Background concentrations of heavy metals and their role in clean up of hazardous waste sites: Application to Ventura and Los Angeles Counties (California)

Heavy metals contaminated sites pose a special challenge to risk managers, regulators, and responsible parties, because, unlike man-made organic compounds such as DDT, trace metals occur naturally in soils. Comparing soil background concentrations to hazardous waste site soil concentrations can determine if the site has elevated levels of inorganic constituents. Those analytes determined to be above background are then identified as chemicals of concern and are evaluated further as part of the risk assessment process. Background data can also be used to set clean up levels for a contaminated site.; Therefore, adequate characterization of background is critical to the Remedial Investigation Feasibility Study Process. This background information should be a valuable tool for professionals working in site assessment/site cleanup within the area of study.; This study focuses on determining background concentrations of heavy metals in soil in the Los Angeles and Ventura Counties in Southern California. Seventeen heavy metals including antimony, arsenic, barium, beryllium, cadmium, chromium, hexavalent chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium, silver, thallium, vanadium and zinc were considered. Descriptive statistics, nonparametric tests and graphical tools were used to describe the data from sixty-five sites and 148 soil samples. The goal was to provide a better understanding of the distribution of background concentrations of heavy metals in this area.; Background soil samples were classified into natural or anthropogenic using heavy metals concentration and applying univariate and multivariate statistics. Multivariate methods identified arsenic, cadmium, copper and lead as key heavy metals to differentiate between natural and anthropogenic background. Heavy metal concentration profiles identified ground surface to a depth of ten feet as the zone most likely to be affected by anthropogenic activities.; Arsenic, barium, cadmium, chromium, cobalt, copper, lead, nickel, vanadium and zinc were found to be the most frequently detected heavy metals in background soil samples in the area of study using standard detection limits. These metals were used to evaluate a cumulative cancer risk and a non-cancer hazard index for natural and anthropogenic background concentrations in the area of study. The risk drivers for both natural and anthropogenic concentrations were arsenic and vanadium.