The North American soil geochemical landscapes project -- 2010 US geological survey update

Abstract

A detailed knowledge of the concentration of chemicals in soil is required for calculation of human exposure to those chemicals via a soil pathway. At present, agencies involved with human and environmental health have no common understanding of soil geochemical background variation for North America and the processes that control this variation. The North American Soil Geochemical Landscapes Project, a tri-national initiative among the United States, Canada, and Mexico, was established to (1) develop a continental-scale design and protocols for generating soil geochemical data and (2) provide baseline soil geochemical data that are useful for a wide range of applications and disciplines, including public health. The Project is based on low-density sample collection over a spatially balanced array of 13,496 sites for the continent (1 sample site per 1,600 sq. km.). The core samples collected at each site include material from a depth of 0-5 cm and soils from the A and C horizons. In the US each sample is analyzed for more than 40 elements and mineralogy. Through partnerships with other federal agencies new data on the distribution of soil bacteria and microbial biomass are being generated. Preliminary results indicate that concentrations of potentially toxic elements in soils commonly vary by 1-2 orders of magnitude. The observed variability is the result of several parameters such as soil parent material, climate, and human activities. Understanding this variation is critical in terms of understanding human exposure and for understanding soil pollution on a national scale. The USGS is committed to the completion of sample collection in the conterminous United States by the end of 2010 field season.