Hemizam potencijalno toksičnih elemenata u zemljištu i njihov uticaj na funkcionisanje vrsta Betula pendula Roth., Acer pseudoplatanus L. i Acer platanoides L. u urbanim sredinama nekoliko industrijskih centara u Srbiji
The chemical properties of potentially toxic elements in soil and their impact on the functioning of the species Betula pendula Roth., Acer pseudoplatanus L. and Acer platanoides L. in urban areas of several industrial centres in Serbia
Doctoral thesis (Published version)
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Habitats in the urban environment and industrial zones are exposed to chronic pollution originating from various mobile and stationary sources, which can result in air, soil and water contamination. All of these, combined with the specific urban climate, including "urban heat islands", are a source of stress for plants. A special type of pollution in urban areas is caused by toxic elements; their content in urban soils varies and their mobility and bioavailability depend on forms and associations with different soil phases. Plants that survive in the urban environment exhibit different structural and functional damage symptoms depending on pollution type and intensity and can be used as biomonitors and/or bioindicators of pollution. Accordingly, the main aim and subject of this doctoral dissertation was to determine the content, bioavailability and mobility of chemical elements in urban soils, their accumulation in different plant parts, and their impact on the functioning of plants in urban habitats. The study area comprised urban parks exposed to various pollution sources in Panţevo, Smederevo, Obrenovac and Belgrade, while three tree species were used: Acer platanoides L., Acer pseudoplatanus L. and Betula pendula Roth. Selected physical and chemical soil parameters and chemical element content in soil and plant material were analysed. Soil samples and plant material were digested in a microwave, using nitric acid and hydrogen peroxide, and the soil samples were extracted according to a modified BCR sequential method. After extraction, Al, As, B, Cd, Cr, Cu, Fe, Li, Mn, Ni, Pb, Se, Sr and Zn concentrations were measured by inductively coupled plasma optical emission spectrometry (ICP-OES). The photosynthetic response of the plants to the effects of potentially toxic elements was analysed by measuring photosynthetic efficiency and photosynthetic pigment content in the investigated species. In addition, morphological symptoms of leaf damage and the condition of the peripheral leaf protection structures were also described, including a chemical analysis of atmospheric particles deposited on the outer surface of the leaves. The results were statistically analysed using correlation analysis, principal component analysis, discriminant analysis, and factorial analyses of variance. It was found that the analysed soils belonged to the class of sandy clay loam and clay loam, characterised a low percentage of moisture and organic matter, and an alkaline reaction, which was the main limiting factor for the absorption of elements by plants, whereby B, Cr, Ni and Pb content in some parks was higher than the maximum allowed concentration in accordance with the regulations of the Republic of Serbia (SG RS 23/94). Moreover, it was found that the investigated elements originated mainly from the parent rock, but that their content was also influenced by anthropogenic sources of pollution and the specific way urban soils are formed. The anthropogenic impact was most pronounced in the parks in Smederevo, Obrenovac and Belgrade. Sequential analysis of soil samples found that Al, Cr and Fe exhibited the lowest mobility at the investigated sites, indicating their strong structural connection with primary and secondary silicate soil minerals and their low availability to plants. Cu, Li, Ni and Pb exhibited poor mobility and were very stable elements, while Zn and B were classified as elements with medium mobility. Manganese and Sr were characterised by the highest level of mobility and potential availability in plants. The measurement and analysis of the accumulation of potentially toxic elements in leaves and bark, photosynthetic efficiency and photosynthetic pigment content revealed that the tested species generally displayed low sensitivity to the stress effects of the accumulated elements and that there were species-specific differences. Based on the analysed morpho - physiological parameters of the investigated plants, a certain gradation was determined in terms of tolerance to the effects of potentially toxic elements: birch > Norway maple > sycamore maple. Bearing in mind all the above, it is clear that the examined species are not good choices for bioindication and/or the biomonitoring of pollution in urban environments, except in the case of Sr, when they could possibly be used as bioindicators.