青岛近海不同天气下生物气溶胶中细菌浓度及存活率分布特征

细菌是大气生物气溶胶中最丰富、分布最广的微生物.利用FA-1撞击式生物采样器连续采集了2020年9月至2021年8月青岛近海大气生物气溶胶分级样品，并利用BacLight^TM试剂染色-荧光显微镜计数方法测定了死/活细菌浓度，分析其浓度与粒径的季节分布特征，并研究了雾、霾和沙尘等特殊天气对细菌浓度及粒径分布的影响.结果表明，采样期间青岛近海生物气溶胶中细菌浓度为(1.06±0.68)×10⁵ cells·m^-3,其中活细菌和死细菌浓度分别为(8.20±4.88)×10³ cells·m^-3和(9.74±6.72)×10⁴ cells·m^-3.细菌浓度分布具有季节差异，死细菌浓度春季、冬季最高，夏季最低；活细菌浓度则变现为春季最高，夏季和秋季较低，冬季最低.生物气溶胶中细菌浓度随月份存在变化，死细菌月均浓度最高值和最低值分别出现在2021年春季3月和夏季6月，而活细菌月均浓度最高值则出现在2021年春季5月，最低值在2020年冬季12月....

Distribution of Bacterial Concentration and Viability in Atmospheric Bioaerosols Under Different Weather Conditions in the Coastal Region of Qingdao

Bacteria are the most abundant microorganisms in atmospheric bioaerosols, widely distributed in the environment. Bioaerosol samples were collected using the FA-1 impact sampler from October 2013 to January 2021 in the coastal city of Qingdao, and samples stained with a BacLight^TM bacterial viability kit were used to measure the concentrations of viable and non-viable bacteria with an epifluorescence microscope. The viable and non-viable bacteria in bioaerosols were characterized during different seasons, with particular attention paid to the distribution characteristics of bacteria on foggy, hazy, and dust days. The results showed that the mean concentrations of total bacteria were (1.06±0.68)×10⁵ cells·m^-3 in Qingdao during the sampling period, and those of viable and non-viable bacteria were (8.20±4.88)×10³ cells·m^-3and (9.74±6.72)×10⁴ cells·m^-3, respectively. The seasonal concentrations of non-viable bacteria were the highest in spring and winter and the lowest in summer, whereas that of viable bacteria was highest in spring, followed by those in summer and autumn, and the lowest in winter. Atmospheric bacterial concentrations fluctuated with by month, and total bacteria presented a similar variation pattern with that of non-viable bacteria. The monthly average concentration of non-viable bacteria showed the highest value in March during the spring and the lowest in June during the summer in 2021, whereas the highest value for viable bacteria occurred in May during the spring in 2021 and the lowest in December during the winter in 2020. Viable bacteria concentrations were significantly positively correlated with temperature and significantly negatively correlated with NO₂, SO₂, and CO. Non-viable bacteria were significantly positively correlated with PM. The bacteria in bioaerosol particles showed bimodal, unimodal, and skewed size distributions, varying with season and month. Under different weather conditions, the concentration of non-viable bacteria on dusty days was significantly higher than that on sunny, foggy, or hazy days, but the bacteria viability was as low as 6.85% due to long-distance transport. Anthropogenic pollution resulted in the lowest viability of bacteria at 4.10% on hazy days, whereas the highest viability in bacteria was 16.26% on foggy days due to high humidity. The size distribution of bacteria in bioaerosol particles under different pollution days showed a bimodal distribution, and the peak size depended on the weather type.