Natural pollutants of Northern Lake Baikal

Abstract

Hot and cold springs in the northwestern shore of Lake Baikal are investigated as natural pollutants of the lake, which can interfere with its chemistry. The study includes chemical analyses of lake water samples from different depths in the North Baikal basin, as well as waters of hot and cold onshore springs, and Baikal tributaries collected in 2007 through 2013. Thermal waters in the shore of Lake Baikal have much higher SO4, Cl, F, Na, and SiO2 concentrations than those in the lake water, as well as ten to hundred times greater enrichments in Li, Rb, Cs, Ga, As and W. Mineral water in cold springs is generally similar to the Baikal water with respect to total dissolved solids (TDS) and major- and trace-element chemistry. However, the Milky cold spring discovered in the lower reaches of the B. Cheremshan River within a few km from the lake stands out in its unusual Ca–Mg–SO4 composition, low pH (3.57) and high TDS (535 mg/l), and trace-element enrichments in Al, Mn, Ni, Co, Zn, Y, and REE. The concentrations of these elements are still higher, up to one or two orders of magnitude, in suspended solids abundant in the spring water. This water composition is typical rather of mine drainage in sulfide mineralization provinces and prompts the existence of a sulfide orebody in the area. Mn, Co, Ni, Zn, and Cd occur in the dissolved form, and their concentrations in stream water near the B. Cheremshan inlet into Baikal are only slightly lower than immediately downstream of the spring; REE and Y are ten times lower because of precipitation from the river water. However, all metals the spring water leaches from the surrounding rocks eventually end up in Lake Baikal. Although the spring has much greater enrichments relative to the Baikal water in a number of elements, it hardly can cause any significant change to the lake composition. Only local chemical anomalies of Mn, Al, Co, Ni, Zn, Cd, REE and Y can be expected in the bottom sediments where the lake uptakes the B. Cheremshan stream.