The Distribution Of Heavy Metals In River Sediment And Response And Functional Development Of Microbiology Community Under Its Stress

Mining and smelting are important sources of heavy metal pollution in the river basin.Heavy metals in leachate from waste rock piles,waste slag piles and runoff from quarry surfaces enter the river with surface runoff.Most of the heavy metals will be deposited in the river sediment,and then affect the microbial habitats,and community abundance and structure.Meanwhile,some characteristics of the microbial community in the sediment will change under the stress of heavy metals.The research on the characteristics of heavy metal content and morphological distribution,and microbial community,especially on the response characteristics and influencing factors of specific or functional microbial populations and activities in sediments polluted by heavy metals and agricultural activities,is of great significance for environmental risk identification,water quality assessment and pollution management of heavy metals.This paper studies the distribution and release characteristics of heavy metals in the sediments of the Xiangjiang River basin.It also analyzes the changes in microbial community response under heavy metal stress in sediment,screens out the dominant functional microorganisms,which are used with functional materials for ecological treatment of heavy metal wastewater,and provides new solutions for ecological purification treatment of heavy metal wastewater.The main innovative results achieved are as follows:1.The sediments in the mainstream of the Xiangjiang River are mainly aluminosilicates,with low carbonate,organic matter,and sulfur contents.The calculation of the geoaccumulation index shows that the heavy metals in the Xiangjiang River sediments have obvious spatial distribution differences,which mainly concentrate in the Songbai section and Zhuzhou-Xiangtan-Changsha section,and there is no trend of further diffusion downstream.As,Cr and V are released due to the instability of Na,K,and Si compounds under aerobic conditions.Cr and U are only released through silicate degradation and gypsum or carbonate dissolution under anaerobic conditions.2.The pollution risk of heavy metals in the sediments of the Lianshui River Basin(a typical lead-zinc mining area)indicates that As,Cr,and Zn in the watershed is more serious.The main sources of heavy metals in the sediments are different: As and Cd are mainly from nature environment,Cr and Cu are mainly from industrial wastewater discharge,and Zn and Pb are mainly from natural and human activities.Pollution risk assessment results show that the pollution risk of Zn is extremely strong,Cr is strong to extremely strong,Cu is medium to stron and Pb is medium.As and Cd pollution levels are relatively low,indicating that the water quality is improving after nearly a decade of effective treatment measures.3.The characteristics of ammonia oxidizing bacteria(AOB)and ammonia oxidizing archaea(AOA)have been analyzed based on the quantitative PCR and high-throughput sequencing.The results show that both AOB and AOA communities are widespread in sediments,and the abundance of AOB is higher than that of AOA,reflecting that bacterial populations occupy a larger niche than archaea.The concentration of heavy metals and nutrients are the dominant factors affecting the composition of AOB and AOA populations.AOA is significantly affected by As and pH,and plays a dominant role in ammonia oxidation,and is more resistant to environmental changes.AOB is highly sensitive to environmental changes and is significantly affected by Cd,Cr,total potassium(TK)and oxidation reduction potential(ORP).These results suggest that heavy metal pollution in the watershed have certain impacts on the ecological function of ammonia-oxidizing communities and biological cycling of nitrogen.4.The P.chrysogenum strainselected from the arsenic waste residue and the iron hydride compound is prepared into an organic complex for the treatment of wastewater with high As(III)concentration.When the dosages of P.chrysogenum strain and ferrihydrite are set to 3%(v/v)and 0.3 g/100 m L respectively,the removal efficiency of As(III)(200 mg/L)is 74.66% at pH 5.5.The removal rate remains 74.47% after reusing 3times.The adsorption kinetics of the composite material for As(III)follows the pseudo-second-order model.The adsorption mechanism is probably mainly due to the effective transport of As(III)at the interface between mycelium and water and organisms.The water film diffusion mechanism is an important way for the biosorption of As(III)in composite materials.5.The application possibility of sulfate-reducing bacteria(SRB)has been carried out after screening and domestication.The microbial immobilization methods and continuous dynamic experiments are used to determine the effects of pH and immobilized materials on the treatment of acidic wastewater(pH 4-7)containing heavy metals.The removal rate of Fe,Mn,Cu,Zn,and Cd can reach more than 95%,and the removal rate is the highest at pH 7.The removal rate of the Fe,Cu,and Zn ions in acid mine wastewater can reach more than 90.0%,and the removal rate of Mn ions is the lowest(24.2%).The removal efficiency is greatly affected by pH.