Hydrogeochemical Characteristics And Sustainable Development And Utilization Of Geothermal Water In The Urban Area Of Chongqing

The development and utilization of the geothermal water has a long history,but most of them are extensive and single-style.As the continuous growth of geothermal wells,unreasonable utilization can easily result in a series of environmental issues.The geothermal water was studied to analyze its hydrogeochemical feature and genesis.It will be meaningful to utilize the medical thermal water,avoid or decease environmental issues,and make sure the sustainable development of geothermal water resources.Water samples from 36 thermal water wells have been collected in the main urban area of Chongqing during the wet season.This paper tested the temperature,pH values,concentrations of cations and anions,minor components and so on.The method of comparative analysis was used to discuss the different forming environment of the geothermal water,cold karst water and precipitation.And the principal component analysis was used to further discuss the control factors of hydrogeological chemistry of the geothermal water and cold karst water,and then made a comparison to their characteristics.It helps to build the formation model of the geothermal water in study area qualitatively,avoid or decrease the possible problems,provide scientific recommendations and build a foundation for future steps.The results show that:the geothermal water in the study area is brackish water with middle low temperature.For most of the geothermal water samples,the radio between(Ca²⁺+Mg²⁺)and(HCO₃^-+SO₄^2-)is around 1:1 relation line.It shows that the geothermal water in the study area mainly dissolves gypsum and carbonate.Moreover,the concentrations of minor components are relatively high in the urban area of Chongqing mainly because of the dissolution of surrounding rock.Also,other factors,like temperature and pH values,can have effects on iron concentrations.During runoff,the geothermal water has a series of physical and chemical reactions with surrounding media resulting in the variation of chemical components.Principal component analysis（PCA）of 12 variables is employed to interpret the different processes that control the hydrogeochemical formations of geothermal water and cold karst water.Through PCA,84.3%of the total amount information are extracted to indicate the formation of the geothermal water.For the geothermal water in Chongqing,the first component separates the dissolution of surrounding rock,and common-ion effect,accounting for 49%of variability in the data.The second component indicates the dissolution of halite,contributing for 14.7%.The third component reflects the effect of pH values,and contribute for 11.7%of variability.The contribute of the fourth component is a few and not representative.Through the comparison with Jiangjia Spring,it is concluded that surrounding rock plays a vital role in both hydrochemical characteristics of cold karst water and geothermal water;and human activities have an obvious effect on cold karst water,but not on geothermal water.The hot resource of geothermal water in Chongqing mainly comes from geothermal warming with good structure of reservoir system.?D and?¹⁸O were used to study water resource of this area and were all around the global and Chongqing meteoric water line.Using special radio method,it was founded that?Na/?Cl values of most geothermal water varied from 1.48⁸.73;?Cl/?Br varied greatly from 92.52²157.22;?Cl/?Ca changed from 0.004 to 0.584;Coefficient of desulfurization is far more than 1.According to Cod of geologic exploration of natural mineral water resources（GB/T13727-2016）and Geologic exploration stand of geothermal resources（GB/T11615-2010）,most of geothermal water can be named as fluorinate,strontium mineral water and have medical value of metasilicate acid and metaboric acid.At present,terrestrial heat utilization has been a certain degree,but it is easy to result in some environmental problems.To achieve the sustainable development,it is necessary to strengthen the basic theory research,optimize the exploitation scheme,dispose the used geothermal water,use dynamic monitoring,construct demonstration project,reinforce the management,expand advertising of geothermal knowledge.