Chapter 2 Contaminants as Tracers for Studying Dynamics of Soil Formation. Mining an Ocean of Opportunities

There is an ever increasing need to make pedology a process-oriented and quantitative scientific discipline. Key tools in this effort are tracers that help quantify the direction and rates of various pedogenic processes over time-scales beyond the reach of field studies. Though not commonly acknowledged, several atmospheric pollutants could be ideal tracers for studying soil forming processes and their rates. This review, among many potential pollutants, focuses on lead (Pb) and spheroidal carbonaceous particles (SCPs) entering the soil through atmospheric inputs. These contaminants enter soils at their surface, where mass fluxes through accumulation, erosion, mixing, and translocation are most vigorous. The rationale for expecting these atmospheric contaminants to be suitable as tracers are; (1) the atmospherically derived fractions can be distinguished within the complex soil matrix, (2) the boundary condition for their inputs to the soil can be well constrained in time and space, and (3) their biogeochemical properties make them suitable proxies for the movement of various solid components in soils. By adapting the pollutants to Simonson's conceptual view of soil formation within a mathematical framework we demonstrate how the vertical distribution of the atmospheric contaminants could be used to infer the mass-fluxes responsible for biogeochemical evolution of soils. Although there could be problems in applying the methods outlined in this paper for weakly contaminated soils with a strong geogenic lead source, the potential for using the methods for soils formed in industrialized urban areas is high.