Trends in Precipitation of Air Pollutants at Estonian Monitoring Stations 1994–2005

This study concentrates mainly on the 12-year time trends of annual average ion concentrations in bulk precipitation from 10 Estonian monitoring stations. Trends revealed by the nonparametric Mann-Kendall test mostly show a statistically significant decline and, according to the order of ion decline per year, three groups of stations could be differentiated: stations directly affected by an industrial region, NE industrial region background stations and natural background stations. Under different international requirements Estonia has undertaken serious obligations to reduce emissions of air pollutants. Total SO2 emissions from power plants in Estonia have fallen from about 60%, and emission of solid particles decreased twenty times during the period of 1990–2005. The highest decline of Ca concentrations occurred during the first three-year monitoring period of 1994–1996, and a high decline of SO4-S in 1997–1999 and 2003–2005.