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Concentrations of Zn2+ in equilibrium with two alkaline soils were calculated from the reactions of EDTA (ethylenediaminetetraacetic acid) chelates. The initial speciation of EDTA was varied to allow equilibrium with Zn2+ concentrations in the soil to be approached from above and below. Fertilizer Zn was added at 0 to 5 mg kg−1 as ZnSO4 and reacted thoroughly with the soil before additions of P or EDTA chelates. Phosphorus was added at 0 or 62 mg kg−1 as a mixture of KH2PO4 and K2HPO4. Concentrations of soluble Zn2+ in unfertilized soil were extremely low, approximately 5 × 10−10 M in the noncalcareous soil at pH 7.2 and 1 × 10−10 M in the calcareous soil at pH 7.6. These Zn2+ concentrations were raised 7‐ to 14‐fold by 5 mg kg−1 of added Zn, and the higher levels persisted for at least 11 weeks. Buffering of Zn2+ by the soils was substantial, ranging from about 15 to 45 (nmol g−1)/(nmol L−1). Additions of P caused small decreases in the concentrations of Zn2+ and other divalent cations in solution. Only in the Zn‐fertilized calcareous soil were the percent decreases in Zn2+ greater than those of the major divalent cations, Ca2+ and Mg2+. This effect of P in the calcareous soil is of special interest because of its apparent selectivity for Zn, but the effect was small as shown by reductions of only 12 to 19% in the [Zn2+]/[Ca2+ + Mg2+] concentration ratio.

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Increasing human activity affects urban ecosystem, including soils. The objective of the study were examine the content of lead, cadmium, copper, zinc, and manganese in soils of city parks and green areas from Bydgoszcz agglomeration, north Poland, estimate their forms and mobility, characterize distribution within soil profile, and estimate their origin – anthropogenic or natural. Three green areas from the older part of the city were selected for the study. Multistep sequential extraction method was conducted for the separation of seven metal fractions. It is concluded that soil studied were contaminated mainly by zinc and lead. These metals exist mainly in relatively non mobile forms i.e. associated with amorphous and crystalline iron oxides and with soil organic matter. The distribution within soil depth varied due to the elution process and variation of mixed soil material and additives.

Purpose The aim of the research was to determine the effect of lithogenic and pedogenic processes on the formation of Luvisols from the area of Vistula glaciation on the base of profile distribution of iron oxides and total iron in relation to texture and physicochemical properties. The indices of weathering of the soil material in genetic horizons were calculated, and changes in the content and forms of iron oxides were evaluated. Materials and methods The predominant type of soil in the study area is Luvisols under agricultural use, formed from silt formations on loam. The analyses were made applying the following methods: grain size composition using the sieve method and hydrometer method, the interpretation of the results was performed according to the World Reference Base for Soil Resources classification, the pH of soils was measured with the potentiometric method, C-organic with the WalkleyBlack dichromate method, the content of the following iron forms was determined (total iron (Fe t ) after the mineralization of soils in the mixture of HF and HClO 4 acids), free iron oxides were extracted using dithionite-citrate-bicarbonate method, and amorphous iron oxides after the ammonium oxalate extraction (using the Philips 9100PU apparatus). The clay mineralogy was estimated by X-ray diffraction analysis. Results and discussion It was observed that total iron enrichment occurs in argic horizons accompanied by iron depletion in luvic horizons, while the profile distribution of iron is similar to the distribution of clay. The (Fe d /Fe t ) ratio indicates a low degree of weathering; the highest values were observed in argic (Bt) horizons, which confirms the effect of the process of pedogenesis on the value of that index. In the soils investigated, crystalline iron oxides generally dominate over the amorphous forms. The mineralogical composition of clay fraction separated from the upper part of soils was different as compared to the underlying material. Conclusions The results of the study showed that iron contents (together with the other indicators) and its forms can be used to distinguish soil layers of different origin. The depth distribution of Fe d , Fe o and Fe t within soil profiles indicates that the soil material may be of different lithogenic origin in the studied pedons.