I have been working with San Diego Water quality data project:

https://www.sandiegodata.org/2018/04/summer-water-quality-data-proj...

Here are data sets:

https://data.sandiegodata.org/dataset?tags=water-project

Regretfully my complete works do not fit into the blog post (or even a few posts) because of a post size restriction (1 Mb). Here is a repository for it: https://github.com/san-diego-water-quality/MyaBakhova

In particular I created a number of maps. You can see below one of them, where sizes of station marks correlate to pollution amounts: