Environmental Role of Rime Chemistry at Selected Mountain Sites in Poland

Abstract

The results of field experiments on fog pollutant deposition enhanced by local mountain climate, completed by the dendrochronological analysis of the forest response, are presented in this paper. In spite of their low absolute altitude (1,000–1,600 m a.s.l), the Sudetes and the Silesian Beskid form a noticeable orographic barrier for the airflow of the humid Atlantic air masses. This results in the increase of cloudiness and fog frequency as well as both atmospheric precipitation and horizontal precipitation volume. Between January and December 2009 the daily samples of atmospheric precipitation and rime were collected on three selected mountain tops of similar height. The selected measurement sites were situated along a 300 km WNW-ESE profile parallel to the direction of the prevailing atmospheric circulation. High day-to-day variability of rime water volume, the total ionic content and chemical composition of the individual samples were typical of each measurement site and depended on the emission patterns, synoptic situation and the local climatic conditions influenced chiefly by terrain relief. Significantly larger rime efficiency and pollution deposition via fog were observed at the westernmost Szrenica Mt site rather than more to the southeast at Śnieznik Mt and Skrzyczne Mt. This difference should be explained by more intense orographic deformation of predominant airflow from the western sector as well as the higher liquid water content of fog in the vicinity of Szrenica. Both temporal and spatial variability of fog deposition correlates closely with the health status of the drilled trees of Norway Spruce (Picea Abies) in the Śnieznik Massif. The averaged annual tree rings width near the local tree line (1,350 m a.s.l.) on the summit dome of Śnieznik decreased by 71% between 1950 and the early 1980s. This is also the area of the highest rate of atmospheric pollutant deposition due to particularly important role of fog. At an altitude of 1,200 m a.s.l. The relevant changes of ring width were different depending on slope aspect: 60% on western slopes well exposed for orographic fog formation and 42% on eastern slopes where fog deposition is less intense. The results of the dendrochronological analysis provide the evidence for the upward trend of tree rings width since 1981–1984 break through up to date, which should be attributed to the progressive reduction of pollutant emission in Central Europe.