Assessing the accumulation of potentially toxic elements in plants

Regression and principal components analyses were applied to understand the accumulation characteristics of potentially toxic elements(PTEs) in plants. The relation between tissue(tc) to soil(sc) Cd concentrations can be expressed as; log(tc) = α' + β' log(sc). For another soil, the equation will change to; log(tc) = α' + β' log(sc'). Based on both equations, the relationship between sc' and sc becomes; log(sc') = (α-α')/β' + (β/β')log(sc). The values of the intercept and slope can be used to evaluate the difference of Cd availability between two soils. The values of α and β were used to characterize Cd accumulation in various plants. Plant families were classified into 3 groups based on α values; (1) low accumulation, Leguminosae; (2) moderate accumulation, Gramineae, Liliaceae, Cucurbitaceae and Umbelliferae; and (3) high accumulation, Chenopodiaceae, Cruciferae, Solanaceae and Compositae. Values of β also enabled to discriminate the families. Principal components analysis was applied to the contents of Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba in leaf samples of 62 species. These elements except for Na could be classified into 2 groups with respect to their accumulation in leaves; the alkali metals and alkaline earth metals. Factors scores of 1st and 2nd components revealed three groups of plant species; alkaliphillic, alkaline earthphillic, and neutral. (author)