Seasonal dynamics of mineral forms of nitrogen in the rivers, snow cover and precipitation at the southwest coast of the Southern Baikal

Abstract

In 2015−2019, we studied the concentrations of mineral forms of nitrogen (NO₃^-, NO₂^- and NH₄ ⁺) in the waters of the Krestovka River and the streams Kamenushka, Bolshaya Cheremshanka and Malaya Cheremshanka as well as in the snow cover of their basins and precipitation of the Listvyanka settlement (southwest coast of Lake Baikal). Towards Lake Baikal the concentrations of the investigated compounds increase as a result of water pollution with domestic wastewater from the Listvyanka settlement. The highest concentrations of nitrates and nitrites are found in the estuary of the Malaya Cheremshanka, and those of ammonium – in the Kamenushka. Nitrate concentrations in the watercourses beyond the Listvyanka settlement have increased compared to the 1950s, which is due to climate change and air pollution. During the study period, the average annual concentrations of nitrates in precipitation and snow cover increased. The maximum concentration of nitrogen compounds in the snow cover is confined to lower parts of these streams. Thus, the snow cover of the Bolshaya Cheremshanka showed the highest nitrate concentrations. We have revealed that nitrate concentration in precipitation increases in the cold season due to air pollution with nitrogen oxides of anthropogenic origin. We indicate that nitrate concentrations in the waters entering Listvennichny Bay are an order of magnitude higher than in Lake Baikal, which can have a negative effect on the Baikal ecosystem.