Air-Water Carbon Dioxide Exchange in the Littoral Zone of Lake Baikal (Ice-Free Period)

Abstract

Lake Baikal is one of the most unique natural environments in Siberia, and it affects to a large extent the natural state in this region. Processes of gas exchange in the air-water system have been studied in Lake Baikal since 2002. Measurements have been carried out in the littoral area on the western shore of Southern Baikal (51°51'N, 105°04'E). The method of accumulative chambers was prioritized for measuring carbon dioxide fluxes in the air-water system. Chemical analysis of the water samples collected every three hours at the chamber locations was carried out in the on-land laboratory. We measured pH, content of dissolved oxygen, bicarbonate, nitrate and phosphate. The CO 2 content in the water was measured from pH values and the bicarbonate concentration. The total sink of CO 2 on the water surface is increasing in the littoral area of Lake Baikal from 20 mg·CO 2· m -2· day -1 in June to 110 mg·CO 2· m -2· day -1 in August. The decrease in the flux rate usually begins in September from 95 mg·CO 2· m -2· day -1 to the zero balance in late October - early November. The maximal rate of mean diurnal CO 2 emissions is recorded in December in the pre-ice period (110 mg·CO 2· m -2· day -1 ). Based on the long-term measurements during all seasons, the sink of atmospheric CO 2 in the littoral zones of Lake Baikal was estimated to be 3 - 5 g·CO 2· m -2 .