Tracing legacy sediment and contaminants from historical gold mining using XRF, XRD and pOSL

    Research output: Contribution to conferenceAbstract

    Abstract

    The gold rush of the 19th century arguably created the most intense impacts on the western slopes of New South Wales, Australia, since first European colonisation. During the period 1851 to 1880, widespread vegetation clearance and soil erosion occurred in conjunctionwith the liberal release of heavy metals from gold mining and processing, both on hillslopes and stream beds. Metal-contaminated sediment accumulated in natural and artificial depocentres in the landscape, such as floodplains and old dams. Similar processes elsewhere have led to notions of chemostratigraphy, where metal-rich sediment can be distinguished in the sediment recordby their chemistry. It has now been >100 years since the end of the gold rush in some areas, and hillslope erosion and sedimentation has continued, leading in places to burial of sediment contaminated by mining and ore processing with relatively clean material, and the transport of contaminated sediment downstream. We used the elemental (XRF), mineralogical (XRD) and luminescence (OSL) characteristics of a sediment profile and the elemental characteristics of soil and sediment throughout the landscapeto assess the preservation potential of chemostratigraphy and determine the spatial distribution of contaminants at the former gold-mining area at Hill End, in eastern NSW, Australia. Sediment chemistry and mineralogy revealed that contaminated sediment generally has poor preservation potential in this landscape but that old chemostratigraphy is preserved in some depositional settings, such as tailings dams. Sediment at the base of one tailings dam had elevated Hg (~18 mg/kg) and As (~221 mg/kg) relative to background samples of Hg (<1 mg/kg) and As (~14 mg/kg) from nearby hillslopes. Portable OSL data showed minor changes between underlying fine-grained, laminated tailings and overlying alluvium, suggesting a slow transition from low-energy lacustrine-style sedimentation in the dam during the peak mining period to higher energy fluvial deposition following dam abandonment after the gold rush. However much of the former mining area has little mining-derived sediment remaining, suggesting thatsuch impacts of historical gold mining are no longer localised to the goldfields. Poor preservation of contaminated sediment at Hill End means that lowland areas downstream of Hill End may have received contaminated sediment transported through watercourses following the goldrush. These techniques, coupled with an understanding of landscape history, sediment delivery and depositional processes, provide more nuanced data than elemental chemistry alone, helping to explain the history and environmental impacts of historical gold mining and subsequent changes in the landscape. These findings can help inform future management strategies for mining-impacted sites and catchments, as well as help in the recognition that potentially hazardous contaminants may now reside downstream of historic goldfields both here and elsewhere.
    Original languageEnglish
    Number of pages1
    Publication statusPublished - 28 Jul 2014
    EventAnnual conference on applications of x-ray analysis (63rd : 2014) - Big Sky, United States
    Duration: 28 Jul 20141 Aug 2014

    Conference

    ConferenceAnnual conference on applications of x-ray analysis (63rd : 2014)
    Abbreviated titleDenver X-ray Conference 2014
    CountryUnited States
    CityBig Sky
    Period28/07/141/08/14

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    Nagle, N., Ralph, T., Gore, D., & Fryirs, K. (2014). Tracing legacy sediment and contaminants from historical gold mining using XRF, XRD and pOSL. Abstract from Annual conference on applications of x-ray analysis (63rd : 2014), Big Sky, United States.