典型排放源黑碳的稳定碳同位素组成研究

采集了我国主要的黑碳排放源(生物质燃烧、民用燃煤和机动车尾气)的烟尘样品,分析烟尘中黑碳(BC)和总碳(TC)与原始燃料的稳定碳同位素组成(δ13C),对比各种δ13C值之间的关联性,评估运用δ13C技术进行BC源解析的潜力.结果表明:①3种典型排放源烟尘样品的δ13CBC与燃料有较好的一致性,且不同排放源的δ13CBC变化范围之间有比较明显的差别:生物质燃料除玉米秸(C4植物,δ13CBC为-13.62‰)显著不同外,C3植物的δ13CBC平均值为-26.49‰±1.17‰;烟煤的平均值为-23.46‰±0.37‰;机动车尾气(包括柴油车和汽油车)的平均值为-25.17‰±0.40‰.②各种排放源的BC形成过程存在程度各异的碳同位素分馏,C4植物(玉米秸)燃烧过程分馏作用较明显(BC的δ13C相对燃料负偏1.62‰),而C3植物和民用煤燃烧过程的分馏较小(分别正偏0.63‰和0.52‰).③BC的纯化手段(CTO-375方法)对生物质烟尘的δ13C有一定的影响(BC和TC的δ13C相差约为0.50‰),对化石燃料烟尘没有影响.上述典型排放源的δ13C数据库可为BC源解析提供依据.

Stable Carbon Isotope of Black Carbon from Typical Emission Sources in China

Smoke particles from the three typical BC emission sources (biomass burning, household coal combustion, and vehicular exhaust) were collected and analyzed for stable carbon isotopes (delta13C) of black carbon (BC), total carbon (TC), as well as the original fuels. The results show that corn stalk (a typical C4 plant, -13.62 per thousand) has the highest delta13C(BC) value, and the average values for C3 plants, bituminous coals, and vehicle exhaust are -26.49 per thousand +/- 1.17 per thousand, -23.46 per thousand +/- 0.37 per thousand, and -25.17 per thousand +/- 0.40 per thousand, respectively. delta13C(BC) values from the three sources are similar to the corresponding fuels, and the ranges of these values are different from each other. Carbon fractionation occurs during the process of BC formation. delta13C(BC) for C4 plant (corn stalk) is lower than that of the fuel by 1.62 per thousand, while the values for C3 plants and coals are higher than that of the fuels by 0.63 per thousand and 0.52 per thousand, respectively. CTO-375 method, which is used to extract BC from TC, affects the stable carbon isotope of smokes from biomass burning to some extent (the difference between delta13C(BC) and delta13C(TC) is nearly 0.50 per thousand), but has little effect on fossil fuel smokes. This delta13C database for typical emission sources provides scientific information on BC source apportionment.