The focus of this study is on the natural spatial variability of trace element concentrations in ground water. The abstract refers to a stochastic model which relates the spatial variability of trace constitutents in ground water to the spatial distribution of sources of these elements in the underlying aquifer medium. Mineral-enriched zones in the soil matrix function as the primary natural sources of trace elements in the aquifer. Based on a representation often used by mineralogists, the occurrence of these sources, or mineral deposits, is modeled as a 2-d spatial Poisson process. The interaction between all the sources in an aquifer, and their corresponding sinks, is considered. Superposition principles are utilized to compute the total trace element concentration at any point in the aquifer from the sum of the contributions from each source.