Industrial and wildfire aerosol pollution over world heritage Lake Baikal.

Lake Baikal is the biggest reservoir of fresh water with unique flora and fauna; presently it is negatively affected by climate change, water warming, industrial emissions, shipping, touristic activities, and Siberian forest fires. The assessment of air pollution - related Baikal's ecosystem damage is an unsolved problem. Ship, based expedition exploring the Baikal atmospheric aerosol loading, was performed over the lake area in July 2018. We combine the aerosol near - water and vertical distributions over the Lake Baikal basin with meteorological observations and air mass transportation simulations. Lidar sounding of aerosol fields in the troposphere assesses the atmospheric background in the pristine areas and the pollution during fire-affected periods. Aerosol optical properties (scattering and spectral absorption) converted to the particle number size, black carbon (BC) mass, and Absorption Angstrom Exponent (AAE) provide the inside into aerosol characterization. Transport of industrial emissions from Krasnoyarsk and Irkutsk regions, and wildfire plumes from Republic of Yakutia relates the pollution sources to the increased concentrations of fine particle numbers, PM10 and BC mass over Southern and Northern/Central Baikal, respectively. The highest PM10 and BC are associated to the harbor and touristic areas of intensive shipping and residential biomass burning. Deposition estimates applied to aerosol data exhibit the pollution fluxes to water surface over the whole Baikal area. AAE marks the impact of coal combustion, residential biomass burning, and wildfires indicating the high pollution level of the Lake Baikal ecological system .

Stratified distribution of nutrients and extremophile biota within freshwater ice covering the surface of Lake Baikal.

Biological entities and gradients of selected chemicals within the seemingly barren ice layers covering Lake Baikal were investigated. Ice cores 40-68 cm long were obtained from in shore and offshore sites of Southern Lake Baikal during the cold period of a year (March-April) in 2007 and 2008. In microscopic observations of the melted ice, both algae and bacteria were found in considerable numbers (>10(3) cells/L and >10(4) cells/ml, respectively). Among all organisms found, diatom was generally the most predominant taxon in the ice. Interestingly, both planktonic and benthic algae were present in considerable numbers (2-4×10(4) cells/L). Dominant phototrophic picoplankton were comprised of small green algae of various taxa and cyanobacteria of Synechococcus and Cyanobium. The bacterial community consisted mostly of short rod and cocci cells, either free-living or aggregated. Large numbers of yeast-like cells and actinomycete mycelium were also observed. Concentrations of silica, phosphorus, and nitrate were low by an order of magnitude where biota was abundant. The profile of the ice could be interpreted as vertical stratification of nutrients and biomass due to biological activities. Therefore, the organisms in the ice were regarded to maintain high activity while thriving under freezing conditions. Based on the results, it was concluded that the freshwater ice covering the surface of Lake Baikal is considerably populated by extremophilic microorganisms that actively metabolize and form a detritus food chain in the unique large freshwater ecosystem of Lake Baikal.