Aerosol composition and sources in the central Arctic Ocean during ASCOS

Abstract

S1 Solutions from positive matrix factorisa-1 tion 2 For this study, a four factor solution was determined to best represent the 3 measured aerosol. A two factor solution separates the Ship Emissions factor 4 from the ambient background aerosol, while a three factor solution includes 5 the Organic factor. It is only with four factors that the Marine Biogenic 6 factor is separated from the Continental factor. Additional factors either 7 identify instrumental noise, or split the existing factors. Figure S1 shows 8 the decrease in Q/Q exp as additional factors are included, where Q exp is 9 the expected Q. We see that including a 5 th factor decreases Q/Q exp by 10 identifying instrumental noise, while additional factors only serve to capture 11 episodic events, often coinciding with ship emissions. Even though Q/Q exp 12 decreased slightly from 3.36 for four factors down to 3.06 for 10 factors, 13 including more factors did not contribute additional information about the 14 measured aerosol. As such, the four factor solution was deemed to give the 15 most information about the measured ambient aerosol. 16 The robustness of the solution can be explored by either varying the initial 17 seed, which changes the set of pseudorandom values used for the initial point 18 (Paatero, 1997), or by using bootstrapping analysis, in which the rows of X 19 are randomly sampled and PMF is executed on the new dataset (as described 20 by Reff et al., 2007). Both of these methods were used and the four factor 21 solution at fPeak =-0.75 was found to be robust: 100 values for the initial 22 seed parameter in the PMF2 program resulted in 90 of the cases giving the 23 solution presented here, while 100 iterations of the bootstrapping analysis 24 S1

Size-resolved atmospheric particulate polysaccharides in the high summer Arctic

“…Based on the hexose fingerprint we therefore speculate that the surface air that mixed with the upper part of the boundary layer was influenced by continental sources. The Chang et al (2011) results from ASCOS also lend strong support to the air originating from continental combustion sources, since elevated levels of acetonitrile (combustion of biomass) and 210 Pb (a continental tracer) were observed.…”

“…Gao et al (2012) estimated the fraction of THNS to be about 1.5-3 % (2.7 % on average) of the organic matter dissolved in surface seawater during ASCOS. By assuming the same fraction of THNS in atmospheric organic particulate matters, the THNS in the organic aerosols studied by Chang et al (2011) would correspond to the order of 10 pmol m −3 THNS. This is comparable to our results, with a measured mass concentration of THNS between 16 and 43 pmol m −3 (between the 25th and 75th percentiles).…”

“…Instead, an indirect comparison utilized the reported levels from a parallel study during ASCOS, the determined organics in the marine sub-micrometer aerosol in air by Chang et al (2011), using an aerosol mass spectrometer. Chang et al (2011) reported a sub-micrometer organic mass of about 0.055 µg m −3 .…”

“…Instead, an indirect comparison utilized the reported levels from a parallel study during ASCOS, the determined organics in the marine sub-micrometer aerosol in air by Chang et al (2011), using an aerosol mass spectrometer. Chang et al (2011) reported a sub-micrometer organic mass of about 0.055 µg m −3 . Gao et al (2012) estimated the fraction of THNS to be about 1.5-3 % (2.7 % on average) of the organic matter dissolved in surface seawater during ASCOS.…”

Source Apportionment of Urban Particulate Matter using Hourly Resolved Trace Metals, Organics, and Inorganic Aerosol Components

“…Zhang et al, 2007;Jimenez et al, 2009;Ng et al, 2010). More recently, PMF was 20 applied to combined organic and inorganic mass spectra to find additional organic source types and provide insight into the characteristics and processes of these sources (Chang et al, 2011;Sun et al, 2012;McGuire et al, 2014). McGuire et al (2014) reported that oxygenated OA factors related to sulphate and nitrate were more effectively resolved by a full mass spectra method including inorganics.…”