Metalliods - Antimony
Mobilisation and dispersal of antimony from antimony-gold mineral deposits in circumneutral pH waters: environmental consequences in Australasia
|
 |
Hillgrove and Macleay River catchment, NSW
Contamination derived from mine waste at Hillgrove has affected stream sediment quality for over 300 km in the Macleay River system to the Pacific Ocean. Much of the stream system is of high-energy type (gravel bed) until the floodplain. Periodic flooding has dispersed contaminated sediment across the floodplain. National sediment guideline values for Sb are exceeded (ISQG-low = 2 ppm Sb, ISQG-high = 25 ppm Sb). The catchment Sb background value in stream sediments is 1.1 ppm. Water quality is greatly affected for 20 km (dissolved Sb averaging 1 mg/L), with values locally exceeding drinking water quidelines (3 µg/L) to the ocean. Arsenic values in stream sediments and in water are similar to those of Sb.
 |  |
|
Photos of 1900's mining in Bakers Creek gorge at Hillgrove, with mine waste disposal into stream. |
|
|
Remnants of historic mine dump adjacent to Bakers Creek. |
HFO with up to 11% Sb and 10% As precipitate out of tailings dam and mine water seepages and cause attenuation of these elements downstream. |
Macleay floodplain
The Macleay floodplain (~600 km2) has been affected by flood-derived contaminated sediments deposited over the past century. Approximately 90% of the floodplain area contains Sb values above the local background value of 0.27 ppm, with As also exceeding the local background value. Approximately 8% of modern swamp environments and 6% of modern levee environments have Sb and As values exceeding current national soil ecological investigation levels of 20 ppm. Maximum Sb values (up to 39.4 ppm) occur in the swamps. Sediment cores taken from many locations in the most contaminated regions show maximum Sb concentrations in the top 20 cm, consistent with modern deposition. Mobilisation of Sb and As into water and plants can occur by redox and pH changes due to acid sulphate soil processes and management practices.
|
 |