Three-Dimensional Measurements of Aerosol Mixing State During CalNex Using Aircraft Aerosol Time-of-Flight Mass Spectrometry.

摘要

Particles in the atmosphere impact human health and climate. Knowledge of the sources of these aerosol particles, as well as how their physiochemical properties evolve once emitted, is key to accurately predict their impacts. As part of CalNex 2010, an aerosol time-of-flight mass spectrometer (ATOFMS) was used in ship and aircraft based measurements to obtain insight into the sources and properties of aerosol throughout California. Comparisons between this and other aircraft campaigns give a unique and unprecedented look into the different types of carbonaceous aerosol in California. Carbonaceous particles were ubiquitous throughout the LA basin. The ports in Long Beach showed higher fractions of soot, from ships and local diesel traffic, compared to other areas. These particles underwent processing and acquired secondary species, such as ammonium and nitrate, rapidly after emission. Aerosol measured near the ports in Long Beach contained high amounts of sulfate and soot, relative to aerosol measured inland which contained more nitrate. In southern California, particulate secondary species were primarily nitrate rather than sulfate as encountered in northern California. Northern California sources were dominated by carbonaceous species produced by secondary biogenic compounds reacting with pollution, agricultural emissions, and traffic. Soot containing particles in northern California were generally much smaller (<100 nm) with less secondary coatings than in southern California. ATOFMS data were compared and validated against satellite optical retrievals. Secondary sources were classified well, but further improvement is needed for classification of primary sources. Six peer-reviewed scientific publications to date have used this dataset, highlighting that the results from the ATOFMS played an important role in improving our understanding of the sources of carbonaceous aerosols in California.