Ambient aerosol size distributions obtained with a compact scanning mobility analyzer, the “Spider” differential mobility analyzer (DMA), are compared to those obtained with a conventional mobility analyzer, with specific attention to the effect of mobility resolution on the measured size distribution parameters. The Spider is a 12 cm diameter radial differential mobility analyzer that spans the 10–500 nm size range with 30 s mobility scans. It achieves its compact size by operating at a nominal mobility resolution R=3 (sheath flow = 0.9 L min⁻¹; aerosol flow = 0.3 L min⁻¹) in place of the higher ratio of sheath flow to aerosol flow commonly used. The question addressed here is whether the lower resolution is sufficient to capture key characteristics of ambient aerosol size distributions. The Spider, operated at R=3 with 30 s up- and downscans, was co-located with a TSI 3081 long-column mobility analyzer, operated at R=10 with a 360 s sampling duty cycle. Ambient aerosol data were collected over 26 consecutive days of continuous operation, in Pasadena, CA. Over the 17–500 nm size range, the two instruments exhibit excellent correlation in the total particle number concentrations and geometric mean diameters, with regression slopes of 1.13 and 1.00, respectively. Our results suggest that particle sizing at a lower resolution than typically employed may be sufficient to obtain key properties of ambient size distributions, at least for these two moments of the size distribution. Moreover, it enables better counting statistics, as the wider transfer function for a given aerosol flow rate results in a higher counting rate.

中文翻译：

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用于环境气溶胶粒径分布测量的便携式、中等分辨率、快速扫描差分迁移率分析仪的功效

将使用紧凑型扫描迁移率分析仪“Spider”差分迁移率分析仪 (DMA) 获得的环境气溶胶粒径分布与使用传统迁移率分析仪获得的结果进行比较，特别注意迁移率分辨率对测量的粒径分布参数的影响。Spider 是一种直径为 12 cm 的径向微分迁移率分析仪，其尺寸范围为 10-500 nm，迁移率扫描时间为 30 秒。它通过在标称流动分辨率R =3（鞘流 =  0.9 L min ^-1；气溶胶流 =  0.3 L min ^-1）下运行来实现其紧凑的尺寸) 代替通常使用的较高的鞘流与气溶胶流的比率。这里解决的问题是较低的分辨率是否足以捕捉环境气溶胶尺寸分布的关键特征。Spider 在R =3 下运行，向上和向下扫描 30 秒，与 TSI 3081 长柱迁移率分析仪并置，在R =10 下运行具有 360 秒的采样占空比。环境气溶胶数据是在加利福尼亚州帕萨迪纳连续 26 天的连续运行中收集的。在 17-500 nm 尺寸范围内，这两种仪器在总粒子数浓度和几何平均直径方面表现出极好的相关性，回归斜率分别为 1.13 和 1.00。我们的结果表明，以比通常采用的分辨率更低的分辨率进行粒度测量可能足以获得环境尺寸分布的关键特性，至少对于尺寸分布的这两个时刻。此外，它可以实现更好的计数统计，因为对于给定的气溶胶流速，更宽的传递函数会导致更高的计数率。