Microbial Activity In Bioaerosols In Qingdao Area

Bioaerosols are airborne particles or large molecules that are alive, carry livingorganisms or are released from living organisms, such as bacteria, fungi, virus, pollen,cell debris, and biofilms. Airborne microorganisms can affect global climate change,environmental quality and human health. Microbial activity is a state or property ofphysiological process or active in microorganisms. Compared to the total amount andconcentration of microbes in bioaerosols, microbial activity is more important tounderstand the impact of bioarosols on the environmental quality and human health.Based on the analysis method of microbial activity in soil, we developed themeasurement method of total microbial activity using FDA （Fluorescein diacetate）hydrolysis in bioaerosols. Bioaerosols samples were collected on polycarbonatemembranes, using a six-stage culturable microorganism FA-1cascade impactors, witha flow rate of28.3L·min-1for40min.150μL40%polyethylene glycol solution wasused to coat on each polycarbonate membrane before collection. After sampling,bioaerosols samples collected on polycarbonate membranes were cut up and put into100mL conical flask with20mL physiological saline. The flask was then shaken at37℃for40min with150r/min.18mL extract liquid was isolated with polycarbonatemembranes after shaking and transferred to50mL conical flask. Then,0.2mL100μg/mL of FDA solution was added into extract liquid to start the hydrolysis. Thereaction was incubated at30℃for150min avoiding light. After incubation wasterminated,1mL chloroform/methanol (2:1v/v) must be added to terminate thereaction if the amount of samples was more than6to ensure all the samples must bedetermined in30min. Finally, fluorescence intensity of each sample was measured byfluorescence spectrophotometry and calculated into concentration of sodiumfluorescein according to sodium fluorescein standard curve. The total microbialactivity in bioaerosols was represented by the concentration of sodium fluorescence.By using the method proposed above, microbial activity was found in the range of0.93×10-3-4.85×10-3μg/mL sodium fluorescein in May,2012, average level ofmicrobial activity is2.51μg/mL sodium fluorescein. Standard deviation (SD) of thetwo paralleled samples ranged from0.10to0.35, average SD is0.20, which indicated the precision of established method is very good and the method can measure themicrobial activity of bioaerosols in atmosphere.Using the established method, the seasonal distribution characteristics of microbialactivity were analyzed in bioaerosols in Qingdao coastal area in2012. The range ofmicrobial activity was from0.93to4.85ng/mL fluorescein sodium in spring, with anaverage being2.51ng/mL fluorescein sodium. The range of microbial activity was inrange of0.74-2.23ng/mL fluorescein sodium in fall, with average of1.29ng/mLfluorescein sodium. The level of microbial activity varied from0.41to2.36ng/mLfluorescein sodium in winter, and the average was0.95ng/mL fluorescein sodium.The average level of microbial activity showed the highest value in spring and lowestin winter in bioaerosols in Qingdao area. And the variation of the level of microbialactivity is higher in spring than those in fall and winter. Monthly level of microbialactivity showed that the microbial activity varied from0.41to4.85ng/mL fluoresceinsodium, with the average from0.58to2.51ng/mL fluorescein sodium. And thehighest microbial activity level appeared in May.2012, followed by Oct.2012, andlowest in Jan.2013.The correlation between microbial activity in bioaerosols and atmospherictemperature appeared positive significant (P<0.01). Negative significant correlationwas between atmospheric relative humidity (in range of39%-89%) and microbialactivity. No significant correlation between microbial activity and wind speed or winddirection. But results showed that microbial activity was higher when wind speed issmall, the wind direction from continent to ocean and in foggy or haze days. Multiplelinear regression model result shows that38.5%percent of variation of microbialactivity in terms of temperature and RH (31%~89%), and no significant correlationbetween wind speed and microbial activity (sig.=0.703).Pearson correlation between aerosol particle number concentration and microbialactivity in bioaerosols was performed, and the results showed that microbial activityhad positive significant correlation with aerosol particle number concentration ofparticle larger than2μm (P<0.01) and1~2μm (P<0.05).But no significant correlationwas found between microbial activity and aerosol particle number concentration of0.7~1μm. Seasonally variation showed that the correlation between microbial activityand aerosol particle number concentration of particle larger than2μm appeared positive significant correlation (P<0.05) in spring; while in fall and winter, microbialactivity only appeared positive significant correlation with aerosol particle numberconcentration of particle size larger than5μm (P<0.05). Furthermore, there is nosignificant correlation between microbial activity and mass concentration of PM2.5inQingdao coastal area.