Major-ion bulk deposition around an active volcano (Mt. Etna, Italy)

Bulk atmospheric deposition of major cations
(Na, K, Ca, Mg) and anions (Cl, F, SO4) were measured
at 15 sites around an active volcano, Mount Etna, from
2001 to 2003. Their composition indicates several natural
sources, among which deposition of plume-derived volcanogenic
gas compounds is prevalent for F, Cl and S.
Plume-derived acidic compounds are also responsible for
the prevailing acidic composition of the samples collected
on the summit of the volcano (pH in the 2.45–5.57 range).
Cation species have complex origin, including deposition
of plume volcanogenic ash and aerosols and soil-dust wind
re-suspension of either volcanic or carbonate sedimentary
rocks.
Variation of the deposition rates during the March 2001–
March 2003 period, coupled with previous measurements
from 1997 to 2000 (Appl Geochem 16:985–1000, 2001),
were compared with the variation of SO2 flux, volcanic
activity and rainfall. The deposition rate was mainly controlled
by rainfall. Commonly, about 0.1–0.9% of HF,
HCl and SO2 emitted by the summit crater’s plume were
deposited around the volcano. We estimate that ∼2 Gg
of volcanogenic sulphur were deposited over the Etnean
area during the 2002–2003 flank eruption, at an average
rate of ∼24 Mg day−1 which is two orders of magnitude
higher than that typical of quiescent degassing
phases.