Modelling of heavy metal transboundary pollution in Europe

Regional-scale three-dimensional Eulerian model applied for calculations of heavy metals (Pb, Cd, and Hg) transport and deposition is presented. Model was developed in the framework of the European Monitoring and Evaluation Program (EMEP) in order to estimate emitter-receptor relationships of countries signed Convention on Long-Range Transboundary Air Pollution (CLRTAP). Model includes such processes as advection, turbulent diffusion, wet scavenging, dry deposition, and chemical transformations for mercury compounds. Natural emissions, mercury re-emission and influx from the background outside the domain are considered. Model resolution is 50x50 km(2). The purposes of this work are the following: first, to calculate fields of concentrations and depositions over Europe, second, to estimate regional budget of heavy metals with regard to model domain, and third, to assess country-to-country depositions for Europe. Meteorological and measurements data, emissions and calculation results refer to 1996. It is shown that typical annually mean air concentration of lead, cadmium, and mercury lay within 5-30 (maximum 500), 0.05-2 (maximum 9), and 1.4-2.5 (maximum 6) ng/m(3), respectively. Calculated values of total deposition vary from 0.5 to 10 kg/km(2)/yr (maximum 50 kg/m(2)/yr) for lead, 25 - 500 g/km(2)/yr (maximum 2400 g/km(2)/yr) for cadmium, and 10 - 100 g/km(2)/yr (maximum 480 g/km(2)/yr) for mercury. Country-to-country deposition matrix analysis reveals that contribution of natural deposition to overall deposition to country is significant in case of mercury and much less important in case of lead and cadmium. However, for some countries natural contribution to deposition of lead and cadmium makes up tens of per cent. Hence, natural sources of heavy metals should be assessed in more detail. Anthropogenic emission estimates are supposed to be the greatest source of uncertainties.