Background values for heavy metals are necessary for the assessment of metal pollution of soils and plants. Samples of cultivated and uncultivated soils, oat grain, and seed heads of orchard grass (Dactylis glomerata) were collected from central, southeastern, and southwestern Norway. Total and easily extractable concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were determined in soil samples and total concentrations in plant samples. Element distributions have been correlated with petrology of soil parent material, type of mineral deposit, soil depth, geographic area, and land use. Concentrations of heavy metals are generally within the lower part of the normal global range. The petrology of the soil parent material has the greatest influence on aqua regia extracted metal concentrations among the factors studied. DTPA extracted metals show less dependence on rock types. Presence of alum shale results in particularly high values for Cd in both soil extracts and in oat grain. Soil cultivation seems to influence the relative concentration of metals in the topsoil. The ratios of easily extractable to total concentrations of metals are primarily related to the organic matter content. Metal concentrations in oat grain can best be predicted by concentrations in DTPA extracts and soil pH among the factors studied. Seed heads of orchard grass are less affected by concentrations in the soil and appear therefore to be a poor indicator of heavy metals in soils.
