Abstract
Abstract. During the POLARCAT-France airborne measurement campaign in spring 2008, several pollution plumes transported from mid-latitude regions were encountered. The study presented here focuses on air masses from two different geographic origins (Europe and Asia) and from 2 different source types (anthropogenic pollution and forest fires). A first case study is dedicated to a European air mass, which was repeatedly sampled and analysed during three consecutive days. Thereby, the evolution of the aerosol properties (size distributions, CO mixing ratio) is characterised and related processes are discussed. In particular, the role of coagulation, condensation and cloud processing in the evolution of the Aitken and the accumulation mode particles are contrasted. A second case study focuses on European air masses impacted solely by biomass burning emissions and Asian air masses with contributions from both biomass burning and anthropogenic emissions. The analysis of aerosol modes highlight a similar behaviour for particle originating from biomass burning (from Europe as well as Asia). In comparison to the predominating aged accumulation mode in biomass burning particles, a still larger aerosol accumulation mode related to Asian anthropogenic emissions can be isolated. These findings corroborate the external mixing of such kind of aerosol size distributions. An electron microscopy study (coupled to X-ray elemental analysis) of particles illustrated soot-like inclusions in several samples. Within samples attributed to forest fire sources, the chemical signature is highly associated with the presence of potassium, which is a characteristic tracer element for biomass burning plumes. The single particle images suggest an internal mixing of sampled individual aerosol particles. Thus, particles are found externally mixed as demonstrated from particle size distributions while they appear internally mixed at the particle scale.
Highlights
Since the polar regions are more sensitive to global change than others (IPCC, 2007), a better understanding of the polar climate system is fundamental
The first case study is related to an European anthropogenic polluted air mass sampled during three consecutive days, in order to study transformation of aerosol particles within pollution plumes transported to the Arctic
During the POLARCAT-France spring campaign, 6 periods related to Eurasian pollution transported to the Arctic were identified using FLEXPART potential emission sensitivity (PES): Four plumes corresponding to Russian fires, located at the north of the Black Sea, subsequently denoted Russian fires (RF) and transported over Europe to the sampling location and two plumes corresponding to air masses containing a mixture of Siberian fires and eastern Asia anthropogenic emissions, called hereafter Asian fires (AF) and Asian anthropogenic (AA), respectively
Summary
Since the polar regions are more sensitive to global change than others (IPCC, 2007), a better understanding of the polar climate system is fundamental. Whereas transformation of anthropogenic pollution aerosol is strongly related to both condensation and coagulation processes (Riemer et al, 2004), the transformation of biomass burning aerosol particles ageing is predominantly explained by the coagulation process at least in the far field of the source region (Fiebig et al, 2003; Dentener et al, 2006; Petzold et al, 2007; Muller et al, 2007) In this context, and within the frame of the 4th International Polar Year (IPY, 2007–2008), the POLARCAT (POLar study using Aircraft, Remote sensing, surface measurements and models, of Climate, chemistry, Aerosols and Transport) project was launched. The main objective of the study presented here is to investigate the physical properties of pollution aerosol particles transported to the Arctic demonstrating aerosol ageing observed from measurement data during the campaign. Instrumentation on board the ATR-42 French aircraft and analysis of air mass origins
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