Water‐soluble organic carbon aerosols during a full New Delhi winter: Isotope‐based source apportionment and optical properties
Water‐soluble organic carbon aerosols during a full New Delhi winter: Isotope‐based source apportionment and optical properties
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DOI：
10.1002/2013jd020041
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发表时间：
2014-03
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通讯作者：
E. Kirillova;A. Andersson;S. Tiwari;Amit Kumar Srivastava;D. S. Bisht;Ö. Gustafsson
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文献类型：
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作者：
E. Kirillova;A. Andersson;S. Tiwari;Amit Kumar Srivastava;D. S. Bisht;Ö. Gustafsson
冬季干旱季节，印度次大陆上空的有机碳气溶胶中，水溶性有机碳(WSOC)占总有机碳气溶胶的20-80%。由于WSOC具有多条一次和二次形成途径，对其来源的刻画较差。在这项研究中，我们提出了2010/2011年冬季特大城市德里PM2.5中WSOC的生物量与化石来源的放射性碳限制。德里位于印度-恒河平原污染严重的北部。化石燃料对德里WSOC的贡献(21±4%)与最近在两个南亚背景站点发现的相似。相比之下，德里WSOC的稳定碳同位素组成与两个受体部位的碳同位素组成相比，13C的丰度较低。虽然也可能受到来源变异性的影响，但这表明近源WSOC受大气老化的影响较小。此外，还对德里WSOC的光吸收性能进行了研究。在365 nm处的质量吸收截面(MAC365)为1.1-2.7m2/g，吸收指数在3.1-9.3之间。使用一个简化的模型，与2010/2011年冬季德里的元素碳相比，WSOC的相对吸收强迫估计在3%到11%之间。总而言之，这项近源研究表明，德里城市的WSOC主要(79%)来自生物质燃烧/生物来源。此外，与南亚区域受体部位的WSOC相比，它受光化学老化的影响较小，并且对直接吸收强迫效应的贡献相对较小。
Water‐soluble organic carbon (WSOC) is a major constituent (~ 20–80%) of the total organic carbon aerosol over the Indian subcontinent during the dry winter season. Due to its multiple primary and secondary formation pathways, the sources of WSOC are poorly characterized. In this study, we present radiocarbon constraints on the biomass versus fossil sources of WSOC in PM2.5 for the 2010/2011 winter period for the megacity Delhi, situated in the northern part of the heavily polluted Indo‐Gangetic Plain. The fossil fuel contribution to Delhi WSOC (21 ± 4%) is similar to that recently found at two South Asian background sites. In contrast, the stable carbon isotopic composition of Delhi WSOC is less enriched in 13C relative to that at the two receptor sites. Although potentially influenced also by source variability, this indicates that near‐source WSOC is less affected by atmospheric aging. In addition, the light absorptive properties of Delhi WSOC were studied. The mass absorption cross section at 365 nm (MAC365) was 1.1–2.7 m2/g with an Absorption Ångström Exponent ranging between 3.1 and 9.3. Using a simplistic model the relative absorptive forcing of the WSOC compared to elemental carbon in 2010/2011 wintertime Delhi was estimated to range between 3 and 11%. Taken together, this near‐source study shows that WSOC in urban Delhi comes mainly (79%) from biomass burning/biogenic sources. Furthermore, it is less influenced by photochemical aging compared to WSOC at South Asian regional receptor sites and contributes with a relatively small direct absorptive forcing effect.