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The first multi-year contributions from organic functional groups to the Arctic submicron aerosol are documented using 126 weekly-integrated samples collected from April 2012 to October 2014 at the Alert Observatory (82.45° N, 62.51° W). Results from the particle transport model FLEXPART, linear regressions among the organic and inorganic components and positive matrix factorization (PMF) enable associations of organic aerosol components with source types and regions. Lower organic mass (OM) concentrations but higher ratios of OM to non-sea-salt sulfate mass concentrations (nss-SO4Combining double low line) accompany smaller particles during the summer (JJA). Conversely, higher OM but lower OM ĝ• nss-SO4Combining double low line accompany larger particles during winter-spring. OM ranges from 7 to 460 ng mĝ'3, and the study average is 129 ng mĝ'3. The monthly maximum in OM occurs during May, 1 month after the peak in nss-SO4Combining double low line and 2 months after that of elemental carbon (EC). Winter (DJF), spring (MAM), summer and fall (SON) values of OM ĝ• nss-SO4Combining double low line are 26, 28, 107 and 39 %, respectively, and overall about 40 % of the weekly variability in the OM is associated with nss-SO4Combining double low line. Respective study-Averaged concentrations of alkane, alcohol, acid, amine and carbonyl groups are 57, 24, 23, 15 and 11 ng mĝ'3, representing 42, 22, 18, 14 and 5 % of the OM, respectively. Carbonyl groups, detected mostly during spring, may have a connection with snow chemistry. The seasonally highest O ĝ• C occurs during winter (0.85) and the lowest O ĝ• C is during spring (0.51); increases in O ĝ• C are largely due to increases in alcohol groups. During winter, more than 50 % of the alcohol groups are associated with primary marine emissions, consistent with Shaw et al. (2010) and Frossard et al. (2011). A secondary marine connection, rather than a primary source, is suggested for the highest and most persistent O ĝ• C observed during the coolest and cleanest summer (2013), when alcohol and acid groups made up 63 % of the OM. A secondary marine source may be a general feature of the summer OM, but higher contributions from alkane groups to OM during the warmer summers of 2012 (53 %) and 2014 (50 %) were likely due to increased contributions from combustion sources. Evidence for significant contributions from biomass burning (BB) was present in 4 % of the weeks. During the dark months (NDJF), 29, 28 and 14 % of the nss-SO4Combining double low line, EC and OM were associated with transport times over the gas flaring region of northern Russia and other parts of Eurasia. During spring, those percentages dropped to 11 % for each of nss-SO4Combining double low line and EC values, respectively, and there is no association of OM. Large percentages of the Arctic haze characterized at Alert likely have origins farther than 10 days of transport time and may be from outside of the Eurasian region. Possible sources of unusually high nss-SO4Combining double low line and OM during September-October 2014 are volcanic emissions or the Smoking Hills' area of the Northwest Territories, Canada.

Since 1999, Environment and Climate Change Canada (ECCC) has been coordinating a multi-laboratory comparison of measurements of long-lived greenhouse gases in whole air samples collected at the Global Atmosphere Watch (GAW) Alert Observatory located in the Canadian High Arctic (82 ∘ 28 ′ N, 62 ∘ 30 ′ W). In this paper, we evaluate the measurement agreement of atmospheric CO 2 , CH 4 , N 2 O, SF 6 , and stable isotopes of CO 2 (δ13 C, δ18 O) between leading laboratories from seven independent international institutions. The measure of success is linked to target goals for network compatibility outlined by the World Meteorological Organization's (WMO) GAW greenhouse gas measurement community. Overall, based on ∼ 8000 discrete flask samples, we find that the co-located atmospheric CO 2 and CH 4 measurement records from Alert by CSIRO, MPI-BGC, SIO, UHEI-IUP, and ECCC versus NOAA (the designated reference laboratory) are generally consistent with the WMO compatibility goals of ± 0.1 ppm CO 2 and ± 2 ppb CH 4 over the 17-year period (1999–2016), although there are periods where differences exceed target levels and persist as systematic bias for months or years. Consistency with the WMO goals for N 2 O, SF 6 , and stable isotopes of CO 2 (δ13 C, δ18 O) has not been demonstrated. Additional analysis of co-located comparison measurements between CSIRO and SIO versus NOAA or INSTAAR (for the isotopes of CO 2) at other geographical sites suggests that the findings at Alert for CO 2 , CH 4 , N 2 O, and δ13 C–CO 2 could be extended across the CSIRO, SIO, and NOAA observing networks. The primary approach to estimate an overall measurement agreement level was carried out by pooling the differences of all individual laboratories versus the designated reference laboratory and determining the 95th percentile range of these data points. Using this approach over the entire data record, our best estimate of the measurement agreement range is -0.51 to + 0.53 ppm for CO 2 , -0.09 ‰ to + 0.07 ‰ for δ13 C, -0.50 ‰ to + 0.58 ‰ for δ18 O, -4.86 to + 6.16 ppb for CH 4 , -0.75 to + 1.20 ppb for N 2 O, and -0.14 to + 0.09 ppt for SF 6. A secondary approach of using the average of 2 standard deviations of the means for all flask samples taken in each individual sampling episode provided similar results. These upper and lower limits represent our best estimate of the measurement agreement at the 95 % confidence level for these individual laboratories, providing more confidence for using these datasets in various scientific applications (e.g., long-term trend analysis). [ABSTRACT FROM AUTHOR]

