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Issue 7, 2012
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Fluvial transport and surface enrichment of arsenic in semi-arid mining regions: examples from the Mojave Desert, California

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Abstract

As a result of extensive gold and silver mining in the Mojave Desert, southern California, mine wastes and tailings containing highly elevated arsenic (As) concentrations remain exposed at a number of former mining sites. Decades of weathering and erosion have contributed to the mobilization of As-enriched tailings, which now contaminate surrounding communities. Fluvial transport plays an intermittent yet important and relatively undocumented role in the migration and dispersal of As-contaminated mine wastes in semi-arid climates. Assessing the contribution of fluvial systems to tailings mobilization is critical in order to assess the distribution and long-term exposure potential of tailings in a mining-impacted environment. Extensive sampling, chemical analysis, and geospatial mapping of dry streambed (wash) sediments, tailings piles, alluvial fans, and rainwater runoff at multiple mine sites have aided the development of a conceptual model to explain the fluvial migration of mine wastes in semi-arid climates. Intense and episodic precipitation events mobilize mine wastes downstream and downslope as a series of discrete pulses, causing dispersion both down and lateral to washes with exponential decay behavior as distance from the source increases. Accordingly a quantitative model of arsenic concentrations in wash sediments, represented as a series of overlapping exponential power-law decay curves, results in the acceptable reproducibility of observed arsenic concentration patterns. Such a model can be transferable to other abandoned mine lands as a predictive tool for monitoring the fate and transport of arsenic and related contaminants in similar settings. Effective remediation of contaminated mine wastes in a semi-arid environment requires addressing concurrent changes in the amounts of potential tailings released through fluvial processes and the transport capacity of a wash.

Graphical abstract: Fluvial transport and surface enrichment of arsenic in semi-arid mining regions: examples from the Mojave Desert, California

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Publication details

The article was received on 14 Feb 2012, accepted on 16 May 2012 and first published on 20 Jun 2012


Article type: Paper
DOI: 10.1039/C2EM30135K
Citation: J. Environ. Monit., 2012,14, 1798-1813
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    Fluvial transport and surface enrichment of arsenic in semi-arid mining regions: examples from the Mojave Desert, California

    C. S. Kim, D. H. Stack and J. J. Rytuba, J. Environ. Monit., 2012, 14, 1798
    DOI: 10.1039/C2EM30135K

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