AIR WATER EXCHANGE DYNAMICS OF 13 VOLATILE CHLORINATED C1-HYDROCARBONS AND C2-HYDROCARBONS AND MONOCYCLIC AROMATIC-HYDROCARBONS IN THE SOUTHERN NORTH-SEA AND THE SCHELDT ESTUARY/

Whereas a lot of marine research work has been done on heavy metals an d semivolatile organic compounds, far less attention has been paid to the fate of volatile organic compounds in this area. This work focuses on 13 volatile organic compounds in marine waters and the marine atmo sphere. During six campaigns in September 1994-December 1995, simultan eous air and water sampling was carried out in both the southern North Sea area and the Scheldt Estuary. Mean water concentrations for indiv idual compounds were in the 2.2-72.9 ppt range (n = 38), whereas atmos pheric concentrations varied between 2.3 and 854 pptv. Samples from th e Scheldt Estuary proved to have elevated concentrations of chlorinate d compounds. A number of water and air samples showed enhanced concent rations of C-2-substituted monocyclic aromatic hydrocarbons, which cou ld not clearly be linked to anthropogenic activities. Back-trajectory calculations showed that a number of over sea atmospheric samples were affected by atmospheric transport from industrial sites, 250-300 km u p wind. Fugacity modeling showed that the North Sea acts as a source t o the atmosphere, not as a sink. Mean water to air mass transfer rates varied between 0.6-52.7 mu g m(-2) day(-1) for all VOCs. it was stati stically shown that water to air exchange rates of tetrachloroethylene , benzene, and toluene were slowed when air masses from continental or igin were at the marine sampling sites instead of air masses from remo te non-continental origin.