Comparison of Mercury Contamination in Four Indonesian Watersheds Affected by Artisanal and Small-Scale Gold Mining of Varying Scale
Artisanal and small-scale gold mining (ASGM) accounts for almost half of anthropogenic mercury (Hg) emissions worldwide and causes widespread water pollution. In Indonesia, several studies have identified harmful levels of Hg in areas affected by ASGM. While most of these studies focus on mining areas with thousands of miners, water contamination in smaller ASGM areas is less understood. We evaluated Hg contamination in four ASGM areas in Central Java of varying scale (from 30 to 3000 amalgamator barrels at each area), including Jatiroto, Kebonsari, Gumelar, and Kulon Progo. At each location, we collected water samples along river transects upstream and downstream of ASGM areas during the dry season (June–July 2017). Total Hg (THg) concentrations in stream water increased by orders of magnitude from upstream to downstream of ASGM activities at Jatiroto (1.35–4730 ng/L), with smaller observed increases at the other locations. Dissolved THg concentrations exceeded USEPA criteria for aquatic life (12 ng/L) at two of the four ASGM areas. THg concentrations in tailings exceeded 150,000 ng/L. Notably, THg concentrations in stream water were not directly related to the scale of mining, with Jatiroto having the highest concentrations as second smallest mining areas of the four in this study. Downstream of the mining areas, the fraction of dissolved methyl Hg to dissolved THg reached 20%, indicating that active Hg methylation occurs in the watersheds. 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.
KeywordsTrace elements Total mercury Methyl mercury Artisanal and small-scale gold mining ASGM Indonesia
Research permits were obtained through Kemenristekdikti, the Indonesian foreign research permitting office (Govt. Regulation no. 41/2006). We are thankful for students and faculty at the Geological Engineering Department of Universitas Pembangunan Nasional (UPN) “Veteran” in Yogyakarta for their assistance and support in conducting this research. We also thank regional and local Indonesian government agencies and leaders that assisted in this research including: the Department of Energy and Natural Resources Central Java Province (Dinas Energi dan Sumber Daya Mineral Provinsi Jawa Tengah), the Department of Mining and Energy in Pacitan East Java Province (Dinas Pertambangan dan Energi Kabupaten Pacitan Jawa Timur), Bpk. Harsono and Bpk. Ketik, and the gracious village leaders who welcomed us into their homes and helped us conduct this research.
Funding was provided by a Geological Society of America Graduate Student Research Grant and a Foreign Language Area Studies (FLAS) fellowship from the US Department of Education through Brigham Young University.
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