Xi'an Key Laboratory of Solid Waste Recycling and Resource Recovery, Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Xi'an Key Laboratory of Solid Waste Recycling and Resource Recovery, Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Chemosphere. 2023 Aug;333:138957. doi: 10.1016/j.chemosphere.2023.138957. Epub 2023 May 16.
Volatile organic compounds (VOCs) emitted from solid fuels combustion (e.g., biomass and coal) are still the dominant precursors for the formation of tropospheric ozone (O) and secondary organic aerosols (SOAs). Limited research focused on the evolution, as known as atmospheric aging, of VOCs emitted during long-timescale observations. Here, freshly emitted and aged VOCs from common residual solid fuel combustions were collected onto absorption tubes before and after passing through an oxidation flow reactor (OFR) system, respectively. The emission factor (EF) of freshly emitted total VOCs is in descending order of corn cob ≥ corn straw > firewood ≥ wheat straw > coals. Aromatic and oxygenated VOCs (OVOCs) are the two most abundant groups, accounting for >80% of the EF of total quantified VOCs (EF). Briquette technology shows an effective reduction of the VOC emission, demonstrating a maximum 90.7% lower EF in comparison to that of biomass fuels. In contrast, each VOC shows significantly different degradation in comparison to EF of freshly emitted and after 6- and 12-equivalent day aging (actual atmospheric aging days calculated from aging simulation). The largest degradations after 6-equivalent days of aging are observed on alkenes in the biomass group (60.9% on average) and aromatics in the coal group (50.6% on average), consistent with their relatively high reactivities toward oxidation with O and hydroxyl radical. The largest degraded compound is seen for acetone, followed by acrolein, benzene, and toluene. Furthermore, the results show that the distinction of VOC species based on long-timescale (12-equivalent day aging) observation is essential to further explore the effect of regional transport. The alkanes which have relatively lower reactivities but high EFs could be accumulated through long-distance transport. These results provide detailed data on fresh and aged VOCs emitted from residential fuels which could be used to explore the atmospheric reaction mechanism.
挥发性有机化合物（VOCs）源自固体燃料燃烧（如生物质和煤炭），它们仍然是对流层臭氧（O3）和二次有机气溶胶（SOA）形成的主要前体。目前，针对长时间观测过程中排放的 VOCs 的演变（即大气老化），相关研究还很有限。在此，我们分别在通过氧化流动反应器（OFR）系统前后，将常见残余固体燃料燃烧产生的新鲜排放和老化 VOC 收集到吸收管上。新鲜排放的总 VOC 的排放因子（EF）按玉米芯≥玉米秸秆＞薪柴≥麦秸＞煤的顺序依次降低。芳香族和含氧 VOCs（OVOCs）是最丰富的两类，占总量化 VOCs（EF）的>80%。型煤技术显示出对 VOC 排放的有效减少，与生物质燃料相比，其 EF 降低了 90.7%。相比之下，每种 VOC 的降解程度与新鲜排放和经过 6 等效天和 12 等效天老化后的 EF（从老化模拟计算出的实际大气老化天数）均有显著不同。在 6 等效天老化后，生物量组中的烯烃（平均降解 60.9%）和煤组中的芳烃（平均降解 50.6%）的降解程度最大，这与它们与 O 和羟基自由基的氧化反应相对较高的反应性一致。最大降解化合物是丙酮，其次是丙烯醛、苯和甲苯。此外，结果表明，基于长时间（12 等效天老化）观测对 VOC 种类的区分对于进一步探索区域传输的影响至关重要。烷烃的反应活性较低，但 EF 较高，可能通过远距离运输而积累。这些结果提供了住宅燃料排放的新鲜和老化 VOC 的详细数据，可用于探索大气反应机制。
