Issue 7, 2012

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

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

Additions and corrections

Article information

Article type
Paper
Submitted
14 Feb 2012
Accepted
16 May 2012
First published
20 Jun 2012

J. Environ. Monit., 2012,14, 1798-1813

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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