Research On Evolution Of Groundwater Quality In The Western Jilin Province

In recent years,groundwater resources and environment have changed significantly with the global climate change and the intensification of human activities.The study on the evolution of groundwater quality in time and space has important theoretical and practical significance to groundwater resource management,conservation and sustainable development and utilization.The western region of Jilin province is an important agricultural production base and petrochemical energy base in Jilin Province,due to the unreasonable development of water and soil resources for a long time,causing serious damage to the ecological environment with soil salinization and desertification problems,geological environment is to change.Therefore,the spatial distribution characteristics and temporal evolution law of chemical composition of groundwater in the western region of Jilin province are studied in order to provide a theoretical basis for rational development,utilization and protection of groundwater.This paper collecting a large number of geological and hydrogeological data and water chemistry data,use the graphical method,statistical analysis method,model method and other means researching evolution of groundwater quality in the western region of Jilin province.The research results are as follows:??the spatial distribution characteristics of groundwater chemistry(1)The spatial distribution of chemical composition of water in the area is controlled by geological and geomorphic conditions.In Taoer River and Central High Plains area,groundwater is mainly bicarbonate type water and salinity is less than 0.5g/L;in the low plains,hydrochemical type changes complex,phreatic water salinity is 1-3g/L;the songla interstream block area,groundwater HCO3-Ca,HCO3-CaMg water,salinity is less than 0.5g/L.(2)For fluoride,total iron and total hardness,those are higher at the center of the basin exceeding the standard phenomenon obviously.In the exceeding area,fluoride concentration is 1-4mg/L,total iron is greater than 0.3mg/L and total hardness is more than 450mg/L;In Hejian songla area,the total iron significantly exceed the standard;the characteristic component is low in other parts.(3)For confined water,the chemical type of water is relatively simple,the salinity is generally lower than that of phreatic water;the excessive area of fluorine and total iron is basically consistent with phreatic water,the content is generally smaller than that of phreatic water;the total hardness is exceeding the standard in little area.?? time evolution characteristics of groundwater chemistry(1)The study took 1980 s as the base year and discussed the characteristics of groundwater change with time after 80s:? After 80 s,the groundwater quality is generally getting worse;? During the time,from 1990 s to 2000 s is a period of groundwater water quality changes,each index significantly increased;from 1980 s to 1990 s and from 2000 s to 2010 s are two period that water quality did not change significantly,the degree of mineralization and the characteristics of component concentration generally decreased from 2000 s to 2010 s,but still higher than in 1980s;? The pollution component "three nitrogen" is on the rise in every period,agricultural pollution has been going on.(2)The evolution characteristics of groundwater quality in the study area show that geological and geomorphic conditions are the basic conditions for controlling water quality distribution,and climate and human activities are the main factors that affect water quality change.? In Taoer River and the Central High Plains area,rock permeability is good,hydraulic gradient is larger,the formation of water chemistry mainly leaching,form low mineralized bicarbonate type water;? Statistical analysis showed that salinity and rainfall are negatively related,in the middle of the basin,shallow groundwater and strong evaporation caused serious soil salinization,groundwater chemistry type is complex emerging the bicarbonate chloride water,Na+,Mg2+ is relatively high,mineralization and Characteristic components are also relatively high;? Since 80 s,with the increase of population and city development rapidly,superposition of human activities and climatic conditions led to dramatic changes to water quality in 1990 s to 2000 s,agricultural pollution is serious,"three nitrogen" content continues to rise;confined water quality has deteriorated.?? establish BP neural network model to predict groundwater qualityConsidering the factor of precipitation,annual precipitation in the future was predicted by the superposition method of Markov chain,combining the water quality data of diving in the western area degree of mineralization and total hardness are forecasted.The BP neural network has good generalization ability,the test set error is less than 10%,the final prediction of a diving observation wells in 2017: salinity is 560mg/L,the total hardness is 366mg/L,the prediction result according with the correlation between index and rainfall,has certain rationality.The establishment of this model is to provide a mean which provide reference for groundwater protection and management work.