Assessment of microbial (bacteria) concentrations of ambient air at semi-arid urban region: Influence of meteorological factors. Applied ecology and Environmental Research

Abstract. In the present study, outdoor airborne microflora (bacteria) at different locations, viz; institutional, health care, commercial, traffic, industrial and agricultural areas of Tirupati a semi-arid urban region, southern peninsular India was investigated during winter season, 2004. Concentrations of airborne viable bacteria averaged between 19 ± 5 CFU/m3 (IE) and 3 ± 5 CFU/m3 (SVU) and observed the following trend among the locations: IE> TG> CBS> TUDA> RUYA> SVU. Airborne Gram-positive bacteria were most abundant, with more than 60 to 90 % of the measured population at each location. Developed regression models have been explained about 50 % (or greater) variation in bacteria concentration at each location (except RUYA), due to the effect of meteorological factors – temperature, RH, and wind speed. Among these factors, wind speed had the most pronounced influence on bacterial concentration, with the regression coefficient (β) varied between 0.225 and 2.092, followed by the temperature. The overall air quality index (ABQI) with respect to bacterial composition of aerosol is found to be 22.33 which signifies that the quality of air is good. The results reveal that the airborne bacteria are contributed from terrestrial (soil) sources greatly followed by the little contribution from point sources