GLOBAL RECONNAISSANCE SURVEY OF METALS IN UNTREATED DRINKING WATER SOURCES

As part of an ongoing global survey, our research group is investigating untreated drinking water sources for the presence of metal contamination. More than 120 sites have been sampled in over 20 countries for the presence of As, Ba, Cd, Cr, Cu, Mn, Ni, Pb, Sb, Se, and Zn. Field sampling was performed by trained NGO staff who used metal chelating polyurethane foam blocks to sequester metals from source water samples. Sample foams were returned to Hope College and were processed through an acid-wash procedure to recover trapped metals. Rinsates were analyzed by ICP-OES techniques. Preliminary analytical results from 45 sites show 47% of the drinking water sources contain metals above background controls. Metals detected were Ba, Cu, Cr, Mg, Mn, and Zn. Zn was the most commonly occurring and Cr the second-most occurring metal. Preliminary synthesis indicates drinking water sources elevated in Cr and Zn are located in predominantly volcanic terranes. Same-site data collected from hollow-membrane filters indicate that suspended particulate load concentrations are generally < 2 ppm at the sites with elevated Zn and Cr. Suspended load particulate matter was recovered from samples from some of the sites analyzed for dissolved metals. Semi-quantitative SEM-EDS analysis of these particulates shows some potential correlation between the presence of a Cr-bearing mineral phase and elevated dissolved Cr concentrations. As more foams from field drinking water sources around the world are returned for metal analysis, potential correlations to site land use, soil substrate, bedrock, and population density will be examined. So far, this project is a reconnaissance survey with small sampling density at any one site. Future work will focus on in-depth sampling of drinking water sources in targeted areas of high metal concentrations, revealed by this study.