Sediments around the globe store huge quantities of hydrophobic organic contaminants (HOC; 1000 tons only for PCB 153). As the inflow of pollution is reduced, HOCs may diffuse out from sediments to the water column. Still, processes affecting the diffusive flux of HOCs back to water are poorly investigated, much due to difficulties in experimental design. In this project we develop and employ a novel flow-through benthic chamber with an infinite sink for measurements of HOC flux from sediment. This will for the first time allow for an in situ assessment of the established paradigm of bioturbation being a significant factor regulating mass transfer of HOCs from sediments. Further, this project involves the investigation of the toxicity of the complex mixture of chemicals released from sediment to water.