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- Zou, Hongyan, 1985-, et al.
(författare)
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Temporal Variation of Chemical Persistence in a Swedish Lake Assessed by Benchmarking
- 2015
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:16, s. 9881-9888
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Tidskriftsartikel (refereegranskat)abstract
- Chemical benchmarldng was used to investigate the temporal variation of the persistence of chemical contaminants in a Swedish lake. The chemicals studied included 12 pharmaceuticals, an artificial sweetener, and an X-ray contrast agent. Measurements were conducted in late spring, late autumn, and winter. The transformation half-life in the lake could be quantified for 7 of the chemicals. It ranged from several days to hundreds of days. For 5 of the chemicals (bezafibrate, climbazole, diclofenac, furosemide, and hydrochlorothiazide), the measured persistence was lower in late spring than in late autumn. This may have been caused by lower temperatures and/or less irradiation during late autumn. The seasonality in chemical persistence contributed to changes in chemical concentrations in the lake during the year. The impact of seasonality of persistence was compared with the impact of other important variables determining concentrations in the lake: chemical inputs and water flow/dilution. The strongest seasonal variability in chemical concentration in lake water was observed for hydrochlorothiazide (over a factor of 10), and this was attributable to the seasonality in its persistence.
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| 2. |
- ZOU, HONGYAN, 1985-
(författare)
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The measurement of chemical persistence in lakes using benchmarking techniques
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The persistence of a chemical that indicates resistance to degradation is one of the core criteria for exposure and hazard assessment of chemicals. However, it is rarely measured in the real environment because of the lack of appropriate methods. The potential of a benchmarking approach to estimate the persistence of organic chemicals in lakes was evaluated by means of a simple multi-media box model. The application of the benchmarking approach to quantify key environmental properties affecting chemical fate was also introduced and applied to: 1. the overall air-water mass transfer coefficient; 2. the sediment burial rate. To know in which cases which system property needs to be quantified, the model was run to identify the dominant physical removal processes for a set of hypothetical chemicals. The maximum value of the persistence in lakes that can be measured due to the limitation of several uncertainties such as the precision of the analysis methods was presented and found to depend on both chemical properties and lake characteristics. By combining benchmarking with a good sampling strategy and analysis methods, it is possible to measure the persistence in a lake of the order of a month or longer for chemicals in large portions of the partitioning space. A framework of how to select an appropriate lake system to assess the persistence of chemicals was introduced.
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| 3. |
- Zou, Hongyan, 1985-
(författare)
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The measurement of chemical persistence in the field by benchmarking : Theory and Experiment
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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