Characterizing the sources and atmospheric chemistry of light-absorbing carbonaceous aerosols using resonance Raman spectroscopy

使用共振拉曼光谱表征光吸收碳质气溶胶的来源和大气化学

• 批准号: RGPIN-2014-05002
• 负责人: Hayes, Patrick
• 金额: $ 2.33万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611379
• 关键词: Characterizing; sources; atmospheric; chemistry; light

The proposed research will utilize ultraviolet resonance Raman (UVRR) spectroscopy to study the chemical composition of light-absorbing organic compounds in atmospheric aerosols. This family of compounds, known as brown carbon, is poorly understood even though research indicates that brown carbon has an important impact on radiative forcing of climate that varies widely depending on location. Moreover, carbonaceous aerosols in general – both organic and back carbon fractions – are currently the subject of intense scientific research because of their important impact on climate and human health. The goal of the proposed research program is to characterize the composition of brown carbon, identify the different sources of brown carbon, and understand the chemical processing of these light-absorbing organic compounds during their atmospheric lifetime. UVRR spectroscopy is a unique tool for studying organic aerosol because it can provide vibrational spectra specifically for chromophores with an absorption band that matches the probing laser wavelength even when those chromophores are mixed with non-absorbing organics in a particle. The UVRR studies will investigate the products of organic reactions carried out in the laboratory that mimic the chemistry occurring in water-laden particles or cloud droplets, which have been linked to brown carbon production. The UVRR spectra of the ‘synthetic’ brown carbon will be measured at multiple wavelengths to identify the chromophores responsible for light absorption. Different precursor compounds will be explored, and the resulting changes in brown carbon composition will be identified. In similar experiments, field samples of organic aerosol will be collected and artificially aged using ammonia gas, which has been show to produce light-absorbing nitrogen-containing organics. The spectra measured in the lab studies will be compared to those collected from field samples to evaluate the contribution of aqueous and cloud droplet chemistry to the observed brown carbon mass concentrations. Analyses on field samples will be performed as well. In addition to quantifying the brown carbon functional group content, statistical methods such as positive matrix factorization (PMF) will be used to identify the different components of brown carbon. The correlations of the brown carbon spectral features and PMF components with emission tracers and photochemical age will then be utilized in the process of assigning different sources to the brown carbon components. The relationship between composition and light absorption will be explored using field data to find characteristics in the light absorption spectra that can be used to constrain brown carbon composition. Many techniques have been applied to the study of organic aerosol composition including mass spectrometry, FTIR spectroscopy, and Raman Spectroscopy. These techniques provide valuable information, but none are capable of selectively analyzing brown carbon, or, at best, they characterize only a small fraction of the brown carbon mass. It is expected that the proposed research will provide new and more complete information regarding brown carbon sources and atmospheric chemistry. Ultimately, the results of this work can be used to constrain and test models of atmospheric aerosols, which are critical for predicting future climate.

拟议的研究将利用紫外线共振拉曼（UVRR）光谱学研究大气气溶胶中吸光有机化合物的化学组成。尽管研究表明棕色碳对气候的辐射强迫有重要影响，但这种化合物家族被称为棕色碳，但根据位置而变化很大。此外，由于它们对气候和人类健康的重要影响，因此碳质气溶胶（无论是有机的和后碳的小分子）当前是强烈的科学研究的主题。拟议的研究计划的目的是表征棕色碳的成分，确定棕色碳的不同来源，并了解这些在大气中终生的浅色有机化合物的化学处理。 UVRR光谱是研究有机气溶胶的独特工具，因为它可以为具有吸收带的发色团提供振动光谱，即使这些发色团与粒子中的非吸收组织混合在一起，该吸收带也可以匹配探测激光波长。 UVRR研究将调查实验室中进行的有机反应产物，以模仿与含水量的颗粒或云液滴中发生的化学作用，这些化学物质与棕色碳的产生有关。 “合成”棕色碳的UVRR光谱将在多个波长下测量，以识别负责轻滥用的发色团。将探索不同的前体化合物，并确定棕色碳成分的变化。在类似的实验中，将使用氨气来收集有机气溶胶的现场样品，并人工老化，氨气已显示出产生含氮的含量的组织。将在实验室研究中测得的光谱与从现场样品收集的光谱进行比较，以评估水和云液滴化学对观察到的棕色碳质量浓度的贡献。 对现场样本的分析也将进行。除了量化棕色碳功能组含量外，还将使用统计方法（例如阳性基质分解（PMF））来识别棕色碳的不同成分。然后将在将不同的来源分配给棕色碳组分的过程中，将使用棕色碳光谱特征和PMF成分与发射示踪剂和光化学时代的相关性。组成与光滥用之间的关系将使用现场数据探索，以在轻度滥用光谱中找到特征，可用于限制棕色碳组成。 许多技术已应用于有机气溶胶组成的研究，包括质谱，FTIR光谱和拉曼光谱法。这些技术提供了有价值的信息，但是没有一个能够选择性地分析棕色碳，或者充其量只能表征棕色碳质量的一小部分。预计拟议的研究将提供有关棕色碳源和大气化学的更完整的新信息。最终，这项工作的结果可用于约束和测试大气气溶胶的模型，这对于预测未来气候至关重要。