In what little time you have left before the exam, click the link and view the podcast lectures by Leeds English Faculty. There are two on The Rime of the Ancient Mariner, looking at the text as an ecological poem 'deeply concerned with the relationship between human beings and their environment.'
http://www.theenglishfaculty.org/a-levels/item/220-language-and-meaning-in-the-rime-of-the-ancyent-marinere-pt2