Measuring Organic Contaminants in Los Angeles’ Ballona Wetland and Creek

Participants: Patrick M. Carter, B.S., Natural Science (’07), M.S. Environmental Science (expected ’09)
Anh P. Nguyen, B.S.E., Civil Engineering (expected ’09)
Patrick J. Stahl, B.S.E., Civil Engineering (expected ’10)

Faculty: Rachel G. Adams, Department of Civil Engineering and Environmental Science, Loyola Marymount University

Abstract: The Ballona Wetlands (Los Angeles, CA) are designated as an ecological preserve with environmental assessment and restoration currently underway. Additionally, the Ballona Creek Estuary is a contaminated body of water for which the Total Maximum Daily Loads (TMDLs) for several hydrophobic organic contaminants (HOCs) have already been established. However, traditional methods for dissolved chemical measurements (e.g., liquid-liquid extraction) are difficult to use for HOCs at the current TMDL-regulated levels. Over the past two summers (June 2006, June 2007), passive samplers (polyethylene devices, PEDs) were deployed in the wetlands to measure the dissolved concentrations of selected TMDL-regulated contaminants: polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and chlorinated pesticides. These recently-developed passive samplers allow for the measurement of contaminants at trace levels. The PEDs were deployed in metal paint buckets fastened to stakes in the wetland channels. These buckets ensured that the PEDs were submerged and sampling water throughout the experiment. The PEDs were deployed at four locations in the wetland and at one location in the Creek for 14 days. Blank PEDs were used to correct for any contamination during deployment and recovery. Upon recovery, the PEDs were cleaned and extracted. The extracts were analyzed using a gas chromatograph-mass spectrometer (GC-MS). The dissolved chemical concentrations were calculated using water equilibrium partitioning coefficients and corrected for cases in which equilibrium is not reached. A third sampling event is planned for July ’08. The measurements will allow scientists and regulators to assess the current HOC levels in the Wetland and Estuary so that these HOCs may be evaluated with respect to the current TMDLs.

Funding: Interdisciplinary Collaborative Project Involving Undergraduate Students in Wetland Research, Merck/AAAS Undergraduate Science Research Program; Summer 2006 – Summer 2009.

Conference Presentations: A.P. Nguyen, P.M. Carter, R.G. Adams. Freely Dissolved Concentrations of Selected PCBs, PAHs, and Chlorinated Pesticides in Ballona Wetland and Creek. Poster at Southern California Conference of Undergraduate Research, Cal State University, Los Angeles, November 17, 2007.

Carter, P.M., R.G. Adams, J. Dorsey, K. Maruya, J. Peng. In situ measurements of hydrophobic organic contaminants in Ballona Wetland and Creek. Poster at Southern California Society of Environmental Toxicology and Chemistry, Lake Arrowhead, CA. April 9 – 10, 2007.

Image caption (above): Anh Nguyen prepares to recover a polyethylene sampler in Ballona Wetland.