Environmental Characteristics Of Suspended Solids In Reservoirs And Their Effects On Water Quality

Supended solids are ubiquitous in natural aquatic environments.Access to clean and safe drinking water is closely related to the human existence.With the accelerating urbanization process,more and more reservoirs have become the main drinking water source of cities.Hence,the water quality problem has gradually become the focus of attention.While the point source and non-point source pollutants flow into the reservoir with runoff from the basin,the physical,chemical and biological effects between suspended particles and pollutants also have an important impact on the water quality.This paper investigated and analyzed stratified water quality and suspended solids in Biliuhe Reservoir.To research the impact of suspended solids on reservoir water quality,we also established a stratified reservoir suspended solids sampling and multi-scale analysis method system.The main contents and conclusions are as follows:(1)After the completion of the reservoir,the hydrodynamic conditions changed,the water environment changed greatly,and suspended solids are few,loose and low-density in reservoirs,so the collection and analysis suspended solid samples were difficult in deep areas.In response to these problems,we developed high fidelity suspended sediment collection equipments.The sample is enriched by multi-stage filtration and auxiliary stirring to improve the filtration efficiency.The changes of water depth and turbidity and the running state of the equipment are obtained in real time by various sensors.And the device operation command is performed through the upper monitoring platform.Compared with exsiting equipments,they have the advantages of sampling in ordered depth,high sampling efficiency.large filtration flux,low filter plugging posibility,and light and quick operation.(2)Limited by the accuracy and resolution of conventional methods,current studies have little knowledge of the occurrence state and microscale characteristics of flocs in reservoirs.In this paper,based on in-situ imaging,optical microscopy,and scanning electron microscopy,an image analysis method was constructed to analyze the micro-scale environmental characteristics of flocs in reservoirs.The underwater camera enables in-situ observation of flocs,which is simpler and more time-efficient than conventional weight analysis methods and solves the defect that the turbidity sensor is insensitive to flocs.It was found that many flocs were found at the water depth of more than 15 m in the bottom of the reservoir.Based on optical microscopy and scanning electron microscopy,the micro-scale structure of flocculated suspended solids was observed in Biliuhe Reservoir.The observation results showed that the flocs of Biliuhe Reservoir were composed of extracellular polymers and various tiny suspended particles.The encapsulated porous flocs have a porosity between 34%and 49%.(3)Microbes involve in many biogeochemical cycles in the reservoir.The suspended particles adsorb many bacteria and other microorganisms.The influence of the phylogenetic composition and ecological function of the free-living(FL)and the particle attached(PA)bacterial community on water quality is not clear.High-throughput sequencing analysis was performed on the 16s rDNA of bacteria extracted from two pore size membranes.The bioinformatics analysis results of PCoA,NMDS and LEfSe showed that the richness and uniformity of PA bacteria were significantly higher than that of FL bacteria,and the phylogenetic composition was significantly different.The FAPROTAX database analysis showed that the difference in ecological function reflects the difference in water quality more than the difference in phylogenetic composition of FL bacteria and PA bacterial communities(4)Previous studies have recognized that water temperature stratification leads to the formation of an anaerobic environment at the bottom reservoir,causing the release of iron and manganese from sediments into water bodies.However,the role of suspended solids has not be considered in the migration and transformation of iron and manganese.Based on the improved analysis method of phosphorus,iron and manganese in suspended solids,this paper analyzes the dynamic characteristics of suspended solids and particulate phosphorus,iron and manganese in deep water reservoirs during different water temperature stratification periods.The migration regulation of iron and manganese among water-suspended matter-sediment was studied in Biliuhe Reservoir.Furthermore,we revealed the influence of suspended solids behaviors changes on the migration of iron and manganese.Accordingly,we established a preliminary multi-dimensional monitoring and management framework of the drinking water reservoir.Considering the influence of suspended solids on the water quality of Biliuhe Reservoir,some measures were recommended,such as multi-level intake,hypolimnetic aeration,optimized water sources,and ecological reduction,and watershed management.