The Evaluation Of Groundwater Quality And The Research On The Health Risks Of The Agricultural Activities In Da'an Irrigation District

Da'an irrigation district is located in the eastern part of Da'an city,west jilin province.The climate of Da'an irrigation district belongs to the semi-arid and semi-humid continental monsoon climate.The district is rich in petroleum,natural gas and groundwater resources,which makes Da'an irrigation district an important agricultural and livestock base in China.However,the district bears issues such as salinization of soil,desertification,etc.In order to solve these problems,government of Jilin province decided to divert water from Nenjiang River to turn dry land into paddy fields and have set up Da'an irrigation district in Year 2007.As the process going on,there were certain economic effects.However,due to the strong evaporation climate,the level of groundwater was pushed up and had formed large area of saline-alkali soil deposition during the operation of the irrigation district.Furthermore,the risk of the groundwater contamination was increased due to the increasing amount of fertilizer to obtain high yields.In this paper,the above problems caused by the change of land use and the deteriorate of the groundwater quality were studied to determine the main factors that affect the groundwater under the agricultural activities of Da'an irrigation district.In this paper,the natural geography,topography and hydrogeological conditions of Da'an irrigation district are described.SPSS software was applied to conduct the correlation analysis among the groundwater chemical factors of the three layers Mapgis professional cartography software and Aquachem software were used to draw the piper trilinear chart,schoeller diagram,Gibbs diagram,box diagram,and contour map to analyze the origin,classification and basic characteristics of the groundwater chemistry The test data of groundwater was used to analyze the quality grade of groundwater in Da'an irrigation district to determin the reasons of the change of the water quality grade.Based on this,the health risk of NO3-and NH4 + in the unconfined water was assessed in Da'an irrigation district.The results of the study show that:(1)The classification of the groundwater in the three layers of Da'an irrigation district mainly belongs to Na-HCO3 type,with the combination of the Ca,Mg and Cl ions as well.The TDS decreases with the deepening of the groundwater,while the pH value remains more or less steady.The hydrochemical action of the groundwater in the three layers is mainly leaching,while the action of the Quaternary unconfined water is mainly evaporation and concentration.The alternation and adsorption action of cation mainly occurs in the process of the replenishment of groundwater from the top to the bottom.(2)The overall content of Triazine in the irrigation district shows that the content of NO3-is far higher than the content of NO2-and NH4+.In the horizontal direction,the NO3-is widely distributed in the Quaternary unconfined water while the NO2-is less regulated and NH4+ is mainly distributed in the fertilization area of the irrigation district.In the vertical direction,the content of NO3-and NH4+ is at the highest level at the groundwater depth of 3-5 meters.The correlation between the ions and Triazine in quaternary unconfined water was no more than 0.5.Among them,the largest correlation with NO3-is HCO3-,and the largest correlation with NO2-is oxygen consumption,and the largest correlation with NH4+ is Mn.(3)The results of the water quality assessment show that the results of the assessment of each factor present a positive trend.The groundwater quality of the sampling points in the three layers mainly belongs to the IV Grade,accompanied by the III Grade and V Grade.The main factors of the above situation of the Quaternary unconfined water are Fe,Mn,F-,As,etc.As well as the Triazine caused by the agricultural activities.The main factors affecting the Quaternary confined water quality and the Neogene confined water water quality are Fe,Mn,F-and As.(4)In the health risk assessment,the high risk area of NH4+ accounts for about 80% of the total study district area and is mainly distributed in the eastern,central and northern parts of the study district.