SEASONAL CHANGES IN ARSENIC CONCENTRATIONS AND HYDROGEOCHEMISTRY OF CANADIAN CREEK, BALLARAT (VICTORIA, AUSTRALIA) KHAWAR SULTAN∗ and KIM DOWLING School of Science and Engineering, University of Ballarat, Mount Helen, Victoria 3353, Australia (∗ author for correspondence, e-mail:
[email protected])
(Received 13 April 2005; accepted 2 September 2005)
Abstract. A 10-month study of surface waters in Canadian Creek (Ballarat, Victoria, Australia) showed the significant influence of historic gold mining waste material. The investigation focussed on the hydrogeochemistry of the surface waters and soils in order to: (1) document the levels and seasonal trends in major, minor and trace elements in the creek, (2) identify the process by which As is released from the soil/waste mining material to surface waters. For most dissolved major and trace elements (Na, Ca, Mg, K, and As) in surface waters, the concentrations decreased with the increasing rainfall and flow conditions except for Al and Fe. Two sites selected along the creek (1500 mg/kg) in the study area. The large As adsorption capacity of Fe and Al could be limiting extreme mobilization into the water. Rainfall with relatively low pH is possibly causing mobilisation of Al, Fe and As from highly alkaline soils (pH ≈ 9.0) into the nearby creek. Keywords: arsenic, metal cations, mining, seasonality, surface water, Australia
1. Introduction The contamination of the environment by metal/metalloids and the elucidation of their pathways through various environmental compartments (Cullen and Reimer, 1989; Alloway, 1990; Smith et al., 1998) such as incorporation into surface water (Smedley and Kinniburgh, 2002 and references therein) and ultimately the food chain, is of global significance. Metals can dissolve directly into river water from abandoned waste material located along the river or indirectly by surface runoff and/or contaminated groundwater (Warner, 1998; Grabowski et al., 2001). Elevated concentrations of arsenic pose risks to plant (Baker et al., 1976), animal (Porcella, 1987; Golub et al., 1998) and human health (Harrington et al., 1978; Hinwood et al., Water, Air, and Soil Pollution (2006) 169: 355–374
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2003). Among the biggest sources of As are ore deposits with sulphide minerals, which may contain arsenic to a level of thousands of ppm. In mining activities, the processing of ores leads to the concentration of As-sulphide minerals which weather geochemically to release As (Nriagu and Pacyna, 1988; Garcia and Alvarez, 2003) and become local sources of contamination. Most of As is immobilized due the presence of various minerals such as Fe and Al oxides. This oxide bound abundant source of arsenic can become mobile under the appropriate geochemical conditions. A sudden pH change by acid rain (pH
