Holistic approach to geochemistry of solid inorganic particles in urban environment

Biogeokemično kroženje elementov je v urbanih okoljih zaradi velikega števila prebivalcev in njihovih različnih dejavnosti precej drugačno kot v naravnih. Zaradi kompleksnosti urbanih okolij, je pri geokemičnih raziskavah treba uporabiti celosten pristop. To pomeni, da s kombinacijo različnih metod preučujemo vsebnosti in pojavljanje potencialno strupenih elementov (PSE) v več urbanih materialih. V okviru doktorske disertacije smo na urbanem območju Maribora raziskovali tla, podstrešni, stanovanjski in cestni prah ter trdne delce nakopičene v snegu in delce v zraku. Opredelili smo lastnosti obravnavanih materialov in geokemične značilnosti Maribora ter vpeljali analizo trdnih delcev v zraku s SEM/EDS. Prevladujoč mineral v tleh je kremen (geogen vpliv), v cestnem prahu dolomit (zimsko posipanje cest) in v podstrešnem prahu sadra, ki je najverjetneje sekundarnega nastanka. Analiza vsebnosti 65 elementov v tleh in vseh treh tipih prahov je pokazala, da se ti materiali po kemični sestavi medsebojno močno razlikujejo. Prevladujoč antropogen izvor smo v vseh materialih, z izjemo stanovanjskega prahu, pripisali Cd, Cu, Pb, Sb, Sn in Zn. Dodatno so v posameznih materialih pretežno antropogenega izvora še nekateri drugi PSE. Na dveh industrijskih območjih (Melje in Tezno) so vsebnosti PSE običajno najvišje, zato predvidevamo, da so večinoma posledica pretekle in sedanje kovinske industrije. V primerjavi s tlemi, so vsebnosti PSE višje v prahovih, kar je deloma posledica razlik v njihovem nastanku in v fizikalno-kemičnih lastnostih, vpliva antropogenih virov ter različnega zadrževalnega časa materialov. Podstrešni prah odraža zgodovinske vplive, cestni prah predvsem današnje vplive industrije in prometa ter stanovanjski prah vplive znotraj stanovanj. Z analizo prahov in delcev v snegu ter zraku s SEM/EDS smo ugotovili, da izmed delcev s PSE v vseh materialih prevladujejo oglati Fe-oksidi. Samo na industrijskem območju Melje se pojavljajo Cu-Zn ostružki, ki najverjetneje izvirajo iz livarne in Fe-Cr (Cu, Mn, Ni) ostružki, najverjetneje iz tovarne kovinskega pohištva ter livarne. Za Tezno so značilni predvsem visoki deleži Fe-oksidov in kroglastih Fe-oksidov, pogosto z nizkimi vsebnostmi Mn in drugih PSE. Glede na rezultate, kemična sestava stanovanjskega prahu odraža predvsem vire znotraj stanovanj in manj zunanje vplive. Izmed notranjih virov smo najbolj jasno prepoznali uporabo vžigalnikov v stanovanjih v katerih stanovalci kadijo, kar se odraža v visokih vsebnostih Ce, Fe in La ter pojavljanju Fe-Ce-La-O kroglic. Biodostopni deleži (BAF) PSE se močno razlikujejo med različnimi elementi, vzorci in materiali. V tleh, cestnem in podstrešnem prahu so večinoma večji v želodčni fazi kot v želodčno-črevesni. Za stanovanjski prah velja obratno. Med najbolj biodostopnimi PSE v želodčni fazi so Cd, Cu, Pb in Zn, katerih povprečni BAF je pogosto nad 40 %, ter v želodčno-črevesni As, Cd, Cu in Ni.Biogeochemical cycling of elements in urban environments differs significantly from natural environments due to high population density and various anthropogenic activities. Because of the complexity of urban environments, a holistic approach to geochemical studies is needed, meaning that contents and occurrences of potentially toxic elements (PTE) in several urban materials are studied by combination of various methods. Soil, attic, household and street dust and solid particles deposited in snow and airborne particles from urban environment of Maribor were studied in presented doctoral dissertation. Characteristics of urban materials and geochemical properties of Maribor were determined. SEM/EDS analyses of airborne particulate matter were successfully introduced to urban geochemical studies. The main mineral in soil is quartz (geogenic origin), in street dust dolomite (winter road gritting) and in attic dust gypsum, which is probably of secondary origin. Determination of 65 element contents in soil and all three dust types revealed that their chemical composition differs significantly. Cadmium, Cu, Pb, Sb, Sn and Zn are predominantly of anthropogenic origin in all studied materials, except in household dust. Additionally, some other PTE in various materials are also of anthropogenic origin. PTE contents are usually highest in industrial zones Melje and Tezno, therefore we assume that they originate from past and present industrial activities. PTE contents are higher in dusts in comparison to soil due to their different origins, differences in physico-chemical properties, anthropogenic influences and different retention times. Attic dust reflects historical influences, street dust reflects mainly influences of present industry and traffic, and household dust influences from the interior of homes. SEM/EDS analysis of PTE-bearing particles in dusts, particles deposited in snow and airborne solid particles showed that angular Fe-oxides predominate in all materials. Cu-Zn and Fe-Cr (Cu, Mn, Ni) shavings are typical for industrial zone Melje. The first particle type probably originates from foundry and the second type from metal furniture factory and foundry. High shares of Fe-oxides and spherical Fe-oxides, often with Mn and other PTE, are typical for industrial zone Tezno. According to the results of presented study, chemical composition of household dust reflects mostly indoor sources and less outdoor influences. Influence of lighter-usage in apartments in which inhabitants smoke was identified. It is reflected in high contents of Ce, Fe and La and occurrence of Fe-Ce-La-O spheres. Bioaccessible fractions (BAF) of PTE differs significantly between different elements, samples and materials. They are mainly higher in stomach than in stomach-intestine phase for soil, street and attic dust. The opposite is true for household dust. The most bioaccessible PTE in stomach phase are Cd, Cu, Pb and Zn, of which the average BAF is often higher than 40 %. The highest BAF in stomach-intestine phase has As, Cd, Cu and Ni