Variation in fluoride content and leaf injury on plants associated with three aluminium smelters in Norway

Fluoride content and leaf injury were recorded in different plant species and genotypes associated with aluminium smelters in northern, continental and maritime parts of Norway. Generally, all deciduous broad-leaved plants were low in fluorides in the spring. The leaf F content increased during the growing season. The F accumulation rate (K) varied with species and exposure conditions. It was highest in Sorbus aucuparia, thus giving a 2–3-fold higher F content in this foliage than in Pinus sylvestris. Also, the within-species variation was great, 20–40%. Plant species and genotypes exhibited a broad range of tolerance to foliar injury. Leaf injury also varied with exposure conditions. Pinus sylvestris was most sensitive, showing clear leaf injury symptoms already at a F content below 50 p.p.m., at the northernmost locality and below 100 p.p.m. under southern maritime conditions. Broad-leaved spontaneous species like Betula pubescens, Salix caprea and Sorbus aucuparia showed similar symptoms at about 100 and 170 p.p.m., respectively. Also plants grown at the generally poorer climatic conditions at high altitudes had lower critical load for leaf injury than the same species grown at lower altitudes. Evaluation of sampling procedure showed that the phenological stage of the plants or sampling time, leaf age — i.e. basal and terminal leaves - and exposure on the tree — luff or lee side — strongly effected the measured fluoride content in the leaves. In comparative studies those conditions have to be taken into consideration. According to the present results, Sorbus aucuparia seem to be the best species for monitoring of antropogenic fluoride by leaf analyses under Norwegian conditions.