2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P76 DISTRIbuTION OF hEAVy METALS IN SOILS
TOMአTóTH, JURAJ ČéRY, Ján TOMáŠ, ALEnA
VOLLMAnnOVá and PETER LAZOR
Department of Chemistry, Faculty of Biotechnology and Food
Sciences, Slovak Univeristy of Agriculture, Tr. A. Hlinku 2,
949 01 Nitra, Slovak Republic,
tomas.toth@uniag.sk
Introduction
The soil quality is derived from its loading by hazardous
substances. The loading of soil occurs when the soil is not
able to lower the negative influences of the heavy metals. The
reference value, which represents natural content of heavy
metals in soil, forms the basis for evaluation of the content of
heavy metals in soil. The important parameters for the input
of heavy metals from soil into plants are: the soil reaction,
the content and the quality of organic matter, the nutrition
of plants, cation exchange and sorption capacity, the microbiological
activity, the oxidation and reduction potential, the
amount and the quality of the clay fraction of soil and the
methods of soil cultivation, etc.
Experimental
The hazardous heavy metals were determined in eight
soil subtypes. Their choice was concentrated on the lowland
regions (Trnovec n/V. – haplic chernozems, Imeľ – eutric
fluvisols, Čičarovce – luvic stagnosols, Dolný Štál – mollic
fluvisols, Veľké Leváre – haplic arenosols, Malanta – haplic
luvisols). We took four parallel soil samples to be able to examine
the soil homogenity of the monitored area. The samples
from the pedological probe were taken from the depth
of 0–0.1 m; 0.20–0.30 m; 0.35–0.45 m. The state of the soil
hygiene was examined by evaluation of the total contents of
Cd, Pb, Cr, Cu and Zn. The total contents were determined after
the mineralization by wet way H 2 SO 4 , HnO 3 and HClO 4
using the method of atomic absorption spectrometry. We also
determined the heavy metals in the pedological probe to be
able to estimate the anthropogenical and geochemical origin
of the heavy metals. The above mentioned heavy metals
were determined in the extract of 2M HnO 3 and in cold. The
mobilizable forms of heavy metals were determined in the
extract with 0.05M EDTA. The mobile heavy metal forms
were determined in extract of 0.01M CaCl 2 .
Results
The valid legislation was used for the evaluation of soil
hygiene. The evaluation is influenced by determination of the
total contents of heavy metals and by the determination of
heavy metals in 2M HnO 3 leach. Contents of heavy metals
in 2M HnO 3 ; 0.05M EDTA and 0.01M CaCl 2 and the percentage
abundance of Zn, Cu, Cr, Pb and Cd in individual
extractants. The following order of extractability for individual
extractants is evident. The results of determination
of actual mobilizable forms are considered to be the most
acceptable. The percentage contents of individual heavy
s493
metals and the total content of heavy metals in highly contaminated
soil are as follows: Zn 1.7–13.9 %; Cu 14.1–62.6 %;
Cr 0.1–1.3 %; Pb 14.6–24.1 %; Cd 12.9–22.8 %. EDTA and
natrium and ammonium of EDTA are able to form stable
and defined complexes with heavy metal cations and they
cause the solubility of carbonates and oxides Fe and Al. The
exctracted contents of heavy metals were measurable during
the use of flame AAS. The mutual interactions of Zn, Cu, Cr,
Pb and Cd with the soil components influence the pH value,
content and quality of organic substances. Apart from the
above mentioned soil properties, there are many other variable
soil properties. The lowest Zn solubility was determined
in subtypes of luvic stagnosols and eutric cambisols with pH
values in the acid part and the quality of mould expressed
by the ratio of humic acids to fluvic acid was the lowest but
on the other hand the percentage of mould has one of the highest
values. The solubility of Cu in 2M HnO 3 and in 0.05M
EDTA was in all soil subtypes the highest and it is especially
valid for haplic arenosols, haplic chernozems, mollic fluvisols
(FL m ). The order of solubility for the determined elements
and and extractants was as follows: 2M HnO 3 > 0.05M
EDTA > 0.01M CaCl 2 .
The lowest amount of Cd and Pb from haplic arenosols
(RM g ) were extracted by extraction with 2M HnO 3 and
0.05M EDTA and the highest amounts of Cd were obtained
from mollic fluvisols, haplic chernozems. The evaluation of
heavy metal contents extracted from individual extractants
at different pH values, the content of mould and its qualitative
composition is not unequivocal and dependence between
variable soil properties and conditions of environment
disappear.
The solubility of Cu in 2M HnO 3 and in 0.05M EDTA
was in all soil subtypes the highest and it is especially valid
for haplic arenosols, haplic chernozems, mollic fluvisols.
The order of solubility for the determined elements and and
extractants was as follows: 2M HnO 3 > 0.05M EDTA > 0.01M
CaCl 2 . We think that the best extractant is 0.05M EDTA with
restriction to Cd, Pb, Cu and partially for Zn. It is not possible
to find an universal extractant for evaulation of heavy metals
mobility in soil.
Conclusions
(i)The extractability for individual ectractans is evident:
2 mol dm –3 HnO 3 : Cu > Cd > Pb > Zn > Cr; 0.05 mol dm –3
EDTA: Cu > Cd > Pb > Zb > Cr; 0,01 moldm –3 CaCl 2 :
Cd > Cu > Pb > Zn > Cr. (ii) It is necessary to emphasize the
differences in solubility between the highly contaminated
eutric cambisols of Stredný Spiš and other analyzed soils.
The different solubility is in all extractants and heavy metals
except the solubility of chromium in 0.05M EDTA and
0.01M CaCl 2 . It is probably connected with the high portion
of heavy metals of immissional origin. The other analyzed
soil subtypes have a low solubility of Zn in HnO 3 and EDTA
in luvic stagnosols.