ATMOSPHERIC INPUT OF LEAD INTO THE GERMAN BIGHT - A HIGH-RESOLUTION MEASUREMENT AND MODEL CASE-STUDY

The atmospheric input of lead into the German Eight is calculated from measured atmospheric concentrations, from modelled as well as measure ment-derived deposition velocities, and from measured wet deposition v alues, with a temporal resolution between 6 and 24 h. The measurements were taken at several coastal sites and on a skip in the German Eight during a 1 wk drift experiment in April 1991. The applied model is a 5-dimensional nonhydrostatic atmospheric mesoscale model. The calculat ed input data depend on deposition velocities and integration time. Du e to variation in dry deposition the atmospheric input values can diff er by a factor of 3. Total deposition values and thus atmospheric inpu t data can differ by a factor of 10. Calculated backward trajectories show that the observed time-lag in the occurrence of concentration max ima can be explained by the travel time of the advected air masses bet ween the measurement sites. By use of backward trajectories and result s of the mesoscale model the measured values are associated with sourc e areas for a day with very high atmospheric lead concentrations. It i s shown that up to 50% of the contaminants can reach the German Eight via long-range transport. Mesoscale atmospheric phenomena also influen ce the wind field and the concentrations.