UPTAKE OF ORGANIC-CHEMICALS IN CONIFER NEEDLES - SURFACE-ADSORPTION AND PERMEABILITY OF CUTICLES

Rates of uptake of organics [(2,4-dichlorophenoxy)acetic acid, triadimenol, lindane, bitertanol, and pentachlorophenol (PCP)] in needles from five different conifer species (Picea abies, Picea pungens, Pinus sylvestris, Abies alba, and Abies koreana) were investigated. Uptake (mole uptake vs time) from aqueous solutions was biphasic. The first phase is attributed to adsorption of the organics on the needle surfaces. The second phase represents uptake into the needles. Surface sorption and uptake into needles increased with lipophilicity of compounds and could be predicted from cuticle/water partition coefficients. Specific surface areas of the needles, determined from monolayer sorption of PCP, varied by more than 1 order of magnitude between different plant species. Since differences in rates of uptake between needles from different species correlated well with specific surface areas, needles with large surface areas showed appreciably higher rates of accumulation of organics at equal environmental concentrations than needles having lower specific surfaces. Implications concerning foliar uptake of organics and exposure monitoring are discussed.