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The transport of volatile organic contaminant (VOC) mixtures in the unsaturated zone is
typically controlled by a combination of transport (i.e., advection, dispersion, and diffusion)
phenomena, phase change (i.e., volatilization, dissolution) and reaction processes (i.e.,
sorption, biodegradation). As revealed from field and laboratory studies, biodegradation is
probably the most important attenuation mechanism of VOCs in the unsaturated zone since it
transforms organic contaminants to harmless products. However, in field applications, it is
usually difficult, time consuming, or expensive to distinguish and quantify biodegradation
among the different natural phenomena and processes, such as diffusion, dispersion,
volatilization and sorption, without the aid of numerical modeling.
Recent experimental studies showed large variations in space and time in the 13C/12C ratio for
many organic compounds and suggested the possibility of using carbon isotope fractionation
as a tool to assess biodegradation of organic contaminants in the unsaturated zone. The
processes that were indicated to likely have the largest effect on the observed isotope ratio
variations are (i) diffusion, which results in molecules with lighter isotopes to diffuse slightly
faster than molecules with heavier isotopes, and (ii) biodegradation as a consequence of a
preferential breakdown of the chemical bonds of the lighter isotopes.
This study used numerical modeling of VOC mixture transport in the unsaturated zone to
quantify the contribution of diffusion and biodegradation to carbon isotope fractionation of
individual compounds, and to evaluate the use of 13C/12C ratio as a possible tool to assess
biodegradation of organic contaminants. The numerical model incorporated transport of
carbon isotope fractions of selected organic compounds and used data from a controlled fuel
source emplacement field experiment and parameters from laboratory-scale studies. Costeffective
modelling of the transport and fate of volatile organic contaminant mixtures was
realized with the use of the recently developed constituent averaging technique [1]. Results
indicated that (i) both diffusion and biodegradation lead to enrichment in 13C compared to the
initial isotope ratio in locations within and close to the contaminant source, (ii) biodegradation
lead to enrichment in 13C while diffusion resulted in smaller 13C/12C ratio in locations further
away from the source, and (iii) the above effect of both processes on the isotope ratio was
increased as a function of time. Modelling results showed that the use of carbon isotope
fractionation at the field represents a promising tool for assessing and possibly quantifying biodegradation of organic contaminants in the unsaturated zone.

The Olympic Rowing and Canoeing Center constructed at Schinias, accommodated the
rowing and canoe – kayak sprint competition of the 2004 summer Olympic Games. This
paper presents the results of a study which aimed at assessing the water quality
characteristics, regarding microbial pollution, of the Olympic rowing and canoeing Center in
relation to alternative inflows scenarios. The study was conducted by using a microbial –
pollution model which describes both physical transport phenomena and biological and
chemical reactions taking place in the water body. Moreover, the mathematical model
incorporates a stochastic approach (based on Monte Carlo technique) in order to take into
account the random variation of the input variables, such as the pollution loads and the
intensity of the solar radiation, which is an essential factor for the fate of faecal coliforms.
The mathematical model takes into consideration the random fluctuation of the constants and
the model’s input data, by creating a range of possible values for each one of them and a
corresponding probability distribution. As a result of this kind of stochastic approach, the
model predicts the concentration of faecal coliforms, not as a single value, but as a set of
possible values. A statistical analysis of this set of values, allows for the estimation of
statistical data like characteristic values that will not be exceeded for given confidence levels.
The mathematical model was applied for a wide range of the monthly inflows entering the
rowing center through the leading channel, which fully cover the discharges of Makaria spring
for three alternative typical hydrologic years (a particularly wet, a particularly dry and a mean
hydrological year).
From the application of the model for several flow patterns into the course it was concluded
that the flow pattern does not affect significantly the spatial and temporal distribution of the
concentration of the faecal coliforms, since dispersion is the governing transport mechanism
in the rowing course. The highest concentrations are observed in an area close to the inlet
point of the leading channel, while in areas located in a longer distance the concentrations are
decreasing.
According to the results of the model the anticipated concentration of faecal coliforms, in
relation to the proposed revision of the 76/160 European Directive on bathing waters, is lower
than 250FC/100ml for the 95% of the samples and thus the rowing and canoeing center is
sorted in the category of excellent quality waters.

The objective of this study was set on three goals: (i) Chemical and radiological
characterization and leaching properties of the mixture of fly and bottom ash, (ii)
Chemical, radiological and mineralogical characterization of the Kastela Bay sediments,
and (iii) Estimation of the influence of TENORM deposition on the quality of sediments.
Samples of the mixture of fly and bottom ash, sediment cores ranging from 0 to 55 cm
and surface sediment samples were analyzed. Enrichment with heavy metals in the
mixture of fly and bottom ash ranged from 1.6 to 36 times while 226Ra and 238U were up to
50 times enriched. Most of the measured heavy metals in the ash were 3-4 times those in
the surrounding soil. It was found that over 37% of the total U could be removed from the
ash by the sea water. The highest enrichment in sediment cores was found for Zn (35.6
times), Pb (16 times), Cr (9.1 times) and Ni (4 times). The highest concentrations of total
uranium were determined at positions in the vicinity of the ash deposit site. Maximum
concentrations of heavy metals were found in deeper sediment segments deposited in
the period of the highest industrial production.

Sea eutrophication is a natural process, however in many cases is considered one of
the major forms of water pollution affecting coastal areas, lakes and reservoirs all over
the world. Many methodologies have been developed for assessing eutrophication and
during the last decades, the contribution of remote sensing techniques has been proved
very useful in this research area. Satellite data from various sensors have been
processed and analysed by research groups all over the world for estimating chlorophyll
a concentrations and consequently, eutrophication conditions in the marine
environment. Further analysis of the spatial structure of the eutrophication phenomenon
that includes detection of the degree of homogeneity and of the directions of maximum /
minimum anisotropy is of great interest as well.
In this study, an attempt was carried out for estimating the anisotropy in chlorophyll a
spatial distributions produced by the process of satellite data. The North Aegean Sea
was used as the case study area and SeaWiFS monthly satellite data acquired for
February, May, July and September 2003 were analysed. As a result, four
eutrophication maps illustrating the eutrophication levels in the North Aegean Sea were
developed and further analysis of their spatial structure was carried out using
variograms. Semi- and surface variograms were developed and the directions of
minimum / maximum anisotropy as well as the degree of spatial correlation of the
eutrophication phenomenon were assessed.