Analysis Of Water Environment Isotope And Shallow Groundwater Chemical Features In Rizhao Region

Under the premise of the regional background of discussed studies area,this paper respectively used hydrogen and oxygen stable isotopes,carbon isotope dating,water chemical analysis and other methods to study and explore the water environment isotope characteristics,chemical features of shallow groundwater and their causes in Rizhao.This study was conducted through the integration analysis of the historical data of the hydrology and geology in Rizhao region,especially the water quality test results and the test data of coastal rainwater samples collected at the time.The hydraulic connection among "three major waters" of atmospheric precipitation,surface water and groundwater can be reflected by characteristics of the waterbody isotope.It is the basis of water chemical research.D,18O analysis results show that:both surface water and groundwater in Rizhao region have intimate affinity with the atmospheric precipitation,and their main source of recharge is vertical infiltration recharge(including the rainfall and snowfall)of the atmospheric precipitation.There is a hydraulic relationship between surface water and groundwater,and the hydraulic relationship during the dry season is stronger than that of the wet season.The analysis results of the 14C dating show that the groundwater in the south bank of Futuan River is mainly the runoff recharge from the upstream,and the recharge path is relatively long.In other areas,the ages of surface water and groundwater are less than 200 years,indicating that most of them are recharged by the modern precipitation with rapid circulation.The analysis results of shallow groundwater chemical features in Rizhao region show that,on the spatial scale,there are differences in water chemical properties in both eastern and western sides by taking the middle low mountains as the watershed,and the eastern coastal shallow groundwater is characterized by "high chlorine and low mineralization",which is very different from inland regions with the same level of mineralization but is characterized by low Cl-content.It's proposed and proved that this is due to the presence of low mountains in the middle part,under the effect of sea wind,the seawater vapor is brought to the inland,which then forms the local rainfalls after settlement due to being blocked by low mountains,thus,the shallow groundwater is recharged.On time scale,it's characterized by "two changes and one constant"."Two changes" mean that since 1990,with the development of industry and agriculture in Rizhao region,the shallow groundwater type in the city has undergone a tremendous change,namely,the relative content of two major components of NO3-and SO42-has gradually increased rapidly.They have participated in the naming of chemistry types,and some of them have occupied an absolute advantage,such as the emergence of NO3-Ca·Na-type water,NO3·SO4-type water or water with more complex types.Studies have shown that the increase in NO3-content is the result of excessive use of nitrogen fertilizer in the agricultural production.The increase in SO42-content is the result of the formation of sulfur settlement after the oxidation of coal-fired SO2."One constant"means that Cl-content has been maintained at a relatively high level during the process,even when the mineralization of groundwater is low it's still the case when its TDS is lower than 0.3 g/L.The research results further revealed that the groundwater quality of Rizhao Coastal Area has been polluted in recent years,which needs the attention.