Model simulation of the atmospheric input of lead and cadmium into the North Sea

Abstract

The long-range transport of Pb and Cd over Europe is simulated with a three-dimensional transport model. The relevant meteorological input data such as wind or precipitation rates are prescribed according to 6-hourly analyses of the “European Centre for Medium Range Weather Forecasts” (ECMWF). Mixed-layer height analyses are from the Norwegian Weather Service. Estimates for the respective emissions are adopted from Pacyna [Norwegian Institute for Air Research Report No. 60/85 (1985)]. The input data are available on a 1.5° longitude-latitude grid. Measured concentrations of Pb and Cd in surface air and rainwater as well as wet deposition are used to validate the model. The simulations suggest that the North Sea pollution takes place predominantly in the vicinity of the main emission sources, i.e. in the southern and western parts of the North Sea. In the remaining part of the North Sea the deposition is smaller, i.e. approximately 30 % of the total. Accordingly, the total atmospheric input of trace metals into the North Sea is probably considerably smaller than suggested in earlier studies [e.g. van Aalst et al. (TNO Report C182/152) 1983a] which assume that the rainwater concentrations measured along the southern and western coasts are representative for the total area of the North Sea. The present model study yields an annual atmospheric input of 1531 t Pb and 14 t Cd, respectively.