Geogenic element behaviour in soil-rainwater interaction at Mt Etna, Sicily: preliminary results

Cluj-Napoca, Romania

Active volcanoes emit considerable amounts of contaminants such as As, Se and V. Previous
studies have shown that the volcanic activity at Mt Etna (Sicily) has a strong influence on local
rainwater compositions. However to date, the behaviour of trace elements in the soils around
Mt Etna is poorly understood. 4-hr batch experiments have been performed with 1:5 soil
solutions of air-dried soil (fraction <2 mm) and synthetic (acid) rainwater (using either
deionized water with a pH of ~6 or a ~500 ppm of sulphuric acid solution with a pH of ~2). In
general trace element concentrations are more enriched in soil solutions with low pH (e.g.
enrichment factor (EF) acid compared to neutral soil solution is up to 4.3x102 for V, 2.5x102
for As and 50 for Se). However, it seems that the EF especially for As and V has a correlation
with the distance to the crater. Additional, some soils located downwind of the volcano have
EFs smaller than 1 (i.e. the elements are more enriched in neutral rainwater), for several
elements like V, As and Se. For As and V the EF seems to be vary with distance to the crater.
Some possible explanations for these trends will be discussed. These results might have
important implications for the chemical composition of the Etnean aquifer, the only water
resource to the one million inhabitants around Mt Etna, as well as the bioavailability and
therefore potential toxicity through agricultural activities, essential to the local economy.