Chemical properties, sources and size-resolved hygroscopicity of submicron black-carbon-containing aerosols in urban Shanghai
Chemical properties, sources and size-resolved hygroscopicity of submicron black-carbon-containing aerosols in urban Shanghai
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DOI：
10.5194/acp-22-8073-2022
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发表时间：
2022-06-22
影响因子：
6.3
通讯作者：
Ge, Xinlei
中科院分区：
文献类型：
--
作者：
Cui, Shijie;Huang, Dan Dan;Ge, Xinlei
难降解黑碳气溶胶（rBC）在空气质量和气候变化中发挥着重要作用，但对rBC及其相关涂层的物理化学性质的高时间分辨率和详细的研究仍然很少。在这项工作中，我们使用的激光只有Aerodyne烟尘粒子气溶胶质谱仪（SP-AMS），专门测量rBC-containing（rBCc）的颗粒，我们比较了它们的属性与总的非耐火亚微米颗粒（NR-PM 1）平行测量的高分辨率AMS（HR-AMS）在上海举行。观察结果表明，总体而言，rBC被厚包覆，包覆层与rBC芯的平均质量比（R-BC）类似于5.0（+/-1.7）。然而，rBC涂层物质的质量与NR-PM 1中那些物质的质量的比率仅为19.1（+/- 4.9）%;硫酸盐倾向于优先凝聚在非rBC颗粒上，因此rBC上的硫酸盐与NR-PM 1硫酸盐的比率仅为7.4（+/- 2.2）%，而大多数（72.7 +/-21.0%）的初级有机气溶胶（POA）与rBC有关。正矩阵因子分解显示，从烹饪排放的有机物没有涂层rBC，和一部分的有机物涂层rBC是从生物质燃烧，这些有机物是无法识别的NR-PM 1。小的rBCc颗粒主要来自交通，而大尺寸的颗粒通常与次要组分混合，通常具有较厚的涂层。硫酸盐和二次有机气溶胶（SOA）的物种主要是通过白天的光化学氧化（SOA的形成，可能与交通相关的POA到SOA的原位化学转化），而夜间的异质性形成占主导地位的硝酸盐，我们还估计了5-19小时的平均时间为这些次级物种涂层rBC。在受船舶排放影响的短时间内，颗粒物的特点是具有高钒浓度（平均6.3 +/- 3.1 ng m（-3））和平均钒/镍质量比为2.0（+/- 0.6）。此外，rBCc颗粒的尺寸分辨吸湿性参数（kappa（rBCc））是基于它们的完整化学表征获得的，并且被参数化为kappa（rBCc）（x）= 0.29-0.14 x exp（-0.006 x x）（其中x范围从150至1000 nm）。在0.1%和0.2%的临界过饱和度（SSC）下，D-50值分别为166（+/-16）和110（+/-5）nm，并且分别有16（+/-3）%和59（+/-4）%的rBCc颗粒可以被激活成云凝结核（CCN）。我们的研究结果对于促进对BC化学的理解以及有效控制大气BC污染是有价值的。
Refractory black carbon (rBC) aerosols play an important role in air quality and climate change, yet highly time-resolved and detailed investigations on the physicochemical properties of rBC and its associated coating are still scarce. In this work, we used a laser-only Aerodyne soot particle aerosol mass spectrometer (SP-AMS) to exclusively measure rBC-containing (rBCc) particles, and we compared their properties with those of the total nonrefractory submicron particles (NR-PM1) measured in parallel by a high-resolution AMS (HR-AMS) in Shanghai. Observations showed that, overall, rBC was thickly coated, with an average mass ratio of coating to rBC core (R-BC) similar to 5.0 (+/- 1.7). However, the ratio of the mass of the rBC-coating species to the mass of those species in NR-PM1 was only 19.1 (+/- 4.9) %; sulfate tended to condense preferentially on non-rBC particles, so the ratio of the sulfate on rBC to the NR-PM1 sulfate was only 7.4 (+/- 2.2) %, while the majority (72.7 +/- 21.0 %) of the primary organic aerosols (POA) were associated with rBC. Positive matrix factorization revealed that organics emitted from cooking did not coat rBC, and a portion of the organics that coated rBC was from biomass burning; such organics were unidentifiable in NR-PM1. Small rBCc particles were predominantly from traffic, while large-sized ones were often mixed with secondary components and typically had a thick coating. Sulfate and secondary organic aerosol (SOA) species were generated mainly through daytime photochemical oxidation (SOA formation, likely associated with in situ chemical conversion of traffic-related POA to SOA), while nocturnal heterogeneous formation was dominant for nitrate; we also estimated an average time of 5-19 h for those secondary species to coat rBC. During a short period that was affected by ship emissions, particles were characterized as having a high vanadium concentration (on average 6.3 +/- 3.1 ng m(-3)) and a mean vanadium/nickel mass ratio of 2.0 (+/- 0.6). Furthermore, the size-resolved hygroscopicity parameter (kappa(rBCc)) of rBCc particles was obtained based on their full chemical characterization, and was parameterized as kappa(rBCc)(x)= 0.29-0.14 x exp(-0.006 x x) (where x ranges from 150 to 1000 nm). Under critical supersaturations (SSC) of 0.1 % and 0.2 %, the D-50 values were 166 (+/- 16) and 110 (+/- 5) nm, respectively, and 16 (+/- 3) % and 59 (+/- 4) %, respectively, of the rBCc particles by number could be activated into cloud condensation nuclei (CCN). Our findings are valuable for advancing the understanding of BC chemistry as well as the effective control of atmospheric BC pollution.