Bromide as an environmental tracer in ground water of the Tucson Basin, Arizona

Abstract

Bromide was used as an environmental tracer to determine the possible sources of natural and man-made recharge to the ground water of the Tucson basin. Numerous well, rainfall, runoff, and sewage samples were collected and analyzed for bromide and chloride. The bromide was determined by neutron activation analysis. Bromide concentrations in the ground water ranged from 0.036 to 2.24 mg/l and the chloride concentrations ranged from 3.2 to 332.2 mg/l. The average Cl/Br ratio of the ground water samples is about 130. The bromide distribution suggests the presence of at least four dominant ground-water zones, each differing in chemical character. This observation agrees with those made in previous investigations which have used different hydrologic and geochemical methods. Most of the ground water in the basin is recharged by natural sources. However, the influence of man-made sources is well documented locally. The results of the bromide analyses strongly suggest that they can be used to delineate different sources of recharge.