Study On The Determination And Application Of Nitrogen,Oxygen And Boron Isotopes

Along with the development of isotopic geochemistry both boron isotope fand nitrogen/oxygen isOtopes in nitrate are used to identify and trace theconiamination sources in groundwater. TWo aspects, progress in isotOpicdetermination method and eXPloitation of geochemical significance of isotopeare essential to the advancement of isotopic geochemistry.Aiming at the shortages of existing methods for determination of N and Oisotopes in nitfate, a new concise method, based on Cs,NO,+ with graPhiteload by positive thermal ionization mass spectrometry (PTIMS), isinvestigated firstly in the first part of this paPer. The new method overcomesthe deficiency such as incomplete pick-up of N. O in sample, prone to becofltaminated by eXtrinsic N. O sources in tfaditional gas isotOpe ratio massspectrometry (GIRMS) methods. The N and O isotopic comPositions inseveral nitYate reagents by differellt producers are determined by this methodand significan diversity is observed.In second pall, boron isotope in aqueous samPles with low boronconcentration is determined using an improved procedure and used to studythe saline-water idrision in Laizhou Bay Region. Consistellt conclusions canbe obtained by traditional salinity means and boron isotoPe method. But largedifferences of boron concentration and boron isotopic comPosition of seawater,brine and freshwater reduce the highest sensitivity of boron isotope method.Three advamages are demonstrated: (1) be suitable for stlldying ifltosion withslight contamination and salinewater-freshwaer interface wth smooth Clfgradient; (2) be suitable for quantifying intrusion degree, and (3) beconvenient to identify intrusion tyPes. All the advanages indicate that boronisotope is an excellent means for seawater intrusion study...