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The influence of aquatic vegetation on the fate and behavior of organic contaminants in small streams – Mesocosm and laboratory experiments

  • Aquatic macrophytes can contribute to the retention of organic contaminants in streams, whereas knowledge on the dynamics and the interaction of the determining processes is very limited. The objective of the present study was thus to assess how aquatic macrophytes influence the distribution and the fate of organic contaminants in small vegetated streams. In a first study that was performed in vegetated stream mesocosms, the peak reductions of five compounds were significantly higher in four vegetated stream mesocosms compared to a stream mesocosm without vegetation. Compound specific sorption to macrophytes was determined, the mass retention in the vegetated streams, however, did not explain the relationship between the mitigation of contaminant peaks and macrophyte coverage. A subsequent mesocosm study revealed that the mitigation of peak concentrations in the stream mesocosms was governed by two fundamentally different processes: dispersion and sorption. Again, the reductions of the peak concentrations of three different compounds were in the same order of magnitude in a sparsely and a densely vegetated stream mesocosm, respectively, but higher compared to an unvegetated stream mesocosm. The mitigation of the peak reduction in the sparsely vegetated stream mesocosm was found to be fostered by longitudinal dispersion as a result of the spatial distribution of the macrophytes in the aqueous phase. The peak reduction attributable to longitudinal dispersion was, however, reduced in the densely vegetated stream mesocosm, which was compensated by compound-specific but time-limited and reversible sorption to macrophytes. The observations on the reversibility of sorption processes were subsequently confirmed by laboratory experiments. The experiments revealed that sorption to macrophytes lead to compound specific elimination from the aqueous phase during the presence of transient contaminant peaks in streams. After all, these sorption processes were found to be fully reversible, which results in the release of the primarily adsorbed compounds, once the concentrations in the aqueous phase starts to decrease. Nevertheless, the results of the present thesis demonstrate that the processes governing the mitigation of contaminant loads in streams are fundamentally different to those already described for non-flowing systems. In addition, the present thesis provides knowledge on how the interaction of macrophyte-induced processes in streams contributes to mitigate loads of organic contaminants and the related risk for aquatic environments.

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Author:Christoph Stang
Title Additional (German):Der Einfluss aquatischer Makrophyten auf den Verbleib und das Verhalten organischer Schadstoffe in kleinen Fließgewässern – Untersuchungen im Mesokosmen- und Labormaßstab
Advisor:Ralf Schulz, Andreas Lorke
Document Type:Doctoral Thesis
Date of completion:2015/11/27
Date of publication:2015/12/02
Publishing institution:Universität Koblenz-Landau, Campus Landau, Universitätsbibliothek
Granting institution:Universität Koblenz-Landau, Campus Landau, Fachbereich 7
Date of final exam:2015/11/26
Release Date:2015/12/02
GND Keyword:Fließgewässer; Makrophyten; Schadstoffbelastung; Schadstoffkonzentration
Number of pages:(VI, 116 S. : graph. Darst.)
Institutes:Fachbereich 7
Licence (German):License LogoEs gilt das deutsche Urheberrecht: § 53 UrhG