2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
In real water systems, several other ions are present,
which can compete with metals measured by DGT. The Ca
and Mg are dominant cations in hard waters. Although the
stability constant for magnesium is lower than for Cd, Cu,
ni and Pb, magnesium can affect DGT measured metals concentrations.
Uptake of Cd, Cu, ni and Pb was not influenced
by magnesium nitrate in the whole concentration range up tu
0.05 mol dm –3 . new discs can be also used in high salinity
waters.
Fig. 3. Ifluence of HA concentration c hA on the normalized values
of the apparent diffusion coefficients (D APP /D TAb ) for Spheron-Oxin
® resin gel (pH ~ 7). ▲Cd, ●Cu, □Ni, ■Pb
In natural waters, variety of ligands occurs that can affect
concentration measured by DGT technique. Iminodiacetic
acid (IDA) was used as a model strong ligand influencing
the uptake of metals. The results of deployment of DGT
units, packed with Spheron-Oxin ® and Chelex 100 resin gels,
in ni solutions containing IDA in the concentration range of
0–0.1 mol dm –3 are shown in Fig. 2.
Diffusion coefficients (D) can be calculated when taking
into account diffusion area (3.14 cm 2 ) and thickness of the
diffusive layer. Those diffusion coefficients can be considered
as apparent diffusion coefficients (D APP ) of the metal under
specific conditions. Their values represent the metal fluxes
per unit deployment time, unit diffusion area, unit metal concentration
in the external solution and unit thickness of the
diffusive gel layer. The difference between both curves relates
to stability constants of both funcional groups. This difference
can be employed in speciation measurements.
Humic acids (HA) are the most widespread natural complexing
ligands. Influence of the concentration of the humic
substance on the D APP is shown in Fig. 3., in which elementspecific
effect of HA can be observed. Similar results were
also obtained in Refs. 3,4 , in which Chelex 100 and Spheron-
Thiol ® resin gels were used. Due to competitive reactions,
s374
Fig. 4. Influence of carbonate concentration on distribution coefficient
of uranium for ■ Spheron-Oxin ® , ▲ Spheron-Salicyl ® ,
and ● Chelex 100 sorbents (pH ~ 6.7)
the complex formation with HA decreases the concentration
of metal species in external solution that can be measured by
DGT.
Uranium, analogously to other heavy metals, forms various
complexes in natural waters with a variety of ligands.
Depending on pH of the solution, uranyl ions are bound in
stable hydroxocomplexes and, especially carbonate complexes
due to dissolved atmospheric CO 2 . Influence of equilibrium
carbonate concentration on distribution coefficient (D g)
of uranium is shown in Fig. 4. It is evident that the resin gel
based on Spheron-Oxin ® appears to be a new useful resin gel
for speciation analysis of uranium in natural waters.
Conclusions
The new resin gel based on Spheron-Oxin® with anchored
5-sulphophenyl-azo-8-hydroxychinoline functional
groups exhibits very strong afinity to Cd, Cu, ni, Pb and U.
In addition to conventional Chelex 100 based gels it can be
applied in DGT technique and provide more information on
heavy metals speciation, especially of uranium in aquatic
systems.
Acknowledgement: This work was performed and supported
within the Institutional research plan AV0Z40310501.
REFEREnCES
1. Dawison W., Zhang H.: nature 367, 546 (1994).
2. Slovák Z.: Bulletin of n.p.Lachema Brno, 1979, 30 p.
3. Dočekal B., řezáčová-Smetková V., Dočekalová H.:
Chem. Pap. 59, 298 (2005).
4. Trávníčková J.: Diploma Thesis. Brno University of
Technology, Brno, Czech Republic, 2008.