ABSTRACT
The need to monitor the dispersion of fossil fuel residues such as fly ash and coal tar in the environment requires new methodologies to be developed which utilize naturally occurring isotopes of the elements strontium (Sr) and lead (Pb) as tracers. Both of these isotopic systems do not exhibit isotopic fractionation, a characteristic of the light stable isotopes (e.g., hydrogen, oxygen). This removes one potential complication in fate/transport studies, the alteration of a contaminant’s or leachate’s isotopic signature via mass dependent isotopic fractionation. Our research began with detailed sampling of soils, groundwater, flora, and coal residues (when available) in the vicinity of both operational and abandoned fossil fuel sites. In order to evaluate these isotopic systems’ effectiveness as tracers of fossil fuel leachate, we developed chemical extraction techniques designed to preferentially extract: (1) fly ash-derived Sr from biogeologic samples in the vicinity of an operating coal-fired power plant and (2) coal tar Pb from soils at an abandoned coal tar site. The Sr and/or Pb isotopic compositions of the fossil fuels at both sites were significantly different (>10 times the standard error of the mean of our analyses) from those of the natural background. Our research indicates that Sr and Pb isotopes are effective tracers of fossil fuel leachates in ecosystems and may be used to place constraints on models developed to assess the impact of fossil fuels on the environment.
