. 2021 Sep 28;18(19):10231. doi: 10.3390/ijerph181910231
© 2021 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 (https://creativecommons.org/licenses/by/4.0/).
Figure 1.
Sample area: the Yellow River Basin.