real environment.  

Paper IV explores the potential of benchmarking thoroughly and the application of benchmarking in a regulatory context. Benchmarking could facilitate more field measurements of persistence, leading to a better understanding of the temporal and spatial variability of persistence in various environments and a basis for lab-to-field extrapolation. Besides quantitative estimation of persistence in the field, benchmarking can be applied to determine the relative magnitude of persistence, called threshold benchmarking which could be a valuable tool in regulatory processes.

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University, 2015. 36 p.
Keyword
chemical benchmarking, persistence, half-lives, modeling, threshold benchmarking
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-116840 (URN)978-91-7649-146-1 (ISBN)
Public defence
2015-06-12, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.

Available from: 2015-04-21 Created: 2015-04-29 Last updated: 2015-10-28Bibliographically approved

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