Mercury (Hg) is a toxic global pollutant of great environmental concern. In August 2017, the UNEP Minamata convention on mercury, a legally-binding international treaty aiming to reduce negative impacts of Hg on the environment, has entered into force. Anthropogenic activities have altered the global Hg cycle to a great extent and many ecosystems are threatened by exposure to elevated levels of Hg and its different species. For instance, neurotoxic and bioaccumulating methyl-Hg is formed under the influence of anaerobic microorganisms in a variety of natural systems but the controls on this key process are still far from being understood. Further active Hg research areas include exchange processes at the atmosphere-soil-plant interface and their importance for understanding atmospheric Hg deposition, the behavior and long-term fate of Hg at contaminated sites, as well as global cycling models assessing the evolution of historic Hg fluxes from different natural and anthropogenic sources. In the past few years, a number of novel research tools based on microbiological, spectroscopic, isotopic, and modelling techniques have been developed to improve our understanding of Hg cycling in the environment. This session presents new contributions on present-day Hg cycling in the environment using field-based, experimental, and/or modelling approaches on local to global scales, as well as contributions focusing on long- and short-term reconstruction of Hg as a pollutant over time using natural archives such as ice-cores, tree-rings, lake sediments and peat bogs. We particularly welcome research addressing the effects of the implementation of the Minamata convention on mercury levels in the environment and new approaches to assess its effectiveness.