Environmental impact of a major copper mine spill on a river and floodplain system

This study examines the impact on channel and floodplain sediments from the accidental release of metal-contaminated waters from the Lady Annie Copper Mine in northwest Queensland, Australia. The spill-impacted Saga Creek and Inca Creek rise in the upper Lake Eyre catchment, which covers ?1.2 million km2 and is one of the world's last and largest unregulated wild river systems. In contrast to other river systems impacted by mining-related spills, the upper reaches of the study system have no history of metal mining, enabling the consequences of a large spill event to be evaluated for its environmental legacy. The contaminated mine water inundated valuable cattle grazing lands and waterholes, resulting in a record fine of $0.5 (Australian) million in 2012. Total extractable metal concentrations from 101 floodplain and channel samples revealed that copper contamination was the principal element of concern with 43% of channel surface and 31% of floodplain surface samples exceeding the Australian guideline value for sediments. Contamination was restricted predominantly to surface sediments (0-2 cm) within ?50 m of the top of the channel bank and within the first 5 km of the impacted catchment. Although downstream sediments showed a definitive metal contamination impact from the spill, the legacy risk posed to grazing cattle is considered low. The implication arising from this study is that while a large single pollution spill can have serious short-term impacts on river systems and their use for agriculture, its environmental legacy in the absence of cumulative impacts from repeated contamination events could be relatively small.15 page(s