Agra is a historic city in the northern part of India, which is famous among international and local tourists alike for the Taj Mahal. The city supports an enormous population which consists of a high proportion of low socioeconomic status (SES) households which still use biomass as a fuel for domestic purposes. Added to the fact, the municipality of Agra does not have an efficient strategy towards disposing of municipal solid wastes (MSW) which are eventually burned off in open atmosphere.
The effects of the MSW and dung cake burning on the air quality of Agra are more than just high emissions of particulate matter into the atmosphere. The dry deposition of the organic matter (OM) and black carbon (BC) on the surface of the monument resulted in the soiling and consequently discoloration of the white marble mausoleum. Apart from the conspicuous effects, it also has adverse health effects on the people, causing premature deaths in the area.
In order to assess the dry deposition rates of air pollutants in the city of Agra targeted specifically towards the Taj Mahal, a combination of analytical and simulative model was chosen. Firstly, the open MSW and dung cake burning inventories were generated per zone of the city and weighted according to the SES of the households. Low SES means high dependence on the low calorific fuel such as dung cake and high SES means better and less emission fuels. The open waste burn rate, TWB (g-MSW day-1), within an electoral ward, from the SES-based waste burning rates is quantified by: TWB =WBR * POP +WBR * - POP (1).
Secondly, the emission rates or the inventories generated were applied in AERMOD (air pollution dispersion model), to spatially characterize the ambient, annually averaged PM2.5 concentrations. The meteorological inputs to AERMOD were given by AERMET (data processor), which was fed by the data from the National Climatic Data Centre (NCDC), the National Oceanic and Atmospheric Administration (NOAA) and the US National Weather Service (NWS). The average particle size of carbonaceous PM species at the surface of the Taj Mahal was quantified using scanning electron microscopy (SEM) (LEO 1530, Carl Zeiss Microscopy) and energy dispersive X-ray (EDX) spectroscopy (Oxford Instruments X-Max detectors), which was found to be ~ 1 μm.
Annual average PM2.5 component concentrations due to open waste and dung cake burning throughout Agra, simulated by AERMOD, found concentrations at the Taj Mahal to be 4.1 (± 3.8) and 0.24 ( ± 0.10) μg m-3 for OM and BC from MSW burning and 0.32 ( ± 9.1 x 10-2) and 0.019 ( ± 9.7x10-4) μg m-3 for OM and BC from dung cake burning. Estimated total annual combined PM2.5 dry deposition to the Taj Mahal is 150 (± 130) mg m-2 from open waste burning and 12 (± 3.2) mg m-2 from dung cake burning. Wet deposition loadings were small in comparison to the dry deposition.
Few measures have been taken to improve the air quality in Agra and reduce the dry deposition of OM and BC on the surface of the Taj Mahal like, restricting the vehicles near the Taj Mahal, closing over 200 excessively polluting enterprises in the city, making scrubbers and filters mandatory on smokestacks of all iron foundries, banning burning of dung cake as fuel.