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Authors |
Carlito Baltazar Tabelin, Marthias Silwamba, Florifern C Paglinawan, Alissa Jane S Mondejar, Ho Gia Duc, Vannie Joy Resabal, Einstine M Opiso, Toshifumi Igarashi, Shingo Tomiyama, Mayumi Ito, Naoki Hiroyoshi, Mylah Villacorte-Tabelin |
| Abstract |
Artisanal and small-scale gold mining (ASGM) operations are major contributors to the Philippines芒聙聶 annual gold (Au) output (at least 60%). Unfortunately, these ASGM activities lacked adequate tailings management strategies, so contamination of the environment is prevalent. In this study, soil contamination with copper (Cu), lead (Pb), zinc (Zn) and arsenic (As) due to ASGM activities in Nabunturan, Davao de Oro, Philippines was investigated. The results showed that ASGM-impacted soils had Cu, Pb, Zn and As up to 3.6, 83, 73 and 68 times higher than background levels, respectively and were classified as 芒聙聵extremely芒聙聶 polluted (CD = 30芒聙聯228; PLI = 5.5芒聙聯34.8). Minerals typically found in porphyry copper-gold ores like pyrite, chalcopyrite, malachite, galena, sphalerite and goethite were identified by XRD and SEM-EDS analyses. Furthermore, sequential extraction results indicate substantial Cu (up to 90%), Pb (up to 50%), Zn (up to 65%) and As (up to 48%) partitioned with strongly adsorbed, weak acid soluble, reducible and oxidisable fractions, which are considered as 芒聙聵geochemically mobile芒聙聶 phases in the environment. Although very high Pb and Zn were found in ASGM-impacted soils, they were relatively immobile under oxidising conditions around pH 8.5 because of their retention via adsorption to hydrous ferric oxides (HFOs), montmorillonite and kaolinite. In contrast, Cu and As release from the historic ASGM site samples exceeded the environmental limits for Class A and Class C effluents, which could be attributed to the removal of calcite and dolomite by weathering. The enhanced desorption of As at around pH 8.5 also likely contributed to its release from these soils. |
Mindanao State
University - Iligan Institute of Technology