Mechanisms of arsenic attenuation in acid mine drainage from Mount Bischoff, western Tasmania

• Published in: The Science of the total environment Vol. 345; no. 1; pp. 219 - 228
• Main Authors: Gault, Andrew G., Cooke, David R., Townsend, Ashley T., Charnock, John M., Polya, David A.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01-06-2005; Elsevier Science
• Subjects: Acid mine drainage; Acids - chemistry; Applied sciences; Arsenic; Arsenicals - analysis; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Monitoring; Exact sciences and technology; EXAFS; Freshwater; Geologic Sediments - chemistry; Industrial wastewaters; Mining; Mount Bischoff; Natural water pollution; Pollution; Pollution, environment geology; Rainwaters, run off water and others; Soil Pollutants - analysis; Speciation; Tasmania; Wastewaters; Water Movements; Water Pollutants, Chemical - analysis; Water treatment and pollution; Australia; Tasmania; Oceania; Australia, Tasmania; Australia, Tasmania, Mount Bischoff; Mount Bischoff; Arsenic; Acid mine drainage; Tasmania; Speciation; EXAFS; Chemical precipitation; Pollutant behavior; Geochemistry; Mobility; Sequential extraction; Iron; Runoff water; Sediments; Dissolution; EXAFS spectrometry; Transport process; Trace element; Selfpurification; Industrial waste water
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2004.10.030

There is a dearth of research concerning the geochemistry of arsenic in acid mine drainage (AMD) in western Tasmania. To help address this, the controls on the mobility and fate of arsenic in AMD and its associated sediment at the Mount Bischoff mine site in western Tasmania were investigated. AMD issuing from the adit mouth contained dissolved arsenic and iron concentrations of 2.5 and 800 mg L
−1, respectively. The aqueous concentration of both arsenic and iron decreased markedly over a 150-m stretch from the adit mouth due to precipitation of hydrous ferric oxides (HFO) and jarosite, both of which are effective scavengers of arsenic. Microwave-assisted digestion of the sediment collected at the adit mouth revealed that the arsenic concentration exceeded 1%. Sequential extraction of this sediment showed that the bulk of arsenic was associated with amorphous and crystalline hydrous oxides of Al and/or Fe. Extended X-ray absorption fine structure (EXAFS) analysis indicated that the solid phase arsenic exists as As(V). EXAFS data were consistent with arsenate tetrahedra substituting for sulphate in jarosite and with corner-sharing complexes adsorbed on ferric oxyhydroxide octahedra. Erosional transport of AMD sediment downstream to higher pH waters may increase the mobility (and hence bioavailablity) of arsenic through dissolution of As-rich jarosite.