On the relation of bottom valley-type reservoir hydrocarbon carbon flux and hydrological structure of water body

Abstract

Circulation of carbon in water bodies is fundamental process of nutriens cycle in water ecosystems. Carbon flux from bottom sediments is the less studied chain of this circulation nowdays. The aim of investigation was the study of HCO3 flux from bottom sediments in the valley-type reservoir and identification of their relation with hydrological structure of water body. Field works and laboratory experiments were fulfilled at Mozhaisk reservoir in 2017-2019. These years differed by weather conditions, level regime and stability of water masses. Hydrological surveys were fulfilled three times during summer period of each year. They included measuring of vertical distribution of hydrological characteristic and sampling of water and bottom sediments. The Kuznetsov-Romanenko tube method was used to study exchange processes. Hydrocarbonate carbon flux from sediments into the water may have a wide range (50-900 mgC/m2day). By comparison of HCO3 flux with hydrological structure it was revealed that in deep (>8 m) regions it depends on stratification and thickness of uniform hypolymnion, where seiches and compensation currents may promote transsedimentation from shallow places to flooded river bed. At the regions with depth <8 m hydrocarbonate carbon flux from sediments depends much more from autochthonic organic matter, produced by phytoplankton. The relationship of the HCO3 flux with the content of organic matter in the soil and its hygroscopic humidity is insignificant.