Project Summary:

This study examines trace element and ²²²radon chemistry in wells sampled by the USGS NAWQA program between 1991, when full implementation of the program began, through August, 2003. For the analysis, 24 minor and major trace elements are examined. These include aluminum (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), boron (B), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Tl), uranium (U), vanadium (V), and zinc (Zn) and ²²²radon (Rn). Physical properties (pH, dissolved oxygen concentration, specific conductance, and temperature), concentrations of major inorganic constituents, nutrients, among other constituents, also were measured. The occurrence and distribution of trace elements is described at the national scale and regionally by major lithology (and principal aquifer), with a focus on areas with high levels of contaminants and exceedences of health based standards. Measured contaminant concentrations are compared to U.S. Environmental Protection Agency (USEPA) drinking-water standards and proposed standards (for radon), including maximum contaminant levels (MCL), health advisories (HA), action levels (AL), and secondary drinking water regulations (SDWR), and to USGS Health-based Screening Levels (HBSL). Factors that relate to the occurrence of selected trace elements, such as geochemistry, redox, and age of water, also will be investigated and interpreted with standard statistical measures.