Agriculture Reference
In-Depth Information
The elements of the fi rst group—Co, Mo, Pb, Cd are characterized by an increased
content in the soil relative to Clarke, which indicates the accumulation of these sub-
stances, but not higher than the MAC level. The coeffi cient of the chemical substance
concentration (Cs) is from 1.61 units Co to 3.42 units Cd. The increased content of
these elements may be due to geochemical characteristics of the parent rock materials.
More numerous second group of elements—Mn, Cr, Sr, As, Ni, Cu, Zn, Mg, Ca,
Fe—shows the defi cit relative to Clarke, its critically low content in the soil, suggest-
ing that there is an element subtraction.
Sample preparation for the determination of chemical elements stationary forms,
associated with the various soil components was performed to obtain the acid extracts
in the microwave decomposition system under pressure Speedwave MWS-2 (made in
Germany BERGHOF Products+Instruments Gmb H), using the individually selected
mode. This process applies extra pure HNO
3
and HCl acids, which additionally under-
went the distillation in the purifi cation system BSB-939-IR.
According to the content, in the form of stationary compounds, bounded with soil
components, elements can be conventionally divided into two groups: calcium, iron,
magnesium, manganese occur in a large amount in the stationary forms (from 64.98
mg/kg—Mn, to 284.90 mg/kg—Ca) and form a small cluster. Other chemical ele-
ments are poor in the soil (0.39 mg/kg—Mo-6.74 mg/kg—Pb) in stationary forms and
form a large group of trace elements.
Mobile element forms were determined by the chemical fractionation. In this
study, after the comparative overview of the most commonly used chemical elements
fractions and extraction agents, the Sposito method appeared to be effective for their
recovery. However, some extraction agents of the method were replaced by those with
similar properties and device-oriented. Furthermore, the oxide fraction, extracted by
the Pampura method, was added to the factions set, offered by Sposito. This fraction-
ation allowed detection of the mobile element compounds in soil samples of 2009-
2011, to determine their chemical fractions and ratio, to conduct a statistical analysis
of samples.
Three fractions (of the total amount of mobile forms) were found to be dominant
for As, Ca, Cd, Co, Mo, Ni, Pb: exchange fraction—26.7 percent (Ni)—29.1 per-
cent (Co), organic—26.6 percent (As)—34.3 percent (Ca) and soluble—18.2 percent
(Ca)—21.8 percent (Co). Elements are bounded with both the various soil components
(mineral components, hydroxides and oxides, colloids) and the organic substance, in
almost equal proportions, form stable complexes with them and play the principal role
in plant nutrition. The water-soluble forms are most mobile, potentially more mobile,
because they are transported by surface and ground waters, are easily involved in bio-
geochemical migration, and are available to plants. In addition, the exchange and the
water-soluble fractions are the reserve of plants nutrition.
Most of the Mg and Sr content in the soil also fall at the organic (28.8 and 28.7%)
and the exchange fraction (22.1 and 26.9%); 17.1 percent of magnesium of the mobile
forms total content is contained in residual compounds. This is a strategic reserve,
bounded with carbonates and bicarbonates Fe, Mn, Al. The manganese proportion in
the organic fraction is 60.6 percent, and only 16.7 percent is in the exchange fraction.
The iron is in the organic—39.1 percent, oxide—28.6 percent, residual fraction—26.2
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