RESTORING THE LOS CERRITOS WETLANDS: ASSESSMENT OF TRACE METAL CONTAMINATION

Of the estimated 6400 hectares of coastal wetlands that existed between San Pedro and Newport Beach along southern California at the time of European arrival, less than 25% remain after a century of rapid urbanization. Because these wetlands serve as crucial refuges along the Pacific Flyway and as nurseries for popular fisheries, restoring undeveloped areas is a priority in re-establishing the health of southern California coastal ecosystems. The Los Cerritos Wetlands Complex is one such area, encompassing approximately 160 hectares of undeveloped, but degraded, salt marsh habitat within the former estuary of the San Gabriel River. The urban setting of the LCWC within the LA basin exposes the substrate to heavy metal contamination from anthropogenic sources, such as municipal discharges, industrial emissions and heavy traffic. In addition, the LCWC has been the site of major oil operations for nearly 90 years, with the resultant in-filling, grading, and potential for spills. Prior to restoration, the CSU-Long Beach undertook a baseline assessment of existing conditions and specific contaminants. The concentrations of nine trace elements (As, Ba, Cd, Cr, Cu, Ni, Pb, Se, and Zn) are analyzed in the sediment to determine if the land should be remediated prior to restoration. These elements are compared to the 2003 Southern California Bight Monitoring Program. As, Ba, Pb, and Zn are enriched compared to the Bight data, exceeding the 90^th percentile in most locations. At discrete locations Ba, a common constituent of drill muds, reaches concentrations of 3%. In other areas, Zn, a common by-product of tire wear, exceeds the values set in the USDA Soil Pollution Control Standards. However, when normalized to iron, most metal concentrations within the wetlands fall within the natural range of the sediment. Localized areas are contaminated and may require remediation prior to restoration.