# The Suitability of Short Rotation Coppice Crops for Phytoremediation of Urban Soils
## 2 Materials and Methods  
### Study Area and Plant Selection  
The experimentation was conducted in the city of Turin (45\({}^{\circ}\)03' N, 7\({}^{\circ}\)40\({}^{\prime}\) E), one of the main urban centers of northern Italy. The Turin climate is humid subtropical (Cfa, according to Koppen-Geiger classification), with cold and wet winters and hot and humid summers. The city is located at 250 m a.s.l., near the Alps, along the river Po. Mean annual precipitation is about 800 mm/year, concentrated mainly in spring and autumn.  
The city was characterized by the heavy metallurgical industry and has suffered from de-industrialization over the past three decades. As a consequence, vast areas of former industrial plants were abandoned, and a new urban planning action had to be devised. A large part of the ex- industrial areas was allocated to green infrastructures such as parks and other types of public spaces. However, the restoration of the green areas was confronted with the problem of soil contamination. In the most polluted sites, classical remediation methods were applied, leaving the moderately contaminated sites originating from diffuse pollution. Diffuse pollution appears to be typical of urban areas due to the variety and continuity of sources emitting pollutants. One example is Pb from gasoline [22].  
The area selected for the experiment was characterized by heavy metal concentrations (Co, Cr, Cu, Ni, Pb, Zn) above the limits defined for green and residential areas by Italian legislation [23]. This was probably caused by past industrial activities and widespread sources such as traffic for Cu, Ni, Pb, and Zn, while for Co, Cr, and Ni (in part) because of the alluvial deposits upon which the soils developed, as described elsewhere [24; 25].  
The surface of the experimental plot was about 0.1 ha. The area presented soil excavated in adjacent areas and mixed with around 10% in weight of compost incorporated in the first 15 cm of soil to improve plant rooting and survival ability.  
The selected species were chosen between species well adapted to the Piedmont area, having a rapid growth, resulting in large biomass production and tolerant to rather high metal concentrations; species were from _Populus_, _Salix_. and _Robinia_ genera.  
As comparative studies demonstrated that different clones respond differently to contamination under different pedo-climatic conditions [20; 26], three clones of each species were chosen (listed in Table 1). Clones were selected basing on previous studies in the area for their productivity in agricultural soils [27; 28; 29] and on previous studies in contaminated soils in Northern Italy for their productivity and tolerance to PTE concentrations (data not published).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Code** & **Genotype** & **Species** \\ \hline P1 & ORION * & _Populus \(\times\)canadensis_ Monch \\ P2 & BALDO * & _P. deltoides_ Marsh. \\ P3 & VILLAFRANCA * & _P. alba_ L. \\ S1 & SI64-017 & _Salix alba_ L. \\ S2 & MOS310 & _S. vininalis_ L. (provenance Czech Republic) \\ S3 & DRAGO & _S. babylonica L. x?_ (natural hybrid selected by CREA) \\ R1 & NORD & _Robinia pseudoacacia_ L. (provenance Northern Italy) \\ R2 & SUD & _R. pseudoaacacia_ L. (provenance Calabria, Southern Italy) \\ R3 & ENERGY & _R. pseudoacacia_ L. (provenance Hungary) \\ \hline \hline \end{tabular}  
* Clones listed in the Italian Register of Forestry Clones.  
\end{table}
Table 1: Species and genotypes used in the experiments.  
Cuttings of _Populus_ and _Salix_ and 1-year old seedlings of different provenances of _Robinia pseudoaccia_ were used.