Supervisors info:
Κωνσταντίνος Κυριακόπουλος Καθηγητής ΕΚΠΑ (Επιβλέπων), Αριάδνη Αργυράκη Επίκ. Καθηγήτρια ΕΚΠΑ, Παναγιώτης Πομώνης Επίκ. Καθηγητής ΕΚΠΑ
Summary:
Nisyros island, Greece, is a stratovolcano known for its intense hydrothermal
activity. On June 2013, during a multidisciplinary field campaign, soil and
plant samples were collected in the caldera area, to determinate the main
mineralogical paragenesis (soils) and to investigate the distribution of major
and trace elements concentrations’ and the possible relationship to the
contribution of deep originated fluids (soils and plants). All the soil samples
were analysed with XRD and were extracted twice, using HNO3 + HCl for one
extraction (closed microwave digestion) and ultrapure de- ionized water for the
other one (leaching extraction). The leaves of plants were gently isolated,
dried and powdered for acid microwave extraction (HNO3 + H2O2). All the
solutions were analyzed for major and trace elements contents by using ionic
chromatography (IC) and inductively plasma spectrometry (ICP-MS and ICP-OES).
Also, atomic adsorption spectrometry (CV-AAS) took place, in order to
determinate Hg concentration in the samples. All data were compared to a local
background sample. The results allow to divide the samples in 2 groups (Lakki
Plain and Stefanos Crater).The latter, collected within one of the main
fumarolic areas, show a mineralogical paragenesis dominated by phases typical
of hydrothermal alteration. Their very low pH values (1.9 – 3.4) evidence the
strong impact of fumarolic gases which are probably also the cause of strong
enrichments in these soils of highly volatile elements like S, As, Se, Bi, Sb,
Tl and Te. The soils of the Lakki Plain, less exposed to the fumarolic
activity, show mineralogical and chemical characteristics intermediate between
the background soil and those of Stefanos crater. Also, the results showed high
enrichment of major and trace elements both in plants and soils respect to the
local background, in particular for Tl, Rb, Zn, Mn, As, Pb, Se, Bi, Al Hg, with
the highest concentrations found close to the most active fumarolic areas of
Stefanos, Kaminakia and Polyvotes and also close to the Geothermal Drill
(exploration well). Moreover, both soils and plants of Lakki Plain showed a
good correlation between Cu-Zn, Cu-Pb, Bi-Pb, Ba-Sr, Bi-Tl, Ti-Al, Ni-Al,
Tl-As, Te-Tl, Te-Se as well as REE’s. From the comparison between Cistus sp.
and Erica sp. we found a significant enrichment in the former respect to the
latter, making Cistus sp. the most suitable plant for biomonitoring studies at
Nisyros.
