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Using recirculating flumes and a response surface model to investigate the role of hyporheic exchange and bacterial diversity on micropollutant half-lives
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.ORCID iD: 0000-0003-1100-1263
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.ORCID iD: 0000-0001-8979-8044
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2019 (English)In: Environmental Science: Processes & Impacts, ISSN 2050-7887, E-ISSN 2050-7895, Vol. 21, no 12, p. 2093-2108Article in journal (Refereed) Published
Abstract [en]

Enhancing the understanding of the fate of wastewater-derived organic micropollutants in rivers is crucial to improve risk assessment, regulatory decision making and river management. Hyporheic exchange and sediment bacterial diversity are two factors gaining increasing importance as drivers for micropollutant degradation, but are complex to study in field experiments and usually ignored in laboratory tests aimed to estimate environmental half-lives. Flume mesocosms are useful to investigate micropollutant degradation processes, bridging the gap between the field and batch experiments. However, few studies have used flumes in this context. We present a novel experimental setup using 20 recirculating flumes and a response surface model to study the influence of hyporheic exchange and sediment bacterial diversity on half-lives of the anti-epileptic drug carbamazepine (CBZ) and the artificial sweetener acesulfame (ACS). The effect of bedform-induced hyporheic exchange was tested by three treatment levels differing in number of bedforms (0, 3 and 6). Three levels of sediment bacterial diversity were obtained by diluting sediment from the River Erpe in Berlin, Germany, with sand (1 : 10, 1 : 1000 and 1 : 100 000). Our results show that ACS half-lives were significantly influenced by sediment dilution and number of bedforms. Half-lives of CBZ were higher than ACS, and were significantly affected only by the sediment dilution variable, and thus by bacterial diversity. Our results show that (1) the flume-setup is a useful tool to study the fate of micropollutants in rivers, and that (2) higher hyporheic exchange and bacterial diversity in the sediment can increase the degradation of micropollutants in rivers.

Place, publisher, year, edition, pages
2019. Vol. 21, no 12, p. 2093-2108
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-176435DOI: 10.1039/c9em00327dISI: 000502303700008OAI: oai:DiVA.org:su-176435DiVA, id: diva2:1375598
Available from: 2019-12-05 Created: 2019-12-05 Last updated: 2020-03-05Bibliographically approved
In thesis
1. How to estimate environmental persistence: Understanding persistence of organic micropollutants in rivers from a multidisciplinary perspective
Open this publication in new window or tab >>How to estimate environmental persistence: Understanding persistence of organic micropollutants in rivers from a multidisciplinary perspective
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic micropollutants such as food additives, pharmaceuticals and personal care products are found in rivers worldwide. Persistence is a key criteria in chemical risk assessment as micropollutants that are persistent pose an exposure hazard to humans and the environment. As biodegradation is the most relevant removal process for many micropollutants in rivers, persistence assessment relies on the estimation of the biodegradation half-life.  This thesis presents new approaches to understand the biodegradation of organic pollutants in rivers.

The application of Junge relationships (previously established for atmospheric pollutants), to river systems, was investigated in paper I to assess if biodegradation half-lives in the Danube river are correlated with variability in measured concentrations. Model scenarios show Junge relationships could potentially be found in measurements performed near the mouth of the river, but Junge relationships were not found in currently available monitoring data. In paper II an experimental design and response surface model were developed to study the effect of hyporheic exchange (induced by flowing water) and bacterial diversity in sediment on dissipation half-lives of two micropollutants in flumes. Faster dissipation was observed in flumes with high bacterial diversity and higher hyporheic exchange, and thus both variables are relevant to study dissipation processes in rivers. The influence of biological factors beyond bacteria diversity is explored in papers III and IV, by characterizing the bacteria community composition of sediment in OECD 308 bottle incubations (a standard test that is often recommended in risk assessment guidelines). In paper III, higher variation in half-lives (e.g. relative standard deviations > 50%) were found for micropollutants with longer half-lives (e.g. from 40 to more than 120 days). Higher variation in half-lives also corresponded to differences in bacteria community composition and specifically to increased or decreased abundance of certain bacteria genera. Although the exact bacteria genera involved in the biodegradation of the micropollutants cannot be determined in papers II or III, our results suggest bacteria community composition and diversity should be considered in the interpretation of biodegradation half-lives since they are related to variability in biodegradation and to understand extrapolation from laboratory to the field. Finally in paper IV, it is investigated if the bacteria communities are affected by the OECD 308 test conditions. Changes in the bacteria communities in the sediment between the initial river community, the beginning and the end of the incubation, at high and a low concentrations are reported. Overall, 8% of bacteria genera increased or decreased in relative abundance in all comparisons, and it is unclear if these small changes in bacteria communities could have had an effect on the observed half-lives in paper III.

This thesis contributes to the understanding of physical and biological factors influencing biodegradation and potential implications for risk assessment of organic micropollutants in rivers.

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science, Stockholm University, 2020. p. 57
Keywords
organic micropollutants, biodegradation, persistence, rivers, flume mesocosms, Junge relationships, OECD 308 bottle incubations
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-176444 (URN)978-91-7797-915-9 (ISBN)978-91-7797-916-6 (ISBN)
Public defence
2020-02-07, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

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

Available from: 2020-01-15 Created: 2019-12-06 Last updated: 2020-01-07Bibliographically approved

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