Global NEST Journal

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.

Estimates of the amount of secondary organic aerosol formed in the atmosphere from the degradation of
traffic C6-C12 hydrocarbon emissions in the city of Athens are presented. Around 1.26 tn of organic aerosol
is estimated to be produced during a six hours air pollution episode from the aromatic hydrocarbons,
the other NMHC groups contributing an additional 0.2 tn. The main contributor to the SOA production is
m-xylene. It accounts, together with toluene, for around 50% of the produced organic aerosol. The main
aerosol products that are expected to form from the Athens NMHC traffic mixture are nitrophenols. Due
to predominant wind flow to the S-SE direction in the area, a portion of these aerosols is likely to contribute
to the SOA burden of the marine atmosphere over SE Mediterranean. These results are also relevant to
ozone abatement strategies involving species-specific NMHC reductions and affecting fine particulate
composition and concentrations.

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.

Samples were taken from Metamorphosis/Attica combined treatment plant for municipal wastewater and
septage, which treats about 12000 m3 d-1 of municipal wastewater and 8000 m3 d-1 of septage, and analyzed
for solids, COD, ammonia, nitrate, orthophosphate, polyphosphate and total phosphorus. Ammonia is
almost completely eliminated within the plant. Orthophosphates show a removal of about 28%, while total
phosphorus is removed by about 15%. The mean value of the ratio (phosphorus eliminated)/(COD eliminated)
in mg g-1 is 8. Assuming suspended-growth nitrification and denitrification kinetics as proposed in
literature, the percentage of nitrifiers in the activated sludge population is estimated at 1.1%. Assuming
that phosphorus removal in the aeration tank is proportional to cell formation, which in turn is proportional
to substrate elimination, the phosphorus content of the activated sludge is estimated at 0.031 gP (gVSS)-1.