Environmental Contaminants of the Southwest

Natural background levels of arsenic are relatively high in Arizona, and a large fraction of drinking water wells exceed the U.S. EPA regulatory level of 10 ppb As (2). Adding to the problem are organo-arsenicals, methyl- and dimethylarsenate, used in Arizona as defoliants in cotton cultivation. Finally, in conjunction with arsenic, numerous abandoned mines and tailing piles throughout the state pose a serious threat to public health through movement of heavy metals via wind and water erosion and acid mine drainage. It is estimated that there are 60,000 to 100,000 abandoned or inactive mine tailings sites in Arizona alone on State, U.S. Forest Service, Bureau of Land Management, and private lands. These sites cover over 300,000 acres. Of the mines surveyed, 3.3% and 13.1% of the sites are categorized as posing an environmental hazard and significant public safety hazard, respectively (3).

Chlorinated solvents originating from dry cleaning or from solvents used in the aviation and microelectronic industries are the most important organic groundwater contaminants in Arizona. Approximately 90% of the federal and state designated superfund sites in Arizona have either trichloroethylene (TCE) or perchloroethylene (PCE) present in the groundwater (1). Past and present use of chlorinated pesticides in agricultural counties have led to accumulation of chlorinated compounds in soil and water.

References Cited:
1. Anonymous. 2000. Superfund programs section site information. Arizona Department of Environmental Quality.

2. Focazio, M. J., A. H. Welch, S. A. Watkins, D. R. Helsel, and M. A. Horn. 1999. A retrospective analysis on the occurrence of arsenic in ground-water resources of the United States and limitations in drinking-water-supply characterizations: U.S. Geological Survey Water-Resources Investigation Report 99-4279. USGS Information Services. [ USGS99-4279 ]

3. McCracken, A. 2004, posting date. Abandoned and Inactive Mines. Arizona State Mine Inspector. Online Publication. [ ASMI ]