Volume 10 [2008]

Seasonal variations in ecological parameters exert a profound effect on the distribution and
population density of both animal and plant species (Odum, 1971). The productivity in terms
of planktonic biomass in freshwater bodies is regulated by various physico-chemical factors
viz., temperature, transparency, pH, total hardness, nitrates, phosphates etc. A field study
was conducted (October 2003 and March 2004) to develop a data-base on seasonal changes
of physico-chemical parameters and nutrient load of the river sediment in Ibadan metropolis.
Quantitative samples of sediments were collected during dry and rainy seasons from 11
stations and analyzed for various physico-chemical parameters and nutrient load. All (except
dissolved oxygen) physico-chemical parameters assessed in this study were higher than the
recommended standard (EPA, 2002). The nutrient load of pore water of Ibadan river system
sediments during rainy and dry seasons was found in the range of: phosphate (2.23-16.2 ppm
and 0.35-2.8 ppm respectively); nitrate (0.22 to 0.9 ppm and 0.47-3.3 ppm respectively);
Nitrite (0.2-0.42 ppm and 0.03-0.3 ppm respectively); Total nitrogen (0.13-0.9ppm and 0.47-
3.4 ppm respectively) and sulphate (70-99.4 ppm and 26.6-120 ppm respectively). The levels
of parameters downstream were significantly elevated than the corresponding levels
upstream. This result suggests that the water quality of Ibadan river system is adversely
affected and impaired by the discharge of domestic, agricultural and industrial wastes, which
is the usual practice in Ibadan. The data generated from this study will guide potential
remediation and other management decisions.

As part of an effort to understand the water quality dynamics in the Kouris Dam and the
impact of possible management strategies, the present study assessed the transport process
of atrazine in this reservoir and the effects of bottom and surface withdrawal schemes. The 2-
D laterally averaged CE-QUAL-W2 model was used in this study. It was found that, during the
period of upstream river discharge, significant vertical variations of atrazine concentrations
could be observed in the epilimnion. The maximum concentrations were found at the depth of
5-8m rather than in the surface in this period. This suggests that the widely used assumption
of complete mixing in the epilimnion is not valid for this period in this reservoir. It was also
found that the dynamics of atrazine in the Kouris Dam were noticeably affected by the
withdrawal schemes. Bottom withdrawal would significantly facilitate the transport of
pesticides in this reservoir and therefore result in noticeably higher pesticide concentrations in
deep layers. However, surface withdrawal is not able to lower atrazine concentrations in the
epilimnion in this reservoir possibly due to the decreased mixing depth corresponding to the
surface withdrawal, although more atrazine would be removed from the reservoir by the
surface withdrawal. These results suggest that it is sensible to integrate withdrawal schemes
into reservoir management system to achieve different water quality objectives under various
scenarios.

ABSTRACT
Pollution from metals and metalloids of the environment of Greece seemed to attract many
researchers and elemental pollutants in air, soil and water have been determined and studied
systematically during the last decade. The most recent of these studies, concerning the last
five years (2003 to 2008), were reviewed and the major problems of the occurrence of heavy
metals in the country’s environment were pointed out.
Regarding the atmospheric environment, the chemical characterization of particulate matter of
the big Greek cities attracted the interest of many authors. Heavy metals and As represented
an important fraction of the particulate matter of the atmosphere of Greek cities, with
increased content in inhalable fraction.
In addition, many works studied the metal content of soil and plants of the Athenian forests,
among with agricultural soils from the countryside. Copper, Fe and Cd were identified as the
most accumulated metals that may pose a long-term threat to soil and aquatic environment.
Most of the reviewed articles concerned the aquatic environment. Rivers and coastal
environment of northern Greece presented increased levels of metals and arsenic, reflecting
the transboundary and local agricultural and industrial activities. Marine environment nearby
the big cities was found reasonably polluted.
Therefore the presented results reflected the human activities: urban areas were reasonably
found more polluted (however without severe exceedence of the regulated values), compared
with the less populated regions. On the contrary, drinking water of the urban populated areas,
due to proper treatment, conformed to the regulated values.

The present work concerns the investigation of the chemical kinetics of H2S selective
oxidation into elemental sulfur, by gas absorption and chemical reaction in Fe3+·(ΝΤΑ)
aqueous solutions. By using initial reactivity data, priority is given to the study of intrinsic
kinetics i.e. to avoid interactions with ligand degradation and the presence of sulfur. A wetted
wall gas-liquid reactor was employed under a batch-recycle regime. The conversion of Fe3+ to
Fe2+ chelate was determined over the pH range ca. 3–6, temperature range ca. 30–60°C and
a short overall per run contact time of phases. The penetration theory was used for the
evaluation of intrinsic reaction rate constant and enhancement factor. Activation energy
values determined from the pertinent Arrhenius plots fall in the range, Εa=17.2– 22.8 kcal
mol-1. These values compare satisfactorily with the value Εa=24 kcal mol-1 obtained from a
similar kinetic study performed in a bubble column reactor and indicates a chemical reaction
control of the overall gas absorption phenomenon. Enhancement factors varied in the
respective ranges Ε =2.7–7.5 (pH=3), E=3.2–14.1 (pH=4), E=5.9–17.0 (pH=5), και Ε=6.7–
20.1 (pH=6) indicating a substantial increase of the mass transfer coefficient due to chemical
reaction. For the experimental conditions applied in this study the following kinetic correlation
was validated: