Study reassesses sediment contamination at Palos Verdes Superfund site completed

SCCWRP has completed a follow-up study assessing the state of sediment contamination along the Palos Verdes shelf a decade after completing the Superfund site’s last ecological condition assessment.

The study, completed in December, will add to historical trend lines tracking the persistent effects of the pesticide DDT and an industrial class of chemicals known as PCBs in seafloor sediment. Although DDT and PCBs were banned decades ago, millions of pounds of the chemicals were discharged along the Palos Verdes shelf in the years prior. The chemicals can continue to exert toxic effects for decades.

During the study, researchers deployed passive samplers across the 17-square-mile Superfund site in 2022 to measure levels of DDT and PCBs that are leaching out of surface layers of sediment into the water column above.

A final report summarizing the study’s findings has been submitted to the U.S. Environmental Protection Agency, Region 9 and is expected to be available later this year.

In a separate but related study, SCCWRP and the Scripps Institution of Oceanography have begun working to develop a modeling tool for predicting how the pesticide DDT and its breakdown products are continuing to bioaccumulate in marine food webs off the coast of Southern California five decades after DDT was banned.

The two-year bioaccumulation study is measuring levels of DDT and its breakdown products – collectively referred to as DDT+ – in sportfish, as well as leaching from surface layers of seafloor sediment.