Modelling studies suggest that the climate and the hydrological cycle are sensitive to the concentrations of ice-nucleating particles (INPs). However, the concentrations, composition, and sources of INPs in the atmosphere remain uncertain. Here we report daily concentrations of INPs and tracers of mineral dust (Al, Fe, Ti, and Mn), sea spray aerosol (Na+ and Cl-), and anthropogenic aerosol (Zn, Pb, NO3-, NH4+, and non-sea-salt SO42-) at Alert, Canada during a three-week campaign in March 2016. The average INP concentrations measured in the immersion freezing mode were approximately 0.005 ± 0.002 L-1, 0.020 ± 0.004 L-1, and 0.186 ± 0.040 L-1 at -15 ºC, -20 ºC, and -25 ºC, respectively. These concentrations are within the range of concentrations measured previously in the Arctic at ground level or sea level. Mineral dust tracers all correlated with INPs at -25 ºC (correlation coefficient, R, ranged from 0.70 to 0.76), suggesting that mineral dust was a major contributor to the INP population. Particle dispersion modelling suggests that the source of the mineral dust may have been the long-range transported dust from the Gobi desert. Sea spray tracers were anti-correlated with INPs at -25 ºC (R = -0.56). In addition, INP concentrations at -25 ºC divided by mass concentrations of aluminum were anti-correlated with sea spray tracers (R = -0.51 and -0.55 for Na+ and Cl-, respectively), suggesting that the components of sea spray aerosol suppressed the ice-nucleating ability of mineral dust in the immersion freezing mode. Correlations between INPs and anthropogenic aerosol tracers were not statistically significant. These results will improve our understanding of INPs in the Arctic during spring. [ABSTRACT FROM AUTHOR]

Long-range transport of aerosol from lower latitudes to the high Arctic may be a significant contributor to climate forcing in the Arctic. To identify the sources of key contaminants entering the Canadian high Arctic an intensive campaign of snow sampling was completed at Alert, Nunavut, from September 2014 to June 2015. Fresh snow samples collected every few days were analysed for black carbon, major ions, and metals, and this rich data provided an opportunity for a temporally-refined source apportionment of snow composition via Positive Matrix Factorization in conjunction with FLEXPART potential emission sensitivity analysis. Seven source factors were identified: sea salt, regional dust, Eurasian fossil fuel combustion, mixed carboxylic acid sources, nitrate processing, Eurasian industrial activities, and regional volcanic and marine biogenic activity. The majority (73 %) of the black carbon in snow, a light-absorbing compound critical to the Arctic radiative balance, was found to be the product of fossil fuel burning with limited biomass burning influence. [ABSTRACT FROM AUTHOR]

The first multi-year contributions from organic functional groups to the Arctic submicron aerosol are documented using 126 weekly-integrated samples collected from April, 2012 to October, 2014 at the Alert Observatory (82.45° N, 62.51° W). Results from the particle transport model FLEXPART, linear regressions among the organic and inorganic components and Positive Matrix Factorization (PMF) enable associations of organic aerosol components with source types and regions. Lower organic mass concentrations (OM) but higher ratios of OM to non-sea-salt sulphate mass concentrations (nss-SO4=) accompany smaller particles during the summer (JJA). Conversely, higher OM but lower OM/nss-SO4= accompany larger particles during winter-spring. OM ranges from 7-463 ng m-3, and the study average is 129 ng m-3. The monthly maximum in OM occurs during May, one month after the peak in nss-SO4= and two months after that of elemental carbon (EC). Winter (DJF), spring (MAM), summer and fall (SON) values of OM/nss-SO4= are 26 %, 28 %, 107 % and 39 %, respectively, and overall about 40 % of the weekly variability in the OM is associated with nss-SO4=. Respective study-averaged concentrations of alkane, alcohol, acid, amine and carbonyl groups are 57 ng m-3, 24 ng m-3, 23 ng m-3, 16 ng m-3 and 11 ng m-3, representing 42 %, 22 %, 18 %, 14 % and 5 % of the OM, respectively. Carbonyl groups, detected mostly during spring, may have a connection with snow chemistry. The seasonally highest O/C occurs during winter (0.85) and the lowest O/C is during spring (0.51); increases in O/C are largely due to increases in alcohol groups. During winter, more than 50 % of the alcohol groups are associated with primary marine emissions, consistent with Shaw et al. (2010) and Frossard et al. (2011). A secondary marine connection, rather than a primary source, is suggested for the highest and most persistence O/C observed during the coolest and cleanest summer (2013), when alcohol and acid groups made up 63% of the OM. A secondary marine source may be a general feature of the summer OM, but higher contributions from alkane groups to OM during the warmer summers of 2012 (53 %) and 2014 (50 %) were likely due to increased contributions from combustion sources. Evidence for significant contributions from biomass burning (BB) was present in 4 % of the weeks. During the dark months (NDJF), 29 %, 28 % and 14 % of the nss-SO4=, EC and OM were associated with transport times over the gas flaring region of Northern Russia and other parts of Eurasia. During spring, those percentages drop to 11 % and 8 % for nss-SO4= and EC, respectively, and there is no association of OM. Large percentages of the Arctic Haze characterized at Alert likely have origins farther than 10 days transport time and may be from outside of the Eurasian region. Possible sources of unusually high nss-SO4= and OM during September-October, 2014 are volcanic emissions or the Smoking Hills' area of the Northwest Territories, Canada. [ABSTRACT FROM AUTHOR]

