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An improved parameterization scheme for size-resolved particle activation ratio and its application on comparison study of particle hygroscopicity measurements between HTDMA and DMA-CCNC
Atmospheric Environment ( IF 5 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.atmosenv.2020.117403
Jiangchuan Tao , Ye Kuang , Nan Ma , Yijia Zheng , A. Wiedensohler , Chunsheng Zhao

Abstract Size-resolved Particle Activation Ratio (SPAR), defined as the size-dependence of CCN activity of aerosol particles, is generally parameterized by a scheme that neglects the contribution of nearly-hydrophobic particles. In this paper, it was found that nearly-hydrophobic particles can contribute up to 20% to the CCN activity for large particles and the estimation of particle hygroscopicity would be significantly biased using the original parameterization scheme. An improved parameterization scheme considering the contribution of nearly-hydrophobic particles was proposed and applied on measurements conducted at a rural site in the North China Plain during summer 2013. For hygroscopic particles in range of 50–70 nm diameter, which might be dominated by organic compounds, their number fraction (fn) and midpoint activation diameter (Da) fitted with the improved scheme were up to 20% lower than the parameters fitted with the original scheme. Both parameterization schemes of SPAR were further applied in a comparison study of aerosol hygroscopicity measurements between Cloud Condensation Nuclei (CCN) Counter coupled with Differential Mobility Analyzer (DMA-CCNC) and Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) during the Xianghe Campaign. Applying the improved scheme, the correlations of derived fn for hygroscopic particles between measurements of DMA-CCNC and HTDMA were improved (R increased by up to 0.2 with the uncertainty of the regression to be about 10%). In addition, for particles smaller than 100 nm, the size-dependence of hygroscopicity parameter and the diurnal cycle of fn derived using the improved scheme, based on the DMA-CCNC measurements were more consistent with those derived with the HTDMA measurements. These results highlight the importance of considering nearly-hydrophobic particles in SPAR curves fitting and in the calculation of aerosol hygroscopicity based on DMA-CCNC measurements.

中文翻译:

改进的尺寸分辨粒子活化比参数化方案及其在HTDMA和DMA-CCNC粒子吸湿性测量对比研究中的应用

摘要 尺寸分辨粒子活化比 (SPAR),定义为气溶胶粒子 CCN 活性的尺寸依赖性,通常由忽略近疏水性粒子贡献的方案进行参数化。在本文中,发现近疏水性粒子对大粒子的 CCN 活性贡献高达 20%,并且使用原始参数化方案对粒子吸湿性的估计会显着偏差。提出了一种考虑近疏水性颗粒贡献的改进参数化方案,并将其应用于 2013 年夏季在华北平原农村地区进行的测量。对于直径在 50-70 nm 范围内的吸湿性颗粒,可能以有机物为主化合物,它们的数量分数 (fn) 和中点激活直径 (Da) 与改进方案拟合的参数比原始方案拟合的参数低 20%。SPAR的两种参数化方案进一步应用于香河战役期间云凝结核(CCN)计数器与微分迁移率分析仪(DMA-CCNC)和吸湿性串联微分迁移率分析仪(HTDMA)之间的气溶胶吸湿性测量的比较研究。应用改进的方案,DMA-CCNC 和 HTDMA 测量之间的吸湿性颗粒的衍生 fn 的相关性得到了改善(R 增加了 0.2,回归的不确定性约为 10%)。此外,对于小于 100 nm 的粒子,使用改进方案导出的吸湿性参数的大小依赖性和 fn 的昼夜循环,基于 DMA-CCNC 测量与那些通过 HTDMA 测量导出的更一致。这些结果强调了在 SPAR 曲线拟合和基于 DMA-CCNC 测量的气溶胶吸湿性计算中考虑近疏水性颗粒的重要性。
更新日期:2020-04-01
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