The major pollutant people focus on nowadays is CO2, but I don't think of CO2 as being the big pollutant that Factorio is tracking. I suspect that soot, sulfur byproducts, and acidic forms of nitrogen are more what's being tracked.

Now, they may still be poorly modeling the absorption properties of water in this regard. :-)

You could very likely be right, but the advertisement for the mod probably wouldn't be a real advertisement if it didn't use subtly twisted facts. ;)

Hmm... Yeah okay, how about the alternative suggestion that has to do with the actual fact that most of the pollution in the real world ends up in our oceans and waters in the form of trash, plastic and industrial wastewater - it would fit if Factorio's pollution also ends up in the waters to a greater degree. I mean, our talented engineer is already doing so much for his environment - so this mod with exactly this background would be the perfect addition. How does that sound? Maybe a bit too macabre...? xD

Sounds good to me. And, also, don't mind my nitpicking. I asked ChatGPT to write a summary for me, and it did a terrible job. :-/ Part of the problem is that it absolutely insists on inserting verbiage that promotes the idea that pollution is bad or that players should be learning how to be good to the environment. And I can't get it to stop. chuckle

Anyway, here is something I wrote that may work better. You don't have to use it. It's your mod, and I'm just a random nitpicker. But, if you want to:

In vanilla Factorio, water absorbs much less pollution than many other kinds of terrain and that seems at odds with reality, give that many of our pollutants end up in the water in the real world. Heck, the oceans even absorb much of the atmospheric CO2 we generate.

This mod increases the pollution absorption of water to better reflect reality. It also has deep water absorb more pollution than shallow water, while "saturated" green water absorbs less overall.

I guess ChatGPT hasn't quite understood the Factorio spirit yet. xD

The suggestion seems reasonable! I'll definitely keep it in mind for the next update. Right now I'm a bit busy with exams and stuff, but that will come asap. ^^

I always assumed water spreads pollution farther because of currents. Pollution from one side of the Pacific finds its way to the other over time.