Uptake, Deposition and Wash Off of Fluoride and Aluminium in Plant Foliage in the Vicinity of an Aluminium Smelter in Norway

Abstract

Uptake, deposition and wash off of fluoride and aluminium in/on plant foliage were studied in two experiments near an Al smelter by growing different plant species under cover with free wind-flow underneath, and in the open, and by washing the leaves. With an average ambient air concentration of 2.2 μg F m³, the F and Al contents in leaves varied between species from 138 to 665 mg F kg⁻¹ and from 150 to 1025 mg Al kg⁻¹when grown under cover. An average of about 60% of the F and nearly 70% of the Al could be washed off covered plants. Uncovered plants had 33–51% lower F content, indicating a considerable precipitation wash off. Precipitation wash off varied with species, probably due to different leaf surface properties. The strong effect of precipitation on plant foliage F has to be taken into consideration when comparing differences in F content between years, localities and species. On average about 40–50% of the F and 55% of the Al could be washed off the leaves of uncovered plants. Washed leaves of plants exposed to precipitation had about 20% lower F content, compared to washed leaves of covered plants, thus indicating leaching of F from leaves exposed to rain. In contrast to fluoride, the Al contents in washed leaves of uncovered plants were about 50–80% higher than in covered washed leaves, thus indicating a significant uptake of Al solved in rainwater through the leaf cuticle.