黑碳(BC)对空气质量产生深远的影响,人类健康,和气候。这里,我们调查了2019年夏季首尔城市难溶BC(rBC)的浓度和大小分布以及含rBC颗粒的混合状态和形态。rBC的质量浓度范围为0.02μgm-3至2.89μgm-3,rBC的每日最大质量,每日最小红细胞质量中值直径(MMD)(110-130nm),在高峰时段,壳核比(Rshell/核)出现了NO2最大值。作为对rBC混合状态的地面观测的第一份报告,这些结果表明,车辆排放是首尔当地rBC的主要来源。与从上游区域传输相关的最大MMD(135-165nm)相比,MMD为127-146nm,最大质量负荷≥1μgm-3伴随着高O3和PM2.5。对于140-220nm的质量当量直径(DrBC),平均Rshell/核是1.25。Rshell/核心每天逐渐增加,与Ox浓度呈正相关,表明rBC颗粒的光化学老化。车辆中rBC和挥发性有机化合物的共同排放促进了白天的内部混合。然而,在>〜30°C的温度下,Rshell/核心趋于低,并且在相对湿度>75%的夜间发现了超过1.25的Rshell/核心的58%的rBC。这些结果表明,通过白天光化学氧化蒸气的涂覆和夜间的吸湿性生长,新发射的rBC颗粒的混合状态发生了变化。此外,延迟时间法揭示了红细胞的形态特征,最常见的是裸露类型(74%),在高峰时段,附加类型(6%)的数量相对较多。因此,建议在夏天,应将交通排放中的rBC颗粒与东北亚城市大气中的冬季污染缓解策略同时考虑。
Black carbon (BC) exerts profound impacts on air quality, human health, and climate. Here, we investigated concentrations and size distributions of refractory BC (rBC) and mixing state and morphology of rBC-containing particles in urban Seoul for 2019 summer. Mass concentrations of rBC ranged from 0.02 μgm-3 to 2.89 μgm-3, and daily maximums of rBC mass, daily minimums of rBC mass median diameter (MMD) (110-130 nm), and shell-to-core ratio (Rshell/core) occurred with NO2 maximums during morning rush hour. As the first report of ground observations on rBC mixing state, these results indicate that vehicle emissions are a major local source of rBC in Seoul. MMDs of 127-146 nm and the greatest mass loadings of ≥1 μg m-3 were accompanied by high O3 and PM2.5, in contrast to the largest MMDs (135-165 nm) associated with transport from upstream regions. The average Rshell/core was 1.25 for the mass-equivalent diameter (DrBC) of 140-220 nm. Rshell/core increased gradually through the day and was positively correlated with Ox concentration, indicating photochemical aging of rBC particles. Co-emissions of rBC and volatile organic compounds from vehicles facilitated internal mixing during the daytime. However, Rshell/core tended to be low at temperature >~30 °C and 58 % of rBC with Rshell/core exceeding 1.25 were found at nighttime under relative humidity >75 %. These results demonstrate that the mixing state of freshly-emitted rBC particles was altered through coating by photochemically oxidized vapors during the day and hygroscopic growth at night. Additionally, the delay-time approach revealed rBC morphological characteristics, the most common being the bare type (74 %), and the attached type (6 %) was relatively large in numbers during morning rush hour. Therefore, it is suggested that during summer, rBC particles from traffic emissions should be considered in parallel to winter pollution mitigation strategies in urban atmosphere of northeast Asia.