Modelling the Fate of Mercury Emissions from Artisanal and Small Scale Gold Mining

Abstract. A mercury (Hg) tracer model based on WRF-Chem has been developed to provide a rapid and relatively simple tool to evaluate the local and regional impact of Artisanal and Small Scale Gold Mining activities which use Hg amalgamation.Artisanal gold mining, its use of mercury amalgamation and its potential for human and environmental harm is mentioned specifically in the Foreword by the Secretary-General of the United Nations António Guterres of the Minamata Convention on Mercury: Text and Annexes (2023 edition, url below). Much of this artisanal mining occurs in the Tropics, and often in densely forested regions and the role of vegetation in the global atmospheric mercury cycle has been shown to be significant in recent years. The model employs a simple lifetime approach to Hg⁰ oxidation based on KPP and an ad hoc deposition scheme which calculates the foliar uptake of Hg⁰_(g) based on the Leaf Area Index, dry deposition of Hg^II_(g) , and the wet deposition of Hg^II_(g) by convective and non-convective precipitation. A number of demonstration simulations are presented using four example domains from South-East Asia and South America, and five from Africa. The results highlight the diversity of the local impacts of ASGM due to land category, geography and meteorology, but also point to the fact that just as there are always local impacts there are also repercussions for the global atmospheric mercury burden (https://minamataconvention.org/sites/default/files/documents/information_document/Minamata-Convention-booklet-Oct2023-EN.pdf).