Assessment of atmospheric assimilation potential for industrial development in an urban environment: Kochi (India).

The assimilation potential (assimilative capacity) of the atmosphere can be represented in two ways: one as the ventilation coefficient and the other as the dispersion potential of emission loads discharged into the region. In the present study, the atmospheric assimilation potential of a typical urban area in Kochi city has been determined with respect to sulfur dioxide (SO(2)). The ventilation coefficient is directly proportional to the assimilation potential of the atmosphere and has been computed using meteorological parameters in all four seasons (winter, summer, monsoon and post-monsoon) of the years 1998-1999 represented by January, April, July and October respectively. The diurnal variation in ventilation coefficients shows that the assimilative capacity of the atmosphere is high during the afternoon and is reduced during the evening and morning in all the seasons. Among all the seasons, monsoon and post-monsoon have the poorest assimilative capacity throughout the day. In the second approach, the assimilation potential is estimated through dispersion modelling in terms of the concentration of pollutants, which is inversely proportional to the assimilative capacity of the atmosphere. The Industrial Source Complex (ISC) dispersion model for point sources has been used to predict the spatial and temporal distribution of SO(2) under three different industrial scenarios (type of industries existing in the Kochi region, refinery and power plant). The model predictions indicate that monsoon is the most critical season having maximum pollution, followed by summer and post-monsoon. Lowest pollution was observed in winter. The assimilative capacity in terms of the ventilation coefficient is very poor indicating high pollution potential in all the seasons. However, dispersion modeling suggests that if industrial development is planned properly, additional industrial sources can be accommodated by restricting the emission loads to be within the assimilation potential of the region.

Air assimilative capacity-based environment friendly siting of new industries--a case study of Kochi region, India.

Air pollution has become a matter of grave concern, particularly in mega-cities and urban areas, where the situation is alarming and becoming more and more severe day-by-day and warrants, therefore, careful planning to facilitate future industrial development. Site selection, with the objective of minimizing adverse environmental impacts based on environmental criteria is a vital prerequisite, particularly for air polluting industries. In order to locate any air polluting industry, the assimilative capacity of the region needs to be assessed carefully and planned accordingly, so that the receiving environment is not adversely affected. Assimilative capacity of a region/airshed, widely represented through the ventilation coefficient by many researchers in the past, does not give a clear picture about the amount of emission load that can be assimilated in a given region. The ventilation coefficient, at best, can only present a broad picture about the air pollution dispersion potential (low, medium or high) of the region. A modified approach, which utilizes air quality modelling as a tool to estimate the maximum allowable emission load that a region can assimilate without violating the stipulated standards, has been used for estimating the assimilative capacity of the air environment. Details of this approach have been presented in this paper through a case study carried out for the Kochi region, located in the Kerala State of India. A variety of emission and meteorological scenarios have been considered and critical emission loads have been estimated. This approach shall provide necessary technical guidance to the environmental regulatory authorities as well as to the industries in planning environment friendly industrial development.