Background composition of pore waters in Lake Baikal bottom sediments

Bottom sediments were studied from 10 central sites within the pelagic zone of the three basins of Lake Baikal, and 16 sites in other regions of the lake. The composition of pore waters in the first two meters of the sedimentary cover was analyzed at 1–3 cm intervals. It was established that the salt composition of pore waters in the sediments was uniform across the entire lake. Background concentrations of each ion in the pore waters was determined from equations using concentration data profiles obtained from all sites of the three lake basins (1250 samples at 26 sites within the entire lake). Similar to the lake waters, background pore waters of Lake Baikal were dominated by calcium bicarbonate with low mineralization. The total concentration of ions in pore waters increased with depth during diagenetic transformations as did the concentrations of bicarbonate and calcium ions. Biogeochemical processes that affect the chemical composition of pore water in Lake Baikal sediments are discussed.