Change in PCB (Clophen A 50) composition when transported from sediment to air in aquatic model systems

PCBs (Clophen A 50) were added to the sediment of laboratory model systems composed of sediment, water, benthic macroinvertebrates and fish. Part of the PCBs left the sediment and a concentration of 0·2–0·7 μg litre⁻¹ was obtained in the water.

The transport of PCBs from water to air includes at least two processes: volatilization and jet drop transport. Volatilization (as indicated by PCBs trapped on polyurethane foam filters) resulted in a transport of 0·2–1·0 μg PCBs a week to air. Less chlorinated PCBs, i.e. tetrachlorobiphenyls, were transported to the air to a greater extent than more chlorine-substituted PCBs.

Transport of PCBs by jet drops from bursting bubbles (as indicated by the amount of PCBs found on jet drop impactors) was of the same magnitude as volatilization, but the proportion of PCB compounds trapped by the impactor plates was identical with that of sediment and water. The process seems mainly to transfer PCBs containing bulk water and particles to the air.

The results suggest that the contaminated sediment of lakes and watercourses may act as a source of PCBs to the atmosphere.