Arsenic speciation and mobility in gold mining-impacted riverine sediments from the Loddon River catchment in Victoria, Australia

Abstract

The Loddon River floodplains, Victoria, southeast Australia, is contaminated with high levels of As (up to 300 mg kg−1) due to re-deposited mine tailings from historical gold mining (1851–1914). Arsenic concentrations often significantly exceed Australia's sediment guidelines (ISQG-high value of 70 ppm). To determine the potential risk associated with As, this study examined the speciation of As and its mineral phase association in sediments along a 60 km stretch of the river, and investigated how As is released under redox cycling conditions. Sequential extraction procedures (SEP) revealed that As is primarily associated with crystalline Feˡˡˡoxyhydroxides (up to 40 %) and residual phases (..