Spatial Distribution Characteristics And Origin Analysis Of Groundwater Hardness In Typical Areas Of Hebei Province

The hardness of water reflects the content of multivalent metal ions in water,high groundwater hardness is bad for human body health,life and the development of industry and agriculture.In this paper,1000 sample points of hardness survey area?11provinces and cities?are allocated reasonably,and then the paper studys the distribution characteristics of hardness,and comprehensively utilizes the ion ratio coefficient method,graphic method,saturation index and multivariate statistics analysis to study the main reasons for the high total hardness of the groundwater of Hutuo River in Shijiazhuang area.The main conclusions are listed below:The variation coefficient method takes into account the population density and Groundwater utilization degree in different provinces and cities,and the distribution scheme of sample points is in line with the actual situation of each province.Along the flow direction,the hydrochemical types of shallow groundwater change from HCO₃-Ca-Mg type through HCO₃-SO₄-Ca-Mg type to HCO₃-Cl-SO₄-Ca-Na-Mg type.When the hardness of groundwater change from I,II,III class to IV class and V class,the SO₄^2- and Cl-milliequivalent concentration percentage increase.The total hardness of groundwater in the study area exceeded the standard with the exceeding standard rate of 85.2%,and it was significantly negatively correlated with pH and well depth at 0.01 level,and positively correlated with TDS and NO₃^-at 0.01 level.The main reasons for the increase of groundwater hardness are water rock interaction,cation exchange reaction and human activities.The active geochemical processes in aquifers are: dissolution of CO₂,dissolution of calcite,incongruent dissolution of dolomite,dedolomitization and precipitation of calcite.The dissolution and precipitation of these minerals can affect the content of calcium and magnesium in groundwater.Organic matter in wastewater will produce CO₂ under the action of microorganisms,and the increase of CO₂ partial pressure resulted in the enhancement of the acid leaching,which made the temporary hardness of groundwater increase,butthe cation exchange reaction is mainly to increase the permanent hardness.In addition,decline of the water table caused by excessive exploitation of groundwater will also increase the hardness of groundwater.According to cluster analysis,the groundwater was divided into three types: I,II,III,and from I to III,the milliequivalent concentration percentage of SO₄^2-,Cl^-and Na+K increased gradually,which was significantly affected by human activities.Factor analysis showed that :?1?leaching of carbonates and silicates and cation exchange reaction caused by industrial and domestic pollution;?2?agricultural pollution;and?3?oxidation-reduction environment of groundwater were the three major factors contributing to groundwater quality especially the total hardness,the contribution rate is respectively 56.3%,17.4% and 12.5%.