Clark, R.B. 1989 (1992 or 2001 3rd, 4th or 5th Edns) Marine Pollution. Oxford : Clarendon Press
(The 5th edition is 'best' but not much has changed in the last few years in the topics that were covered about heavy metals)
For an introduction to Toxicology and more detail on all aspects of Ecotoxicology:
Walker CH, Hopkin SP, Sibly RM, & Peakall DB 2001 Principles of Ecotoxicology London: Taylor and Francis