Three-step extraction of heavy metals in agricultural soilslon

Osnovna agrokemijska svojstva, te 4 različite frakcije (modificiranom trostupanjskom BCR metodom) i ukupna koncentracija teških metala (Fe, Mn, Zn, Cr, Ni, Cu, Pb i Cd) analiziarni su u 22 uzorka 4 različite grupe tala: urbani vrtovi, oranice, kalcizirano oranično tlo, te tlo kontaminirano kadmijem. Cilj je bio utvrditi koncentraciju ukupnih teških metala i različitih frakcija, te usporediti frakcije u različitim tlima. U analiziranim tlima utvrđen je najveći ukupni sadržaj Fe, zatim Mn, Zn, Cr, Cu, Ni, Pb i Cd. U prvoj frakciji odnosi se značajno razlikuju od odnosa ukupnih količina. Oksidirajuće i rezidualne frakcije u jednakom su slijedu kao i ukupne koncentracije, dok su u reducirajućoj frakciji izuzetak Pb i Cr. Udio ispitivanih metala mijenja se po frakcijama. U izmjenjivoj je najveći udio Cd, a najmanji Fe, dok je u rezidualnoj obrnuto. S obzirom na pH reakciju, utvrđeno je da su u kiselim tlima veći udjeli izmjenjivih prvih frakcija Cu, Fe i Pb, a manji udjeli Zn, Mn, Cr i Ni nego u alkalnim tlima. Povećanje humoznosti smanjuje udio izmjenjive, a povećava udio reducirajuće i oksidirajuće frakcije Pb. Humoznost značajno utječe i na odnose frakcija Ni i Zn. Regresijskim jednadžbama moguće je predvidjeti frakcije na temelju ukupne koncentracije, kiselosti i humoznosti tla. Odnosi frakcija teških metala mogu biti u tri osnovna redoslijeda, najkarakterističnijih za Cr (4-3-2-1), Fe (4-2-3-1) i Pb (2-4-3-1). Cu, Ni i Zn sličniji su po odnosu frakcija Fe i Cr, a Mn i Cd sličniji su frakcijama Pb. Utjecaj kalcizacije na koncentracije analiziranih teških metala je značajan, jer smanjuje prosječne koncentracije izmjenjive prve frakcije Fe, Zn, Cu, Ni, Pb, Cd.The 22 soil smples from Osijek-baranja and Vukovar-srijem counties were analysed. Basic agrochemical soil properties and 4 fractions of heavy metals were analysed. The total heavy metal content (Fe, Mn, Zn, Cr, Ni, Cu, Pb i Cd) was determined by summarizing all 4 extracted fractionc. There were 2 basic groups of soils: urban garden, (9 samples) and arable land used as gardens (6 samples). Also, limed arable land and contaminated soil were analysed. The aim of research was to determine total heavy metals concentrations, as well as different metals’ fractions, and the impact of pH and organic matter. Soil samples were analysed using BCR three-step extraction of heavy metals. The highest total content of Fe was determined, followed by Mn, Zn, Cr, Cu, Ni, Pb and Cd. The sequence of the first fraction differ significantly from the total contents. Oxidizing and residual fractions was in the same sequence as total concentration, while in the reducing fraction exceptions were Pb and Cr. Share of metals changes by fractions. Cd was the largest share in removable fraction, Fe the lowest, while residual fraction was vice versa. Given the pH reaction, it was found that in acidic soils was higher proportions of exchangeable first fraction of Cu, Fe and Pb, and a smaller of Zn, Mn, Cr and Ni than in alkaline soils. Increasing humus content decreases exchangeable share, and increases the share of the reducing and oxidizing Pb fractions. Humosity significantly affects fraction of Ni and Zn. The fraction can be predicted by regression equations based on total concentration, acidity and humus content of the soil. Relationships fraction of heavy metals may be in three main sequence, the most characteristic of Cr (4-3-2-1), Fe (4-2-3-1) and Pb (2-4-3-1). Cu, Ni and Zn are more similar to Fe and Cr, Mn and Cd to Pb. Effect of liming on the concentration of the analyzed heavy metals is significant, because it reduces the average concentration of exchangeable first fraction Fe, Zn, Cu, Ni, Pb, Cd