Numéro |
J. Phys. IV France
Volume 107, May 2003
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Page(s) | 1005 - 1008 | |
DOI | https://doi.org/10.1051/jp4:20030468 |
J. Phys. IV France 107 (2003) 1005
DOI: 10.1051/jp4:20030468
The mobility of arsenic in a Canadian freshwater system receiving gold mine effluents
V.P. Palace, C.L. Baron, R.E. Evans, K. Wautier and L. BrinkworthDepartment of Fisheries and Oceans, Freshwater Institute, 501 University Crescent, Winnipeg R3T 2N6, Canada
Abstract
The mobility of arsenic in freshwater systems is dictated by its partitioning between
the solid and dissolved fractions in the sediments and their interstitial waters. Arsenic is largely
associated with ferric iron in the form of oxyhydroxides in oxic waters and sediments as arsenate
As (V). In deeper anaerobic sediments arsenic is released from iron oxyhydroxides because of the
reduction of iron from the ferric to the more soluble ferrous state. Reducing environments can
also be encountered in sediments relatively close to the sediment-water interface when there are
high rates of biological activity that consume oxygen and create a reducing environment. For the
past several years we have examined the relationships between organic carbon content of surface
sediments, bottom water anoxia, redox zonation of sediments and the release of arsenic from
freshwater sediments to the overlying waters. These studios have been performed using
limnocorrals to isolate columns of water and their underlying sediments in Balmer Lake, a shallow
freshwater system in Central Canada that has served as the final repository for tailings from two
gold mines for more than 40 years. Our results indicate that surface sediments with higher organic
carbon content are more susceptible to developing late season bottom water anoxia that can
facilitate the subsequent release of arsenic from sediments to the overlying water. These results
have implications for metal mining operations where reduced metal loadings from effluents or
mine closure are expected to result in higher biological productivity and greater organic matter
deposition to sediments.
© EDP Sciences 2003