The effect of dust storm on the microbial quality of ambient air in ahvaz city and dust source identification using numerical modeling

Airborne particles are considered to be an important indicator of air quality and high concentrations of these particles cause many health problems. Around the world, it is impossible to avoid contact with bio-aerosol contamination in urban life. The presence of pathogenic microorganisms in dust storms can cause diseases such as pneumonia, asthma, and other respiratory infections. The aim of this study was to investigate the relationship between airborne particles with airborne microorganisms in normal and dusty days. The sampling method was quick take 30 equipped with a single-stage sampler at the elevation of 1.5 to 2 meters above the ground. Air flow was 14.3 L/min and its duration was 5 min. The original samples were diluted several times (10-5 - 10-4) to reduce the microbial population sufficiently to obtain separate colonies upon plating. All cultures were incubated at environmental temperature (25 ± 2 °C) for 3 to 5 days and repeated twice. Any increase in PM10 concentrations were in agreement with an increase of bacterial and fungal concentrations during dusty days in Ahvaz city during the warm period (April to September) in 2011. The concentration of particles in June, July and August was greater than the standard value. The results of the present study illustrated that the average number of bacteria and fungi, respectively, in dusty days was 5 and 1.7 times that of normal days. Also, the predominant species of bacteria and fungi during the occurrence of dust storms were Bacillus sp. (45% of total bacteria) and Aspergillus sp. (44% of total fungi), respectively. Therefore, any increase in the number of airborne microorganisms (bacteria and fungi) during dust storms can cause biologically harmful effects on human health. Based on the annual and seasonal changes in meteorological parameters and HYSPLIT, it can be seen that the probable origin of airborne particles are neighbouring countries to southwestern Iran, especially the northwestern parts of Iraq and the eastern parts of Syria.