BORON ISOTOPE APPLICATION FOR TRACING SOURCES OF CONTAMINATION IN GROUNDWATER

Boron isotope composition and concentration of sewage effluent and pri stine and contaminated groundwater from the Coastal Plain aquifer of I srael have been determined. The application of boron compounds, especi ally sodium perborate as a bleaching agent in detergents, leads to an enrichment of boron in wastewaters. Anthropogenic boron in wastewater is isotopically distinct from natural boron in groundwater and thus ca n be utilized to identify the source of contamination. It is shown tha t delta(11)B (where delta(11)B = [((B-11/B-10)(sample)/(B-11/B-10)(NBS 951))-1] X 1000) values of raw and treated sewage effluents from the Dan Region Sewage Reclamation Project (delta(11)B = 5.3-12.9 parts per thousand) overlap those of natural nonmarine sodium berate minerals ( -0.9 parts per thousand to +10.2 parts per thousand) but differ signif icantly from those of regional uncontaminated groundwater (similar to 30 parts per thousand) and seawater (39 parts per thousand). Groundwat er contaminated by recharge of treated sewage yields a high B/Cl ratio with a distinctive anthropogenic isotopic signature (7-25 parts per t housand). Elemental B and delta(11)B variations reflect both mixing wi th regional groundwater and boron isotopic fractionation associated wi th boron removal by adsorption onto clay minerals. The distinctive iso topic signature of anthropogenic boron can be recognized, however, in most samples and differs significantly from those of natural sources o f contamination in the Coastal Plain aquifer of Israel, such as marine -derived saline groundwater (35-60 parts per thousand). This enables u tilization of the boron isotope composition of groundwater as a tracer for identification and quantification of contaminants in groundwater.