The cycling of mercury through the environment

This paper reviews what is now known about the mercury cycle in the aquatic environment and indicates where the gaps in our knowledge lie. It describes the aquatic chemistry of mercury in the presence of chloride ions and the sulfate-sulfide system, the affinity of mercury for the sulfhydryl group in proteinaceous matter, the formation of methylated mercury compounds by microbial mediation, and the tendency for mercury in solution to adsorb on suspended solids. The paper then describes how mercury behaves in a typical local aquatic system based on facts known from its chemistry. It presents, finally, an estimate of the global cycle of mercury, and concludes that although man has created serious local problems by his indiscriminate discharge of mercury into the environment, he has had but negligible effect on a global scale.