Volume 2 [2000]

The oxidation of NO over Co-, Pt- and Rh-based catalysts was studied by combined catalytic activity
and FT-IR studies. The activity of Co-, Pt- and Rh-based catalysts was measured in the presence and
absence of H2O and SO2 in the feed. The activity studies showed that the support (Al2O3, TiO2, ZrO2)
of Pt catalysts significantly affects the extent of the oxidation reaction, in addition to the metal content
and calcination temperature over Co/Al2O3 catalyst. The highest activity was measured over 5 %
Co/Al2O3 calcined at 450 °C, while Pt/ and Rh/Al2O3 catalysts exhibited significant activity (absence of
SO2). The presence of 200 ppm SO2 inhibited irreversibly the NO oxidation mainly over Co/ and
Rh/alumina. In the presence of 10 % H2O in the feed the activity of all catalysts weakly decreased,
reversibly. FT-IR studies, over fresh Rh/Al2O3, showed the formation of Rh-NO+, Al-NO2 and Al-NO3
species, while over presulfated catalyst only the Rh-NO+ species was detected. Activity and FT-IR
studies were used to propose a mechanism for the NO oxidation, in the presence and in the absence of
SO2.

Aeration is one of the most common stages in the liquid waste clarification process. Most aeration
tanks are equipped with aeration devices that inject oxygen to enhance the biodegradation of the liquid
waste. In this work an aeration process is simulated, where the air is injected from the bottom of a
cylindrical tank. Two numerical models are developed and two different geometries are considered.
Their results are verified against published data. Both models solve the momentum, continuity and k-
å equations for the relevant phases. The first model considers liquid and gas phases as homogeneous
fluid. The calculated velocity refers to the mixture of the phases. The second model assumes liquid and
gas as two distinct phases. Velocity and volume fraction profiles portray the induced motion of the liquid
and the extent of the aeration process. Regarding the two different geometries, the first assumes a
flat free liquid surface, while the second a liquid surface free to swell according to the gas injection rate.
It is shown that the second geometry gives more accurate results.

The changes in greenhouse gases and aerosols emissions are expected to lead to regional and global
changes in temperature, precipitation, and other climate variables. The degree to which human conditions
and the natural environment are vulnerable to the potential effects of climate change is a key concern
for governments and the environmental science community. Regional differences in climate
change and its impacts have recently been identified as current gaps in the present scientific knowledge.
Air quality regional impacts of global climate change, namely the effects on photochemical production,
are not a common subject of scientific studies. The main objective of this paper is to provide a basis of
scientific information for policy makers and public use by the assessment of the vulnerability of
Portuguese air quality to climate change. A General Circulation Model was applied in order to provide
initial and driving meteorological boundary conditions, assuming a present climate situation and a scenario
of double carbon dioxide concentration in the atmosphere, for higher resolution mesometeorological
and photochemical models. Results emphasise a possible significant impact of the climate
change scenario on the photochemical pollution, namely at noon.

The structure and function of communities and biological systems favorable and unfavorable to salt
production in the ponds of solar saltworks are described. Favorable systems maintain a diverse biota
and power the organisms at levels that enable a saltworks to economically and continuously produce
high quality salt at design capacity. Unfavorable systems-the result of disturbances and high concentrations
of nutrients in the water-are dominated by a few species that release massive quantities of
organic substances, decrease pond surface areas and volumes, and decrease salt quality and quantity.
Management practices to obtain and maintain favorable systems under a variety of conditions are
reviewed.