IDENTIFICATION OF GROUND-WATER CONTAMINATIONS BY LANDFILLS USING PRECISE BORON ISOTOPE RATIO MEASUREMENTS WITH NEGATIVE THERMAL IONIZATION MASS-SPECTROMETRY

Precise boron isotope ratio measurements with negative thermal ionizat ion mass spectrometry were used for the identification of ground water contaminations by leakages of landfills. BO2- thermal ions were produ ced to determine the B-11/B-10 isotope ratio, which was expressed as d elta(11)B Value in parts per thousand normalized to the standard refer ence material NIST SRM 951. For example, household waste influences th e boron isotope ratio by specific components such as washing powder. I n the case of one investigated landfill low delta(11)B values correlat e well with high boron concentrations in contaminated seepage water sa mples and vice versa for uncontaminated ground water samples. Possible boron contributions of rainwater were taken into account! determining a boron content of 2.3 mu g/L and a delta(11)B value of 13.1 parts pe r thousand for a representative sample. Such low boron concentrations were determined by isotope dilution mass spectrometry (detection limit 0.3 mu g/L) whereas higher contents were also analyzed by a spectroph otometric method. However, different sources of contamination could on ly be identified by the isotope ratio and not by the concentration of boron.