There is great concern for contamination of sensitive ecosystems in high latitudes by long-range transport of heavy metals and other pollutants derived from industrial areas in lower latitudes. Atmospheric pollution of heavy metals has a very long history, and since metals accumulate in the environment, understanding of present-day pollution conditions requires knowledge of past atmospheric deposition. We use analyses of lead concentrations and stable lead isotopes ( 206 Pb/ 207 Pb ratios) of annually laminated sediments from four lakes in northern Sweden (∼65°N) to provide a decadal record of atmospheric lead pollution for the last 3000 years. There is a clear signal in the sediments of airborne pollution from Greek and Roman cultures 2000 years ago, followed by a period of "clean" conditions 400-900 A.D. From 900 A.D. there was a conspicuous, permanent increase in atmospheric lead pollution fallout. The sediments reveal peaks in atmospheric lead pollution at 1200 and 1530 A.D. comparable to present-day levels. These peaks match the history of metal production in Europe. This study indicates that the contemporary atmospheric pollution climate in northern Europe was established in Medieval time, rather than in the Industrial period. Atmospheric lead pollution deposition did not, when seen in a historical perspective, increase as much as usually assumed with the Industrial Revolution (1800 A.D.).
Abstract. The EMEP/MSC-W model has been used to compute atmospheric nitrogen deposition into the Baltic Sea basin for the period of 12 yr: 1995-2006. The level of annual total nitrogen deposition into the Baltic Sea basin has changed from 230 Gg N in 1995 to 199 Gg N in 2006, decreasing 13 %. This value corresponds well with the total nitrogen emission reduction (11 %) in the HELCOM Contracting Parties. However, inter-annual variability of nitrogen deposition to the Baltic Sea basin is relatively large, ranging from −13 % to +17 % of the averaged value. It is mainly caused by the changing meteorological conditions and especially precipitation in the considered period. The calculated monthly deposition pattern is similar for most of the years showing maxima in the autumn months October and November. The source allocation budget for atmospheric nitrogen deposition to the Baltic Sea basin was calculated for each year of the period 1997-2006. The main emission sources contributing to total nitrogen deposition are: Germany 18-22 %, Poland 11-13 % and Denmark 8-11 %. There is also a significant contribution from distant sources like the United Kingdom 6-9 %, as well as from the international ship traffic on the Baltic Sea 4-5 %.
SUMMARYA high-resolution regional model for sulphate aerosols is used to investigate the effects of spatial and temporal averaging of radiative forcing. Mie theory is used to calculate the aerosol optical properties. The strong hygroscopic growth with increasing relative humidity is taken into account. The results for the regional area selected in our study (Europe and much of the North Atlantic) show that earlier global studies may have underestimated the magnitude of the radiative forcing due to sulphate aerosols by up to 30-40% due to coarse spatial and/or temporal resolution, at least over certain regions. This underestimation in global models of the water uptake is important for all strongly scattering hygroscopic aerosols. Our results imply that representation of relative humidity at even higher spatial resolution than used in this study may be of importance. This could be incorporated in models using subgrid-scale parametrizations of the relative humidity.
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