Chromium and Lead Concentrations in Soils and Plants at the Chumash Creek Dump, San Luis Obispo, CA.

Chromium and Lead Concentrations in Soils and Plants at the Chumash Creek Dump, San Luis Obispo, CA

Michael A. Wallace

ABSTRACT

            Deposition of anthropogenic materials in the environment can potentially affect heavy metal concentrations in  soil, vegetation and water.  This study was conducted to determine whether refuse from a former dump site had affected chromium or lead concentrations in the area.  Soil, plant and water samples were collected using a grid pattern from the area near Chumash Creek in San Luis Obispo, CA.  Soil and plant extracts were made using US EPA Method 3050a, nitric acid digestion, to measure total chromium and lead at the sample locations.  These soil samples were also extracted using US EPA Method 1311 (TCLP) to measure bioavailable chromium and lead at the sample locations.  A Chumash Creek water sample was also collected approximately 30 m downstream of the dump. Metal concentrations were determined using a flame atomic absorption spectrophotometer.  Total chromium ranged from 196.50 mg kg^-1 to 33.84 mg kg^-1.  Total lead ranged from 246.94 mg kg^-1 to 85.50 mg kg^-1.  The TCLP extracted chromium and lead concentrations were below the method detection limits.  The water and plant sample chromium and lead concentrations were below the method detection limits as well.  Some chromium and lead may have been introduced to the site as a result of desposition of anthropogenic waste, however, the levels of mobile chromium and mobile lead were found to not exceed EPA standards.  The deposition of anthropogenic wastes to the Chumash Creek Dump area did not show a significant risk of introducing bioavailable chromium or lead to the area.