A perspective on metals in soils

Soil contaminated with metals from a variety of sources can be toxic to plants and animals, including humans. The extent of contamination is often determined by comparison with the total elemental composition of an uncontaminated soil, although some leaching tests have also been proposed. In any event, knowledge of the natural background concentrations of metals at the site is required. Analysis of a control sample from the site will provide some information, but soils are still inherently variable. This review summarizes the total elemental composition of soils not known to be contaminated from anthropogenic sources. The total concentrations of 50 metals reported for these soils were shown to be log‐normally distributed, making the geometric mean (GM) and geometric standard deviation (GS) appropriate. Thus, 99.7% of the data should fall between GM/GS³ and GM*GS³. Fifteen metals were above the upper 99.7% limit and eight were below the lower limit. Most fell between the 99.9% limits of GIWGS⁴ and GM*GS⁴. The exceptions are nine metals (At. Ca, Fe, Mg, K Na, S, Si, and Ti) present at high concentrations with large GS values of 7500 to 66,400. GSs exceeding 5.0 probably indicate distributions with multiple modes. For K and Si, the arithmetic mean may be more appropriate. Available information on the concentrations of metals in relation to soil taxonomy is included, along with some specific data for soils in the Northeast. Data for the EPA target analytes are tabulated to assist regulators and others in cases where the soil is contaminated and remediation is required.