GEOGENIC CONCENTRATIONS OF SEVENTEEN METALS IN THE TORREY SANDSTONE, SAN DIEGO, CALIFORNIA

The Embayment area of San Diego County contains 17 recognized formations. The geogenic metals concentrations within these formations has not been adequately assessed. In this study, we present the results of over 50 in-situ geogenic soil samples from the Torrey Sandstone Formation of San Diego, California. All of the soil samples were analyzed for metals following EPA 6000 / 7000 Series Methods on an ICP Mass Spectrometer. The 95% UCL for 17 metals was calculated using the statistical software package ProUCL.

The EPA Region 9 Soil Screening Level for Arsenic at residential sites is 0.67 mg/kg. Our results show the Arsenic concentrations in the Torrey Sandstone exceed this and other commonly used health risk soil screening levels utilized by many regulatory agencies in California. Understanding the range of geogenic metals concentrations in sediments provides crucial information that regulatory agencies need to determine remediation thresholds.

Additional research is needed to assess the bio-availability of the Arsenic, the potential impact to human health and the environment, and the impact these results may have on current regulatory thresholds for assessing soils on residential and commercial properties in San Diego County. Further research is currently underway to identify the range of concentrations of metals in additional formations throughout the San Diego Embayment.