Abstract
Abstract. Submicron aerosol particles collected simultaneously at the mountain peak (2182 m a.s.l.) and at a forested mid-mountain site (1300 m a.s.l.) on Whistler Mountain, British Columbia, Canada, during June and July 2010 were analyzed by Fourier transform infrared (FTIR) spectroscopy for quantification of organic functional groups. Positive matrix factorization (PMF) was applied to the FTIR spectra. Three PMF factors associated with (1) combustion, (2) biogenics, and (3) vegetative detritus were identified at both sites. The biogenic factor was correlated with both temperature and several volatile organic compounds (VOCs). The combustion factor dominated the submicron particle mass during the beginning of the campaign, when the temperature was lower and advection was from the Vancouver area, but as the temperature started to rise in early July, the biogenic factor came to dominate as a result of increased emissions of biogenic VOCs, and thereby increased formation of secondary organic aerosol (SOA). On average, the biogenic factor represented 69% and 49% of the submicron organic particle mass at Whistler Peak and at the mid-mountain site, respectively. The lower fraction at the mid-mountain site was a result of more vegetative detritus there, and also higher influence from local combustion sources. The biogenic factor was strongly correlated (r~0.9) to number concentration of particles with diameter (Dp)> 100 nm, whereas the combustion factor was better correlated to number concentration of particles with Dp<100 nm (r~0.4). The number concentration of cloud condensation nuclei (CCN) was correlated (r~0.7) to the biogenic factor for supersaturations (S) of 0.2% or higher, which indicates that particle condensational growth from biogenic vapors was an important factor in controlling the CCN concentration for clouds where S≥0.2%. Both the number concentration of particles with Dp>100 nm and numbers of CCN for S≥0.2% were correlated to temperature. Considering the biogenic influence, these results indicate that temperature was a primary factor controlling these CCN concentrations at 0.2% supersaturation.
Highlights
British Columbia, Canada, during June and July 2010 were nuclei (CCN) was correlated (r ∼ 0.7) to the biogenic facanalyzed by Fourier transform infrared (FTIR) spectroscopy tor for supersaturations (S) of 0.2 % or higher, which indifor quantification of organic functional groups
Sciences but as the temperature started to rise in early July, the biogenic factor came to dominate as a result of increased emissions of biogenic volatile organic compounds (VOCs), and thereby increased formation of 1 Introduction secondary organic aerosol (SOA)
Positive matrix factorization (PMF) has been applied to FTIR spectra in order to investigate and quantify sources of submicron organic aerosols at Whistler Peak (2182 m a.s.l.) and Raven’s Nest (1300 m a.s.l.) during the Whistler Aerosol and Cloud Study (WACS) 2010 campaign at Whistler Mountain, British Columbia
Summary
The measurements in this study were performed simultaneously at two sites on Whistler Mountain: Whistler Peak (WHI), at an altitude of 2182 m a.s.l.; and Raven’s Nest (WRN), a mid-mountain site at 1300 m a.s.l. Raven’s Nest is located near halfway between Whistler Village (650 m a.s.l.) and WHI. WHI is approximately 400 m above the tree line. Raven’s Nest is surrounded by forest composed mostly of coniferous trees such as fir, hemlock and cedar. These sites may be influenced from biomass burning aerosols in the summer, but during WACS 2010 such an influence was present only during the last three days of the study. Vancouver is the closest large city to Whistler, located approximately 100 km to the south. The two sites employed in this study are described more extensively in Macdonald et al (2013), Pierce et al (2012), and Wong et al (2011)
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