GIS applications in air pollution modeling
Air quality models play a very important role in formulating air pollution control and management strategies by providing information about better and more efficient air quality planning. Line source models are used to simulate the dispersion of pollutants near the highways and/or roads, where vehicles continuously emit pollutants of varying characteristics. Since the early 1970's, various highway dispersion models have been developed using different methodologies/techniques to take care of oblique and parallel winds, low wind speed, increased turbulence near the roads due to vehicle wakes and regarding treatment of dispersion of exhaust gases near the roads. These models were continuously upgraded and modified based on the field experiments, numerical and physical modeling results. Several highway dispersion models, mostly Gaussian based, are being used to predict pollutant concentrations near the highways/roads. These models, despite several assumptions and limitations are used throughout the world, including India, by the regulatory agencies to carry out air pollution prediction analysis due to vehicular traffic near the roads/highways as a part of the environmental impact assessment (EIA) procedure.
The above modelling approach had the drawback that it was not oriented towards the needs of the transportation planners who design and implement control strategies and require more feedback from typical transportation system improvement and management strategies had on the air pollution levels. The above limitation was removed to a great extent by the integration of the geographical information system (GIS) with the existing air pollution modelling approach. While, GIS does not improve implicitly the accuracy of various input data, nor does it improve the accuracy and predictive capabilities of various air pollution models, but by using GIS, these data as well as a variety of other types and resolutions of spatial data, required for emission modelling can be brought together into an integrated modelling environment and thus drastically helping the decision making process. In the present paper, an attempt has been made to briefly summarise the various limitations and inadequacies of the vehicular pollution modelling approach presently used in India. Further, a case study of vehicular pollution modelling using CALINE 4 highway dispersion model along the NH-2 highway, has been included in the paper to demonstrate the integrated vehicular pollution modelling approach using GIS.
Status of Vehicular Pollution in India
Motor vehicles have been closely identified with increasing air pollution levels in urban centers of the world (Mage et al, 1996; Mayer 1999) . Besides substantial CO2 emissions, significant quantities of CO, HC, NOx, SPM and other air toxins are emitted from these motor vehicles in the atmosphere, causing serious environmental and health impacts. Like many other parts...