|Austrian Bio-Indicator Grid - Fluorine
|Fluorine is mostly emitted as hydrogen fluoride (HF), silicon tetrafluoride (SiF4) or as dust. Hydrogen fluoride is the most phytotoxic air pollutant, but is only relevant close to emitters (ca. 1-5 km). Fluorine is mainly taken up through the stomata and in insignificant amounts through the roots. HF is dissolved in the cell water and transported to the leaves’ edges and tips by the sap flow and the transpiration flow, respectively. As a consequence, apical and marginal necroses on the leaves occur. HF inhibits a broad range of enzymes, i.e. it inhibits enzymes containing calcium or magnesium as a cofactor by binding to these elements. Addition reactions with cations take place and the phosphate metabolism is disturbed. Further effects are lowering of the cytosolic pH (in the case of HF), inhibition of and also increase in (at low concentrations) respiration, as well as chlorophyll degradation.
Fluorine damage on black pine
Important emitters are the glass-, ceramic- and brick making industries, aluminium production as well as fertilizer- and metalworking industries. Fluorine compounds can also play a role in the thermal recycling of plastics.
Results of the Austrian Bio-Indicator GridFluorine is not measured at all plots in the Austrian Bio-Indicator Grid, but the plots of the Bio-Indicator Grid are integrated into local measuring grids close to emitters. By means of that integration, the temporal development of the effects related to the fluorine impact in the investigated area can be extrapolated, using current data. At the moment, the fluorine impact around 30-35 Austrian emitters is monitored with local bio-indicator grids.
In terms of plant analysis, the most well inspected area in Austria lies in Ranshofen in the district of Braunau, where at the beginning of the nineties an aluminium works was closed down. Here the first investigations were made in the fifties by the University of Natural Resources and Applied Life Sciences. The peak values at that time were above 1400ppm (140 mg%F). First samples for the determination of fluorine were taken in 1957. With the introduction of the Austrian Bio-Indicator Grid in 1983, there were 39 plots set up (with 2 spruces in each plot) in the district of Braunau to monitor the development in this area; 5 of these plots were close to the works (<5km). The investigation area in Braunau was one of the few cases where an assessment of the air pollution was possible from the data of the Bio-Indicator Grid alone. Usually, the grid density of the Bio-Indicator Grid alone is insufficient for that purpose. In this district as well as in others, the grid density had to be reduced as a cost-cutting measure. From 1983-88 there were still 39 measuring plots, from 1989-92 only 28 and since 1993 only 12 plots – of these 12 plots just one is close to the works (300m). In the following diagram, the development of the maximum fluorine content in the needle sets 1 and 2 is shown.
Until the works was closed down, there was a striking upward trend in the maximum fluorine content up to above 200ppm (20 mg%F). After the closing down – as expected – the fluorine pollution went down just as quickly. As soon as 1994, the fluorine contents in both needle sets had fallen below the threshold values specified in the Austrian forest law “Zweite Verordnung gegen Forstschädliche Luftverunreinigungen, BGBl. Nr. 199/1984” (0,8 mg%F in needle set 1 and 1,0 mg% F in needle set 2).