Contaminant/Natural Background Values: Timing and Processes

Abstract

Natural geochemical background concentrations have been taken in the past as average crustal contents (Table 5–1). This is not compatible with environmental geochemistry research on specific pollution problems because of the great variation in composition of the rock types comprising the crustal surface (Table 2–1). This leads to variations in soil and other overburden chemistry. Chemical variations among flora and fauna likely reflect their growing and feeding in an area of varying geology. Added to this are the chemical changes rock materials undergo during weathering and from diagenesis. Natural background varies with other factors such as the sample used (Table 6–1), the size fraction or organism part analysed, and the analytical methodology employed.