Theme

Photographer credit: Robert Walker, Robert Walker Photography

The theme of the University of Arizona Superfund Basic Research Program continues the achievements of previous grants (P42ES04940), which is to support the development of a risk assessment process for metal and organic contaminants through toxicologic and hydrogeologic studies and through development of innovative remediation technologies. Our application emphasizes hazardous waste issues in the Southwestern U.S. (and Mexican Border) due to the unique arid nature of this environment. However, the results of our studies are not limited to the Southwest since the main toxicants being examined, arsenic and halogenated hydrocarbons, are ubiquitous throughout developed countries. Thus, this project will contribute to our understanding of toxicology and remediation of hazardous waste sites and environmental pollution nationally and internationally.

It should be noted that most hazardous waste sites contain mixtures of pollutants or co-contaminants. Although our SBRP Program will be emphasizing particular hazardous wastes (e.g. arsenic and halogenated hydrocarbons), our field studies actually will test remediation technologies at sites that contain contaminant mixtures (e.g. PCE and diesel; multiple metals).

Hazardous chemicals emphasized

Schematic of arsenic biotransformation.

Arsenic
Due to the geology and environment of the Southwest, arsenic is present in soil and water, often exceeding regulatory limits. Arsenic is present in water supplies due to natural sources and to leaching into surface waters from over 300,000 acres of mine tailings. Soils are impacted in this arid environment due to wind-borne distribution of dust from arsenic-laden mine tailings across Arizona. The new EPA drinking water standard will mandate the capping of wells or treatment (removal of the arsenic) from the water before it can be used for consumption. Thus, our SBRP emphasizes studies to understand exposures to arsenic, processing of arsenic in the body, low-level toxic effects of arsenic, arsenic cycling in the environment, and remediation techniques to remove arsenic from water and to retain it in deposited residuals.

Halogenated hydrocarbon mixture collected from the Park-Euclid WQARF Site in Tucson, AZ.

Halogenated Hydrocarbons
Halogenated hydrocarbons remain an emphasis of our SBRP Program since these hazardous chemicals are arguably the most common organic contaminant found in groundwater throughout the Southwest. For example, trichloroethylene (TCE) is a common pollutant in groundwaters of the Southwest. TCE contamination at the Tucson International Airport Area Federal Superfund Site in south Tucson is a primary example of the impact of exposure to hazardous chemicals on documented health effects in the surrounding community. Perchloroethylene (PCE) is also commonly found in Arizona State Superfund sites. In fact, close to home there is a major underground plume of a PCE and diesel mixture that is threatening the wells on the south end of the University of Arizona campus. Thus, our Program will continue to address halogenated hydrocarbon contaminated hazardous waste sites to understand the health effects of these contaminants, their transport behavior, and to develop new, more effective methods for remediation.

Pit mine in Ajo, AZ.

Mine tailings
Mine tailings (300,000 acres in Arizona alone) are acknowledged to be an emerging issue in the Southwest. A variety of toxic metals including arsenic, lead, and cadmium are present in conjunction with adverse environmental conditions, e.g., low pH. Spread of these metal toxicants occurs through a combination of wind and water erosion resulting in measured elevated levels in wildlife even significant distances from the tailings site. Our Program addresses a low-cost technology, phytostabilization, and its potential for long-term stabilization of the extensive mine tailings-impacted lands found in the Southwest.