There is an increasing interest in understanding ambient bioaerosols due to their roles both in health and in climate. Here, we deployed an Ultraviolet Aerodynamic Particle Sizer to monitor viable （fluorescent） bioaerosol concentration levels at city centers （highly polluted） and their corresponding suburbs （near pristine） （total 40 locations） in 11 provinces featuring different climate zones in China between July 16 and 28, 2013. The concentration levels of viable bioaerosol particles （BioPM） of 〉0.5 μm were measured, and corresponding percentages of BioPM% （biological fraction of total PM） and BioPM2.5% （biological fraction of PM2.5） in particulate matter （PM） and BioPM, respectively, were determined. For some key cities, indoor viable bioaerosol levels were also obtained. In addition, bacterial structures of the air samples collected across these monitoring locations were studied using pyrosequencing. BioPM concentration levels ranged from 2.1 ×10^4 to 2.4 × 10^5/m3 for city centers [BioPM% = 6.4 % （4-6.3 %）] and 0.5 × 10^4 to 4.7 × 10^5/m3 for suburbs [BioPM% = 10 % （4-8.7 %）]. Distinctive bioaerosol size distribution patterns were observed for different climate zones, e.g., some had fluorescence peaks at 3 μm, while the majority had peaks at 1 μm. Ambient bacterial aerosol community structures were also found different for different geophysical locations. Results suggest that there was a poor overall relationship between PM and BioPM across 40 monitoring locations （R2= 0.081, two-tailed P value = 0.07435）. Generally, city centers had higher PM concentrations than suburbs, but not BioPM and BioPM%. Indoor bioaerosol levels were found at least tenfold higher than those corresponding outdoors. Bacillus was observed to dominate the bacterial aerosol community in the air sample.
Kai WeiYunhao ZhengJing LiFangxia ShenZhuanglei ZouHanqing FanXinyue LiChang-yu WuMaosheng Yao
Aerosol chemistry is often studied without considering microbial involvements. Here, we investigated time-and size-resolved bacterial aerosol dynamics in air. Under high particulate matter(PM) polluted episodes, bacterial aerosols exhibited a viability of up to 50%–70% in the 0.56–1 μm size range, at which elevated levels of SO42-, NO3- and NH4+ were concurrently observed.Engineered or acclimated for both industrial use, bacteria such as Psychrobacter spp., Massilia spp., Acinetobacter lwoffii,Exiguobacteriumaurantiacum and Bacillusmegaterium were shown to have experienced massive abundance shifts in polluted air on early mornings and late afternoons, on which rapid new particle formation events were widely reported. Here, Psychrobacter spp. were shown to account for >96% abundance at a corresponding PM2.5 level of 208 μg/m3. These observed bacterial aerosol changes corresponded to the PM2.5 mass peak shift from 3.2–5.6 μm to the high viability size range of 0.56–1 μm. Additionally,elevated levels of soluble Na, Ca, Mg, K, Al, Fe and P elements, required for bacterial growth, were observed to co-occur with those significant bacterial aerosol structure shifts in the air. For particular time-resolved PM2.5 pollution episodes, Acinetobacter,Psychrobacter and Massilia were shown to alternate in dominating the time-resolved aerosol community structures. The results from a HYSPLIT trajectory model simulation suggested that air mass transport played a minor role in affecting the observed bacterial aerosol structure dynamics. All the data here suggested that airborne bacteria in the size range of 0.56–1 μm could be extensively involved in aerosol chemistry in highly polluted humid air.
Ting ZhangXinyue LiMinfei WangHaoxuan ChenMaosheng Yao
Nanoscale zero-valent iron(nZVI)particles are increasingly being investigated in removing aqueous contaminants.Here,we have demonstrated its inactivation and magnetic removal of bacteria and endotoxins from environmental wastewater samples.Varying dosages(10–1,000 lL)of 0–6 days aged nZVI with a concentration of 5 mg/mL for 2 mL wastewater samples were tested,and relevant removal efficiencies were determined using culturing method for bacteria and limulus amebocyte lysate(LAL)for endotoxins.The supernatants of wastewater samples after reacting with nZVI and subsequent magnetic separations were subjected to spectroscopic,qPCR and DGGE analysis.Overall,high magnetic bacterial removal efficiencies were observed up to 3–4 logs for 1 mL nZVI,while the removal efficiencies decreased sharply down to0.5 log for 10 lL nZVI.qPCR and DGGE results revealed that higher dosages of nZVI caused severe bacterial cell membrane ruptures,releasing significant amounts of DNA up to 107–108gene copies/mL when 1 mL nZVI was used.Richer DGGE patterns were observed for higher nZVI dosages.In addition,regardless of the dosages(10–1,000 lL)we have observed more than 90%removal of endotoxins from the wastewater samples.The described technology has great promise to be used as a point-of-use water purification solution for various purposes.
