Impact/Purpose:

(1) Determine contribution of biogenic sources to PM2.5 at representative U.S. sites and seasons via 14C ambient measurements.

(2) Investigate effect of (biogenic) ethanol-containing fuel on 14C estimates of mobile source-caused ambient PM2.5, anticipating greater future use of ethanol as a gasoline additive.

(3) Use 14C as a validation tool for CMAQ simulations and proposed biogenic SOA molecular tracers.

(4) Experimentally characterize monolith organic denuders for possible use in minimizing positive organic artifact in carbonaceous aerosol sampling.

Description:

The radiocarbon (14C) content of a sample measures the fraction of the sample's carbon originating from non-fossil-fuel (biogenic) sources. The most important of these sources are biomass burning (mostly winter, but wildfires can contribute in other seasons as well) and secondary organic aerosol (SOA) from biogenic VOC (summer). Previous measurements, both 14C and organic compound speciation, have suggested that such sources can be significant contributors to ambient PM2.5. This task will generate a comprehensive database of 14C and organic speciation results from field studies carried out at geographically diverse U.S. sites and during different seasons, to better assess the contribution of such sources on national and annual scales. The task also includes comparisons of the 14C results with proposed molecular organic tracers of biomass burning and SOA, and 14C comparisons with CMAQ simulations of biogenic PM2.5 for the same sites and dates that 14C data were obtained. Related activities will include 14C measurements on PM emissions from the combustion of (biogenic) ethanol-containing fuel, and investigation of monolith organic denuder technology for minimizing positive organic artifact in the collection of carbonaceous PM samples.

Record Details:

Record Type:PROJECT

Start Date:10/01/2004

Projected Completion Date:09/01/2006

OMB Category:Other

Record ID: 135583

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Project Information:

Progress :Prior to FY05 work related to this task was dispersed across multiple tasks (12187, 15099, and 9571). As of 10/1/04 these efforts, including planned outputs, have been consolidated in the present task. Work initiated under the previous tasks that will be completed under the present task includes 14C field sampling in Nashville TN, Tampa FL, RTP NC, Duke Forest NC and from small engine emissions, and associated lab analysis of the collected samples from each of these studies. Related work completed under the previous tasks include published journal articles on the contribution of biogenic sources to VOC in Azusa CA (J. Geophys. Res., 107(D8), 2002) and to PM2.5 in Houston TX (J. Geophys. Res. 107(D22), 2002).



Relevance : Radiocarbon measurements provide what is arguably a definitive estimate of the biogenic fraction of PM2.5 samples. The proposed research directly supports NAAQS PM2.5 Implementation by quantifying what is a likely large (and mostly uncontrollable) portion of PM2.5, providing results that are necessary for setting realistic PM2.5 NAAQS that take account of this irreducible "natural" contribution. Work under this task will also serve to validate other less certain but simpler experimental methods that provide a more detailed breakdown of biogenic PM2.5 into SOA and biomass-burning components. Another aspect of the task is the use of radiocarbon measurements to validate CMAQ estimates of biogenic SOA, thus providing the opportunity for validation of the current CMAQ SOA module at a level of detail not previously possible. The task is a highly collaborative one linking efforts in HEASD (ECAB & PMRB), AMD, and NRMRL. This task supports APG 189 and APM 499 (FY06).

Clients :OAQPS (Tom Pace, Joann Rice, Joe Paisie), Florida DEP (Tom Atkeson)

Project IDs:

ID Code :20579

Project type :OMIS