LONG-TERM STUDY OF ATMOSPHERIC MERCURY DEPOSITION AT MONITORING STATIONS IN LITHUANIA

The results of the long-term study of atmospheric mercury concentrations in the rain water carried out at the Aukstaitija and Zemaitija integrated monitoring stations are presented in this work. The bulk precipitation samples at both stations were collected every week during the 2007-2017 period. The mercury measurement method is based on the absorption of radiation by mercury vapour at the 253.7 nm line. The monthly samples of precipitation after preparation were analysed using a mercury analyzer 'Gardis' developed at our institution. The average annual concentrations, deposition amounts and trends of mercury in the precipitation over the period of 2007-2017 were analysed. The tendency of average monthly mercury concentrations in the precipitation at the Zemaitija station was continuously increasing before 2011, however, after 2012 it has a decreasing tendency which was contrary to that at the Aukstaitija station. At the same time, the tendencies of average monthly amounts of mercury deposited with precipitation showed decreasing amounts, especially at the Zemaitija station. Explanation of the above-mentioned phenomenon is complicated and the main reason is very changeable air mass trajectories and irregularity of precipitation.