Abstract

The results of field experiments on fog pollutantdeposition enhanced by local mountain climate, completed by thedendrochronological analysis of the forest response, are presentedin this paper. In spite of their low absolute altitude (1,000-1,600 ma.s.l), the Sudetes and the Silesian Beskid form a noticeable orographicbarrier for the airflow of the humid Atlantic air masses.This results in the increase of cloudiness and fog frequency as wellas both atmospheric precipitation and horizontal precipitationvolume. Between January and December 2009 the daily samples ofatmospheric precipitation and rime were collected on three selectedmountain tops of similar height. The selected measurement siteswere situated along a 300 km WNW-ESE profile parallel to thedirection of the prevailing atmospheric circulation. High day-todayvariability of rime water volume, the total ionic content andchemical composition of the individual samples were typical ofeach measurement site and depended on the emission patterns,synoptic situation and the local climatic conditions influencedchiefly by terrain relief. Significantly larger rime efficiency andpollution deposition via fog were observed at the westernmostSzrenica Mt site rather than more to the southeast at S ´ nie_znik Mtand Skrzyczne Mt. This difference should be explained by moreintense orographic deformation of predominant airflow from thewestern sector as well as the higher liquid water content of fog inthe vicinity of Szrenica. Both temporal and spatial variability of fogdeposition correlates closely with the health status of the drilledtrees of Norway Spruce (Picea Abies) in the S ´ nie_znik Massif. Theaveraged annual tree rings width near the local tree line (1,350 ma.s.l.) on the summit dome of S ´ nie_znik decreased by 71% between1950 and the early 1980s. This is also the area of the highest rate ofatmospheric pollutant deposition due to particularly important roleof fog. At an altitude of 1,200 m a.s.l. The relevant changes of ringwidth were different depending on slope aspect: 60% on westernslopes well exposed for orographic fog formation and 42% oneastern slopes where fog deposition is less intense. The results ofthe dendrochronological analysis provide the evidence for theupward trend of tree rings width since 1981-1984 break through upto date, which should be attributed to the progressive reduction ofpollutant emission in Central Europe.

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