Study On Salinity Of Formation Water In The Fourth Stage Planning Area Of Yu-Shen Mine Area

With the attention paid to the environmental protection of mining areas,China has given more stringent requirements for the discharge and utilization of mine water.High salinity mine water(salinity greater than 1000mg/L)generally has to be desalted before it can be discharged or comprehensively utilized.Therefore,it is of great significance for mining area planning and mine design to study the salinity of groundwater.The fourth stage planning area of Yu-Shen mine area is located in the western part of the Jurassic coalfield of northern Shaanxi in the north of Ordos basin,and it is under planning and construction at present.This paper takes the salinity of different aquifers in the fourth stage planning area of Yu-Shen mine area as the research object,through the analysis of groundwater circulation conditions and hydrochemical characteristics,the spatial development law of groundwater salinity,influencing factors and regional prediction of high salinity water distribution are studied,which has important guiding significance for the planning and construction and environmental protection of the fourth phase planning area of Yu-Shen mine area.On the basis of collecting the data of previous laboratory analysis of water samples,the hydrochemical characteristics of groundwater in the study area are expounded by means of statistical analysis and Piper three-line diagram.The main hydrochemical type of groundwater of the Quaternary Salawusu formation is HCO3-Ca type,the lower Cretaceous Luohe formation aquifer is dominated by HCO3-Na type,The main hydrochemical type of groundwater of the Middle Jurassic Anding formation aquifer is SO4-Na and HCO3-Ca·Mg·Na type,The main hydrochemical type of groundwater of the Zhiluo formation and Yan'an formation aquifers are mainly SO4-Na type,and some areas of Yan'an formation aquifers are Cl-Na type salt water.The isoline map of groundwater salinity of each aquifer is compiled by using the method of spatial interpolation.It is found that there is an obvious zoning phenomenon of groundwater salinity in the plane,which is controlled by groundwater dynamic field.The overall salinity of groundwater increases gradually with the runoff path,and reaches the highest salinity in the discharge area.The vertical zonation of groundwater salinity is obvious.The salinity of aquifers with a depth of 200 m is generally about 300mg/L,the salinity of Jurassic aquifers increases with the increase of groundwater depth.The salinity of the aquifer of Zhiluo formation in the depth of 200m-500m is generally 28 1mg/L?4692mg/L,the degree of salinity of the aquifer of Yan'an formation with a depth of more than 300m is mostly about 1378mg/L,in which the maximum salinity is 7031mg/L,which belongs to high salinity groundwater.The sources of main ions in groundwater are determined by correlation analysis and ion proportion relationship,and the chemical control mechanism of groundwater is analyzed using methods including Gibbs graphs,ions ratios and ratio end element diagram and so on.It is concluded that the chemical evolution of groundwater in the study area is mainly formed by water-rock interactions such as the dissolution of evaporite minerals,silicate minerals,carbonate minerals and cation exchange.The main influencing factors of groundwater salinity in the study area include hydrodynamic conditions,geological structure,stratigraphic lithology,groundwater depth,climate,water temperature and human activities.Based on the analysis of the main factors affecting the salinity of groundwater in Yan'an formation of the study area,groundwater velocity,water temperature,groundwater depth and lithologic structure index are selected as the main controlling factors of salinity.The model of adaptive particle swarm optimization for least squares support vector machine is used to predict the salinity of Yan'an formation in the study area.the prediction results are compared with support vector machine model,least square support vector machine model and the model of the model of particle swarm optimization support vector machine with the same data.It is found that the fitting accuracy of the APSO-LSSVM model is high and the error rate is relatively small.The APSO-LSSVM model is applied to the prediction of groundwater salinity of Yan'an formation in Erlintu No.3 mine field.The results show that the distribution range of groundwater salinity of Yan'an formation in Erlintu No.3 mine field is 411.56?6809.68 mg/L,and 99.35%of the area in the mine field belongs to high salinity groundwater.In the light of the desalination process of high salinity mine water,according to the requirement of mine "zero discharge" and the principle of classification and reuse,a high salinity water treatment process combining "underground direct filtration system" and double membrane method-"ultrafiltration+nanofiltration technology" is proposed for brackish water.