Abstract:

Carbonaceous aerosols (CAs) are pollutants in ambient aerosols, including organic carbon (OC) and elemental carbon (EC). OC can be divided into water soluble organic carbon (WSOC) and meth soluble organic carbon (MSOC) according to its solubility. The CAs from Nepal, a developing country in South Asia, can be transported over long distances into the Tibetan Plateau, thus affecting the Himalayan atmospheric composition and climate. It is of great significance to study the CAs from primary sources in Nepal for the protection of Himalayan environment. In addition, accurately knowing the emission factors (EFs) of the chemical components of carbon-containing aerosols and clarifying the influencing factors of pollutant emission factors can provide a theoretical basis for pollutant emission reduction. However, the current research on CAs from primary sources in Nepal is still limited, especially the emission characteristics of WSOC and MSOC. Thus, the EFs of CAs from biomass burning and vehicle emissions and corresponding influencing factors in Kathmandu (the capital of Nepal) were investigated in this study. EF_OC (53±7.8) g?kg^-1 and EF_WSOC (46±9.8) g?kg^-1 emitted by mud stove was 1-2 orders of magnitude higher than that emitted by iron and brick stoves. EF_EC (5.5±0.4 g?kg^-1) by mud stove was 5 times higher than that emitted by iron and brick stoves. Therefore, it is suggested that converting mud stove to iron stove can reduce pollutants emitted by biomass combustion in Nepal. As for the vehicles emission, the lowest EF value was observed at uniform speed (40 km h^-1) compared with the EFs of CAs at the low speed (10 km?h^-1) and high speed (70 km?h^-1) states. Thus, it is suggested that Nepal should add dedicated lanes for buses and motorcycles to avoid traffic jams and reduce emissions. This study provides a reliable scientific basis for the emission reduction of local air pollutants.

Key words: carbonaceous aerosols, biomass burning, vehicles emission, field measurement, emission factors

摘要：

含碳气溶胶是大气气溶胶中的污染物，包括黑碳（EC）和有机碳（OC）。根据OC的溶解性，可将其分为水溶性有机碳（WSOC）和甲醇溶解有机碳（MSOC）。尼泊尔是南亚的发展中国家，该地区的含碳气溶胶可以长距离传输进入青藏高原，进而影响喜马拉雅大气组分和气候。因此，研究尼泊尔地区的一次源含碳气溶胶对保护喜马拉雅的环境具有重要的意义。另外，准确获知含碳气溶胶化学组分的排放因子（EF），明确污染物排放因子的影响因素，可为污染物减排提供理论依据。然而，目前对于尼泊尔一次源排放的含碳气溶胶研究有限，尤其是WSOC和MSOC的排放特征报道仍为空白。基于此，在尼泊尔的首都加德满都，实地测定生物质燃烧和机动车尾气排放的含碳气溶胶排放因子，分析了排放因子的影响因素。结果表明，泥炉排放的EF_OC (53±7.8) g?kg^-1和EF_WSOC (46±9.8) g?kg^-1高于铁炉和砖炉的排放因子1－2个数量级。此外，泥炉排放的EF_EC (5.5±0.4) g?kg^-1也高于铁炉和砖炉的排放因子5倍，因此，建议将尼泊尔地区普遍使用的泥炉改造为铁炉，可以降低生物质燃烧排放的污染物。对于机动车尾气排放源而言，相比于低速（10 km?h^-1）和高速（70 km?h^-1）状态，机动车在匀速（40 km?h^-1）状态下，含碳气溶胶的排放因子最低。因此，建议尼泊尔当地增加公交车和摩托车专用道，避免交通堵塞，以达到减排的目的。该研究为当地的大气污染物减排提供了可靠的科学依据。

关键词: 含碳气溶胶, 生物质燃烧, 机动车尾气, 野外实测, 排放因子