Background

Cationic surfactants are known to sorb strongly to soils and sediments in the environment. This strong sorption might imply low bioavailability and thus low ecotoxicity and bioaccumulation as well as no long range transport. However, analysis of the freely dissolved form of these chemicals is a challenge due to the low concentrations in the environment. This hampers direct conclusions from the field as well as from test systems in which realistic concentrations are to be used.

Major aims (contribution IRAS)

Improve the analytical procedure of the freely dissolved concentration of cationic surfactants in environmental samples, including sediment suspension. This work will focus on the use of solid-phase microextraction (SPME) method, and it will build on experience that has been gathered at IRAS in recent years ("Bioavailability of surfactants in marine sediments" funded by ERASM and performed at IRAS, Utrecht University 2004-2007). Sorption studies will be performed to elucidate the contribution of sorption to clay minerals to the overall sorption capacity of natural sediments. Measuring freely dissolved concentrations in the pore water phase of a sediment toxicity test in combination with a water only exposure will clarify whether the pore water hypothesis is also valid for cationics, i.e., whether adverse effects to biota are solely controlled by the freely dissolved concentration in the pore water.

Work at IRAS will focus on:

• To improve the analytical procedure for measurement of the freely dissolved concentration of cationic surfactants in environmental samples, including sediment suspension.
• To generate sorption data for cationic surfactants to humic matter, minerals and whole sediments.
• To generate toxicity data for a benthic organism in sediment as well as in "water only" tests for cationic surfactants.
• To compare effect concentrations, measured as freely dissolved concentrations in pore water, with effect concentrations in a toxicity tests with a "water only" exposure.