In Front of a Burning Sky

I spent a few days on and off on this, and I'm quite pleased with the end result, though I still see tons of things wrong with it. My main concerns are the gas wafting from his mask and the general quality of the picture. Also, the river in the foreground was supposed to be covered in a sheen of rainbow oil, but I couldn't for the life of me manage to pull it off. If anybody has any suggestions on how to improve...?