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The subject of the paper was to determine chromium and cadmium fractions in the soils treated with tannery organic materials. Methods, characteristics of experimental materials and the tested soils were presented in the first part of the paper. After four years of investigations soil samples were collected for the assessment of the total content of chromium and cadmium and their fractions. Results of a sequential chemical extraction confirmed literature data on the weak mobility of this metal in the soil. After application of the studied fertilisers, the share of the most mobile Cr fractions was slight. Iron oxides and residual fractions were most important for chromium accumulation. Cadmium mobility in the soil and its easy uptake by plants is related to a considerable share of mobile forms. A large share of mobile form was noticed in the analysed soils (54.5-68.3%). Exchangeable fraction bound smaller amounts of cadmium (6.8-13.2%). Similar amounts of cadmium were accumulated in the fractions bound to manganese oxides (8.5-19.6%). Organic matter did not contribute to this element binding and the amounts of cadmium stored in this fraction were 2.3-6.6%. Only very small amount of cadmium was accumulated in the form bound with the initial minerals.
The present investigations aimed at determining the effect of various organic materials, i.e. farmyard manure (FYM), organic tannery sludge and compost of such sludge and peat on lead, copper and nickel fractions content in soil. Doses of peat compost and organic sludge were calculated according to the nitrogen amount per a FYM dose. After four years of experiment, fractions of Pb, Cu and Ni compounds were assessed in the soil from individual plots using the Zeien and Brummer's sequence chemical extraction method. Heavy metal contents were determined using a ICP-AES in JY 238 Ultrace apparatus. Lead accumulated mainly in the form bound with organic matter and with amorphic iron oxides. This metal distribution reveals its slight share in the mobile and exchangeable forms. Composts and sludge introduced into the soil did not affect any significant changes of the individual lead forms share as compared to FYM and NPK treated plots and the control. Some amount of copper occurred as mobile forms in all the soils. In the soil of all the treated plots, copper occurred mainly bound with organic matter and amorphic iron oxides. The basic share of nickel was found in the residual fraction bound with internal crystalline nets of initial elements. Beside the residual form, nickel was connected mainly with organic matter.
The paper presents distribution of zinc, manganese and iron in fractions of soil treated with tannery sludge and compost of tannery sludge and peat, and, for the sake of comparison, the soil from a plot treated with farmyard manure (FYM), and mineral fertilisers. Total soil contents of zinc ranged from 38.0 to 47.3 mg kg-1 of soil. The share of mobile zinc forms ranged between 6.05-7.93%. Percentage of the exchangeable form was between 5.8-7.5% of the total Zn contents, while the share of forms bound with organic matter ranged between 10.7 and 12.7%. A considerable part of zinc was bound with manganese and iron oxides. Between 30.14- 43.72% of Zn were found in the residual form. Organic and mineral treatment influenced the share of easily soluble manganese compounds. It ranged between 15.6-19.7%. The least of manganese (1.0-2.0%) occurred in the compounds with crystalline iron oxides. The exchangeable form constituted between 3.4-4.2%, organic fraction accumulated slightly more. Manganese oxides retained the most of the element. Trace amounts of iron were revealed in the first three fractions. The biggest part of this metal was found in sparingly soluble compounds, mainly oxides (over 40%) and on residual fraction (over 30%).
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