ABSTRACT: The atmospheric input of lead into the German Bight is calculated from measured atmospheric concentrations, from modelled as well as measurement-derived deposition velocities, and from measured wet deposition values, with a temporal resolution between 6 and 24 h. The measurements were taken at several coastal sites and on a ship in the German Bight during a 1 wk drift experiment in April 1991. The applied model is a 3-dimensional nonhydrostatic atmospheric mesoscale model. The calculated input data depend on deposition velocities and integration time. Due to variation in dry deposition the atmospheric input values can differ by a factor of 3. Total deposition values and thus atmospheric input data can differ by a factor of 10. Calculated backward trajectories show that the observed time-lag in the occurrence of concentration maxima can be explained by the travel time of the advected air masses between the measurement sites. By use of backward trajectories and results of the mesoscale model the measured values are associated with source areas for a day with very high atmospheric lead concentrations. It is shown that up to 50% of the contaminants can reach the German Bight via long-range transport. Mesoscale atmospheric phenomena also influence the wind field and the concentrations.

KEY WORDS: North Sea · German Bight · Atmospheric input · Dry deposition · Wet deposition · Atmospheric lead concentration · Mesoscale model

Published in MEPS Vol. 156 (1997) on September 25
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997