Issue 2

Instrumental data time series show an average global warming of approximately 0.90C over
the last century. Eastern Mediterranean air temperature follows the northern hemisphere (NH)
secular trend till 1970s, while the NH warming of the last 30 years is not noticeable in the
eastern Mediterranean till 1990s. National Observatory of Athens (NOA) meteorological time
series start from the last decades of the 19th Century, therefore are at first suitable for
detection of long term trends in the region. In this study we investigate whether the abrupt
increase of the NOA air temperature time series, which appears during the last few years, is
the finger-print of the broader scale climatic change or it is a discontinuity in the record of
urban effect or of station’s problems origin. It is shown that NOA air temperature records
display a statistically significant discontinuity attributable to change of the station thermometers
on 1995 and therefore NOA records must be treated with caution for long term air temperature
trends detection.

Photocatalysis by titanium dioxide (TiO2) is a water treatment method. Pseudomonas
aeruginosa is a microorganism resistant to chlorine and UV-C irradiation. TiO2 photocatalytic
technology can destroy bacteria, which are resistant to oxidative destruction of cell membrane
caused by sole UV irradiation. This study aims to investigate the total mineralization of the
bacterium (P. aeruginosa) to the extent of death and cell-mass destruction using TiO2
photocatalytic oxidation process. In this work the effects of parameters such as amount of
TiO2, irradiation time, initial concentration of bacterium, presence of ascorbic acid and effect
of cell wall on removal of P. aeruginosa were studied. The data, which were obtained in this
study, showed that the optimum concentration of TiO2 was 325 ppm. Also at the initial
concentration of TiO2 equal to 325 ppm and initial microorganism MPN / 100 ml equal to 300
and after 75 min UV irradiation time, P. aeruginosa removal efficiency was 94.3 %. Removal
efficiency of P. aeruginosa in the absence of TiO2 or UV irradiation was very low. Decreasing
the concentration of microorganisms increased its removal efficiency. Removal efficiency of
spheroplast cells was more than intact cells of P. aeruginosa, which shows the important role
of cell wall on cell resistance against chemical agents. Ascorbic acid had inhibitory effect on
this process.

The present study focuses on the exploitation of sweet sorghum biomass as a source for
hydrogen in continuous and batch systems. Sweet sorghum is an annual C4 plant of tropical
origin, well-adapted to sub-tropical and temperate regions and highly productive in biomass.
Sweet sorghum biomass is rich in readily fermentable sugars and thus it can be considered
as an excellent raw material for fermentative hydrogen production. Extraction of free sugars
from the sorghum stalks was achieved using water at 30°C. After the extraction process, a
liquid fraction (sorghum extract), rich in sucrose, and a solid fraction (sorghum cellulosichemicellulosic
residues), containing the cellulose and hemicelluloses, were obtained.
Hydrogen production from sorghum extract was investigated using mixed acidogenic
microbial cultures, coming from the indigenous sorghum microflora and Ruminococcus albus,
an important, fibrolytic bacterium of the rumen. Hydrogen productivity of sorghum residues
was assessed as well, using R. albus.
The highest hydrogen yield obtained from sorghum extract fermented with mixed microbial
cultures in continuous system was 0.86 mol hydrogen per mol of glucose consumed, at a
hydraulic retention time of 12 hours. This corresponded to a hydrogen productivity of 10.4 l
hydrogen per kg of sorghum biomass and was comparable with those obtained from batch
experiments. On the other hand, the hydrogen yield obtained from sorghum extract treated
with R. albus was as high as 2.1-2.6 mol hydrogen per mol of glucose consumed. Hydrogen
productivity of sorghum residues fermented with R. albus reached 2.6 mol hydrogen per mol
of glucose consumed. In total, the productivity of sorghum biomass (that of sorghum extract
plus that of sorghum residues) could be 60 l hydrogen per kg of sorghum biomass if R. albus
is used.

The direct assessment of denitrification suffers from a number of problems. A mass balance
model is simple and widely accepted to calculate nitrogen (N) loss as a denitrification
component. The objective of study was to estimate the potential N loss a denitrification from a
tropical paddy in the central region of Thailand. N inputs to and outputs from field were
measured by direct method. Inputs of N to the site were commercial fertilizer, precipitation,
irrigation water, seeds and pre-cultivation soils. Outputs of nitrogen from the site were leaching
to groundwater, harvested crops, loads in surface runoff, post harvest soils and loss from the
field as denitrification. Biological N fixation, groundwater contribution, ammonium volatilization
and contribution to weed growth were ignored. Based on the three month observation, the total
amount of N load in irrigation, precipitation, fertilizer, drainage, percolation and plant uptake
were 9.22, 10.85, 100, 4.65, 18.20 and 80.57 kg ha-1 respectively. The difference of total N in
the soil before and after cultivation was not significant and taken as constant value. Sum of N
loss calculated as denitrification component from the nitrogen mass balance model was 16.7 kg
ha-1 and rate of loss was 0.19 kg ha-1 d-1. It means that the contribution of applied N fertilizer to
the atmosphere was 13.6% of total N input; indicating one of the major source pollutants.