Aerosol pH indicator and organosulfate detectability from aerosol mass spectrometry measurements

摘要: Abstract. Aerosol sulfate is a major component of submicron particulate matter (PM 1 ). Sulfate can be present as inorganic (mainly ammonium sulfate, AS) or organosulfate (OS). Although OS thought to smaller fraction of total in most cases, recent literature argues that this may not be the case more polluted environments. Aerodyne aerosol mass spectrometers (AMSs) measure sulfate, but it has been difficult apportion AS vs. detected ion fragments are similar. Recently, two new methods have been proposed quantify separately from AS with AMS data. We use observations collected during several airborne field campaigns covering wide range sources and air mass ages (spanning the continental US, marine remote troposphere, Korea) targeted laboratory experiments investigate performance validity the proposed methods. Four chemical regimes defined categorize the factors impacting fragmentation. In areas high ammonium nitrate concentrations high aerosol acidity, decomposition fragmentation is influenced by multiple complex effects, estimation does not seem possible current regions lower acidity (pH  >  0) (fraction  0.3), proposed OS might reliable, although application these methods often produced nonsensical results. However, ambient neutralized varies somewhat within studies, adding uncertainty, possibly due variations effect organics. Under highly acidic conditions (when calculated pH   0 balance  0.65), fragment ratios show clear relationship acidity. The measured (and lesser extent, the H y SO x + /  SO ratio) promising indicator rapid  0, including when gas-phase NH 3 HNO available. These results allow an improved understanding important intensive properties ambient aerosols.