2.4. Pot experiment and plant analyses
Three treatments were examined: untreated soil (control), soil amended with
OFMSW, and soil with added EDDS.
Phytoextraction trials were performed in 6 L closed-bottom pots each filled with 5 kg of air-dried and sieved soil. Three replicates were performed by block randomized experimental design.
In the OFMSW treatment, soil was mixed with the organic matter at the rate of
265 g dry matter (dm) of OFMSW per pot.
Maize (Zea Mays L.) was chosen for the plant test because of its high biomass
yields and heavy metal tolerance.
Moreover, it represents a commonly cultivated crop in the study area (North
Italy).
Three seeds of maize were sown in each pot.
Fifteen days from sowing, the number of maize plants was reduced to one. Maize pots were fertilized with 1.3 g of N (NH4NO3), 0.42 g of P(KH2PO4), and 0.35 g K (K2PO4).
Pots were kept in a controlled outdoor greenhouse with a day/night regime of 16/8 h and a light intensity of 350–400 mmol photonsm2 s1.
During the day, the air temperaturewas 26–28 C and at night it was 16–18 C.
Pots were maintained at a 60% water holding capacity by adding deionized water every two days.
Thirty-five days after sowing,EDDS treatment was carried out by 10 mmol EDDS per kg soil as a 0.5 mM solution (pH ¼ 10.1) (Luo et al., 2006).
Sixty days after sowing, the aboveground biomass was harvested, carefully
washed using deionized water, dried at 60 C until constant weight, weighed, and
then finely ground.
The heavy metal content of the harvested plants was then
determined as reported for soil.