Airborne fluoride contamination of soils and olive trees near an aluminum plant. Measurements and simulations

Abstract

Data from a multimedia survey on fluoride contamination in the vicinity of an aluminum plant are presented and applied along with multimedia‐based simulation modeling techniques in order to investigate the long term response of fluoride in soils and seasonal trends of accumulation by olive trees. Results from the modeling analysis are in fair agreement with observed data. Soils show elevated fluoride concentrations that decrease with distance from the source and depth below the surface. Fluoride is largely retained in the upper 5 cm of soil. Sensitivity analyses showed that accumulation of fluoride is dominated by atmospheric loading. The strong retention of fluoride in the calcareous soils of the area with high organic matter and clay content, is also an important factor for controlling its accumulation in these soils. In the case of olive tree leaves, direct deposition is the main source for fluoride accumulation during the year; washoff is the dominant sink during the wet months; during dry months, however, physical processes such as wind removal, growth dilution, etc appear to be the dominant sinks controlling fluoride accumulation in vegetation. In general, the modeling effort provides a plausible description of the long term response of fluoride in soils and also of the seasonal dynamics of its accumulation in vegetation.