Geochemistry of iron in soils of Vojvodina, Sumadija and Northern Pomoravlje [Serbia, Serbia&Montenegro]

During a large-scale sample collection, a regular orthogonal 10 x 10 km grid has been used to avoid bias in site location. From the set of about 3000 samples from Vojvodina, Sumadija and Northern Pomoravlje (Serbia, Serbia&Montenegro), a selection of samples (from the arable layer 0-25 cm) has been taken to represent the most important soil types. The presented results have shown a wide range of iron contents, from 0.73 to 10.86% Fe. Statistical analysis of the results obtained from 103 samples has shown an average value of 4.06% Fe, with the standard deviation of 1.682 and the coefficient of variation of 41.49%. Iron contents lower than 2.10% have been found in 4.32% of the samples, medium and average values (2.10-4.97% Fe) have been found in 55% of the samples, values higher then the average have been found in 26.3% of the samples and the contents higher than 7.86% have been found in 13.96% of the samples. Arenosols and rigosols developed on aeolian sands have shown the lowest levels of total iron, from 0.73 to 1.82% Fe. On the other side, ranker developed on serpentinite has shown maximum contents, between 8.53 and 10.86% Fe. Soils developed either on loess or Tertiary clay parent rocks (halomorphic soils, some marshy humogleys and vertisols) have shown a wider range of results (1.33-4.65% Fe) with a shift of results towards average values. The majority of the investigated soils that have fallen within the group between 3.00 and 4.96% Fe were represented by pseudogley, eugley, luvisol, fluvisol, eutric cambisol, ranker and redzine. Semigley and chernozem have shown a wider range of distribution of results, from 2.18 to 7.72% Fe. Generally, the analyzed soils have shown lower average results compared with the available literature data. Chemical speciation has shown that an average iron content of 84.24%, with the range from 70 to 92%, was primarily associated with residual forms bound to the silicate lithogenic fraction. An average of 12.69%, with the range from 6 to 26%, has been found as Fe-Mn-oxide/hydroxide fraction. Organic-matter-bound iron (1-9%) and exchangeable and carbonate-bound iron (0.09-1.92%) have been present to a lesser extent.