Analyses Of Hydrochemical Characteristics Of The Groundwater And Nitrogen Pollution Sources Of The Liguan Riparian Area By The Means Of The Isotope

The riparian wellhead area is one of the most common types of groundwaterexploitation in the north of China. In recent years, these problems such as the absenceof water resources and the deterioration of water environment had already been theserious threat to this type of riparian wellhead area. It was vital significance to haveadequate knowledge of the hydrochemical characteristics of groundwater and identifythe pollution sources for scientifically exploiting the riparian wellhead area andpreventing the pollution of groundwater.This study aimed at investigating thehydrochemical characteristics and pollution sources of the groundwater in Liguanriparian wellhead area in Shenyang, on the basis of a field pollution sourcesinvestigation and a series of hydrochemical sampling campaigns, with multivariatestatistical methods of cluster analysis and factor analysis. A systemic study in respectof the environment of groundwater in the area was conducted depending on thesework. At the same time, it applyed the nitrogen and oxygen isotopes of nitrate tofurther recognize the pollution sources of nitrogen in the area. It mainly obtained thefollowing conclusions.⑴The analysis of hydrochemical type and hydrochemical cluster indicated: thehydrochemical characteristics of groundwater were different between the south andthe north of the area. The characteristics of the south were the lower Eh values, thehigher pH values, in the relative reducing environment, owning the high concentrationof ammonia nitrogen. The hydrochemical type was mainly HCO₃·SO₄-Ca·Na. Thecharacteristics of the north were the higher Eh values, the lower pH values, in therelative oxidation environment, owing the high concentration of nitrate, TDS andchlorine. Its hydrochemical type was HCO₃·SO₄-Ca·Na except for Cl·SO₄-Ca·Naand SO₄·Cl-Ca·Na.⑵The analysis results of factor analysis indicated: the hydrochemicalcharacteristics of groundwater in the area were principally controlled by three factors.There were in turns those hydrochemical effects which were less affected by the Hun river, such as weathering dissolution of minerals, exchange effect of cations, leachingof pollutants on surface; the region of hydrochemical characteristics which was deeplyinfluenced by the infiltration of the Hun river and was prone to the pollution ofammonia nitrogen; the region of hydrochemical characteristics which was controlledby the oxido-reduction environment of iron and manganese. Based on distributioncharacteristics of the control area of every factor, it deduced that the pollution ofammonia nitrogen in the south was principally derived from the infiltration of the Hunriver and agricultural activities; the pollution of nitrate and ammonia nitrogen in thenorth mainly originated from the vertical infiltration of surface pollution sources suchas the daily life of residents and industrial activities.⑶The summation of nitrate in the denitrifier method which had already beenimproved was not less than15ug. The experience precision of δ¹⁵N was better whichhad a precision SD better than0.780‰; The experience precision of δ¹⁸O was poorwhich had a precision SD better than1.805‰. Besides, there was no influence on theexperience results of δ¹⁵N and δ¹⁸O whether0.1MKCL or ultrapure water was chosenas the soil extract.⑷The analysis results of the nitrogen and oxygen isotopes of nitrate showed:There were no differences between the sources of nitrate in the sourth and north. Thenitrate in the groundwater mainly originated from manure and sewage, the minoritywas from NH₄⁺in fertilizer. The nitrate of the top soil in the south was principallyderived from NH₄⁺in soil and NH₄⁺in fertilizer, the minority was from NO₃^-fertilizer.The nitrate of the top soil in the north mainly originated from manure and sewage.