Fjölrit RALA - 15.06.2004, Page 63

Trace element pollution in Italian volcanic soils:
the case study of the Solofrana river valley
P. Adamo1, A. Basile2, C. Colombo3, R. D’Ascoli4, R. De Mascellis2, L. Gianfreda1,
L. Landi5, M.A. Rao1, G. Renella5, F.A. Rutigliano4, F. Terribile1, M. Zampella1
1 Department ofSoil, Plant and Environmental Sciences, University ofNaples Federico II; 2 Institutefor
Mediterranean Agricultural and Forest Systems, CNR, Ercolano (NA); 3 Department ofAnimal, Plant and
Environmental Sciences, University ofMolise; 4Department of Environmental Sciences, Second University of
Naples; sDeparment ofSoil Science and Plant Nutrition, University ofFlorence
The Solofrana river valley is an agriculture based area of southem Italy characterised by a
huge concentration of tanning plants (-160). Despite the recently observed decline in Cr
content in river water (Adamo et al., 2001) the soils from the valley still contain this and other
trace elements in concentrations above usual levels, mainly as a consequence of the long use
of the polluted river waters as a source of irrigation, of the frequent river overflow as well of
the widespread use of metal-rich agricultural materials. The high metal retention properties of
the volcanic soils of the valley might play a key role to maintain the elements in soil for a
long time. A suspect that an increase of soil contamination could cause severe damage to
crops suggested soils have to be supervised (Adamo et al., 2003).
A multidisciplinary study, taking into consideration pedoenvironmental, micromorfological,
chemical, hydrological, biological and microbiological analyses, was carried out in 2001
restricting attention to overflooded soils. Crossing in a GIS environment different land
information (soil, hydrology, flood and land use maps) three study sites of about 700 m2 with
the same soil type, Humic Haplustand (Soil Survey Staff, 1998), not cultivated by 5 years and
affected by different numbers of floods were selected: 1) El, flooded in 1981; 2) E2, flooded
in 1981 and 1993; 3) E3, flooded in 1981, 1993 and 1998. At the E3 site, flooded again in
2002, soil and sediments were sampled soon after the event as E4 site. A site without flooding
(C site) as control was also individuated. The selection of not cultivated sites was produced in
order to avoid the influence of agriculture treatments over microbe activities, hindering the
influence of the trace metals.
Pedological profiles were opened on the two extreme cases: Pl, the not polluted control site
(C site), and P2, the site subjected to 3 flood events (E3 site). Soil sampling was carried out
following different operative methods and at different depths, according to the analyses to be
performed.
Soils were classified as sandy-loam (clay content 127-205 g kg"1), with neutral-subalkaline
pH according with carbonates presence. All the soils had a good amount of organic C (23-52
g kg"1), total N (2.2-4.1 g kg' ) and available P (19-45 mg kg"1). In general, soil properties
showed some grade of variability, especially in E3 and E4 soils, probably because of the
disturb caused from the recent overflowing events.
Copper and Chromium were the main soil contaminants: their total content in many cases
was higher than the limits established by the current Italian legislation (DL 92/99: Cu 100 mg
kg"1; DM 471/99: Cu 120, Cr 150 mg kg"1). The distribution of total content among studied
soils suggested for Cu and Cr different sources. Only Cr accumulation was related to
overflowing events. Cu accumulation was most likely attributable to past agricultural use of
fertilizers and pesticides.
Sequential chemical extractions indicated for all polluted soils preferential association of Cr
and Cu with oxidizable forms, whereas in non polluted soils both elements mostly occurred in
residual mineral forms of a silicate and oxide nature. For both metals the soluble and
exchangeable forms made always a small contribution to the total. Significant amounts of Cr
and Cu were recovered in the acid ammonium oxalate extraction, suggesting association of
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