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首页> 外文期刊>Atmospheric chemistry and physics >Evaluating the degree of oxygenation of organic aerosol during foggy and hazy days in Hong Kong using high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS)
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Evaluating the degree of oxygenation of organic aerosol during foggy and hazy days in Hong Kong using high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS)

机译：使用高分辨率飞行时间气溶胶质谱仪（HR-ToF-AMS）评估香港在有雾和朦胧的日子中有机气溶胶的氧化程度

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The chemical characteristics of organic aerosol (OA) are still poorly constrained. Here we present observation results of the degree of oxygenation of OA based on high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) measurements made at a coastal site in Hong Kong from late April to the end of May in 2011. Two foggy periods and one hazy period were chosen for detailed analysis to compare the changes in the degree of oxygenation of OA due to different processes. Using HR-ToF-AMS measured inorganic species as input, the Extended Aerosol Inorganic Model (E-AIM) predicted a fine-particle liquid water content (LWCfp) up to 85 μg m-3 during the foggy days. Particle concentration as measured by HR-ToF-AMS was up to 60 μg m-3 during the hazy days and up to 30 μg m-3 during the foggy days. The degree of oxygenation of OA, as indicated by several parameters including the fraction of m/z 44 in organic mass spectra (f44), the elemental ratio of oxygen to carbon (O: C), and the carbon oxidation state ( styleCombining double low line"border-top: 1px solid #000; color:#000;">OSc), was evaluated against the odd oxygen (Ox) concentration, LWCfp, ionic strength (IS), and in situ pH (pHis). Observations suggest that the high concentration of OA (on average 11 μg m-3) and the high degree of oxygenation (f44 Combining double low line 0.15, O: C Combining double low line 0.51, and styleCombining double low line"border-top: 1px solid #000; color:#000;">OSc Combining double low line -0.31) during the hazy period were mainly due to gas-phase oxidation. During the foggy periods with low photochemical activities, the degree of oxygenation of OA was almost as high as that on the hazy days, and significantly higher than that during non-foggyon-hazy days. However, the OA evolved quite differently in the two foggy periods. The first foggy period in late April saw a larger LWCfp and a lower Ox concentration and the OA were made up of ～ 20 % semi-volatile oxygenated organic aerosol (SVOOA) as resolved by positive matrix factorization (PMF). In the second foggy period in mid-May, higher Ox concentration and lower LWCfp were observed, and the OA were found to contain > 50 % low-volatility oxygenated organic aerosols (LVOOA). An examination of the particle characteristics (pHis, IS, and LWCfp) suggests that partitioning may have been the dominating process through which oxygenated species were incorporated into the particle phase during the first foggy period, while oxidation in the aqueous phase dominated over gas-phase processes during the second foggy period.
机译：有机气溶胶（OA）的化学特性仍然受限制。在这里，我们根据4月下旬至5月底在香港沿海地区进行的高分辨率飞行时间气溶胶质谱（HR-ToF-AMS）测量，得出OA氧合度的观察结果。 2011年。选择两个有雾期和一个朦胧期进行详细分析，以比较不同工艺导致的OA氧合度的变化。使用HR-ToF-AMS测量的无机物作为输入，扩展气溶胶无机模型（E-AIM）预测在大雾天中的细颗粒液体水含量（LWCfp）高达85μgm-3。通过HR-ToF-AMS测量的颗粒浓度在朦胧的日子中高达60μgm-3，在有雾的日子中高达30μgm-3。 OA的氧化程度，由几个参数表示，包括有机质谱中的 m / z 44分数（ f 44），氧与碳的元素比（O：C），并针对奇数氧（Ox）评估了碳的氧化态（ styleCombining doublelow line“ border-top：1px solid＃000; color：＃000;”> OSc ）浓度，LWCfp，离子强度（IS）和原位pH（pHis）。观察结果表明，高浓度的OA（平均11μgm-3）和高的氧合度（ f 44结合双低线0.15，O：C结合双低线0.51和<跨度样式合并双低线“ border-top：1px实线＃000;颜色：＃000;”> OSc 混合双低线-0.31）的原因主要是由于气相氧化。在光化学活性低的雾期，OA的氧化程度几乎与朦胧的日子相同，并且明显高于非有雾/非朦胧的日子。但是，在两个有雾时期，OA的发展差异很大。在4月下旬的第一个有雾时期，通过正矩阵分解（PMF）解析，LWCfp较大，Ox浓度较低，并且OA由约20％的半挥发性含氧有机气溶胶（SVOOA）组成。在5月中旬的第二个雾期中，观察到较高的Ox浓度和较低的LWCfp，并且发现OA包含> 50％的低挥发性含氧有机气溶胶（LVOOA）。对颗粒特征（pHis，IS和LWCfp）的检查表明，分配可能是占主导地位的过程，在第一个有雾期间，含氧物质通过该过程掺入颗粒相中，而在气相中水相中的氧化占主导在第二个大雾时期的过程。

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