Dr Farzana Kastury
Future Industries Institute | University of South Australia
Abstract: Geological processes that cause gold deposition, often cause arsenic (As) enrichment in the soil. Gold ore processing [e.g., milling, cyanidation, high temperature roasting (calcination)], generally changes As speciation, while releasing it into the environment. Consequently, many legacy gold mining regions in the world have widespread As contamination in soil and water. Gold was discovered in Victoria, Australia in 1851 and supplied as much as 30% of the world’s gold in that decade. This study investigated As exposure from 30 legacy gold mining wastes from Bendigo, Victoria, Australia. Samples were dried and sieved to <2 mm, <250 µm, <53 µm and <20 µm particle size fractions. Total and bioaccessible concentrations of As and co-contaminants of interest [e.g., Antimony (Sb), Cadmium (Cd) and Lead (Pb)] was analyzed using aqua-regia digestion and USEPA method 1340 respectively. As relative bioavailability (RBA) was assessed using a mouse model in selected samples (<250 µm fraction, n = 8). As speciation in the <250 µm fraction was analyzed by X-ray Absorption Spectroscopy. The results showed that As concentration in the <250 µm soil particle fraction ranged from 68.2 - 14,984 mg/kg, while several samples contained elevated Sb (up to 6,073 mg/kg), Cd (up to 51.5 mg/kg) and Pb (up to 10,304 mg/kg). High concentrations of co-contaminants were mostly associated with calcinated samples. Speciation analysis showed that As-V was the dominant oxidation form in the samples. Calcinated samples contained As-V as yukonite and as coprecipitated with calcite. As adsorbed onto Al/Fe dominated the remaining samples with smaller amounts of Kankite and arsenopyrite. While neither particle size, nor co-contaminants influenced bioaccessibility greatly, As RBA was influenced by As speciation and presence of Sb. This is the first study that provides detailed characterization of legacy gold mining waste in Victoria and provides unique insights into factors that influence As exposure.
Host：Assist. Prof. Hongbo Li
Nanjing University
Time：09:00am Oct 31, 2022 (Beijing time)
Zoom ID: 816 9975 7155
Bilibili: 25002335
