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随着对碳气溶胶吸光性认识的提高,近年来吸光有机碳——BrC(brown carbon,棕色碳)的吸光问题成为继BC(black carbon,黑碳)之后国际大气环境领域的新热点.基于已有的研究报道,将BrC大体分为焦油类物质、类腐殖质(HULIS)和其他吸光性有机气溶胶三大类,其来源包括一次排放和二次生成2种.由于BrC缺少BC所具有的类石墨烯结构,致使颗粒间较为分散,加之含氧官能团比重较高,因而在水及有机溶剂中均有较强的可溶性.BrC的光学性质通常借助AAE(ngstrm吸收波长指数)、MAE(质量吸收效率)、RI(折射率)及SSA(单次散射反照率)来表示,其中由于BrC分子结构中缺少sp2杂化成分,形成了区别于BC的典型特征,即AAE>1(而对于BC,其AAE=1)).虽然已有借助于光学法、热光法、化学法和质谱法进行BrC测定的报道,但目前没有公认的标准测定方法和参考物质,测定结果实际依赖于选定的测定方式.在排放估算研究方面,BrC远落后于BC,致使有些排放估算方法多以相伴的BC排放量作为参照.建议今后对BrC研究应主要面向气候影响、生成机理、测定方法、排放因子与控制策略等领域来展开.
In recent years, the light absorption of BrC (brown carbon) has become a new hot spot in the field of international atmospheric environment after BC (black carbon) It has been reported that BrC can be divided into three major categories: tar, HULIS and other light-absorbing organo-aerosols. The sources include primary discharge and secondary production. Since BrC lacks BC Graphene-like structure, resulting in more dispersed particles, combined with a higher proportion of oxygen-containing functional groups, which have strong solubility in water and organic solvents.BrC optical properties are usually based on AAE (ngstrm absorption wavelength index) MAE, RI, and SSA (single scattering albedo). The lack of sp2 hybridization in the molecular structure of BrC resulted in the formation of a typical characteristic different from that of BC, ie AAE> 1 ( While for BC, AAE = 1).) Although there have been reports of BrC measurements by means of optical methods, thermo-optical methods, chemical methods and mass spectrometry, there are currently no standard methods and reference materials known and the results are actually dependent In the selected measurement method In terms of estimation studies, BrC lags far behind BC, so some of the emission estimation methods are mostly based on the BC emissions associated with it.It is suggested that the future BrC studies should mainly address such issues as climate impact, formation mechanism, determination methods, emission factors and control strategies To expand.