Abstract
Mercury (Hg) contamination in soil and forage plants is toxic to ecosystems, and artisanal and small-scale gold mining (ASGM) is the main source of such pollution in the Bombana area of Indonesia. Hg contamination in soil and forage plants was investigated by particle-induced X-ray emission analysis of samples collected from three savannah areas (i.e., ASGM, commercial mining, and control areas) in the Bombana area. Hg contents of forage plants in the ASGM area (mean 9.90 ± 14 µg/g) exceeded those in the control area (2.70 ± 14 µg/g). Soil Hg contents (mean 390 ± 860 µg/g) were also higher than those in the control area (mean 7.40 ± 9.90 µg/g), with levels exceeding international regulatory limits. The Hg contents of 69% of soil and 78% of forage-plant samples exceeded critical toxicological limits. Thus, the Hg levels observed in this study indicate that contamination extending over large areas may cause major environmental problems.
Highlights
The United Nations Environment Programme (UNEP) has determined that Indonesia is the third-largest producer of mercury (Hg) emissions in the world, after China and India [1], with artisanal and small-scale gold mining (ASGM) being a major and increasing contributor [2,3]
Soil mean; standard deviation; and median, minimum, and maximum Hg contents are given in ASGM area, compared with control areas
The maximum soil Hg content recorded in the ASGM area was 2500 ppm, and the lowest concentrations in the commercial mining and control areas were below the detection limit
Summary
The United Nations Environment Programme (UNEP) has determined that Indonesia is the third-largest producer of mercury (Hg) emissions in the world, after China and India [1], with artisanal and small-scale gold mining (ASGM) being a major and increasing contributor [2,3]. There are ~300,000 artisanal gold miners working in ~1000 areas throughout Indonesia [5], with the increasing workforce being due to shifts in employment from the agricultural and fishing sectors. Illegal gold mines in rural areas provide an alternative livelihood even though significant capital investment is required [4]. Savannah areas in Indonesia contain placer-type gold deposits, and the potential of ASGM attracts migration, creating social conflict and economic complexity [6]. Natural sources of Hg in the atmosphere include volcanic emissions (80–600 tonnes yr–1 ) [7], geothermal activity, cinnabar deposits, and forest fires, which cycle Hg through the atmosphere via dry and wet deposition, with >90% of released Hg entering the terrestrial environment [8]
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