Volume 10 - 2008

Heterogeneous Catalysis and Electrocatalysis can be used very effectively on air pollution
control. Air emissions coming either from mobile sources or from stationary sources, including
volatile organic emissions, nitrogen oxides, hydrocarbons and carbon monoxide could be well
converted to harmless non-pollutants at reasonable temperatures with cost-effective systems
utilizing heterogeneous catalysis and suitable catalysts. Some of the disadvantages of
conventional heterogeneous catalysts are the high production cost (since most of them are
metal supported catalysts), the short life time (due to the catalyst deactivation) and the
weakness to control their activity during the catalytic process. A new phenomenon of Solid
State Electrochemistry called Electrochemical Promotion of Catalysis (EPOC) combined with
classical heterogeneous catalysis could be applied in order to overcome some of the above
problems.
In this paper we are trying to show with characteristic examples how EPOC could be useful in
environmentally important reactions (oxidations, reductions, etc). The results show that EPOC
reveals great perspectives in environmental issues and especially in gas emissions treatment
technology. The utilization of EPOC could be really useful since we can increase the catalytic
activity, alter the selectivity to the desirable products and simultaneous control the reaction
rate during a given electrocatalytic process.

A bench-scale biofiltration system was developed to evaluate the NOx removal efficiency
under high oxygen concentration. The system had been running for 120 days and kept on a
steady NOx removal rate above 80%. A stable NOx removal with an efficiency of more than
80% from the gas phase can be obtained by the bioreactor concept, when flue gas containing
NO (400-600 ppmv) and a certain O2 concentration (0-20%). In the blank experiment, less than
35% NO was removed as oxygen increased. The tendency of the three curves about NO
removal rate with various O2 concentrations was mainly similar but some differences in the
highest and lowest removal rate happened in the definite O2 concentration range. Oxygen was
shown to have a significant effect on NOx removal at the first two or three days when oxygen
concentration increased sharply. The higher concentration NO influent gas contained, the
longer time the microflora need to regain activities. Compared with humidifier, microbial
regenerator which was incorporated in biofilter can improve aerobic denitrifying bacteria
activity by applying alternating oxic–anoxic conditions in the presence of nitrate and nitrite.
Oxidation-Reduction Potential (ORP) and Dissolved Oxygen (DO) were used to control the
dose of carbon source.

The aim of this study is to estimate future potential changes in duration of extreme dry and
wet spells and rainfall intensity in Eastern Mediterranean. For this purpose, daily
precipitation amounts, deriving from the regional climate model of UK Hadley Centre
HadRM3P have been used for the present (1960-1990) and the future period 2070-2100 on
0.44° x 0.44° latitude by longitude grid. Future data are based on B2 IPCC emission
scenario.
For the identification of precipitation extremes three climatic indices were employed: a)
CWD (Maximum number of consecutive wet days), b) CDD (Maximum number of
consecutive dry days) and c) SDII (quotient of precipitation amount of wet days and the
number of wet days of the period). They were calculated for the present and future period,
on a seasonal and annual basis.
A general future tendency was found towards drier Eastern Mediterranean, with reduced
rainfall intensity. Longer dry spells are expected in all seasons, except autumn, with the
largest increase in the southern part of the area. Extreme wet spells will shorten everywhere
during all seasons, except autumn. Precipitation intensity was found reduced for all seasons
and mostly for summer in South Aegean Sea.

In this study, the variability and trends of the mean annual and seasonal surface air
temperature in Greek peninsula are examined. The climatic data used, concern mean monthly
values of air temperature of 20 meteorological stations of the Hellenic Meteorological Service,
for the period 1951-2000.
The air temperature time series for each station are analyzed, so that the variability and
trends be described. Regarding the annual time series, a cooling trend is observed since the
early 1960’s till the middle of the decade of 1970, when the trend reverses to heating till
nowadays. It is remarkable that the today air temperature levels do not exceed the levels of
the middle of the century. During the winter, it is crystal clear that a cooling trend exists from
the middle of the decade of 1950 to the end of the decade of 1980, especially in the south
region of the country. Afterwards an increasing trend is obvious till nowadays. The pattern in
spring appears a slight heating trend in the northern region of Greece and a cooling trend in
the south. The summer time series are similar to the annual ones, so the contribution of
summer to annual variability is unquestionable. Generally speaking, the air temperature in
autumn follows the same distribution in time.
In the process, the Factor Analysis is applied on the mean annual and seasonal air
temperature and thereafter the regions, within the air temperature covariates, are defined.
Finally, the application of spectral analysis to annual and seasonal air temperature is
regarded necessary so that the periodicities are derived.