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Zn fractionation and availability in different soil aggregate fractions from Isfahan region, Central Iran

ABSTRACT Zinc (Zn) distribution in different soil aggregates can affect Zn availability. In this study, the effect of soil aggregate-size fractions on Zn distribution and availability was determined in some heavy metal-contaminated soils. Air-dried samples were fractionated into four different aggregate-size fractions (2.0–4.0, 0.25–2.0, 0.05–0.25 and <0.05 mm). Extraction efficiency of available Zn determined by using Mehlich-3, DTPA-TEA, Mehlich-1 and H2O methods in different aggregates and relation between extracted Zn and corn indices were studied. Moreover, the Tessier fractionation scheme was applied to determine the partitioning of Zn in different aggregates. Among all the extractants, Mehlich-3 showed better extractability of Zn from soils and the highest amount of extracted Zn was found in the <0.05 (87.65 mg kg−1) and 0.05–0.25 (80.86 mg kg−1) mm fractions. Zn extracted by Mehlich-3 and DTPA-TEA in the <0.05 and 0.05–0.25 mm fractions had significant correlation with the amount of Zn in corn. Also, correlation coefficients between carbonate-bound and Fe–Mn oxide-bound Zn and available Zn in <0.05 and 0.05–0.25 mm aggregates was higher than other aggregates, suggesting that this two fraction of Zn in finer aggregates constituted the major available Zn pools in the studied soils.