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The soil adsorption behaviour of atrazine and its photodegradation intermediate 4,6-diamino-2-chloro-1,3,5-
s-triazine (I), was evaluated by measuring partition coefficients on five representative European topsoils using
classical batch experiments. From this study, (I) appears to be less immobilised than atrazine itself, especially
for typical agricultural soils. Consequently, (I) has a higher tendency to reach the saturated zones, and
hence, the groundwater. In order to remove atrazine and its degradation products from groundwater prior
to making it drinkable, photocatalytic degradation onto membranes immobilizing 30±3 wt.% TiO2 has been
investigated as a possible technology to mineralize these waters satisfactorily. For this purpose, experiments
have been carried out using a pilot-plant facility, with 0.02 - 0.10 mmol L-1 solutions of atrazine, as well as
of compound (I) and of 2,4,6-trihydroxy-1,3,5-s-triazine (II). When employing an excess of hydrogen peroxide
as the oxidizing agent, the monitoring of chemical oxygen demand (COD), as well as control by HPLC,
showed that (II) was a photostable degradation product, owing to its resistance to attack by hydroxyl radicals.
On the other hand, when kinetic runs were carried out onto membranes in the presence of dissolved
oxygen only or of sub-stoichiometric quantities of H2O2, (II) could be quantitatively mineralized. A mechanism
has been proposed, based on the possible direct involvement of holes in the irradiated semiconductor
surface, together with superoxide anions, these latter being produced by the reaction of conduction band
electrons with dissolved oxygen. This mechanism, which is inhibited by an excess of hydrogen peroxide,
owing to its reaction yielding hydroxyl radicals by any route, is also substantiated by previous experiments,
carried out in the presence of ozone, with and without photocatalytic promoters.

The toxic effects of the herbicide Atrazine, its degradation products deethyl-atrazine and deisopropylatrazine,
and the herbicide metolachlor were examined in unialgal cultures of Chlorella fusca var-fusca.
The toxicity of a mixture of atrazine and metolachlor was also evaluated using the same bioassay system.
Cell numbers were determined daily and growth rates were calculated for a period of 4 days. The order of
toxicity of chemicals was atrazine>metolachlor>deethyl-atrazine>deisopropyl-atrazine. The presence of a
mixture of atrazine and metolachlor in toxic concentrations lower than the EC50 resulted in reduced toxicity
(antagonism) in comparison with the toxicity caused by the sum of toxic actions of the same levels of
concentration from single chemicals.

The photocatalytic degradation of protocatechuic acid, a biorecalcitrant polyphenolic compound typically
found in olive processing and wine distillery waste waters, has been investigated in aqueous heterogeneous
solutions containing semiconductor powders (TiO2, ZnO) as photocatalysts, both in the presence of
artificial and natural illumination. The disappearance of the organic molecule follows, approximately a
pseudo-first kinetic order according to the Langmuir-Hinshelwood model. Various commercial
photocatalysts have been compared with respect to their overall efficiency as well as the production of
CO2. Among them, ZnO shows the highest photocatalytic activity. The effect of H2O2 on the reaction rate
has been ascertained.

An attempt is made for a first general study of the relation between high/very high concentrations of
nitrogen dioxide and ozone with the discomfort index (DI) values. The nitrogen dioxide data of
«Patision» station and ozone data of «Liosia» and «Marousi» station have been analysed. The relation
between air pollution episodes and the corresponding values of DI during the period 1993-1995 have
been examined for the Greater Athens Area (GAA). For the warm period of the year, the frequency of
the DI values for different levels of air pollution in the GAA is also examined.