Volume 12 [2010]

The dependence of Cd(II) and Cu(II) uptake by yeast cells on the age and temperature of cell culture
was studied. Saccharomyces cerevisiae, Kluyveromyces marxianus and Debaromyces Hansenii
were chosen as typical yeasts, while Cd(II) and Cu(II) as typical metal pollutants. Our results
revealed that higher metal uptake was obtained by cells grown at the optimum temperature (30 oC)
of cell culture. It was also found that the exponential phase cells resulted in a higher metal uptake
than the stationary ones. A first interpretation of relevant bibliographic data concerning the effect of
growth phase on metal uptake is proposed, assuming that limited qualitative changes in the cell wall
structure take place as the cells pass from exponential to stationary phase, in addition to quantitative
modifications, which have been reported in the literature. According to our interpretation the relative
abundance among quantitative and qualitative alterations of cell wall, determines if stationary or
exponential cells attain the higher metal binding capacity. An indication supporting our approach
may be the fact that our hypothesis implies a decrease of pKa values of cell wall carboxyl groups
with the age of cells, which is consistent with data reported by other authors.

Activated carbon (AC) amendment for reduction of contaminant exposure in polluted soils and
sediments has recently emerged as a promising remediation technique. Here, we provide a short
overview of the state-of-the-art in activated carbon (AC) amendment to such sites. Most studies not
only in sediments but also in soils were carried out in the laboratory and only a few in the field.
Consequently, practical experience at the field scale is largely lacking, and feasible engineering
approaches for AC amendment still need to be developed, especially for soils. The effectiveness of the
AC treatment was evaluated by comparison of pollutant concentration reduction in the various
endpoints with those in the unamended control matrix. Endpoints in use comprise pollutant
concentrations in benthic organisms, depletive and non-depletive methods to quantify pollutant
exposures, as well as various toxicity endpoints of plants. Half of the studies in soils and 68% of the
studies in sediments showed reduced pollutant availabilities of >50% after AC amendment. Observed
low reductions (<50%) might be due to low exposure time, insufficient equilibrium time for coke
breeze, biochar, and granulated AC, overload of AC material, different uptake pathways of benthic
organisms, and pollutant reductions outside the dynamic range of toxicity endpoints. Further research
is needed to establish ideal AC amendment conditions to sediments and soils, leading to significantly
reduced pollutant bioavailability.

Through transportation accidents or intentional releases, plastic pellets (small granules 1-5 mm in
diameter) are widely distributed in the ocean all over the world. These pellets accumulate organic
pollutants and can be used for the determination of diffusive seawater pollution. Pellets
demonstrating a certain degree of erosion are expected to have enough contact time with the water
pollutants and thus, reach sorption equilibrium with the water phase. In the present study, eroded
pellets collected from Greek beaches, were separated into polyethylene (PE) and polypropylene
(PP). Polycyclic aromatic hydrocarbons (PAHs, i.e. naphthalene, phenanthrene, and pyrene) were
used as model compounds to study the uptake kinetics into these eroded pellets. Naphthalene
uptake demonstrates similar kinetics in both eroded PE and PP. Phenanthrene and pyrene uptake
demonstrates slower kinetic rates by eroded PE than by virgin PE and similar kinetic rates by eroded
and virgin PP. These observations are then used to evaluate PAHs measurements in pellets
sampled from two sampling sites in Saronikos Gulf. It is concluded that seawater in Loutropyrgos
beach is polluted by PAHs more than seawater in Aegena island. PAH pollution in both sampling
sites is of pyrogenic origin.

In our experimental work the opportunities of improving of mechanical properties of rubbers and their
composites have been investigated. On the one hand the reuse of milling product of recycled
rubbers (recycled crumb rubbers) has been studied and the effects of the filler and compatibilizers
applicable in rubber composites on the mechanical properties either. The rubber composites were
exposed to different mechanical stresses (tensile, fatigue tensile) and Shore A hardness and density
of the specimens have also been determined. Morphology of the composites and the interaction
between the fillers and the rubber has been studied on SEM graphs. Recycled crumb rubber was
added in different concentrations to the basic mixture of rubber. Significant improvement of
mechanical properties could be achieved by mixing 22m/m% used crumb rubber to the basic
mixture. Tensile strength at break of composites containing recycled crumb rubber increased with
nearly 20% compared to the original basic mixture containing no crumb rubber. Density decreased
with 2-3% and Shore A hardness with 6% comparing the aforementioned composites. Different
types of compatibilizing additives have also been applied in the system containing crumb rubber
which showed different effectiveness in case of the properties, e.g. tensile strength at break. Adding
compatibilizing additives to the basic mixture of rubber did not make the density changed while
Shore A hardness changed similarly to the trend observed in case of tensile strength at break.