Multiscale Chemical Composition of Carbonaceous particles and Coatings (MC4)

黑碳(BC)粒子是大气科学中一个重要且高度相关的研究领域。它们是由人类活动以火灾和运输排放的烟尘的形式大量产生的。自前工业时代以来，大气中BC的浓度一直在增加，对全球气候的影响一直是变暖，因为这些颗粒可以吸收入射的辐射。此外，这些颗粒还能够通过大气局部变暖来改变区域气候和天气模式。然而，BC对大气的确切影响很难预测，因为确切的光吸收特性因颗粒物的确切来源而异。此外，大气过程会导致颗粒与其他颗粒混合，并从气相反应中获得涂层。这些效应实质上改变了气溶胶的吸收特性，但很难预测。传统上，由于缺乏合适的仪器来直接测量BC和颗粒上任何涂层的化学成分，这些影响的研究一直受到阻碍。为了满足这些需求，Aerodyne Research Inc.、水滴测量技术公司和曼彻斯特大学正在合作开发烟尘粒子气溶胶质谱仪(SP-AMS)。它使用近红外线激光蒸发含有BC的颗粒，然后用质谱仪对生成的蒸汽进行分析。由于不含BC的粒子不会吸收激光，因此不会被检测到。在这种情况下，SP-AMS只选择性地测量BC颗粒及其涂层，因此该仪器可用于选择性地研究其涂层的混合状态和化学成分。多尺度碳质颗粒和涂层化学组成(MC4)将使用这一新型仪器和一套其他测量方法来研究大气中碳质颗粒的来源和演化，这反过来将导致更好的模式处理和更准确的碳质颗粒气候影响预测。此外，将在实验室开展开发工作，以提高仪器灵敏度和数据质量，准确确定检测下限，并制定操作规程。这将最大限度地提高后续实验工作的有效性。测量将在洛杉矶、曼彻斯特和诺福克北部海岸的韦伯恩大气天文台进行。需要各种各样的地点来表征范围广泛的气溶胶。涂层和混合的测量将与基于自动滤光片的方法的光吸收测量进行比较。这将与基于气相VOC测量的气溶胶自排放以来所经历的化学处理量的估计进行比较。不同来源和类型的BC颗粒将通过数值因子分析进行识别和表征。这些研究的结果将推动对模型界有用的参数化。这将使更准确地评估BC颗粒在其大气寿命过程中的气候影响，并导致总体上更准确的区域和全球气候预测。

Black carbon (BC) particles are an important and highly relevant area of study in atmospheric science. These are produced in large quantities by human activities in the form of soot from fires and transport emissions. Concentrations of BC in the atmosphere have increased since pre-industrial times and the effect on global climate has been one of warming, as these particles can absorb incident radiation. In addition, these particles have the ability to alter regional climate and weather patterns through localised warming of the atmosphere. However, the exact effects of BC on the atmosphere are hard to predict, as the exact light-absorbing properties vary according to the exact source of the particles. In addition, atmospheric processes can cause the particles to become mixed with others and obtain coatings from gas phase reactions. These effects substantially change the absorption properties of the aerosol but are hard to predict. The study of these effects has traditionally been hampered by the lack of suitable instrumentation that can directly measure the chemical composition of BC and any coatings on the particles. To address these needs, the Soot Particle Aerosol Mass Spectrometer (SP-AMS) is being developed through a partnership between Aerodyne Research Inc., Droplet Measurement Technologies and the University of Manchester. This uses a near infra red laser to vaporise particles containing BC before the resultant vapours are analysed using mass spectrometry. Because particles that do not contain BC do not absorb the laser light, these are not detected. In this manner, the SP-AMS selectively measures only BC particles and their coatings, so therefore this instrument can be used to study the mixing state and the chemical composition of their coatings selectively. Multiscale Chemical Composition of Carbonaceous particles and Coatings (MC4) will use this novel instrument in conjunction with a suite of other measurements to study the sources and evolution of BC particles in the atmosphere, which will in turn lead to better model treatments and more accurate predictions of BC's climatic impacts. In addition, development work will take place in the laboratory to improve instrument sensitivity and data quality, accurately determine detection limits and formulate an operational protocol. This will maximise the effectiveness of subsequent experimental work. Measurements will take place in Los Angeles, Manchester and the Weybourne Atmospheric Observatory on the north Norfolk coast. A wide variety of sites is needed to characterise a broad range of aerosols. The measurements of coating and mixing will be compared with optical absorption measurements from automated filter-based methods. These will compared with estimates of the amount of chemical processing that the aerosol has undergone since emission based on gas phase VOC measurements. Different sources and types of BC particles will be identified and characterised using numerical factor analysis. The results from these studies will drive parameterisations that will be of use to the modelling community. This will allow the more accurate evaluation of the climatic impacts of BC particles over the course of their atmospheric lifetimes and lead to more accurate regional and global climate predictions in general.