ASSESSMENT OF HEAVY METAL CONTAMINATION IN SPRING WATER AND WATERCRESS (NASTURTIUM OFFICINALE) IN THE VICINITY OF THE TAR CREEK SUPERFUND SITE, OTTAWA COUNTY, OKLAHOMA

Historic lead and zinc mining in the Tri-State Mining District, Ottawa County, Oklahoma has caused lead and cadmium contamination of groundwater within the Boone aquifer (U.S. EPA, 1994). The Boone aquifer crops out in several locations on the jurisdictional lands of six Native American Tribes. Tribal members in this area continue to practice traditional lifeways and are concerned about the health effects of consuming potentially contaminated spring water or wild plants growing in or near spring water. The purpose of this study was to assess the level of contamination of spring water and watercress (Nasturcium officinale) on or near Tribal jurisdictional lands. Results were compared to Maximum Contaminant Levels (MCLs) set by the U.S. EPA for drinking water and Provisional Tolerable Weekly Intake (PTWI) levels for metals in food recommended by the Joint FAO/WHO Expert Committee on Food Additives. Concentrations of As, Cd, or Pb in spring water did not exceed established MCLs. However, statistical analyses indicated a significant (p < 0.05), negative correlation existed between concentration of As, Cd, and Zn in spring water and linear distance from the Superfund boundary (As: p = 0.02, R = - 0.42; Cd: p = 0.01, R = - 0.56; Zn: p = 0.00, R = - 0.67). These data suggest that movement of contaminated groundwater away from the Superfund has resulted in increased metal concentrations in spring water outcropping from the Boone aquifer. Concentrations of metals in watercress associated with spring water were as high as 14.8 ppm As (average 2.8 ppm), 14 ppm Cd (average 6.3 ppm), 16.9 ppm Pb (average 7.4 ppm), and 749.0 ppm Zn (average 206.8 ppm). Results indicated that watercress leaves and stems from all sites contained concentrations of metals that exceeded the PTWI limit for children. For adults, metals concentrations within watercress exceeded the PTWI limit at all sites except for two. The two sites that did not exceed the PTWI limit for an adult were found to safely support the consumption of only one portion size of 100 g per week for an adult.