No abstract

This paper analyzes the results of the automatic (in situ) recording of the regional transport of pollutants from the large regional coal-fired thermal power plants in the atmospheric boundary layer above the southern basin of Lake Baikal. Due to high stacks (about 200 m), emissions from large thermal power plants rise to the altitudes of several hundreds of meters and spread over long distances from their source by tens and hundreds of kilometers. The continuous automatic monitoring of the atmosphere in the southern basin of Lake Baikal on top of the coastal hill (200 m above the lake) revealed the transport of a large number of sulfur oxides and nitrogen oxides in the form of high-altitude plumes from thermal power plants of the large cities located 70 to 100 km to the northwest of the lake (Irkutsk and Angarsk). The consequence of such transport is the increased acidity of precipitation in the southern basin of Lake Baikal and the additional influx of biogenic nitrogen compounds to the lake ecosystem. The spatial scale and possible risks of such regional transport of air pollution for the lake ecosystem require further closer study.

Abstract. Mass development of the cyanobacteria Dolichospermum (D. lemmermannii as the dominant species) was reported in the coastal zone of Bol shye Koty Bay (western coast of the southern basin), towards the end of July to the beginning of August in 2019. Blooms were observed as 1 1.5-m wide bands adjoining the shoreline and stretched uninterrupted over 2 km. Abundance of cyanobacteria in blooms varied within 7.2 71.9 thousand cell mL-1, with 0.73 7.20 g m-3 biomass attained. Maximal concentration was observed opposite the biological station of Irkutsk State University, a frequently visited place that was hosting participants of several conferences at that time. Hydrochemical analysis of samples collected four days after continuous heavy rains showed much higher concentrations of nutrients in contrast with the data obtained a week before (24 July), which is normal for that season. Nutrient concentrations were elevated relative to long term averages by 3 to 30 fold: with phosphate concentrations up to 0.200 mg L-1, ammonium ions 0.29 mg L-1, and nitrates 0.31 mg L-1. Possible reasons for the harmful freshwater cyanobacterial bloom that is unusual for this part of the lake are discussed. Excessive proliferation of common cyanobacteria D. lemmermannii in the open lake areas was affected by several factors: long-lasting heavy rains, zero wind, high air (from 13 15 at night to 29 in daytime) and water temperatures (from 15 to 19.2 ); and absence of isolated septic tanks in the nearshore zone.