| Abstract | Urbano geokemijsko istraživanje u gradu Sisku i njegovoj okolici provedeno je da se utvrdi sadržaj potencijalno toksičnih elemenata (PTE-a) As, Ba, Cd, Cr, Co, Cu, Hg, Mo, Ni, Pb, Tl, V i Zn u tlu te procijeni rizik za okoliš i zdravlje ljudi.
Grad Sisak je staro rimsko naselje, s razvijenom prometnom mrežom i teškom industrijom. Smješten je na kvartarnim aluvijalnim siliciklastičnim naslagama rijeka Kupe i Odre, karbonatnim naslagama rijeke Save i praporu. Područje Siska je ravničarsko s visokom razinom podzemnih voda i čestim poplavama. U takvim uvjetima razvila su se hidromorfna tla, a u urbanom dijelu prevladavaju tehnogena tla.
Uzorkovanje tla je napravljeno na dubini od 0 do 10 cm, gustoća uzorkovanja je bila 4 uzorka/km2 u urbanom dijelu i 1 uzorak/km2 u ruralnoj okolici. U urbanom području iskopane su tri pedološke jame, a u poljoprivrednoj okolici dvije. Tlo iz njih je uzorkovano po horizontima. Na uzorcima tla iz pedoloških jama napravljene su pedofizikalne, pedokemijske i mineraloške analize (primjenom rentgenske difrakcije na prahu), određeni su glavni elementi (XRF) i elementi u tragovima (ICP MS). Na njima je napravljena i skevencijalna ekstrakcijaska analiza po BCR metodi za Cr, Cu, Ni, Pb i Zn. U površinskim uzorcima tla određeni su elementi u tragovima (ICP MS). Na svim uzorcima određena je pH vrijednost suspenzije tla s H2O, KCl i CaCl2.
Sadržaj PTE-a u tlu u pedološkim jamama je generalno nizak, a povišene vrijednosti pretežito su utvrđene u površinskim horizontima. Izdvojene geokemijske frakcije Cr, Cu, Ni, Pb i Zn u uzorcima tla iz pedoloških jama imaju slijedeću generalnu distribuciju sadržaja metala po frakcijama: rezidualna (RES) > reduktivna (ORG) ili oksidativna (FEMN) > karbonatna (CARB). Variranje sadržaja metala po frakcijama i po horizontima je uglavnom veliko. Razlike između profila u pedofizikalnim svojstvima, pedokemijskim analizama, sadržaju minerala, oksida i PTE-a te u distribuciji izabranih metala u geokemijskim frakcijama ovise o intenzitetu antropogenih utjecaja na tlo, geogenom porijeklu matičnog materijala i pedogenetskim procesima.
U pedološkim jamama procijenjeni su: (1) rizik otpuštanja metala u okoliš ovisno o pH vrijednosti tla, (2) rizik od zakiseljavanja tla, (3) potencijalni rizik za zdravlje ljudi prema upotrebi i namjeni zemljišta, (4) rizik za okoliš temeljem zbrojene prve tri geokemijske frakcije SEA i (5) rizik za okoliš temeljem samo CARB frakcije. Tlo u pedološkim jamama je pretežito alkalično do neutralno, ima dobar puferni kapacitet i sadržaj PTE-a u njemu nije jako visok te je zbog toga procijenjeni rizik za okoliš i zdravlje ljudi zanemariv ili jako nizak.
Prostorna raspodjela PTE-a u površinskih 10 cm tla prvenstveno je uvjetovana geološkom podlogom i antropogenim utjecajima. U siliciklastičnim naslagama aluvija rijeka Kupe i Odre povećani su sadržaji svih istraživanih PTE-a osim Cd, Hg i Pb. U starom Sisku PTE-i se akumuliraju od antičkog vremena te su povećani sadržaji As, Ba, Cd, Cu, Hg, Mo i Pb, dok je koncentracija ostalih PTE-a oko ili niža od medijana. Sadržaj PTE-a povećan je u industrijskoj zoni iz koje su oni dispergirani vjetrom na okolna naselja i poljoprivredna zemljišta. Uz prometnice mogu biti povišene vrijednosti As, Ba, Cd, Cu, Mo, Pb i Zn. Prema rezultatima faktorske analize izdvojeno je 8 faktora. Geokemijsku sliku Siska i okolice je oblikovalo više geogenih i antropogenih čimbenika: matični materijal rijeka Kupe, Odre i Save i prapor na jugu (FA: 2, 3, 4 i 5), razvijena naselja u antici, posebno talionice i kovnice novca u Rimsko doba (FA: 6 i 8) i razvijena industrija u 20. stoljeću (FA: 1, 4, 6 i 7). Slabiji utjecaj imaju obrtničke radionice i tvornice s kraja 19. st. i prometna mreža regionalnog karaktera (FA: 1 i 7). Značajano je i raspršenje onečišćivala zrakom u naseljima i posebno oko termoelektrane (FA: 1, 2, 4, 6,). U starom Sisku vidljiv je i utjecaj otpadnih voda (FA 8).
