Study On Enrichment Law Of Metasilicate, Strontium And Selenium In Groundwater In The Upper Watershed Of Xiaoluan River

This thesis is based on the Chengde District Hydrogeological Survey Project?DD20190311?and the upper Xiaoluanhe River Basin?Yudaokou Bashang Plateau?as the research area,aiming to study the regularity of mineral element enrichment in groundwater.In this paper,we will gradually discuss the enrichment mechanism and influencing factors of mineral elements in groundwater from the analysis of water chemical composition,geological evolution background,rock mineral chemical composition,and water-rock interaction analysis.Providing research reference for further development and protection of mineral water resources.In this paper,the basic geological-hydrogeological conditions of the study area will be understood by means of data collection,field hydrogeological survey and sampling analysis in the early stage;Using Arcgis to study the spatial distribution characteristics of each component of water chemical components;Using piper trilinear nomograph,hydrogen and oxygen isotope analysis,Gibbs diagram analysis,ion proportional coefficient method to analyze hydrochemical type and Hydrochemical origin.Analyzing the geological structure and evolution of the sedimentary environment in the area to obtain geochemical data of related mineral elements,according to regional geological data and previous research results;Analyzing the influence of formation lithology,structural space,hydraulic alternation,CO₂ and other conditions on the water-rock action in the study area;Comprehensive analysis of the above research results summarizes the enrichment law of groundwater mineral elements in the area.The research shows that the pH of groundwater in this area is mostly between7.00 and 10.2,all of which are weak alkali-alkaline,the average TDS is 274.43mg/L,and the water quality is generally excellent;Groundwater originates from atmospheric precipitation,and the formation of hydrochemical type is mainly HCO₃-Ca·Mg,and the formation of ionic components comes from water-rock interaction with leaching.The source minerals are silicate rock,carbonate rock,and sulfate rock salt,and the cation alternating adsorption is less;The chemical data of various types of rock and earth indicate that the content of metasilicate,strontium and selenium is relatively large,the content of Se in the soil is 0.032⁰.11mg/kg,basic basalt minerals are mainly olivine,plagioclase,pyroxene,Sr content is 490?g/g in basalt and 672?g/g in andesite;This area is a rift-depression basin controlled by deep and large faults,with large basalt thickness,well-developed pores,well-developed faults,good hydraulic alternation,and sufficient CO₂.The mineral element enrichment model is summarized as"enrichment model of basalt fracture-hole fissures in rifted depression basins":CO₂-dissolved rainfall infiltrates and leaches selenium-rich and low-strontium soil,supplements the dissolved CO₂ in the soil,and enters the basalt-based pore-fractured aquifer along various types of fault-porosity fissures.All kinds of rocks?basalt,andesite,tuff,shale,clay rock,etc.?have water-rock interaction,and metasilicate,strontium,selenium and other components are transferred to groundwater.Environmental,structural space,CO₂ content and other influences are eventually discharged into natural mineral water through spring eyes.The selenium content in the groundwater in this area is generally high,followed by more strontium content,and the metasilicate content is generally close to the standard.