New numerical approaches for urban and regional air pollution modeling and management

S. ENRIQUE PULIAFITO; DAVID G. ALLENDE; RAFAEL P. FERNANDEZ; FERNANDO H. CASTRO; PABLO G. CREMADES

Advanced Air Pollution

INTECH Open Access Publisher- Europe

Lugar: Rijeka; Año: 2011; p. 429 - 454

Air pollution is a complex problem that plays a key role in human well-being, environment and climate change. Since cities are, by nature, concentrations of humans, materials and activities, air pollution is clearly a typical phenomena associated to urban centers and industrialized regions. Moreover, since approximately half of the total population of the world live in medium to large cities, it is very important to evaluate the air quality levels of the atmosphere in order to assess the possible health impact from exposition.Air quality modeling and monitoring have become useful tools to environmental management and policies. Some examples of the application of air quality models for scientific research and governmental issues are: i)  determination of the pollution level at urban centers; ii)  inspection of the compliance of criteria, standards and legislation; iii) assessment of the impact of new facilities to human health, iv) selection of the best location for a monitoring network, v)  contribution of an actual or future industry/highway to the ambient concentration of atmospheric pollutants, gases and aerosols; vi)  impact of different emissions scenarios to the air quality of  urban center/region and their relation to Global Climate Change.Air pollution modeling is at present a well developed field, though it is still growing. Several air quality models have been developed originally to be applied in scientific research, but lately, they have been adapted as regulatory instrument to characterize air pollution problems. In general, every air quality study implies estimation of some pollutants concentration at a region of interest. The characteristics of each specific problem determine the physical and chemical processes involved, and consequently, the best model to use. Among the important criterion for choosing software are: dimension of the area under study, number of pollution sources, chemical species and time scale of the episode.We will see a clear distinction of different temporal and spatial scales of air pollution phenomena in this chapter. Consequently, local scale problems, such as the impact of traffic or industrial sources,  cannot be treated the same as long range problems, due to the influence of regional scale processes, such as the chemical transformation or the deposition of pollutants which may not need to be taken into account in a shorter scale. We will give a practical but complete description of uses and application of the most common and more recent developed models. For short-range transport, models with a Gaussian approach, such as ISC3 and AERMOD, are used to study the interactions of emissions and concentrations in urban streets and surrounding urban neighborhoods. CALPUFF, a non steady-state puff dispersion model, is used at urban scales, with meteorological inputs provided by either on-site measurements or a separate meteorological model simulation such as WRF. The development of the new WRF/Chem model (WRF with Chemistry) constitutes an adaptable and useful tool intended to perform the ?on-line? modeling of the chemistry and meteorology over a wide range of scales. Its main applications are the study of secondary pollutants and aerosols formation in an urban and regional context.The precision and resolution of air quality models is highly dependent on the resolution of the input data included in the models. This work/chapter will also present how to prepare detailed input data necessary for the application of models. We will pay special attention to three main sources of information required for a correct modeling: a) emission inventories, b) meteorological data, and c) topographic fields. Emission inventories normally include an estimation (either modeled or measured) of direct and indirect emissions of primary pollutants from different types of sources: vehicular, industrial, residential, and fugitive, distinguishing between the natural and anthropogenic contributions. Meteorological data sets are usually provided by direct measurement or by numerical modeling. They are composed of scalar and vectorial fields such as surface temperature, pressure, humidity, precipitation, wind direction and wind intensity. Whenever available, they are complemented with vertical profile of other similar meteorological variables, obtained by radiosondes at different locations. The topographic description of the domain requires detailed information of the terrain elevation, and several earth surface physical fields such as land use and land cover.The correct manipulation of these three types of databases and their distribution and organization in gridded domain of variable size and resolution is usually performed using GIS software and/or atmospheric models pre-processing tools. Also, different softwares and graphical tools can be used in order to represent the output results at different scales, times and/or dimensions. The output results of the models are usually compared to data from monitoring stations, so we will devote a section to describe the general methodology to evaluate results from models. The last section of this chapter will show the results of modeling and monitoring for several Argentine cities. The test-cases shown were selected with the aim of describing the process, from selecting the appropriate model depending on the details of the problem complexity to evaluation of results with on site measurements.In summary the main outline of the chapter is as follow.A) An introductive section of the general air pollution problem and the use of models by scientist and environmental agencies. This section includes a description of evolution from simple local pollutant dispersion model to more complex regional air quality numerical prediction methods; presenting the state of the art of recent models and future developments. B) The methodology section will describe different approaches to obtain the emission inventories (top down or bottom up), and the use of meteorological and topographic information, associated to geographical information systems (GIS). In addition, it will show a comparison of different models (i.e., ISC3, AERMOD and CALPUFF), from the point of view of their capacity to treat complex physical and chemical interactions. Furthermore, this section will describe how to include regional meteorological models such as WRF in air quality models. C) The result section will show the application of the above models in several cities of Argentina: Mendoza, Buenos Aires and Bahía Blanca. D) A final section will conclude and present a summary discussion of the chapter.