270
Air Pollution and Turbulence: Modeling and Applications
This scientifi c knowledge has been the basis for several air quality management
strategies including different international conventions, such as the convention on
long-range trans-boundary air pollution, whose original purpose was to deal with
acidifi cation and eutrophication, but is currently also clearly related to photochemical pollution implying the reduction of ozone precursors. It is within this scope
that the member states of the United Nations Economic Commission for Europe
(UNECE, 1999) have included the concepts of critical load and level for planning
pollution abatement strategies and as a basis for international agreements concerning
limitation of emission of air pollutants, namely, the ozone precursors. Air quality
legislation that includes ozone and its main precursors as pollutants, whose ambient
air concentration levels have to be controlled within certain air quality thresholds, is
also part of the established strategy to manage air quality.
In Europe, the Air Quality Framework Directive (FWD) (96/62/EC) regulates air
pollutant effects on both human health and ecosystems, and it includes mechanisms
to assure their protection. A fundamental requisite of the FWD is the defi nition of
an evaluation program of ambient air quality in the territories of the member states.
This evaluation program should include tropospheric ozone which it should cover
via three main components: the monitoring of air quality, emission inventories, and
atmospheric modeling.
In the United States, air pollution control strategies date from 1955 with the
Air Pollution Control Act followed by the Clean Air Act of 1963. The Clean Air
Act, which was last amended in 1990, requires the United States Environmental
Protection Agency (USEPA) to set National Ambient Air Quality Standards
(NAAQS) for pollutants considered harmful to public health and the environment.
Since 2003, there has been the Clear Skies Act—cleaner air, better health, brighter
future—which is a mandatory program that will dramatically reduce and cap emissions of sulfur dioxide (SO 2 ), nitrogen oxides (NO x ), and mercury from electric
power generation.
From this increase in knowledge and number of strategies, an improvement in
ozone pollution levels would be expected. However, long-term data from the air
quality monitoring networks indicate a still increasing trend in ozone background
surface levels in the northern hemisphere (Brasseur et al, 2003; UE, 2003). However,
analysis of these ozone values is not an easy task, and it is possible to fi nd different trends according to time-averaged values under study (e.g., peak values present
a different pattern from median ones), or the type of monitoring station used. This
complex behavior only confi rms the nonlinearity of photochemical pollution.
Chemical transport models (CTMs) can be important tools to better understand
and estimate photochemical air pollution and are quite extensively used to evaluate
and forecast air quality.
10.2 PHOTOCHEMICAL AIR POLLUTION MODELING
The spatial and temporal distribution of ozone in the troposphere is controlled by
several processes that are responsible for its production and removal. These processes
lead to a complex equilibrium dependent upon different factors that, if meteorological conditions are favorable, lead to high levels of ozone. The different sources and
© 2010 by Taylor and Francis Group, LLC
Air Pollution and Turbulence: Modeling and Applications
This scientifi c knowledge has been the basis for several air quality management
strategies including different international conventions, such as the convention on
long-range trans-boundary air pollution, whose original purpose was to deal with
acidifi cation and eutrophication, but is currently also clearly related to photochemical pollution implying the reduction of ozone precursors. It is within this scope
that the member states of the United Nations Economic Commission for Europe
(UNECE, 1999) have included the concepts of critical load and level for planning
pollution abatement strategies and as a basis for international agreements concerning
limitation of emission of air pollutants, namely, the ozone precursors. Air quality
legislation that includes ozone and its main precursors as pollutants, whose ambient
air concentration levels have to be controlled within certain air quality thresholds, is
also part of the established strategy to manage air quality.
In Europe, the Air Quality Framework Directive (FWD) (96/62/EC) regulates air
pollutant effects on both human health and ecosystems, and it includes mechanisms
to assure their protection. A fundamental requisite of the FWD is the defi nition of
an evaluation program of ambient air quality in the territories of the member states.
This evaluation program should include tropospheric ozone which it should cover
via three main components: the monitoring of air quality, emission inventories, and
atmospheric modeling.
In the United States, air pollution control strategies date from 1955 with the
Air Pollution Control Act followed by the Clean Air Act of 1963. The Clean Air
Act, which was last amended in 1990, requires the United States Environmental
Protection Agency (USEPA) to set National Ambient Air Quality Standards
(NAAQS) for pollutants considered harmful to public health and the environment.
Since 2003, there has been the Clear Skies Act—cleaner air, better health, brighter
future—which is a mandatory program that will dramatically reduce and cap emissions of sulfur dioxide (SO 2 ), nitrogen oxides (NO x ), and mercury from electric
power generation.
From this increase in knowledge and number of strategies, an improvement in
ozone pollution levels would be expected. However, long-term data from the air
quality monitoring networks indicate a still increasing trend in ozone background
surface levels in the northern hemisphere (Brasseur et al, 2003; UE, 2003). However,
analysis of these ozone values is not an easy task, and it is possible to fi nd different trends according to time-averaged values under study (e.g., peak values present
a different pattern from median ones), or the type of monitoring station used. This
complex behavior only confi rms the nonlinearity of photochemical pollution.
Chemical transport models (CTMs) can be important tools to better understand
and estimate photochemical air pollution and are quite extensively used to evaluate
and forecast air quality.
10.2 PHOTOCHEMICAL AIR POLLUTION MODELING
The spatial and temporal distribution of ozone in the troposphere is controlled by
several processes that are responsible for its production and removal. These processes
lead to a complex equilibrium dependent upon different factors that, if meteorological conditions are favorable, lead to high levels of ozone. The different sources and
© 2010 by Taylor and Francis Group, LLC