| Globally,groundwater is the most important freshwater source and plays an important role in human life.However,research shows that groundwater can only supply about a third of the population drink around the world.At the same time,due to the increasing human disturbance,groundwater in many countries and areas has been polluted in different degree,with causing a range of problems such as heart disease.Suzhou is a key agricultural products base such as alimentary crop,cotton,oil plants in the North China Plain.Meanwhile,groundwater is the most important drinking and irrigation water sources in the area.Therefore,groundwater quality research and its influencing factors is extremely important for supporting the safety of the regional water supply.In this study,the groundwater in Chengxi water source area,Suzhou City,Anhui Province,was systematically measured for the contents of 10 ions(F-,Cl-NO3-,PO43-,SO42-,Na+,K+,Mg2+,Ca2+and HCO3-)in 22 shallow groundwater samples(the first aquifer and the second aquifer have 11 samples each).Firstly,water quality of different aquifers was evaluated using drinking water indexes(WQI)and various irrigation indexes(SAR,KR,Na%,RSC,MH and PI).Then,the difference of evaporation intensity between surface water and groundwater was analyzed by using hydrogen and oxygen stable isotopes(?D and ?18O)method.Finally,Gibbs,multiple ion-relationship plots were used to explore the sources and influencing factors of ions in groundwater,combined with correlation analysis and principal component analysis.The results are as follows:(1)In the first aquifer,the dominant cation and anion were Na+and HCO3-,respectively.The average concentration of ions from high to low were:HCO3-,Na+,SO42-,Mg2+,Cl-,Ca2+,NO3-,K+,PO43-,F-.The second aquifer samples have higher Na+content relative to the first aquifer,but the contents of other ions were lower,and the mean concentrations of the maj or ions were in the order of HCO3->Na+>SO42->Mg2+>Cl->Ca2+>K+>PO43->NO3->F-.The major hydrochemical type of two aquifers was HCO3Na-Mg.(2)Considering only the major ions,WQI index results show that shallow groundwater was suitable for drinking,and F-took a high contribution in the study area(accounted for 19%),Therefore,the potential threat of F to drinking water should be paid more attention to.In addition,the water quality evaluation of various irrigation indexes shows that the most of the water samples were unsuitable for irrigation because of high Na+,Mg2+,and HCO3-contents.(3)The analysis results of hydrogen and oxygen stable isotopes show that groundwater in the study area was recharged by precipitation.The evaporation strength of surface water was more intensively than groundwater.The evaporation intensity of Tuo River was more intensively than Xinbian River,and the evaporation intensity of first aquifer water was more intensively than second aquifer water.At the same time,groundwater of some sampling sites had direct connection with surface water.(4)For the two aquifers in this study,the Gibbs diagram shows that the ion composition was controlled by water-rock dominance.Further,the ion-relationship plots analysis shows that hydrochemical composition of groundwater main affected by silicate weathering,to a less extent,carbonate dissolution.Moreover,Na+was mainly derived from silicate weathering,Mg2+mainly weathered from silicate weathering,HCO3originated from the reaction of dissolved CO2 in water with silicate.At the same time,the process of ion exchange was positive in groundwater.(5)Base on mathematical statistical analysis,9%of the second aquifer samples were infulenced by human activities.Compared with the second aquifer,the first aquifer samples were more significantly affected by human factors(accounting for 55%).Figure [20] Table [11] Reference [101]... |
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