Spatial And Temporal Distribution Characteristics Of Groundwater Environmental Quality In Eastern Gui’an New Area

Gui’an New Area is a new urban area under construction in Guiyang City,Guizhou Province,of which eastern part has superior resources and better ecological environment quality.The construction there brings great pressure on water ecology and water environmental system.Therefore,the purpose of this study is to protect the groundwater environmental quality in this area,and to develop and utilize groundwater resources reasonably.In this study,based on the collected regional geological data and field survey data,the environmental geological conditions in the study area were analyzed in detail.Besides,according to 84 groundwater samples collected in the field in January,May,September and November in 2020,by adopting to flame atomization,ion chromatography,spectrophotometry and other test methods,using SPSS,MAPGIS,origin,ArcGIS and other software,and referring to mathematical statistics,shukalev classification,ion ratio method,single factor evaluation,improved Nemero evaluation based on principal component method,matter-element model based on cluster analysis and other methods and theories,the characteristics of groundwater hydrochemistry,water environmental quality and spatial-temporal distribution characteristics of groundwater in the study area were systematically studied.The main achievements are as follows:（1）According to the statistics and analysis of test data of groundwater quality,the order of ion concentration of conventional hydrochemical components in groundwater is:Ca²⁺>Mg²⁺>Na⁺>K⁺,HCO₃^->SO₄^2->Cl^->F^-;The hydrochemical types of groundwater are mainly HCO₃-Ca,HCO₃-Ca·Mg,HCO₃·SO₄-Ca and HCO₃·SO₄-Ca·Mg,among which HCO₃-Ca is the most widely distributed and HCO₃·SO₄-Ca·Mg is the least;The content of heavy metal ions such as Al,As,Mn,Fe,Se is very low.Based on the Gibbs diagram,ion ratio diagram and the analysis of the existing n environmental geological conditions,it is concluded that the geological background and weathering of rocks are the main factors affecting the hydrochemical characteristics of groundwater.（2）In this study,the single factor evaluation method and two multi factor evaluation methods are used to evaluate the groundwater environmental quality.Results show that the groundwater environmental quality in the study area is generally good.The proportion of groundwater quality grade is 84.52%to 91.67%,and that of theⅣandⅤclass water is 8.33%to15.48%.By comparing the principle,calculation process and evaluation results of the two multi factor evaluation methods,it is concluded that the improved Nemero evaluation method is more suitable for the study area.Therefore,according to the evaluation results of the method,the spatial and temporal zoning map of water quality drawn by Arc GIS software shows that areas of poor water quality are mainly distributed in the eastern part of the study area,such as Dangwu,Shiban,Huchao and other areas,and the main exceeding ions are NO₃^-、NO₂^-and NH₄⁺.The main reasons for exceeding the standard are the use of agricultural fertilizer and the random discharge of domestic sewage.（3）Based on the principle and method of GIS,the temporal and spatial distribution map of groundwater chemical composition is drawn.Combined with the existing data,the temporal and spatial variation rules and influencing factors of pollution ions,conventional components and heavy metal concentrations are analyzed.Results show that control of formation lithology,interaction between water and rock,and human activities are the main factors influencing the temporal and spatial variation of groundwater ion concentrations in this area.