. 2021 Jun 26;18(13):6863. doi: 10.3390/ijerph18136863
© 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 5.
Spatial distribution of ecological sources.