Accumulation of airborne fluorides in forest trees and vegetation

Abstract

SummaryThe accumulation of fluoride in natural vegetation exposed to emissions from five aluminium smelter plants in Norway was studied during the years 1990–93. About 2000 leaf, bark and twig samples of 60 plant species, collected mostly during the growing season, were analysed. Rowan (Sorbus aucuparia) was widespread and common in the areas studied, and was used as a reference species. Fluoride concentrations in monthly samples of rowan leaves were linearly related to fluoride exposure (average fluoride concentration in ambient air × days since leaf emergence). The accumulation coefficient for rowan was estimated to be 1.7 m3/g dry wt. day. Most other species had values between 0.3 and 1.5; the median for all species was 0.8. The fern Dryopteris filix‐mas was exceptional, containing on average three times greater fluoride concentrations man rowan. High background levels indicated that soil uptake contributed significantly to the fluoride accumulation in this species. The fluoride concentrations in bark and shoots of trees were mostly low compared with leaves, but the bark of Betula pendula and B. pubescens had very high concentrations.