Abstract. The Humidified Tandem Differential Mobility Analyzer (HTDMA) is widely used to obtain the hygroscopic properties of submicron particles. Aerosol size-resolved hygroscopicity parameter κ measured by HTDMA will be influenced by the contribution of multiply charged aerosols, and this effect has seldom been discussed in previous field measurements. Our calculation demonstrates that the number ratio of multiply charged particles is quite considerable for some specific sizes between 100 nm and 300 nm, especially during the polluted episode. The multi charges will further lead to the shrinking effect of aerosol hygroscopicity in HTDMA measurements. Therefore, we propose a new algorithm to do the multi-charge correction for the size-resolved hygroscopicity κ considering both the shrinking effect and multi-charge number contribution. The application in field measurements shows that the relatively high hygroscopicity in the accumulation size range will lead to the overestimation of the particle's hygroscopicity smaller than 200 nm. The low hygroscopicity in coarse mode particles will lead to the underestimation of accumulation particles between 200 nm and 500 nm. The difference between corrected and measured κ can reach as large as 0.05, highlighting that special attention needs to be paid to the multi-charge effect when the HTDMA is used for the aerosol hygroscopicity measurement.

中文翻译：

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多次充电对HTDMA气溶胶吸湿性测量的影响

摘要。加湿串联微分淌度分析仪（HTDMA）被广泛用于获得亚微米颗粒的吸湿性能。通过HTDMA测量的气溶胶尺寸分辨的吸湿性参数κ将受到多电荷气溶胶的贡献的影响，这种影响在以前的现场测量中很少讨论。我们的计算表明，对于100 nm至300 nm之间的某些特定尺寸，尤其是在污染事件中，带多重电荷的粒子的数量比非常可观。多重电荷将进一步导致HTDMA测量中气溶胶吸湿性的缩小效应。因此，我们提出了一种新算法，该算法同时考虑了收缩效应和多电荷数贡献，从而对尺寸分辨的吸湿性κ进行多电荷校正。现场测量中的应用表明，在累积尺寸范围内相对较高的吸湿性将导致高估小于200 nm的颗粒的吸湿性。粗模式粒子的低吸湿性将导致低估200 nm至500 nm之间的累积粒子。校正后的κ与实测的κ之差可以达到0.05，这突出表明，当将HTDMA用于气溶胶吸湿性测量时，需要特别注意多电荷效应。粗模式粒子的低吸湿性将导致低估200 nm至500 nm之间的累积粒子。校正后的κ与实测的κ之差可以达到0.05，这突出表明，当将HTDMA用于气溶胶吸湿性测量时，需要特别注意多电荷效应。粗模式粒子的低吸湿性将导致低估200 nm至500 nm之间的累积粒子。校正后的κ与实测的κ之差可以达到0.05，这突出表明，当将HTDMA用于气溶胶吸湿性测量时，需要特别注意多电荷效应。