Inter Disciplinary Program in Climate Studies, Indian Institute of Technology Bombay, Powai, Mumbai, India.
Environmental Science and Engineering Department, Indian Institute of Technology Bombay, Powai, Mumbai, India.
Chemosphere. 2022 Aug;301:134681. doi: 10.1016/j.chemosphere.2022.134681. Epub 2022 Apr 22.
Organic aerosols (OA) play significant roles in several atmospheric processes and adversely impact human health. This study examines the key structural units present in water- and methanol-soluble organic carbon (WSOC, MSOC) fraction of OA from emission sources (traffic and biomass cooking) and an urban background location in India. Proton nuclear magnetic resonance (H NMR) spectroscopy was employed to assess the distribution of non-exchangeable proton structural groups of the OAs. Organic carbon, elemental carbon, black carbon, and water-soluble organic carbon (WSOC) analyses were also conducted. The H NMR analysis corroborated that the WSOC and MSOC fractions hold similar H structural groups; however, they differ in their relative distribution and absolute concentrations across the ambient locations and source emissions. The relative contribution of the proton structural groups to OA was in the order C-H > H-C-C=> H-C-O > Ar-H. The aliphatic concentration was lower in the morning tunnel entry aerosols when compared to other tunnel aerosols, whereas the unsaturated structures (H-C-C= ) were present in all the tunnel aerosols within a range of 47.2-62.3 μmol/m. The aromatic groups were the maximum in the firewood aerosols, about 1.4 and 3.7 times higher than the crop residue and the mixed fuel aerosols, respectively. The total functional groups, i.e., the sum of all the observed groups, significantly correlated with C-H (r = 0.96) and WSOC (r = 0.7), suggesting the higher contribution of aliphatic groups in the WSOC fraction. WSOC examined in this study fits well in the established H NMR source identification fingerprints of urban aerosols. However, biomass cooking aerosols do not fit the established biomass burning organic aerosols (BBOAs) boundaries, exhibiting a smaller relative contribution of carbon-oxygen double bonds and a less oxidised character than open-field burning. Our results provide essential insights into the nature of urban atmospheric, near-traffic and biomass cooking OAs in India.
有机气溶胶 (OA) 在多种大气过程中发挥着重要作用，并对人类健康产生不利影响。本研究考察了来自排放源（交通和生物质烹饪）和印度城市背景位置的 OA 中水溶性有机碳 (WSOC) 和甲醇可溶性有机碳 (MSOC) 部分中的关键结构单元。质子核磁共振 (H NMR) 光谱用于评估 OA 中非交换质子结构基团的分布。还进行了有机碳、元素碳、黑碳和水溶性有机碳 (WSOC) 分析。H NMR 分析证实，WSOC 和 MSOC 部分具有相似的 H 结构基团；然而，它们在不同的环境位置和源排放物中的相对分布和绝对浓度存在差异。质子结构基团对 OA 的相对贡献顺序为 C-H > H-C-C => H-C-O > Ar-H。与其他隧道气溶胶相比，早晨隧道入口气溶胶中的脂肪族浓度较低，而所有隧道气溶胶中均存在不饱和结构（H-C-C=），范围在 47.2-62.3 μmol/m。在木柴气溶胶中，芳香族基团的含量最高，分别比农作物残余物和混合燃料气溶胶高约 1.4 和 3.7 倍。总官能团，即所有观察到的基团之和，与 C-H（r=0.96）和 WSOC（r=0.7）显著相关，表明 WSOC 部分中脂肪族基团的贡献更高。本研究中检查的 WSOC 很好地符合已建立的城市气溶胶的 H NMR 源识别指纹。然而，生物质烹饪气溶胶不符合已建立的生物质燃烧有机气溶胶 (BBOAs) 边界，表现出较小的碳-氧双键相对贡献和较少的氧化特征，而不是露天燃烧。我们的结果为印度城市大气、近交通和生物质烹饪 OA 的性质提供了重要的见解。
