An assessment of the OECD study on long range transport of air pollutants (LRTAP)

Abstract

Based on a survey of the sulphur emission in Europe and measurements at about 70 ground stations and by aircraft, atmospheric dispersion models have been used to evaluate the long range transfer of sulphur pollutants in Europe. The annual mean sulphur dioxide concentrations range from ~ 20 μg m −3 in rural areas close to the major source regions to ~2 μg m −3 in remote areas of the northern and western Europe. The annual mean aerosol sulphate concentrations are lower, ~10 μg m −3 and fall off more gently to ~0.5 μg m −3 in remote areas. The pattern of wet deposition shows enhanced values in areas exposed to polluted air masses and locally increased precipitation. Qualitatively the main features of the concentration fields are reproduced by the model calculations, but full quantitative agreement cannot be expected because of the many approximations made. However, on an annual basis, a correlation coefficient of 0.9 was obtained between observed and calculated values. Estimates of the annual transfer of pollutants from one country to other countries are given for 1974. These amounts are, however, dependent on variations in the annual weather pattern. Future plans for monitoring and evaluation of the long range transport of air pollutants in Europe are outlined. Experience indicates that considerable improvements could probably be obtained by introducing more detailed formulations of the chemical reactions and deposition processes in the atmospheric dispersion models.