Source Apportionment of PM2.5 in the Southeastern United States Using Solvent-Extractable Organic Compounds as Tracers

Abstract

A chemical mass balance (CMB) receptor model using particle-phase organic compounds as tracers is applied to apportion the primary source contributions to fine particulate matter and fine particulate organic carbon concentrations in the southeastern United States to determine the seasonal variability of these concentrations. Source contributions to particles with aerodynamic diameter < or =2.5 microm (PM2.5) collected from four urban and four rural/suburban sites in AL, FL, GA, and MS during April, July, and October 1999 and January 2000 are calculated and presented. Organic compounds in monthly composite samples at each site are identified and quantified by gas chromatography/mass spectrometry and are used as molecular markers in the CMB model. The major contributors to identified PM2.5 organic carbon concentrations at these sites in the southeastern United States include wood combustion (25-66%), diesel exhaust (14-30%), meat cooking (5-12%), and gasoline-powered motor vehicle exhaust (0-10%), as well as smaller but statistically significant contributions from natural gas combustion, paved road dust, and vegetative detritus. The primary sources determined in the present study when added to secondary aerosol formation account for on average 89% of PM2.5 mass concentrations, with the major contributors to PM2.5 mass as secondary sulfate (30+/-6%), wood combustion (15+/-12%), diesel exhaust (16+/-7%), secondary ammonium (8+/-2%), secondary nitrate (4+/-3%), meat cooking (3+/-2%), gasoline-powered motor vehicle exhaust (2+/-2%), and road dust (2+/-2%). Distinct seasonality is observed in source contributions, including higher contributions from wood combustion during the colder months of October and January. In addition, higher percentages of unexplained fine organic carbon concentrations are observed in July, which are likely due to an increase in secondary organic aerosol formation during the summer season.

Evaluation of elemental carbon as a marker for diesel particulate matter

“…This technique did not completely separate diesel-and gasolinepowered vehicles but can be used to estimate the contribution of motor vehicles to EC concentration, which is found to be very consistent with other studies listed in Table 5. Zheng et al (2002) employed a molecular marker chemical mass balance model to apportion the sources of atmospheric particulate matter in eight cities in the Southeastern US for one-month of each season between the spring of 1999 and the winter of 2000. Table 5 presents the average fraction of EC from diesel in fine particulate matter in each season, which was calculated to be 92% in the summer and 74% in the Table 5.…”

Characterisation of solvent extractable organic constituents in atmospheric particulate matter: an overview

“…Some of the researches have also focused upon the assessment of natural versus anthropogenic contributions to the carbonaceous aerosol by searching molecular markers or tracers (Abas et al 1995, b, Alves and Pio, in press, Cass 1998, Elias et al 1999, Fraser et al 1999, Gogou et al 1996, Hawthorne et al 1988, Kavouras et al 2001a, Khalil and Rasmussen 2003, Lau et al 2006, Li and Kamens 1993, Nolte et al 2001, Oros and Simoneit 2001a, b, Rinehart et al 2006, Rogge et al 2006 2003, Schauer et al 1996, Sheesley et al 2003, Simoneit 1989, Simoneit and Elias 2001, Simoneit and Mazurek 1989, Simoneit et al 1990, 1993, b, 2004a, b, Standley and Simoneit 1994, Zheng et al 2002. Source-receptor reconciliation by chemical mass balance (CMB) has been used to characterise the composite sources of organic compounds that includes gasoline vehicle exhaust, meat cooking, cigarette smoke, wood burning, etc.…”

“…Source-receptor reconciliation by chemical mass balance (CMB) has been used to characterise the composite sources of organic compounds that includes gasoline vehicle exhaust, meat cooking, cigarette smoke, wood burning, etc. (Calhoun et al 2003, Feng et al 2006, Khalil and Rasmussen 2003, Li and Kamens 1993, Mazurek 2002, Robinson et al 2006a, b, Schauer et al 2002a, Zheng et al 2002.…”

“…Aliphatic diacids and aromatic di-, tri-, and tetraacids have also been reported as indicators of SOA in urban atmospheres, as they can be quantified readily using standard GC/MS techniques (Fine et al 2004d, Schauer et al 2002a, Zheng et al 2002. Nevertheless, in aerosol samples enclosing a mixture of both SOA and primary source emissions, the origins of these compounds have not yet been definitively identified (Sheesley et al 2004).…”

Comment on “Aerosol organic carbon to black carbon ratios: Analysis of published data and implication for climate forcing” by T. Novakov et al.

“…There is also abundant evidence that biogenic emissions in rural areas contribute substantially to secondary organic aerosol formation in rural atmospheres, based on source allocation and 14 C-based studies [Tanner et al, 2004]. Further, the contribution of secondary organics to total aerosol carbon clearly varies widely, both seasonally and spatially [Zheng et al, 2002]. Therefore there is no sound reason to expect that OC/EC ratios should be consistent between urban and rural/ background locations-indeed, we have every expectation that they should increase during transport from urban to rural locations due to secondary aerosol formation.…”