Changes in the Geochemistry of Land Waters at Climate Warming and a Decrease in Acid Deposition: Recovery of the Lakes or Their Evolution?

The paper presents results of a long-term (1990–2018) study of changes in the geochemistry of land waters in the Kola region as a consequence of climate warming and a regional- and global-scale decrease in the emission of acid-forming gases. The work is based on materials acquired by studying 75 small lakes in the region every four to five years in the period of time of 1990 through 2018. Reliable trends toward a temperature rise over a 28-year study period were revealed based on the analysis of weather archives. It was found out that the content of anthropogenic sulfates in the water significantly decreased and the acid-neutralizing capacity of waters increased due to the reduction in the anthropogenic sulfur emissions into the atmosphere. An increase in the content of organic matter and nutrients in the water of lakes has been proven, which is reliably associated with an increase in the regional temperatures. A number of lakes in acid-vulnerable regions retain critical values of the acid-neutralizing capacity of waters, which may be associated with both local and transregional transport of polluted air masses. The analysis of the chemical variability the waters in a long-term series of observations demonstrates the evolutionary development of lakes and changes in the biogeochemical cycles as a consequence of the transformation of the watersheds under the influence of a decrease in acid deposition from the atmosphere on the catchment areas and climate warming in the region. [ABSTRACT FROM AUTHOR]