Determination of the Principal Pathways of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans to Lolium multiflorum (Welsh Ray Grass)

Abstract

This study presents experimental evidence that dry gaseous deposition is the dominant pathway of relatively involatile organic contaminants like polychlorinated dibenzo-p-dioxins and dibenzofurans to Welsh ray grass, an important species in agricultural food chains. The uptake pathways of these compounds to Welsh ray grass were studied under near natural conditions using a system of greenhouses and outdoor plots. Dry gaseous deposition was found to be the principal pathway of Cl 4 -Cl 6 DD/F to the grass leaves. The contribution of dry deposition of small particles (<2.9μm)to the grass levels was negligible for all compounds studied. There was some evidence that the deposition of large particles was an important pathway for the uptake of Cl 7 DD and Cl 8 DD, particularly during the autumn period when the particle-bound concentrations of these compounds were higher. Soil-related pathways did not measurably influence the substance levels in the grass.