I would like to suggest the reading of the following papers:

1.https://www.elsevier.com/books/advances-in-ultra-low-emission-control-technologies-for.

2.ttps://www.ge.com/power/transform/article.transform.articles.2018.mar.come-hele-or...

3.https://www.top-ee.com/coal-fired-power-plant

please be more clear, make a distinction (both can be measured and there are special techniques/procedures to apply):

emissions from the stack or

air quality in the limits of the plant