Research On Spatio—Temporal Evolution Of Karst Groundwater During The Urbanization Of Guiyang

As a significant part of water resources and important supplementary sources,the amount and quality of karst groundwater are closely related to people's daily life and work.With the rapid development of urbanization,the influence of human activities on the groundwater has been strengthened.In recent years,under the influence of both natural conditions and human activities,the spatial distribution features and evolutionary process have been affected to some extent.It is especially important to understand the characteristics of groundwater evolution during the urbanization for preventing further deterioration of groundwater quality and realize the sustainable utilization of groundwater resources.This article,on the basis of systematic analysis of long-time measured data of groundwater and basic theory and methods of hydrogeology and hydrogeochemical,has examined dynamic characteristics and spatial distribution of karst groundwater in Guiyang.The evolutionary laws and mechanism or susceptivity were discussed behind groundwater spatio-temporal evolution during the urbanization of Guiyang.Which has important theoretical and practical significance for pollution preventing and comprehensive management as well as sustainable use.Major achievements are as follows.?1?Results show that the monthly fluctuation is low and average variation was 0.68m.The water level was consistent with the trend of rainfall,which mainly form were single peak and multi-peak type.The single-peak response period was less than 1 month and the multi-peak type was 2-3days.Inter-annual dynamic type was characterized by the uplift,which were affected by rainfall and exploitation.The area of water level amplitude which less than 0.5m were reducing gradually and the range of more than 1m were expanded.In the process of urbanization,groundwater level in urban and suburban areas was obviously increased as the leakage of sewer line as well as farming irrigation and decreasing in production.?2?Groundwater quality was weakly alkaline and TDS was less than 1g/L and increased with the development of urbanization.The average concentration of Ca²⁺was generally higher than other canons and HCO₃^-was major anion.Piper figures revealed that water chemistry types consisted by HCO₃-Ca and HCO₃-Ca·Mg,which transformed into HCO₃·SO₄-Ca and HCO₃·SO₄-Ca·Mg.SO₄^2-,which input by human interaction,was the main variables for transformation of water chemistry.?3?Karst groundwater was obvious polluted during the urbanization.Anthropogenic input leaded to a higher concentration of K⁺,Na⁺,Cl^-,NO₃^-,NO₂^-and NH₄⁺."Three nitrogen"had became the main indicator of groundwater pollution during the urbanization in Guiyang.The pollution trends of NH₄⁺and NO₂^-have been gradually alleviated.However,the problem of NO₃^-is still serious.?4?The determinative factors of groundwater hydrogeochemical evolution included water–rock interaction and human activity in the urbanization of Guiyang.Pearson correlation coefficient matrix and ion scale coefficient indicated that Ca²⁺,Mg²⁺,and HCO₃^-were derived from the dissolution of aquifer minerals.The collective effect between gypsum dissolving and agricultural activities play an important role in SO₄^2-.Na⁺,K⁺,Cl^-and NO₃^-were accounted for external sources.The chemical characteristics of groundwater water,which formed by water-rock interaction,are obviously changed by urbanization,and the influence of human activities is increasing.?5?The geochemical sensitivity of karst groundwater system has a significant response to the development of urbanization.Na⁺is most sensitive canon in the aquifers of the central urban area with higher urbanization degree,where also have strong susceptivity on HCO₃^-.The fellow ones are Ca²⁺and SO₄^2-.The sensitive factors of the rapid development of urbanization are Ca²⁺>SO₄^2->HCO₃^->Cl^->Na⁺>Mg²⁺>NO₃^->K⁺,which different from others.HCO₃^-and Ca²⁺are sensitive factor in the suburbs with low urbanization degree.The evolution of geochemical sensitivity factors in karst groundwater systems during urbanization of Guiyang are closely related to human activities.