**5. Heavy metal contents in leaves of selected ornamental plant species growing in green areas adjacent to selected transportation routes in the city of Poznań (western Poland)**

Effects of soil pollution with heavy metals may be identified by analyzing their content in plants. Plants may be considered good bioindicators of environmental pollution with heavy metals. Most frequently healthy leaves are indicator parts of plants; however, it depends on the species and occasionally even on the cultivar.

The aim of the analyses conducted by the authors in September 2012 was to determine contents of selected heavy metals in leaves of trees growing in the vicinity of transportation routes in Poznań (western Poland).

#### **Material and methods**

It was decided to conduct analyses on healthy plants with no symptoms of damage. Leaves of trees were collected from the central parts of long shoots, distributed at various sides around the circumference of the crown. A total of 15 - 20 leaves were collected from each tree. Leaves were collected from 10 trees of a given genus (1 bulk sample comprised approx. 150 - 200 leaves). The collected material was dried at a temperature of 45 - 50°C and then homogenized. In order to determine total forms of heavy metals they were mineralized in a mixture of nitric and perchloric acids (v:v=3:1; Σ 30 cm3). Following mineralization Cd, Cr, Pb and Ni contents were determined by atomic absorption spectrometry (AAS) in a Carl Zeiss Jena apparatus.

High variation was observed in the contents of heavy metals in leaves of tested trees (*Acer sp., Betula sp., Robinia sp., Salix sp., Tilia sp.*), (Table 4). Mean content of cadmium amounted to 1.18 - 1.74 mg Cd kg-1 (for *Tilia sp.* and *Betula sp.*), for chromium it was 0.46 - 0.82 mg Cr kg-1 for *Tilia sp.* and *Acer sp.* (except for *Betula sp.* – trace content), that of lead ranged from 1.55 to 3.28 mg Pb kg-1 (for *Betula sp.* and *Salix sp.*, respectively). Nickel content ranged from 1.63 mg Ni kg-1 (for *Tilia* sp.) up to 2.23 mg Ni∙kg-1 (for *Betula sp.)*

Table (5) present contents of heavy metals in leaves of selected genera of trees reported by Tomašević et al. [117], Lawal et al. [81] and Knezevic et al.[76]. In this study cadmium and nickel contents in leaves did not exceed the levels detected by those authors. In contrast, they found markedly lower chromium contents in leaves of *Tilia* sp., *Aesculus hippocastanum* and *Azadirachta indica.* In this study the content of lead in leaves was markedly lower than that recorded by those researchers for *Tilia* sp. and *Aesculus hippocastanum*, while it was comparable to that in *Azadirachta indica* and *Paulownia elongata* (Tables 4 and 5).


**Table 4.** Contents of heavy metals (mg kg-1 d.m.) in leaves of selected genera of trees growing in Poznań (tr. – trace amounts)


dl detection limit

**4.1. Concluding remarks**

586 Environmental Risk Assessment of Soil Contamination

chromium and nickel.

**of Poznań (western Poland)**

Poznań (western Poland).

significantly affect habitat conditions for plants.

the species and occasionally even on the cultivar.

absorption spectrometry (AAS) in a Carl Zeiss Jena apparatus.

kg-1 (for *Tilia* sp.) up to 2.23 mg Ni∙kg-1 (for *Betula sp.)*

Based on analyses of soils collected from green areas located in the vicinity of selected transportation routes in the city of Poznań, Poland in most examined locations an alkaline reaction pH >7.4 (46.7% soil samples) and a neutral reaction (37.8%) were found, which may

Moreover, most tested soil samples contained low amounts of soluble forms of cadmium, lead,

**5. Heavy metal contents in leaves of selected ornamental plant species growing in green areas adjacent to selected transportation routes in the city**

Effects of soil pollution with heavy metals may be identified by analyzing their content in plants. Plants may be considered good bioindicators of environmental pollution with heavy metals. Most frequently healthy leaves are indicator parts of plants; however, it depends on

The aim of the analyses conducted by the authors in September 2012 was to determine contents of selected heavy metals in leaves of trees growing in the vicinity of transportation routes in

**Material and methods** It was decided to conduct analyses on healthy plants with no symptoms of damage. Leaves of trees were collected from the central parts of long shoots, distributed at various sides around the circumference of the crown. A total of 15 - 20 leaves were collected from each tree. Leaves were collected from 10 trees of a given genus (1 bulk sample comprised approx. 150 - 200 leaves). The collected material was dried at a temperature of 45 - 50°C and then homogenized. In order to determine total forms of heavy metals they were mineralized in a mixture of nitric and perchloric acids (v:v=3:1; Σ 30 cm3). Following mineralization Cd, Cr, Pb and Ni contents were determined by atomic

High variation was observed in the contents of heavy metals in leaves of tested trees (*Acer sp., Betula sp., Robinia sp., Salix sp., Tilia sp.*), (Table 4). Mean content of cadmium amounted to 1.18 - 1.74 mg Cd kg-1 (for *Tilia sp.* and *Betula sp.*), for chromium it was 0.46 - 0.82 mg Cr kg-1 for *Tilia sp.* and *Acer sp.* (except for *Betula sp.* – trace content), that of lead ranged from 1.55 to 3.28 mg Pb kg-1 (for *Betula sp.* and *Salix sp.*, respectively). Nickel content ranged from 1.63 mg Ni

Table (5) present contents of heavy metals in leaves of selected genera of trees reported by Tomašević et al. [117], Lawal et al. [81] and Knezevic et al.[76]. In this study cadmium and nickel contents in leaves did not exceed the levels detected by those authors. In contrast, they found markedly lower chromium contents in leaves of *Tilia* sp., *Aesculus hippocastanum* and

<sup>1</sup> Tomašević et al. 2004; 2 Lawal et al. 2011, 3 Knezevic et al. 2009

**Table 5.** Contents of heavy metals (mg kg-1 d.m.) in leaves of selected genera of trees
