Transformation of logwood combustion emissions in a smog chamber: formationof secondary organic aerosol and changes in the primary organic aerosol upondaytime and nighttime aging
Transformation of logwood combustion emissions in a smog chamber: formationof secondary organic aerosol and changes in the primary organic aerosol upondaytime and nighttime aging
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DOI：
10.5194/acp-16-13251-2016
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发表时间：
2016-10
影响因子：
6.3
通讯作者：
P. Tiitta
中科院分区：
文献类型：
--
作者：
P. Tiitta
抽象的。来自小规模木材燃烧排放的有机气溶胶（OA）没有很好地代表目前的排放清单和模型，虽然他们大大有助于大气颗粒物（PM）水平。在这项工作中，一个29立方米的烟雾室在ILMARI设施的东芬兰大学被用来调查形成的二次有机气溶胶（SOA）从一个小规模的现代砖石加热器通常用于北方欧洲。排放物在烟雾室中氧化老化各种黑暗（即，O3和NO3）和UV（即，OH）条件下，OH浓度水平为（0.5-5）× 106分子cm−3，实现了长达18 h的等效大气老化。气溶胶质谱仪的特点是直接OA排放和SOA形成的三种木材（桦木，山毛榉和云杉）燃烧使用两个点火过程（快速点火与VOC-NOx的比例为3和缓慢点火的比例为5）。黑暗和UV老化增加了SOA的质量分数，平均SOA生产2.0倍的初始OA质量负荷。SOA增强被认为是更高的慢点火相比，快速点火条件。正矩阵分解（PMF）被用来分离SOA，初级有机气溶胶（POA）及其亚组的总OA质谱。PMF分析确定了两个POA和三个SOA的因素，与三个主要的氧化剂：臭氧，硝酸根和OH自由基。有机硝酸盐（ONs）被观察到直接从木材燃烧和氧化过程中通过NO3自由基（暗老化），这表明小规模的木材燃烧可能是一个重要的ON源。POA在加入臭氧后被氧化，形成老化的POA，并且在老化7小时后，超过75%的原始POA被转化。这一过程可能涉及蒸发和均相气相氧化以及颗粒有机物的非均相氧化。结果一般证明，原木燃烧排放物是大气中密集化学处理的主题，这些转化的时间尺度相对较短，即，小时
Abstract. Organic aerosols (OA) derived from small-scale wood combustion emissions are not well represented by current emissions inventories and models, although they contribute substantially to the atmospheric particulate matter (PM) levels. In this work, a 29 m3 smog chamber in the ILMARI facility of the University of Eastern Finland was utilized to investigate the formation of secondary organic aerosol (SOA) from a small-scale modern masonry heater commonly used in northern Europe. Emissions were oxidatively aged in the smog chamber for a variety of dark (i.e., O3 and NO3) and UV (i.e., OH) conditions, with OH concentration levels of (0.5–5) × 106 molecules cm−3, achieving equivalent atmospheric aging of up to 18 h. An aerosol mass spectrometer characterized the direct OA emissions and the SOA formed from the combustion of three wood species (birch, beech and spruce) using two ignition processes (fast ignition with a VOC-to-NOx ratio of 3 and slow ignition with a ratio of 5). Dark and UV aging increased the SOA mass fraction with average SOA productions 2.0 times the initial OA mass loadings. SOA enhancement was found to be higher for the slow ignition compared with fast ignition conditions. Positive matrix factorization (PMF) was used to separate SOA, primary organic aerosol (POA) and their subgroups from the total OA mass spectra. PMF analysis identified two POA and three SOA factors that correlated with the three major oxidizers: ozone, the nitrate radical and the OH radical. Organonitrates (ONs) were observed to be emitted directly from the wood combustion and additionally formed during oxidation via NO3 radicals (dark aging), suggesting small-scale wood combustion may be a significant ON source. POA was oxidized after the ozone addition, forming aged POA, and after 7 h of aging more than 75 % of the original POA was transformed. This process may involve evaporation and homogeneous gas-phase oxidation as well as heterogeneous oxidation of particulate organic matter. The results generally prove that logwood burning emissions are the subject of intensive chemical processing in the atmosphere, and the timescale for these transformations is relatively short, i.e., hours.