Abstract by Natalie Barkdull
Mercury contamination from four artisanal and small scale gold mining areas in Java, Indonesia
Artisanal and small scale gold mining (ASGM) is the largest source of anthropogenic mercury (Hg) worldwide. We evaluated Hg contamination across four ASGM areas in Central Java, Indonesia of varying scale. At each location, we collected water samples upstream and downstream of ASGM areas during the dry season (June-July 2017). Notably, Hg concentrations in stream water were not directly related to the scale of mining. For example, Kebonsari had 300 amalgamators but the lowest total Hg concentrations, while Jatiroto had <100 amalgamators and the highest Hg concentrations (>4730 ng/L). Hg concentrations in three areas exceeded USEPA criteria for freshwater aquatic life. Hg concentrations in amalgamator waste exceeded 150000 ng/L. Downstream of the mining areas, MeHg:THg ratios reached 20%, indicating that active Hg methylation occurs in streams. These results, which represent a best-case scenario, suggest that Hg from ASGM activities may contaminate downstream rice cultivation and fish stocks. Further study is needed to investigate Hg transport in the wet-season when rainfall and high stream discharge may mobilize contaminated sediment near mining areas.