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. 2019 Mar 11;16(5):883. doi: 10.3390/ijerph16050883

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© 2019 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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Study area with sampling sites along the River Wurm (W1–W5) and the River Haarbach (H1 and H2). © Data source ELWAS-WEB 2019, dl-de/by-2-0 (www.govdata.de/dl-de/by-2-0) https://www.elwasweb.nrw.de.