Low-pressure and nascent yields of stabilized Criegee intermediates CHOO and CHCHOO in ozonolysis of propene.

The yields of stabilized Criegee intermediates (sCIs), both CHOO and CHCHOO, produced from ozonolysis of propene at low pressures (7-16 Torr) were measured indirectly using cavity ringdown spectroscopy (CRDS) and chemical titration with an excess amount of sulfur dioxide (SO). The method of monitoring the consumption of SO as a scavenger and the production of secondary formaldehyde (HCHO) allows characterization of the total sCI and the stabilized CHOO yields at low pressure and in a short residence time. Both the total sCI and the stabilized CHOO yields in the propene ozonolysis were found to decrease with decreasing pressure.

Low-Pressure and Nascent Yields of Thermalized Criegee Intermediate in Ozonolysis of Ethene.

The yields of thermalized formaldehyde oxide (CHOO, the simplest Criegee intermediate) produced from ozonolysis of ethene at low pressures were measured indirectly using cavity ringdown spectroscopy (CRDS) and chemical titration with an excess amount of sulfur dioxide (SO). The method of monitoring the consumption of SO as a scavenger allows better characterization of the CHOO at low pressure and short residence time. The yield of thermalized CHOO from ethene ozonolysis was found to decrease with decreasing pressure.

Atmospheric observation-based estimation of fossil fuel CO emissions from regions of central and southern California.

Combustion of fossil fuel is the dominant source of greenhouse gas emissions to the atmosphere in California. Here, we describe radiocarbon (CO) measurements and atmospheric inverse modeling to estimate fossil fuel CO (ffCO) emissions for 2009-2012 from a site in central California, and for June 2013-May 2014 from two sites in southern California. A priori predicted ffCO mixing ratios are computed based on regional atmospheric transport model (WRF-STILT) footprints and an hourly ffCO prior emission map (Vulcan 2.