Abstract
Mining is known to be a major source of metal contamination for fluvial systems worldwide. Monitoring and understanding the effects on downstream water and sediment quality is essential for its management and to mitigate against detrimental environmental impacts. This study aimed to examine the effects of the small-scale, abandoned, hydraulic Black Creek gold mine on the geochemical content of fine (<63 μm) stream bed and floodplain sediment in the Horsefly watershed (British Columbia, Canada), which is a part of the Quesnel River basin. Concentrations of As, Cd, Se and Zn were determined byaqua regiadigestion and the modified BCR (European Community Bureau of Reference) sequential extraction procedure followed by inductively coupled plasma-optical emission spectroscopy or inductively coupled plasma-mass spectrometry. Age-depth models for the floodplain cores were constructed using excess Pb-210 and Cs-137 activity concentration profiles. The results show that the mine caused local As contamination of the Horsefly River floodplain sediment during the first years of operation, but at present the contamination is mainly contained in the Black Creek. Present-day and recent concentrations of Cd, Se and Zn in the Horsefly River are elevated and this is probably derived from other upstream mining activities. The spatial and temporal changes in heavymetal concentrations suggest a slight, but not particularly widespread, mining effect on the finesediment geochemistry in the Horsefly River system.
Highlights
ACTIVE and abandoned mine sites represent a major environmental problem for fluvial systems worldwide (Du Laing et al, 2007, 2009) and the related pollution can decrease water and sediment quality, thereby impacting aquatic ecosystems and human health
The increase in As concentrations at the time of mining is in agreement with the elevated values associated with the source material from the Black Creek mine site
In the case of Se and Zn, the residual concentrations for the cores downstream of the Black Creek confluence exceed those for the upstream cores
Summary
ACTIVE and abandoned mine sites represent a major environmental problem for fluvial systems worldwide (Du Laing et al, 2007, 2009) and the related pollution can decrease water and sediment quality, thereby impacting aquatic ecosystems and human health. In British Columbia, mining has been prevalent in the interior region since the 1850s (BC Heritage Rivers Program, 2014; Horsefly Historical Society, 1981). Mining activities are generally characterized by the diversion and pollution of water, and mine drainage is one of the province’s main sources of chemical threats to surface- and groundwater quality (Environment Canada and Ministry of Environment, Lands and Parks, 1993). Environmental risks in a mine’s area of influence are of particular concern as many rivers in British Columbia are major spawning habitats for several salmon species (Albers and Petticrew, 2012; BC Heritage Rivers Program, 2014)
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