Research On Biogeochemical Characteristics Of Sulfur And Zonation In Hypolentic Zone In The Ordos Desert Plateau

Surface water resources are very scarce at the Erdos desert plateau, and itsecosystem is very vulnerable. Lakes and wetlands are widely distributed in theregion, which are important regional groundwater drainage planes, and are parts ofthe Ordos Relict Gull National Nature Reserve. Thus, the quantity and quality ofthese lakes and wetlands has an important impact on the maintaining of the naturalresources and local ecosystems.Sulfur, as one of the important elements that control the redox condition in theHypolentic Zone, is extensively involved in a series of complex biogeochemicalprocesses, such as carbon cycle, water acidification, the formation of iron andmanganese and other metallic minerals, trace metals redox process, a number oftoxic heavy metals and inorganic elements (e.g. arsenic) migration andtransformation, distribution of microbial communities, biological growth andreproduction, etc. Thus, sulfur is an ideal element for the research of biogeochemicalprocesses in the Hypolentic Zone. Previous studies have mostly concentrated in thebiogeochemical processes of N, P and other nutrient elements, heavy metals andother pollutants, but the study of sulfur are few. Therefore, a systematic study of thebiogeochemical behavior of sulfur and its main controlling factors in the HypolenticZone is very urgent and important.This thesis is funded by the National Natural Science Foundation of “SurfurBiogeochemistry in the Hypolentic Zone of Lake in Desert Plateau Area”, andselects the Etuokeqi Dake Lake as the research object. Based on the extensiveresearch work conducted in the early phase of the project, and by application of insitu water level and water temperature monitoring, environmental isotopesandmolecular biology techniques, we systematically studied the hydrodynamic, waterchemical evolution, sulfur cycle and biogeochemical behavior characteristics of thegroundwater in the Hypolentic Zone. These findingsmay enrich the knowledge ofbiogeochemical processesoccur in the Hypolentic Zone, and provide a scientific basisfor the protection of the Lake-Wetland ecosystem.In this paper, based on water stable isotope tracing, we reveals the sources ofpore water, the hydrodynamic exchange pattern and intensity in the HypolenticZone.Based on hydrodynamic method and thermal tracing,the relationship betweengroundwater and lake water is quantified, both of the calculated values are2×10-6m/s.With the migration of pore water and the interaction of different end-memberbody of water, the distribution of pH, Eh and DO of the pore water in the HypolenticZone show zonation patterns.Leaching, evaporation and mixing processes controls the evolution of the waterchemistry in the Hypolentic Zone.Sulfate reduction, sulfide deposition/oxidation and sulfur dissolution/precipitation of minerals are identified in the Hypolentic Zone. In these processes,Eh, DO, pH, organic carbon microbes and sulfur are closely interrelated with eachother.Results from molecular biology research techniques indicate that it there has arich microbial community structure and diversity in the Hypolentic Zone.Microorganisms affected by the redox potential, Relative reduction in the area ofmicrobial structure and diversity richer, better uniformity and individuals,meanwhile genome sequence results prove the existence of SOB (Sulfur-oxidizingbacteria) and SRB (Sulfur-reducing bacteria) in Hypolentic Zone.During the lake-groundwater interaction, the biogeochemistry of sulfur with aclear zonation. According the spatial characteristic of Eh, DO and sulfides, microbial,the Hypolentic Zone can be divided into the reduction zone containing hydrogensulfide, hydrogen sulfide-free reduction zone, the transition zone, the oxidized zone,reflecting the zonation of biogeochemical sulfur in Hypolentic Zone.