C14 measurements from Beachon Rombas Campaign Manitou Experimental Forest, Colorado, July/August 2011 PIs: Chris Geron and John Offenberg: Contact information: Chris Geron Senior Scientist U.S. Environmental Protection Agency National Risk Management Research Laboratory Mail Drop E305-02, 109 TW Alexander Dr. Research Triangle Park, NC 27711 Phone (919) 541-4639 Fax (919) 541-7885 Geron.chris@epa.gov Filter samplers: Tisch 220 Liters per minute (volumetric) samplers. PM2.5 cyclone used to exclude all but PM2.5 aerosol. Sampled for 71.5 hours with filter changes at 4-6pm local time (MST). Exception: Filter 1 (day of year 206) = 23.5 hour sample. 90 mm pre-baked Quartz fiber filters; 77mm effective filter diameter Filters were kept in individual pre-baked sealed packets at -5 C until analysis at RTP, NC. DOY = Day of Year (July 22, 2011 = 203) TC is average total PM2.5 carbon concentration for the sampler period in ug/m^3 (Volumetric - Ambient T/P) OC = organic carbon on filter (area basis): Units = ug/cm^2 EC = elemental carbon on filter (area basis): Units = ug/cm^2 fMC = fraction of modern (non-fossil fuel-based) to total C: unitless Measurement uncertainty TC: < 5% fMC: 0.001%