Vertical Profile of Water and Sediment in Lake Oigon

Determining vertical variation of water quality parameters is contributed to a better understanding of the true nature of lakes. Lakes are classified into holomictic and meromictic lakes by their mixing mode; the former occurs physicochemical mixing between the surface and deep waters, while the latter layers of lake water occur unmixed for years, decades, or centuries. Lake Oigon is the only Meromictic Lake identified in Mongolia. Few Mongolian lakes have been studied in different seasons but not in the vertical directions. Therefore, we studied the vertical profile of water and sediment parameters in Lake Oigon for two years. Physico-chemical parameters in water were measured on-site, while sediment parameters were determined off-site. Salinity in lake water ranged from 21.3 to 65.9 g/L which represented mesosaline to hypersaline. In oxic, sub-oxic, and anoxic zones, the physico-chemical parameters of Lake Oigon were varied a lot in longitudinal ways lake and seasonal variation observed as well. However, most parameters were stable in the anoxic zone, regardless of seasons, indicating that no water movement was at the bottom of the lake. Layered sediments with salt indicating hardly exchange with lake water at the anoxic zone. The statistical correlation and principal component analysis between the various physico-chemical parameters of lake water and lake sediment were computed. This study provides the basic information for future research on the characteristic of the vertical profile, impact on the ecosystem, and environmental assessment for Lake Oigon.