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

Abstract

Staništa u urbanoj sredini i u industrijskim zonama izločena su hroničnom zagađivanju poreklom iz različitih mobilnih i stacionarnih izvora što kao rezultat moče imati kontaminaciju vazduha, zemljišta i voda, a u kombinaciji sa specifičnom urbanom klimom uključujuši i „gradska ostrva toplote“ predstavlja izvor stresa za biljke. Poseban vid zagađenja u urbanim sredinama predstavlja zagađenje toksičnim elementima čiji je sadrčaj u urbanim zemljištima promenjiv, a njihova mobilnost i biodostupnost zavisi od oblika i asocijacije sa različitim fazama zemljišta. Biljke koje opstaju na urbanim staništima pokazuju različite strukturne i funkcionalne simptome oštešenja u zavisnosti od tipa i intenziteta zagađenja i mogu se koristiti kao biomonitori i/ili bioindikatori zagađenja. U skladu sa tim, osnovni cilj i predmet ove doktorske disertacije je bio da se utvrdi sadrčaj, biodostupnost i mobilnosti hemijskih elemenata u urbanim zemljištima, njihova akumulacija u različitim delovima biljaka, kao i njihov uticaj na funkcionisanje biljaka na urbanim staništima. Poligoni za istračivanja su bili urbani parkovi, izločeni različitim izvorima zagađenja u: Pančevu, Smederevu, Obrenovcu i Beogradu, a kao model vrste koriššene su tri drvenaste vrste: Acer platanoides L., Acer pseudoplatanus L. i Betula pendula Roth. Analizirane su osnovne fizičko - hemijske karakteristike zemljišta, i sadrčaj hemijskih elemenata u zemljištu i biljnom materijalu. Uzorci zemljišta i biljnog materijala pripremeljeni su vlačnom digestijom u mikrotalasnom digestoru pomošu azotne kiseline i vodonik peroksida, a uzorci zemljišta su podvrgnuti i modifikovanoj BCR sekvencijalnoj ekstrakciji. Nakon ekstrakcije, u rastvorima je određivana koncentracija Al, As, B, Cd, Cr, Cu, Fe, Li, Mn, Ni, Pb, Se, Sr i Zn metodom induktivno spregnute plazme sa optičko emisionom spektrometrijom (ICP-OES). Analiziran je fotosintetički odgovor biljaka na efekte potencijalno toksičnih elemenata merenjem efikasnosti fotosinteze i koncentracije fotosintetskih pigmenata ispitivanih vrsta i detektovani su i opisani morfološki simptomi oštešenja listova i stanja struktura periferijskih zaštita listova uključujuši i hemijsku analizu atmosferskih čestica deponovanih na spoljašne površine listova. Rezultati su statistički obrađeni koriššenjem korelacione analize, analize glavnih komponenti, diskriminantne analize i faktorijalne analize varijansi. Utvrđeno je da analizirana zemljišta pripadaju klasi peskovito-glinovite ilovače i glinovite ilovače, da ih odlikuje mali procenat vlage, organske materije i alkalna reakcija koja predstavlja glavni limitirajuši faktor za usvajanje elemenata od strane biljaka, pri čemu je sadrčaj B, Cr, Ni i Pb u pojedinim parkovima viši od maksimalno dozvoljenih koncentracija saglasno pravilniku Republike Srbije (SG RS 23/94). Utvrđeno je takođe da ispitivani elementi uglavnom vode poreklo iz matičnog supstrata, ali i da na njihov sadrčaj utiču antropogeni izvori zagađenja i specifičan način formiranja urbanih zemljišta. Antropogeni uticaj je najizračeniji u parkovima u Smederevu, Obrenovcu i Beogradu. Sekvencijalnom analizom uzoraka zemljišta utvrđeno je da najmanju mobilnost u ispitivanim zemljištima imaju Al, Cr i Fe, ukazujuši na njihovu snačnu strukturnu povezanost sa primarnim i sekundarnim silikatnim mineralima zemljišta i njihovu slabu dostupnost biljkama. Cu, Li, Ni i Pb su slabo mobilni i veoma stabilni elementi, dok se Zn i B svrstavaju u grupu srednje mobilnih elemenata. Mangan i Sr odlikuje najveša mobilnost i potencijalna dostupnost biljkama. Merenje i analiza akumulacije potencijalno toksičnih elemenata u listovima i kori, efikasnosti fotosinteze i sadrčaja fotosintetičkih pigmenata su pokazale da ispitivane vrste generalno pokazuju malu osetljivost na stresne efekte akumuliranih elemenataali i da postoje razlike specifične za vrstu. Na osnovu analiziranih morfo - fizioloških parametara ispitivanih biljaka, utvrđena je određena gradacija u smislu tolerantnosti na efekte potencijalno toksičnih elemenata: breza > mleč > javor. Imajuši u vidu sve navedeno, jasno je da ispitivane vrste ne mogu biti dobar izbor za bioindikaciju i/ili biomonitoring kvaliteta urbane sredine, izuzev u slučaju Sr gde bi eventualno mogle da se primene kao bioindikatori.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.