Influence of seasonal variation on concentration of fungal bioaerosol at a sewage treatment plant (STP) in Delhi

Ambient levels of viable bioaerosol (fungi) were measured at six different sections of a sewage treatment plant in Vasant Kunj, New Delhi. The sampling was carried out for fungal fractions of bioaerosols during the month of June 2012 to May 2013 covering all the four seasons of India, i.e., monsoon, post-monsoon, winter, and pre-monsoon. Sampling was done thrice in a month with the help of a six-stage viable cascade impactor for 10 min each at a flow rate of 28.3 l min−1. Temperature and relative humidity were also recorded during each sampling. It was found that among all the six sites, maximum and minimum fungal concentrations were 1,200 and 829 CFU m−3 in pre-monsoon; 1,198 and 802 CFU m−3 in monsoon; 1,289 and 868 CFU m−3 in post-monsoon; and 516 and 279 CFU m−3 in winter seasons, respectively. A good regression of fine over coarse fungal bioaerosols was observed in all the four seasons. In total, eight genera of fungi were identified, and among the eight genera identified, four, e.g., Mucor, Rhizopus, Aspergillus, and Penicillium, were found in maximum number during all the seasons. This study has revealed interesting results in context to the relationship between concentrations of fungal bioaerosols and environmental factors as well as interparticle size relationship of fungal bioaerosols.