Are biogenic emissions a significant source of summertime atmospheric toluene in the rural Northeastern United States?

Abstract

Abstract. Summertime atmospheric toluene enhancements at Thompson Farm in the rural northeastern United States were unexpected and resulted in a toluene/benzene seasonal pattern that was distinctly different from that of other anthropogenic volatile organic compounds. Consequently, three hydrocarbon sources were investigated for potential contributions to the enhancements during [2004][2005][2006]. These included: (1) increased warm season fuel evaporation coupled with changes in reformulated gasoline (RFG) content to meet US EPA summertime volatility standards, (2) local industrial emissions and (3) local vegetative emissions. The contribution of fuel evaporation emission to summer toluene mixing ratios was estimated to range from 16 to 30 pptv d −1 , and did not fully account for the observed enhancements (20-50 pptv) in [2004][2005][2006]. Static chamber measurements of alfalfa, a crop at Thompson Farm, and dynamic branch enclosure measurements of loblolly pine trees in North Carolina suggested vegetative emissions of 5 and 12 pptv d −1 for crops and coniferous trees, respectively. Toluene emission rates from alfalfa are potentially much larger as these plants were only sampled at the end of the growing season. Measured biogenic fluxes were on the same order of magnitude as the influence from gasoline evaporation and industrial sources (regional industrial emissions estimated at 7 pptv d −1 ) and indicated that local vegetative emissions make a significant contribution to summertime toluene enhancements. Additional studies are needed to characterize the variability and factors controlling toluene emissions from alfalfa and other vegetation types throughout the growing season.

Eddy covariance emission and deposition flux measurements using proton transfer reaction – time of flight – mass spectrometry (PTR-TOF-MS): comparison with PTR-MS measured vertical gradients and fluxes

“…The fragment ion from para-cymene accounts for about 80 % of total ions from para-cymene based on our E/N ratios for both instruments (Tani et al, 2003;Ambrose et al, 2010). A few studies have claimed that toluene can be directly emitted from plants (Heiden et al, 1999;White et al, 2009) from orange trees (Ciccioli et al, 1999). Our observation of m/z 93 flux and vertical gradient showed upward flux throughout the day ( Fig.…”

Multi-year (2004–2008) record of nonmethane hydrocarbons and halocarbons in New England: seasonal variations and regional sources

“…However, the fact that the ratio increases in the summer is indicative of an additional source or enhanced emissions of toluene in this region. White et al (2009) illustrated that the anomalous toluene behavior at TF could not be fully explained by fuel evaporation and industrial emissions and provided evidence for a biogenic contribution to the summer toluene enhancements. It was also noted that the toluene enhancements were larger with each successive year (White et al, 2009).…”

“…White et al (2009) illustrated that the anomalous toluene behavior at TF could not be fully explained by fuel evaporation and industrial emissions and provided evidence for a biogenic contribution to the summer toluene enhancements. It was also noted that the toluene enhancements were larger with each successive year (White et al, 2009). This trend continued into 2007 when the highest toluene/benzene ratios (mean=2.1) were observed (Fig.…”

Characterization of aerosol associated with enhanced small particle number concentrations in a suburban forested environment

“…The gas collected in these canisters was analyzed off-line using the gas chromatographic system with several columns and detectors described by Sive et al [2005] and White et al [2010], allowing for accurate quantification of over 100 different VOC compounds. Specifically, a-pinene and isoprene are used as indicators of BVOC precursors to SOA [Hoffmann et al, 1997;Kroll et al, 2006], toluene is used as an indicator of a mixed biogenic-anthropogenic [White et al, 2009] primary aromatic precursor to SOA , and isopropyl nitrate is used as an additional indicator of secondary processing of anthropogenic emissions [deGouw et al, 2005].…”