Department of Civil Engineering, Indian Institute of Technology, Kanpur, India.
Department of Civil Engineering, Indian Institute of Technology, Kanpur, India; Centre of Environmental Science and Engineering, CESE, IIT Kanpur, India.
Environ Pollut. 2018 Jan;232:310-321. doi: 10.1016/j.envpol.2017.09.079. Epub 2017 Sep 30.
Real time chemical characterization of non-refractory submicron aerosols (NR-PM) was carried out during post monsoon (September-October) via Aerosol Mass Spectrometer (AMS) at a polluted urban location of Kanpur, India. Organic aerosol (OA) was found to be the dominant species with 58% contribution to total NR-PM mass, followed by sulfate (16%). Overall, OA was highly oxidized (average O/C = 0.66) with the dominance of oxidized OAs (60% of total OA) as revealed by source apportionment. Oxidized nature of OA was also supported by very high OC/EC ratios (average = 8.2) obtained from simultaneous offline filter sampling. High and low OA loading periods have very dramatic effects on OA composition and oxidation. OA O/C ratios during lower OA loading periods were on average 30% higher than the same from high loading periods with significant changes in types and relative contribution from oxidized OAs (OOA). Comparison of OA sources and chemistry among post monsoon and other seasons revealed significant differences. Characteristics of primary OAs remain very similar, but features of OOAs showed substantial changes from one season to another. Winter had lowest OOA contribution to total OA but similar overall O/C ratios as other seasons. This reveals that processing of primary OAs, local atmospheric chemistry, and regional contributions can significantly alter OA characteristics from one season to another. This study provides interesting insights into the seasonal variations of OA sources and evolution in a very polluted and complex environment.
利用气溶胶质谱仪（AMS），在印度坎普尔污染城市地区进行了后季风期（9 月至 10 月）非难挥发亚微米气溶胶（NR-PM）的实时化学特征研究。结果表明，有机气溶胶（OA）是主要成分，占 NR-PM 总质量的 58%，其次是硫酸盐（16%）。总体而言，OA 高度氧化（平均 O/C=0.66），通过源解析揭示了氧化 OA 的主导地位（占总 OA 的 60%）。OA 的氧化性质也得到了支持，因为从同步离线滤膜采样中获得了非常高的 OC/EC 比值（平均为 8.2）。高和低 OA 负荷期对 OA 组成和氧化有非常显著的影响。在低 OA 负荷期，OA O/C 比值平均比高负荷期高出 30%，且氧化 OA（OOA）的类型和相对贡献发生了显著变化。对后季风期和其他季节的 OA 来源和化学性质进行比较，发现存在显著差异。一次有机气溶胶的特征非常相似，但 OOAs 的特征从一个季节到另一个季节发生了很大变化。冬季 OOA 对总 OA 的贡献最低，但与其他季节的总 O/C 比值相似。这表明，一次有机气溶胶的处理、当地大气化学和区域贡献可以显著改变从一个季节到另一个季节的 OA 特征。这项研究提供了对一个非常污染和复杂环境中 OA 来源和演化季节性变化的有趣见解。
