Impact of air pollution on the microbial concentration of new town

Abstract

In this study, bioaerosol concentrations are collected from various locations at Newtown, Kolkata. For the first part of the study, correlation between bioaerosol concentrations with respect to the levels of criteria pollutants was observed. It was found that with increase in criteria pollutants, an average decrease in concentration of fungi and bacteria was prevalent at all sampling locations. However, the seasonal variation of these microorganisms was not dependant solely on the levels of criteria pollutants, but also on meteorological factors such as temperature and humidity. The microbial colonies have shown a general trend of sparse growth in the winter months of November and December and have shown relatively more growth in monsoon season. Further, crustal enrichment of the sampling sites were also studied in order to study the impact of heavy metals on microbial concentration. It was observed that, while areas with Ca enrichment promoted fungal growth and Zn promoted bacterial growth in some areas, areas with maximum Cr enrichment showed a marked decrease in the microbial concentrations. In the second part of the study, one criteria pollutant (SO₂) and UV-C were selected to observed change in enzyme activities on isolated strains of fungi and bacteria in laboratory condition. Activities of enzymes in these microorganisms depend on their intrinsic physicochemical properties and are sensitive to SO₂ and UV-C, hence they are used as indicators of pollution in ambient air. Airborne bacteria and fungi were collected by impaction onto agar plates placed in an Andersen Two Stage Sampler following which four species of bacteria and fungi each were identified and purified based on their uniqueness in the locations. 25ppm of SO₂ and 625 μW/cm² UV-C were applied for 3, 6 & 12 hours after inoculation in two enzyme-substrate broths to study the effect of stress on the production of three enzymes like protease, RNAse and catalase. It was found that greater amount of enzyme was produced on application of SO₂ stress than on application of UV-C. Catalase enzyme, though produced in least amount was found to have the least variation when impact of hourly exposure was studied. Preference towards growth media in case of both fungi and bacteria remained the same in case of SO₂ stress, as that in the non-stress condition while it changed in case of application of UV-C stress. Lastly, while all the four strains of bacteria showed similar characteristics on application of stress, Aspergillus fumigatus was found to be the most resilient under every stressed condition. Keywords: ambient air pollution, enrichment factor, sulfur dioxide pollution, UV-C pollution, microbial physiology, microbial enzyme