Abstract:

Except of dry and precipitation induced wet deposition, there also exist other pathways of atmospheric pollutants flux into the ground. These are different kinds of atmospheric deposits in the form of hydrometeors, which do not belong to precipitation category, such as: dew, hoarfrost, rime and liquid fog deposit. Due to the fact that such hydrometeors are formed within near-ground layer of air, where emission takes place, the observed pollutant concentrations are significantly higher than those typical for atmospheric precipitation. In this paper the results of monitoring of atmospheric deposits chemistry in some selected sites in Poland during the period between 2004 and 2007 are presented. The average total ionic content (TIC) of dew, hoarfrost, liquid fog and rime was 219, 283, 110 and 105 meq/l respectively, while typical TIC value for precipitation was 37 meq/l. In all types of atmospheric deposits different ions play an important role: Ca²⁺ and SO₄^2- in dew, NH₄⁺ and SO₄^2- in rime, Na⁺ and Cl^- in hoarfrost, NO₃^- in fog. Acidic (pH<5.0) and strongly acidic (pH<4.0) atmospheric deposits, such as rime and fog, were observed only in the mountainous regions. The average equivalent ratio of Cl^-/Na⁺ for hoarfrost, rime and fog samples was apparently close to the seawater value, whereas for dew ones in all stations this ratio was significantly higher in comparison with seawater. Very high values were observed for dew samples collected in urban inland and coastal stations, where the concentration level of Cl^-  was 3 to 4 times higher than Na⁺. The higher contribution of sodium ions (in comparison with chloride ions) was reported only in dew samples collected at rural inland stations. The NO₃^-/SO₄^2- ratio in hoarfrost, rime and dew samples ranges over a wide interval, but in general concentration of SO₄^2- is higher than NO₃^-. Only in fog samples, the average values of this ratio are close to 1, what means, that NO₃^- and SO₄^2- ions are on the similar concentration level in this type of atmospheric deposit. The lowest values of nss-SO₄^2-/SO₄^2- and nss- Ca²⁺/Ca²⁺ were observed only in hoarfrost and rime in lowland urban station localized close to the Baltic coast, because of high contribution of SO₄^2- and Ca²⁺ originated from sea-salts. When you take into account both concentration and volume of deposited water, dew and hoarfrost become a significant component of wet deposition over the lowland part of the territory of Poland, responsible for additional 50-75% deposited pollutants when compared with the precipitation itself. In the mountains of southern Poland, fog deposition in the form of rime and liquid deposit tend to be more important pathway than dew and hoarfrost. At numerous high elevated and well exposed sites pollutant deposition via fog droplets even exceeds deposition via precipitation, which leads to destructive environmental results, particularly in mountain forest ecosystems.

Brief Biography of the Speakers:

Dr eng. Żaneta Polkowska

A researcher in Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology, Gdansk, Poland; specialist in modern analytical techniques applied for determination of atmospheric pollutants (used in environmental protection). Nowadays, her main interests are : the presence of pollutants and their concentration levels in atmospheric precipitation and runoff waters in relation to the prevailing meteorological conditions.

Dr Mieczyslaw Sobik

A researcher in Department of Meteorology and Climatology, University of Wroclaw, Poland; specialist in mountain climatology and deposition processes of atmospheric pollutants. His main interest is the role of fog on water balance and pollutant deposition in mountain forest ecosystems of Central Europe.