浙南仙居盆地水化学特征及成因分析OA北大核心CSTPCD

The Xianju basin is a typical hydrogeological unit and the main basin in the watershed of southern Zhejiang in which socio-economic activities are concentrated.Therefore,studying the hydrochemical characteristics of this basin is important for the development and utilization of groundwater resources and for the water environmental protection in southern Zhejiang.To reveal the hydrochemical characteristics of surface water and groundwater in the basin,we comprehensively analyzed the hydrochemical characteristics and origins of surface water and shallow groundwater in the Xianju basin with mathematical methods,Piper trilinear diagrams,principal component analysis,and ion ratios. The results show that HCO3-Ca·Na dominates the hydrochemical type of the Xianju basin,with Ca2+and Na+as the dominant cations,and HCO3 as the dominant anion.The pH values range from 6.48 to 7.81,indicating an overall hydrochemical characteristic of being slightly alkaline to neutral.The values of Total Dissolved Solids(TDS)of groundwater range from 45.5 mg·L-1 to 288 mg·L-1,while TDS values of surface water range from 20.1 mg·L-1 to 95.8 mg·L-1.The variation coefficients of major ions in groundwater are generally higher than those in surface water,with K+,Na+,Cl-,and NO3 showing larger variations,especially NO3-with a maximum coefficient of 36.80 mg·L-1 and a minimum of 0.13 mg·L-1.TDS values range from 45.50 mg·L-1 to 288.00 mg·L-1 in groundwater,and from 20.10 mg·L-1 to 95.80 mg·L-1 water. Principal component analysis indicates that the hydrochemical characteristics in the Xianju basin are mainly influenced by rock weathering and human activities.Rock weathering accounts for 67.89％of the influence,while human activities contribute 12.74％.Silicate weathering plays a predominant role in rock weathering processes,followed by carbonate weathering,with negligible influence from evaporite dissolution.In terms of correlation analysis of hydrochemical parameters,strong correlations are observed among values of TDS,K+,Na+,Ca2+,Mg2+,Cl-,SO42-,and HCO3-in surface water,while NO3-values show weaker correlations with those of other hydrochemical components.In groundwater,values of TDS correlate significantly with those of Na+,Ca2+,Mg2+,Cl,and HCO3-,whereas values of HCO3-show strong correlations with those of TDS,Na+,Ca2+,and Mg2+.Values of NO3-show weak correlation with those of other chemical components.Ca2+,Mg2+,and HCO3-primarily originated from silicate rock dissolution,and secondarily from calcite dissolution in carbonate rocks.K+,Na+,Cl-mainly originated from silicate rock dissolution,and partially from anthropogenic sources. The reverse exchange of Na+with Ca2+or Mg2+contributes to an increase of Na+contents in hydrochemical compositions,and groundwater exhibits stronger ion exchange capacity compared to surface water.NO3-primarily originated from anthropogenic activities.Surface water quality is mainly influenced by industrial and mining activities,possibly related to fluorite mining in Jiaoshan township and central Bulu township in the upstream basin.Groundwater,on the other hand,is affected by a complex array of factors including industrial and mining activities,agriculture,and domestic sewage.Spatially,there is a distinct zonation of major ion contents in groundwater and surface water in the basin.From the upper reaches to the lower reaches of Yong'an Creek,the transition occurs from the phenomenon that major ion contents are influenced by natural dissolution to phenomenon that the contents are jointly influenced by natural dissolution and human activities.From the edge to the center of basin,natural dissolution processes in groundwater gradually intensify.The areas with a dense population and with intensive agricultural activities are more susceptible to human activity. In conclusion,the findings provide a scientific basis for the rational exploitation and protection of regional water resources.Understanding the hydrochemical characteristics and spatial distribution of water bodies in the Xianju basin is crucial for the sustainable utilization of water resources and environmental conservation in southern Zhejiang.