Seasonal analysis of submicron aerosol in Old Delhi using high-resolution aerosol mass spectrometry: chemical characterisation, source apportionment and new marker identification
Seasonal analysis of submicron aerosol in Old Delhi using high-resolution aerosol mass spectrometry: chemical characterisation, source apportionment and new marker identification
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DOI：
10.5194/acp-21-10133-2021
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发表时间：
2021-07-07
影响因子：
6.3
通讯作者：
Nemitz, Eiko
中科院分区：
文献类型：
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作者：
Cash, James M.;Langford, Ben;Nemitz, Eiko
我们利用高分辨率气溶胶质谱仪（HR - AMS）首次呈现了旧德里亚微米颗粒物（PM1）的实时成分。旧德里是世界上污染最严重的地区之一，在污染最严重的季风后时期，PM1浓度达到约750μg/m³，在此期间，PM1比季风前时期增加了188%。在季风前（24%）和季风（24%）时期，硫酸盐在无机PM1质量分数中占比最大，而在季风后时期硝酸盐占比最大（8%）。在这三个时期，有机物在质量分数中占主导地位（54% - 68%），并且通过正矩阵因子分解（PMF）对有机质量进行源解析分析，发现两个与燃烧相关的因子对季风后时期的增长贡献最大（35%）。第一个PMF因子，半挥发性生物质燃烧有机气溶胶（SVBBOA），与周边各邦的地球观测火灾次数高度相关，这表明其来源与农作物秸秆燃烧有关。第二个是固体燃料有机气溶胶（SFOA）因子，由于其多环芳烃（PAHs）含量高以及通过AMS测量到的多氯二苯并二噁英（PCDDs）和多氯二苯并呋喃（PCDFs）的新型标记物种类，与当地露天焚烧有关。解析出两个交通因子：一个是类烃有机气溶胶（HOA）因子，另一个是富氮类烃有机气溶胶（NHOA）因子。NHOA中的N化合物主要是腈类物质，此前在AMS测量中未被识别出来。它们的多环芳烃组成表明NHOA与柴油有关，HOA与压缩天然气和汽油有关。这些因子合起来在季风前和季风时期对一次PM1质量的相对贡献最大，在季风后时期贡献位居第二。一个烹饪有机气溶胶（COA）因子与二次因子半挥发性氧化有机气溶胶（SVOOA）有很强的联系。与同地点挥发性有机化合物（VOC）测量值以及AMS测量的有机氮氧化物（OrgNO）的相关性表明，SVOOA是由老化的COA形成的。还发现从季风前到季风后氯化物浓度显著增加（522%），这与SVB - BOA和SFOA密切相关，表明农作物秸秆燃烧和露天垃圾焚烧是造成这种情况的原因。减少交通排放将有效降低一年中大部分时间的污染物浓度。为了降低季风后的峰值，在制定新的空气质量政策时，应考虑诸如火葬柴堆、固体废弃物焚烧和农作物秸秆焚烧等污染源。
We present the first real-time composition of submicron particulate matter (PM1) in Old Delhi using high-resolution aerosol mass spectrometry (HR-AMS). Old Delhi is one of the most polluted locations in the world, and PM1 concentrations reached similar to 750 mu g m(3) during the most polluted period, the post-monsoon period, where PM1 increased by 188% over the pre-monsoon period. Sulfate contributes the largest inorganic PM1 mass fraction during the pre-monsoon (24 %) and monsoon (24 %) periods, with nitrate contributing most during the post-monsoon period (8 %). The organics dominate the mass fraction (54 %-68 %) throughout the three periods, and, using positive matrix factorisation (PMF) to perform source apportionment analysis of organic mass, two burning-related factors were found to contribute the most (35 %) to the post-monsoon increase. The first PMF factor, semi-volatility biomass burning organic aerosol (SVBBOA), shows a high correlation with Earth observation fire counts in surrounding states, which links its origin to crop residue burning. The second is a solid fuel OA (SFOA) factor with links to local open burning due to its high composition of polyaromatic hydrocarbons (PAHs) and novel AMS-measured marker species for polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Two traffic factors were resolved: one hydrocarbon-like OA (HOA) factor and another nitrogenrich HOA (NHOA) factor. The N compounds within NHOA were mainly nitrile species which have not previously been identified within AMS measurements. Their PAH composition suggests that NHOA is linked to diesel and HOA to compressed natural gas and petrol. These factors combined make the largest relative contribution to primary PM1 mass during the pre-monsoon and monsoon periods while contributing the second highest in the post-monsoon period. A cooking OA (COA) factor shows strong links to the secondary factor, semi-volatility oxygenated OA (SVOOA). Correlations with co-located volatile organic compound (VOC) measurements and AMS-measured organic nitrogen oxides (OrgNO) suggest SVOOA is formed from aged COA. It is also found that a significant increase in chloride concentrations (522 %) from pre-monsoon to post-monsoon correlates well with SVB-BOA and SFOA, suggesting that crop residue burning and open waste burning are responsible. A reduction in traffic emissions would effectively reduce concentrations across most of the year. In order to reduce the post-monsoon peak, sources such as funeral pyres, solid waste burning and crop residue burning should be considered when developing new air quality policy.