Passive samplers used to detect low levels of sediment-associated contaminants

SCCWRP and its partners have shown that passive sampling technology can be used to detect chemical contamination in San Diego Bay sediment, a key finding in an ongoing study exploring whether legacy contaminants found in fish tissue are coming from contaminated bay sediment or somewhere else.

The passive sampling devices – made of polyethylene film and deployed in San Diego Bay for a month – were able to detect low levels of sediment-associated contaminants that are dissolving back into the water column. Traditional sampling techniques typically cannot detect the low contaminant levels that passive sampling can.

Analyses of the initial passive sampling deployment using gas chromatography-mass spectrometry (GC-MS) showed that contaminant levels in the surface sediment layer were consistently higher than in the water column just above it, indicating that contaminants are diffusing out of the sediment into the water.

The goal of the passive sampling study is to examine whether sediment contaminants are spreading extended distances through the water column. A common assumption in sediment management is that most legacy chemical contaminants that have bioaccumulated in fish tissue collected at a given site originated with contaminated sediment at the site.