Mercury in the natural environment: Biogeochemical cycles and associated health risks

Abstract

Mercury (Hg) is an integral part of Earth's biogeochemical cycles, yet anthropogenic activities significantly elevate its environmental presence, posing considerable ecological and human health risks. Human exposure primarily arises from the consumption of Hg-contaminated freshwater and marine fish. The Minamata Convention on Mercury, initiated by the United Nations Environment Programme (UNEP), aims to mitigate global Hg emissions, reinforced by comprehensive monitoring efforts. The biogeochemical cycling of Hg is complex, encompassing intricate processes of distribution, transformation, and bioaccumulation that connect sources to exposure pathways. Thus, evaluating Hg biogeochemical behavior and potential environmental hazards is crucial in the global scientific fraternity. Although global policies address direct Hg emissions, comprehending its biogeochemical cycling remains challenging and continues to spur scientific investigation. Coal combustion is a significant source, accounting for approximately 60 % of Hg emissions, especially in geologically predisposed regions, with atmospheric deposition being a key factor, leading to elevated Hg levels in terrestrial soils. Health risks associated with Hg exposure are more acute in soil-contaminated environments than in aquatic systems, with ingestion posing greater risks than dermal contact. This review focuses on the biogeochemical cycling of Hg in the natural environment, highlighting contamination patterns and providing updated insights into Hg's impact on aquatic and terrestrial ecosystems.