Passive samplers used to measure DDT at offshore dump sites

SCCWRP and the Scripps Institution of Oceanography have successfully used passive sampling technology to measure the concentrations of the pesticide DDT and other legacy contaminants that are diffusing out of seafloor sediment into the water column at a former industrial waste dump site in the San Pedro Basin.

The analysis, completed in September, has provided researchers with the data they need to develop models that will estimate how much of this chemical contamination that became attached to sediment decades ago is re-entering the water column over time, and the exposure risks it poses for aquatic life.

The deployment of passive samplers at the dump site was the first such attempt to deploy passive samplers at this site following its discovery in 2021. The site received thousands of barrels and bulk waste from the former Montrose Chemical Corporation in Los Angeles County, which was at the time the largest DDT manufacturer in the nation.

Passive sampling devices consist of thin membrane films that can detect low levels of contaminants in surface layers of sediment that dissolve into the water column. Researchers may return to the site – located between the mainland and Catalina Island – to deploy additional passive samplers.