ICMGP - Conference Presentation

Abstract Information :

Worldwide, mercury (Hg) pollution and the associated environmental and health concerns have been the subject of fierce debates in artisanal mining regions, resulting in strong corrective actions by many governments (e.g., the destruction of small, private artisanal mining platforms). Historically scientific efforts to understand Hg impacts from artisanal and small-scale gold mining (ASGM) have focused on the oxidation of metallic Hg, the production of methylmercury and subsequent bioaccumulation in aquatic biota, and the health implications related to vapor exposure and contaminated fish consumption. The importance of elucidating the transformations of metallic Hg into methylmercury (MeHg) is undeniable, but other sources of Hg such as release from flooding of hydroelectric reservoirs, forest fires, erosion of the riverbanks, as well as regional and global atmospheric emissions can also contribute to Hg bioaccumulation in fish. In many ASGM regions it is unknown if liquid Hg from gold mining or subsequent dry deposition from burning of Hg amalgams directly drives elevated fish Hg burdens and/or if it is a function of numerous sources coupled to ecosystem susceptibility for Hg methylation. Understanding the relative contributions of these sources is imperative before corrective actions are executed by local governments, but often liquid Hg is viewed as the main contamination source due to high visibility in reports and media. Measurements of Hg stable isotope values can provide the opportunity to fully investigate how liquid Hg from ASGM contributes to fish Hg concentrations. This approach is well studied for sediments but the data allowing us to differentiate liquid ASGM Hg (e.g., elemental) from atmospheric deposition is lacking for fish. This presentation will discuss the current applications of Hg stable isotopes at ASGM sites as well as adaptive study designs to assess sources of Hg available to food webs.