Rapidly rising temperatures and loss of snow and ice cover have demonstrated the unique vulnerability of the high Arctic to climate change. There are major uncertainties in modelling the chemical depositional and scavenging processes of Arctic snow. To that end, fresh snow samples collected on average every four days at Alert, Nunavut, from September 2014 to June 2015 were analyzed for black carbon, major ions, and metals, and their concentrations and fluxes reported. Comparison with simultaneous measurements of atmospheric aerosol mass loadings yields effective deposition velocities which encompass all processes by which the atmospheric species are transferred to the snow. It is inferred from these values that dry deposition is the dominant removal mechanism for several compounds over the winter while wet deposition increased in importance in the fall and spring, probably due to enhanced scavenging by mixed-phase clouds. Black carbon aerosol was the least efficiently deposited species to the snow. These measurements are a unique data set for comparison to models that incorporate deposition to high Arctic snow. [ABSTRACT FROM AUTHOR]

In order to generate a local daughter scale from the material defining the international delta13C and delta18O stable isotope ratio scales (NBS19-calcite),1,2 the carbon and oxygen must be liberated to the gas phase, usually as CO2, using acid digestion of the calcite with H3PO4. It is during this conversion step that systematic errors can occur, giving rise to commonly observed discrepancies in isotopic measurements between different stable isotope laboratories. Scale consistency is of particular importance for air-CO2 isotope records where very small differences in isotopic composition have to be reliably compared between different laboratories and quantified over long time periods.3 The information is vital for estimating carbon budgets on regional and global scales and for understanding their variability under the conditions of climate change. Starting from this requirement a number of CO2 preparations from NBS19 were made at Environment Canada (EC) and analyzed in our laboratories together with Narcis II, a set of well-characterized CO2 samples in sealed tubes available from the National Institute for Environmental Studies (NIES).4,5 Narcis II is very homogeneous in delta13C and delta18O with the isotopic composition close to NBS19-CO2. Among our laboratories the results for delta13C agreed to within +/-0.004 per thousand. The same level of agreement in delta13C was obtained when CO2 was generated from NBS19-calcite using different experimental procedures and conditions in the other two laboratories. For delta18O, the corresponding data were +/-0.011 per thousand when using NBS19-CO2 produced at EC, but discrepancies were enhanced by almost one order of magnitude when NBS19-CO2 was prepared by the other laboratories using slightly different reaction conditions (range=0.13 per thousand).In a second series of experiments, larger amounts of CO2 prepared from NBS19 at the Max-Planck-Institut für Biogeochemie (MPI-BGC) were analyzed together with Narcis II and then mixed into CO2-free air. The resulting artificial air samples then were measured by the same three laboratories for the stable isotopic composition of CO2 using locally established extraction and evaluation procedures. Comparison of the results with the prior CO2 values and between the laboratories revealed additional systematic differences owing to the local CO2 extraction processes and standardization procedures. For delta13C the results showed a narrow range of discrepancies of about 0.02 per thousand; for delta18O cumulative disagreements in the range of 0.1 per thousand were observed. From these results the following conclusions are inferred: NBS19-CO2 is a reliable primary anchor to the VPDB delta13C scale. Although prepared by different methods an accuracy of better than +/-0.003 per thousand has been reached. This applies to sample amounts of 5 mg calcite or more.NBS19-CO2 can be used as a general anchor to the VPDB delta18O scale only for accuracy requirements of +/-0.1 per thousand. For a higher scale resolution additional agreements regarding details of the acid digestion reaction will have to be worked out and agreed upon.Narcis II-CO2 comprises an ideal set of test samples for the VPDB scale. The delta13C value is +1.923+/-0.003 per thousand (combined uncertainty); delta18O is between -2.50 and -2.65 per thousand versus VPDB-CO2, with most of the variation in this figure depending on details of the NBS19-CO2 preparation used for the calibration. (Ampoule to ampoule homogeneity is better than 0.01 per thousand.)When mixing NBS19-CO2 into artificial air and using this to test performance between laboratories, the delta13C offsets are small with a remaining discrepancy of only 0.02 per thousand. For delta18O, systematic disagreements are considerably larger than those found for the pure CO2 comparison. Further experimental clarification is required.Artificial air samples such as NBS19-CO2 in air can be used as reliable anchors to create a unified stable isotope scale between different laboratories. An adjustment of local scales based on these air standards appears to be necessary for improving data comparability., (Copyright (c) 2009 John Wiley & Sons, Ltd.)