Rizik otpuštanja PTE-a u mobilnu fazu tla ovisno o pH vrijednosti i rizik od zakiseljavanja tla su jako nizak jer su tla na istraživanom području dominantno alkalična do neutralna i imaju dobar puferni kapacitet. Potencijalni rizik za zdravlje ljudi za pojedinačne PTE-e i potencijalni kumulativni rizik za sve PTE-e procijenjen je usporedbom sadržaja metala u tlu i njegovih propisanih graničnih vrijednosti u Prijedlogu graničnih vrijednosti sadržaja metala u tlu prema upotrebi i namjeni zemljišta. Rizika za okoliš nema za As, Cd, Co, Cr, Hg, Mo i Tl. Rizik od onečišćenja postoji za Ba, Cu, Ni, Pb, V i Zn na dijelu poljoprivrednih površina, a za Pb uz frekventnije prometnice. Povećani sadržaji PTE-a su u starom Sisku i oko industrijskih postrojenja na jugu koja ugrožavaju okolna naselja Kanak, Caprag, Capraške Poljane i Crnac. Onečišćeno je samo naselje Kanak koje je smješteno između željezare, rafinerije i termoelektrane. Ono je onečišćeno s Ba, Pb i Zn te je kumulativni rizik u njemu najveći u istraživanom području i iznosi 18,61. |
| Abstract (english) | A geochemical investigation of the urban area of the Sisak city and its surroundings was carried out to determine the concentration and spatial distribution of the potentially toxic elements (PTEs) As, Ba, Cd, Cr, Co, Cu, Hg, Mo, Ni, Pb, Tl, V and Zn in the soil and to assess the risk for the environment and human health.
The city of Sisak is old Roman settlement, with developed transport network and heavy industry. The city is located at the quaternary alluvium with siliciclastic deposits of the rivers Kupa and Odra, carbonate deposits of river Sava and loess. Area of Sisak is lowland zone with high level of underground waters, often flooded. The hydromorphic soils are developed in such an area, while technosols prevaile in the urban part of the area.
Composite samples were taken in the topsoil layer from a depth of 0–10 cm with a sampling density of 4 sample/km2 in the urban area and 1 sample/km2 in rural area. Three pedological profiles in the urban area and two profiles in the agricultural surroundings were dug out. The soil horizons along pedological profiles were sampled. The soil samples from the profiles were studied in details using pedophysical, pedochemical and mineralogical analyses (X-ray powder diffraction, XRD), X-Ray Fluorescence for major elements (XRF), Inductively Coupled Plasma Mass Spectroscopy for trace elements (ICP MS) and sequential extraction analyses (SEA) after BCR for Cr, Cu, Ni and Zn determination. The trace elements (ICP MS) were determined in the topsoil samples. Soil pH in the soil suspension with H2O, KCl and CaCl2 was measured in all soil taken samples.
The concentrations of the PTEs in soil horizons from pedological profiles were generally low with some enrichment mainly in the top horizons. Extracted geochemical fractions of Cr, Cu, Ni, Pb and Zn produced the following general distribution of metals in analyzed fractions: residual (RES) > reducible (ORG) or oxidisable (FEMN) > extractable (CARB). Considerable variation in the concentration of metals in the extracted fractions and along the horizons was observed. The differences among pedological profiles in the pedophysical characteristics, pedochemical analyses, content of minerals, oxides and PTEs as well as the distribution of selected metals in geochemical fractions depend on the intensity of anthropogenic influences on soil, geogenic origin of parent material and pedogenetic procesess.
The following risks were assessed in the pedological profils: (1) the risk of metal mobilization in the environment in relation to the pH value of the soil, (2) the risk of soil acidification, (3) pottentially risk and pottentialy cumulative risk for human health according to land use, (4) the risk for the environment based on the sum of the CARB, ORG and FEMN geochemical fraction of SEA and (5) the risk for the environment based only on the CARB fraction. Soils in the pedological profiles were mainly alkaline to neutral in reaction, with a good buffer capacity and the concentration of PTEs was not very high. Therefore, the risk for the environment and human health is considered minor or very low.
Spatial distribution of PTEs at the surface primarily depends on the lithological composition and anthropogenic input. The siliciclastic alluvium of the rivers Kupa and Odra was enriched in all PTEs except Cd, Hg and Pb. In the old part of Sisak PTEs were accumulated from antique time and the concentrations of As, Ba, Cd, Cu, Hg, Mo and Pb were elevated, while the others PTEs were around or below median. Elevated concentrations of PTEs were observed in the industrial zones, from which they were dispersed by wind to the neighboring residential areas and agricultural land. A low increase of As, Ba, Cd, Cu, Mo, Pb and Zn content was registered along the frequent roads. Factor analysis yielded 8 factors. The geochemical pattern of the soils of Sisak city and its surroundings is the result of different geogenic and anthropogenic influences: lithological composition of the rivers Kupa, Odra and Sava and loess at the south of the investigation area (FA: 2, 3, 4 and 5), antique settlements, especially melting plants and mints of coins in Roman time (FA: 6 and 8) and highly developed industry in the 20th century (FA: 1, 4, 6 and 7). The contribution of craft production and factories from the end of the 19th century and regional traffic network (FA: 1 and 7) is less pronounced. Dispersion of contaminants by air in the residential areas and particularly around thermoelectric plant was significant (FA: 1, 2, 4, 6,). In the old part of Sisak influence of waste waters was evident (FA 8).
The risk of mobilization of PTEs in the environment in relation to pH and the risk of soil acidification were very low due to the predominantly alkaline to neutral soil reaction and good buffer capacity. The potential risk for human health of the individual PTE and potentially cumulative risk of all PTEs were assessed based on the comparison of metal concentrations in soil and its prescribed limit values in the Proposal for the limit values of metal concentration in the soil according to land use. There is no risk for human health for As, Cd, Co, Cr, Hg, Mo and Tl in the whole investigation area. A low risk for Ba, Cu, Ni, Pb, V
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and Zn was observed in some agricultural areas and for Pb along more frequent roads. The increased contents of PTEs in the old Sisak and around industrial facilities at south represent a threate for adjacent settlements Kanak, Caprag, Capraške Poljane and Crnac. A considerable contamination with Ba, Pb and Zn was observed in the Kanak area which is located between the steel works, refinery and thermal power plant. The settlement Kanak is contaminated with Ba, Pb and Zn and has the highest cumulative risk (18.61) in the entire investigation area. |
