Most of human exposure to atmospheric pollutants occurs indoors, and the components of outdoor aerosols may have been changed in the way before reaching indoor spaces. Here we conducted real-time online measurements of mass concentrations and chemical composition of black carbon and the non-refractory species in PM_2.5 in an occupied office for approximately one month. The open-close windows and controlled dampness experiments were also performed. Our results show that indoor aerosol species primarily originate from outdoors with indoor/outdoor ratio of these species typically less than unity except for certain organic aerosol (OA) factors. All aerosol species went through filtration upon transport indoors. Ammonium nitrate and fossil fuel OA underwent evaporation or particle-to-gas partitioning, while less oxidized secondary OA (SOA) underwent secondary formation and cooking OA might have indoor sources. With higher particulate matter (PM) mass concentration outdoors than in the office, elevated natural ventilation increased PM exposure indoors and this increased exposure was prolonged when outdoor PM was scavenged. We found that increasing humidity in the office led to higher indoor PM mass concentration particularly more oxidized SOA. Overall, our results highlight that indoor exposure of occupants is substantially different from outdoor in terms of mass concentrations and chemical species.

中文翻译：

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办公室中增加通风和湿度的气溶胶颗粒成分、来源和影响的实时表征

人类接触大气污染物的大部分时间发生在室内，室外气溶胶的成分在到达室内空间之前可能已经发生了变化。在这里，我们对 PM _2.5中黑碳和非难熔物质的质量浓度和化学成分进行了实时在线测量在一个被占用的办公室里大约一个月。还进行了开闭窗和控制湿度实验。我们的结果表明，室内气溶胶物种主要来自室外，除了某些有机气溶胶 (OA) 因素外，这些物种的室内/室外比例通常小于 1。所有气溶胶物质在室内运输时都经过过滤。硝酸铵和化石燃料 OA 经历了蒸发或粒子到气体的分配，而氧化程度较低的二次 OA (SOA) 经历了二次形成，烹饪 OA 可能来自室内。由于室外的颗粒物 (PM) 质量浓度高于办公室，自然通风的增加会增加室内 PM 的暴露，并且当清除室外 PM 时，这种增加的暴露会延长。我们发现，办公室湿度的增加会导致室内 PM 质量浓度升高，尤其是 SOA 氧化程度更高。总体而言，我们的结果强调，就质量浓度和化学种类而言，居住者的室内暴露与室外有很大不同。