Metal contents in stinging nettle (Urtica dioica L.) as affected by soil characteristics

Uptake by plants is a potential pathway of metal transfer to the human food-chain. A correct quantification critically affects the outcome of environmental risk assessment. Using data for soil and plants (Urtica dioica L.) from 382 locations north-east of Ghent, the relation between soil characteristics (clay content, organic carbon content, CEC, soil pH and total metal content) and plant concentrations of metals was studied. Plant metal contents of Zn and Mn varied widely for low values of clay (< 10%), CEC (< 15 cmolc/kg) and organic carbon (< 3%) in the soil, and were lower and less variable for higher values of these soil parameters. No systematic trend was observed as a function of soil pH. For other metals (Cd, Co, Cr, Cu, Fe, Ni and Pb), ranges in plant metal concentrations were not affected by the soil characteristics studied. Bulk soil parameters do not constitute sufficient information for a precise prediction of plant metal contents in the field.