北京市不同季节室外细菌气溶胶分布特征及其环境影响因素分析

为了解北京市室外细菌气溶胶的分布特征，基于培养法分析了2020年9月—2021年5月不同季节细菌气溶胶浓度及粒径的分布特征，探讨气象因素(温度和相对湿度)和空气颗粒物(PM₁₀和PM_2.5)对细菌气溶胶分布特征的影响. 结果表明:①北京市室外细菌气溶胶平均浓度为447.10 CFU/m3 (每立方米空气中的菌落形成单位)，呈春季〔(648.55±537.24)CFU/m3〕>冬季〔(324.50±181.99)CFU/m3〕>秋季〔(319.59±305.07)CFU/m3〕的特征，不同季节细菌气溶胶浓度差异不显著. ②北京市室外约80%的细菌气溶胶直径大于2.1 μm，细菌气溶胶浓度在第2级(粒径为4.7~7.0 μm)显著降低，峰值粒径出现在第1级(粒径>7.0 μm). 粒径大于7.0 μm的细菌气溶胶在春季与秋季以及春季与冬季之间均存在统计学差异 (p均小于0.05). 可进入人体下呼吸道的细菌气溶胶(≤4.7 μm)比例近50%(冬季、秋季、春季占比分别为61.0%、58.9%、41.6%)，冬季空气中可进入人体下呼吸道的细菌气溶胶比例最高. ③Spearman相关性分析表明，室外环境细菌气溶胶浓度与相对湿度呈显著负相关(p<0.05)，与PM₁₀浓度呈显著正相关(p<0.05)，表明细菌气溶胶浓度受气象因素和空气污染物的影响. 研究显示，北京市室外环境中可进入人体下呼吸道的细菌气溶胶比例近50%，冬季细菌气溶胶暴露风险最高. 

Seasonal Distribution Characteristics of Bacterial Aerosols and Their Correlations with Environmental Factors in Beijing,China

In order to understand the distribution characteristics of outdoor bacterial aerosols in Beijing and the seasonal patterns of outdoor pollutants, the characteristics of bacterial aerosol concentrations and particle sizes were analyzed using a culture method from September 2020 to May 2021. The effects of meteorological factors (e.g., temperature and relative humidity) and air particulate matter (PM₁₀ and PM_2.5) pollution on the characteristics of bacterial aerosols were further discussed. The results showed that: (1) The average concentration of airborne bacteria in Beijing was 447.10 CFU/m3 (Colony-forming unit per cubic meter of air) with spring ((648.55±537.24)CFU/m3) > winter ((324.50±181.99)CFU/m3) > autumn ((319.59±305.07)CFU/m3). However, the seasonal difference was not significant. (2) About 80% of bacterial aerosols were larger than 2.1 μm, the concentration was significantly reduced in the second stage (4.7-7.0 μm), and the peak particle size appeared in the first stage (>7.0 μm). The bacterial aerosol with the particle size larger than 7.0 μm showed statistical differences between spring and autumn, and between spring and winter (p<0.05). The proportion of bacterial aerosol (≤4.7 μm) that can enter the lower respiratory tract of human body was about 50% (61.0% in winter, 58.9% in autumn, and 41.6% in spring). The proportion of bacterial aerosol that can enter the lower respiratory tract of human body in winter was the highest. (3) Spearman correlation analysis showed that outdoor environmental bacterial aerosol concentration had a significant negative correlation with relative humidity (p<0.05), and was positively correlated with PM₁₀ concentration (p<0.05), indicating that bacterial aerosol concentration was significantly affected by meteorological factors and air pollutants. The results show that the proportion of bacterial aerosol that can enter the lower respiratory tract of human body in the outdoor environment of Beijing is close to 50%, and the proportion is the highest in winter with a higher exposure risk.