Page 155 - Plant-Based Remediation Processes

146 T. Vamerali et al.

Fig. 8.2 Aerial view of study area. Yellow dots: soil sampling (33); red dots: exploratory ditches
(6); Roman numbers (I–IV): areas for floral analysis. Arrow: north

The carry-over topsoil (layer a) generally had low metal contents, below the
Italian Guideline Values (IGV) for ‘Green public, private and residential areas’
(Italian Legislative Decree 152/2006). Metal concentrations in cinders were het-
erogeneous across the sampling area, but on average very high, exceeding the IGV
by as much as 45 times for As, 23 for Cu, 16 for Zn, 5 for Co and Pb, and 2.5
for Cd. Arsenic and Cu levels were particularly high and exceeded the less
restrictive IGV for ‘Industrial sites’ (i.e., 50 and 600 mg kg 1 DW, respectively)
(Table 8.1). The total amounts of Fe and S in the cinders were about 10 and 5 times
higher than in cultivated soil, with concentrations of 97 % and 0.39 %, respectively.
In spite of this, bioavailable Fe was not very high, comparable with the agricultural
silty-loam soil at the experimental farm of the University of Padova (24 vs.
1
18 mg kg ).
The particular stratigraphy, together with abundant precipitation—the historical
mean annual value of the site is 1,000 mm—led to the selection of a specific
spontaneous flora. Analysis of the vegetation cover by visual evaluation (Pignatti
and Mengarda 1962) during spring 2004 in four buffer zones identified in the
surroundings of the soil-sampled area (Fig. 8.2) was believed to be useful in
providing criteria for species selection for the planned phytoremediation setting.
Buffer zones I and IV were colonised by both herbaceous and woody species,
whereas the vegetation was mainly herbaceous in buffer zones II and III. For
species with an appreciable degree of cover (>5 %), shoot samples (young branches

for trees) were collected in early spring, washed and oven-dried (105 C, 24 h) to
determine metal concentrations. Our hypothesis was that a correlation exists
between the extent of species diffusion and their metal accumulation.