ABSTRACT
Geochemistry deals with the physical, chemical and biological principles that influence and/or control the fractionation, migration, deposition and distribution of chemical elements (and their isotopes) and compounds in the spectrum of materials that make up the Earth’s crust. Surface and near-surface crustal matter are the focus of applied studies in environmental geochemistry as well as in geochemical exploration for mineral and hydrocarbon resources. Samples used in such studies comprise a varied group of solids, liquids, gases, and biological forms[1]. Each sample is unique as to what its chemical signatures represent in terms of volume and area as well as natural and/or contaminant components. A rock outcrop sample gives the chemistry at the point the rock was collected whereas a stream sediment or water sample carries chemical signals of earth materials from the entire upstream water-shed including mineral deposits and/or contaminants. The stream sediment also signals low concentrations of chemical elements which could suggest areas with weathered products deficient in one or more than one essential nutrient. Similarly, a soil sample has a chemistry representive of the pit from which it is collected (perhaps 700-1000 cm3). It reflects the natural chemistry of the underlying rock from which the soil formed plus contaminants that may have been added to it at the sample site (e.g., from atmospheric deposition). Chemical signals from vegetation samples derive from a volume of soil that is as extensive as their root systems or of an aquifer system where roots tap groundwater to sustain growth (to millions of cm3)[2].
