Physical and chemical properties of pollution aerosol particles transported from North America to Greenland as measured during the POLARCAT summer campaign

B Quennehen,G Ancellet,A Schwarzenboeck,A Stohl,K S Law,J Schmale,J Schneider,S Crumeyrolle,H Sodemann

doi:10.5194/acp-11-10947-2011

Abstract

Abstract. Within the framework of the POLARCAT-France campaign, aerosol physical, chemical and optical properties over Greenland were measured onboard the French ATR-42 research aircraft. The origins of CO excess peaks detected in the aircraft measurements then have been identified through FLEXPART simulations. The study presented here focuses particularly on the characterization of air masses transported from the North American continent to Greenland. Air masses that picked up emissions from Canadian boreal forest fires as well as from the cities on the American east coast were identified and selected for a detailed study. Measurements of CO concentrations, aerosol chemical composition, aerosol number size distributions, aerosol volume volatile fractions and aerosol light absorption (mainly from black carbon) are used in order to study the relationship between CO enhancement (ΔCO), aerosol particle concentrations and number size distributions. Aerosol number size distributions (normalised with their respective ΔCO) are in good agreement with previous studies. Nonetheless, wet scavenging may have occurred along the pathway between the emission sources and Greenland leading to a less pronounced accumulation mode in the POLARCAT data. Chemical analyses from mass spectrometry show that submicrometer aerosol particles are mainly composed of sulphate and organics. The observed bimodal (Aitken and accumulation) aerosol number size distributions show a significant enhancement in Aitken mode particles. Furthermore, results from the thermodenuder analysis demonstrate the external mixture of boreal fire (BF) air masses from North America (NA). This is particularly observed in the accumulation mode, containing a volume fraction of up to 25–30% of refractory material at the applied temperature of 280 °C. NA anthropogenic air masses with only 6% refractory material in the accumulation mode can be clearly distinguished from BF air masses. Overall, during the campaign rather small amounts of black carbon from the North American continent were transported towards Greenland during the summer POLARCAT observation period, which also is a valuable finding with respect to potential climate impacts of black carbon in the Arctic.

Highlights

The Polar regions are known to be more strongly impacted by global warming than other regions (IPCC, 2007)
We identified 13 periods when air masses originated from the North American continent
We found 12 periods related to Canadian boreal forest fires as well as 1 time window with air masses of American anthropogenic origin

Summary

Introduction

The Polar regions are known to be more strongly impacted by global warming than other regions (IPCC, 2007). B. Quennehen et al.: Physical and chemical properties of Arctic aerosols surface measurements and models, of Climate, Chemistry, Aerosols and Transport) project was launched during the 4th International Polar Year (IPY) (2007–2008). The principal objective within the French POLARCAT program has been to increase our knowledge about long range transport of short-lived pollutants (particulates and gases) to the Arctic. The French ATR-42 research aircraft performed 24 scientific flights out of Kiruna, Sweden, in spring (not treated in this study) and twelve flights from Kangerlussuaq, Greenland, in summer 2008. The ATR-42 was equipped with instrumentation measuring the physical, optical, and chemical properties of the aerosols

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Conclusion