**9. The amount of ash (%) after incineration of aboveground parts of** *Miscanthus × giganteus*

Aboveground parts of *Miscanthus × giganteus* were incinerated at a temperature of 450ºC in a Linn Elektro Therm furnace. Incineration was performed in two stages:


According to Kalembas [70] in ash of *Miscanthus sinensis* Thumb. the content of individual

**The second year of growth**

3 1.45 1.48 1.65 1.38 5 3.06 2.53 3.06 2.84 10 7.69 6.69 7.69 7.22

250 25.51 15.94 23.33 23.13 1000 40.37 28.09 36.38 35.72 5000 136.49 45.23 63.25 69.90

Both in soil and in a mixture of soil and peat a lower cadmium content was recorded after the second year of culture except for substrates contaminated with 10 mg Cd dm-3, in which this

When analyzing lead content in tested substrates after the completion of growth a lower Pb content was found also in the second year except for a mixture of mineral soil with peat, to

In the substrate being a mixture of soil with peat lower contents of cadmium and lead were observed in comparison to those recoded in mineral soil in all the experimental variants (Tables

\*homogeneous categories were identified with the Duncan test, p=0.05 (values denoted with identical letters do not

**Table 10.** Cadmium contents (extracted with Lindsey's solution) in substrates (in mg dm-3) after the completion of

**Type of pollution Substrate Year of growth**

**Substrates**

**Mineral soil Mineral soil + highmoor peat**

**The first year of growth**

**The second year of growth**

**1st year 2nd year**

mineral soil 0.09 c 0.07 b soil + peat 0.07 b 0.05 a

mineral soil 2.23 d 1.09 b soil + peat 1.79 c 0.77 a

mineral soil 4.12 d 2.65 c soil + peat 2.51 b 1.32 a

mineral soil 6.37 b 6.39 b soil + peat 5.43 a 5.22 a

heavy metals ranks in the following decreasing levels: Zn>Cd>Pb>Ni>Cu>Cr.

**The first year of growth**

dependence was not observed (Table 10).

which lead was not introduced (table 11).

Control (native content of Cd mg dm-3)

> Weak pollution (Cd 3 mg dm-3)

Medium pollution (Cd 5 mg dm-3)

Strong pollution (Cd 10 mg dm-3)

plant growth in the first and the second year of analyses

**Table 9.** Metal concentration indexes in aboveground parts of *Miscanthus x giganteus*

**Metal**

Cd

Pb

10 and 11).

differ significantly)

**Dose of metal (mg dm-3)**

600 Environmental Risk Assessment of Soil Contamination

Incineration was performed on 20 randomly selected samples of aboveground dry matter of *Miscanthus × giganteus.* Assuming dry matter used in the incineration process as 100%. after combustion a mean 8.20% ash was obtained (SD 0.55), (Table 12).

The amount of ash left after combustion of aboveground parts of *Miscanthus × giganteus* was analyzed in terms of empirical probability distribution. Mean observations of the amount of ash were ordered in the so-called stemplot. in which separate intervals called classes were identified. Five classes were determined for the amount of ash left after incineration and next the number of observations (the so-called class frequencies) belonging to them were specified for each class. In order to ensure uniqueness of classification of observations it was assumed that classes are left side open intervals and right side closed intervals. Moreover, frequencies were added which when multiplied by 100 determine the percentage of observations of the amount of ash left after combustion of plants as classified to individual classes.

Among all observations after the combustion process the highest percentage (40%) was found for the amount of ash within the range of 8.44 to 8.88%. The amount of ash within the range of 8.00 to 8.44% ranked second constituting 30% observations.

In a study conducted by Kalembasa [70] largest content of raw ash was obtained from the *Sida hermaphrodyta* Rusby. (59.5 kg t-1), less *Miscanthus sinensis* Thumb. (52.5 kg t-1) and at less *Salix sp.* (31.5 kg t-1).


**Table 12.** The stemplot for the amount of ash (%) obtained after combustion of aboveground pars of *Miscanthus × giganteus*
