Laboratory for Atmospheric Research, Department of Civil & Environmental Engineering, Washington State University , Pullman, Washington 99164.
Environ Sci Technol. 2014 Jan 21;48(2):938-46. doi: 10.1021/es4040045. Epub 2013 Dec 30.
Soil and leaf litter are significant global sources of small oxidized volatile organic compounds, VOCs (e.g., methanol and acetaldehyde). They may also be significant sources of larger VOCs that could act as precursors to secondary organic aerosol (SOA) formation. To investigate this, soil and leaf litter samples were collected from the University of Idaho Experimental Forest and transported to the laboratory. There, the VOC emissions were characterized and used to drive SOA formation via dark, ozone-initiated reactions. Monoterpenes dominated the emission profile with emission rates as high as 228 μg-C m(-2) h(-1). The composition of the SOA produced was similar to biogenic SOA formed from oxidation of ponderosa pine emissions and α-pinene. Measured soil and litter monoterpene emission rates were compared with modeled canopy emissions. Results suggest surface soil and litter monoterpene emissions could range from 12 to 136% of canopy emissions in spring and fall. Thus, emissions from leaf litter may potentially extend the biogenic emissions season, contributing to significant organic aerosol formation in the spring and fall when reduced solar radiation and temperatures reduce emissions from living vegetation.
土壤和落叶是小的氧化挥发性有机化合物（VOCs，如甲醇和乙醛）的重要全球来源。它们也可能是较大 VOCs 的重要来源，这些 VOCs 可能是二次有机气溶胶（SOA）形成的前体。为了研究这一点，从爱达荷大学实验林采集了土壤和落叶样本，并运送到实验室。在那里，对 VOC 排放进行了特征描述，并通过暗反应和臭氧引发反应来驱动 SOA 的形成。单萜类化合物主导了排放特征，排放速率高达 228 μg-C m(-2) h(-1)。所产生的 SOA 的组成与由氧化辐射松排放物和α-蒎烯形成的生物源 SOA 相似。测量的土壤和落叶中单萜的排放速率与模型化的冠层排放进行了比较。结果表明，春季和秋季表层土壤和落叶中单萜的排放可能是冠层排放的 12%至 136%。因此，落叶的排放可能会延长生物源排放季节，当太阳辐射和温度降低时，减少活体植被的排放，从而在春季和秋季导致大量有机气溶胶的形成。
