In order to evaluate the potential impact of the Arctic anthropogenic emission sources it is essential to understand better the natural aerosol sources of the inner Arctic and the atmospheric processing of the aerosols during their transport in the Arctic atmosphere. A 1-year time series of chemically specific measurements of the sub-micrometre aerosol during 2015 has been taken at the Mt. Zeppelin observatory in the European Arctic. A source apportionment study combined measured molecular tracers as source markers, positive matrix factorization, analysis of the potential source distribution and auxiliary information from satellite data and ground-based observations. The annual average sub-micrometre mass was apportioned to regional background secondary sulphate (56%), sea spray (17%), biomass burning (15%), secondary nitrate (5.8%), secondary marine biogenic (4.5%), mixed combustion (1.6%), and two types of marine gel sources (together 0.7%). Secondary nitrate aerosol mainly contributed towards the end of summer and during autumn. During spring and summer, the secondary marine biogenic factor reached a contribution of up to 50% in some samples. The most likely origin of the mixed combustion source is due to oil and gas extraction activities in Eastern Siberia. The two marine polymer gel sources predominantly occurred in autumn and winter. The small contribution of the marine gel sources at Mt. Zeppelin observatory in summer as opposed to regions closer to the North Pole is attributed to differences in ocean biology, vertical distribution of phytoplankton, and the earlier start of the summer season.

Ambient air is a core medium for monitoring of persistent organic pollutants (POPs) under the Stockholm Convention and is used in studies of global transports of POPs and their atmospheric sources and source regions. Still, data based on active air sampling remain scarce in many regions. The primary objectives of this study were to (i) monitor concentrations of selected POPs in air outside West Africa, and (ii) to evaluate potential atmospheric processes and source regions affecting measured concentrations. For this purpose, an active high-volume air sampler was installed on the Cape Verde Atmospheric Observatory at Cape Verde outside the coast of West Africa. Sampling commenced in May 2012 and 43 samples (24h sampling) were collected until June 2013. The samples were analyzed for selected polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB) and chlordanes. The concentrations of these POPs at Cape Verde were generally low and comparable to remote sites in the Arctic for several compounds. Seasonal trends varied between compounds and concentrations exhibited strong temperature dependence for chlordanes. Our results indicate net volatilization from the Atlantic Ocean north of Cape Verde as sources of these POPs. Air mass back trajectories demonstrated that air masses measured at Cape Verde were generally transported from the Atlantic Ocean or the North African continent. Overall, the low concentrations in air at Cape Verde were likely explained by absence of major emissions in areas from which the air masses originated combined with depletion during long-range atmospheric transport due to enhanced degradation under tropical conditions (high temperatures and concentrations of hydroxyl radicals).

Abstract. Our current understanding of Arctic carbonaceous aerosol (CA) is rudimentary and there is a lack of long-term observations for many components, such as organic aerosol (OA), exceptions to this include equivalent black carbon (eBC) and methane sulfonic acid (MSA).  To address this, we analyzed long-term measurements of organic carbon (OC), elemental carbon (EC), and source-specific organic tracers from 2017 to 2020 to constrain CA sources in the rapidly changing Arctic. We also used absorption photometer (aethalometer) measurements to constrain equivalent BC from biomass burning (eBCBB) and fossil fuel combustion (eBCFF) using Positive Matrix Factorization (PMF).  Our analysis showed that organic tracers are essential to understand Arctic CA sources. For 2017 to 2020, levoglucosan had a bimodal seasonality, with a signal from residential wood combustion (RWC) in the heating season (H-season; November to May) and from wildfires (WF) in the non-heating season (NH-season; June to October), demonstrating a pronounced inter-annual variability in the WF influence. Biogenic secondary organic aerosol (BSOA) species (2-methyltetrols) from isoprene oxidation appeared only in the NH-season, peaking in July to August. Intrusions of warm air masses from Siberia in summer caused three- and ninefold increases in 2-methyltetrols compared to 2017 to 2018, in 2019 and 2020, respectively, warranting investigation of the local vs. the long-range atmospheric transport (LRT) contribution, as certain Arctic vegetation has highly temperature sensitive biogenic volatile organic compounds (BVOC) emission rates. Primary biological aerosol particles (PBAP) tracers (various sugars and sugar-alcohols) were elevated in the NH-season but evolved differently, whereas cellulose was completely decoupled from the other PBAP tracers. Peak levels of most PBAP tracers and of 2-methyltetrols were associated with WF emissions, demonstrating the importance of measuring a broad spectrum of source specific tracers to understand sources and dynamics of CA. Finally, CA seasonality is heavily influenced by long-range atmospheric transport (LRT) episodes, since background levels are extremely low. E.g., we find the OA peak in the NH-season is as strongly influenced by LRT as is EC during Arctic Haze (AH).  Source apportionment of CA by Latin Hypercube Sampling (LHS) showed a mixed contribution from RWC (46 %), fossil fuel (FF) sources (27 %), and BSOA (25 %) in the H-season, whereas BSOA (56 %) prevailed over WF (26 %) and FF (15 %) in the NH-season. Source apportionment of eBC by PMF showed that FF combustion dominated eBC (70 ± 2.7 %), whereas RWC (22 ± 2.7 %) was more abundant than WF (8.0 ± 2.9 %). Modeled BC concentrations from FLEXPART attributed an almost equal share to FF (51 ± 3.1 %) and BB. Both FLEXPART and the PMF analysis concluded that RWC is a more important source than WF. However, with a modeled RWC of 30 ± 4.1 % and WF of 19 ± 2.8 %, FLEXPART suggests relatively higher contributions to eBC from these sources. We find that OA (281 ± 106 ng m−3) is a significant fraction of the Arctic PM10 aerosol particle mass, though less than sea salt aerosol (SSA) (682 ± 46.9 ng m−3) and mineral dust (MD) (613 ± 368 ng m−3) as well as typically non-sea-salt sulfate (nssSO42−) (314 ± 62.6 ng m−3), originating mainly from anthropogenic sources in winter and from natural sources in summer. FF combustion was the prevailing source of eBC, whereas RWC made a larger contribution to eBCBB than WF.

<p>Atmospheric observatories in the remote areas represent the primary infrastructure for the state-of-the-art meteorological and climate research and play a crucial role in Climate Change comprehension. However, the World Meteorological Organization Global Atmosphere Watch (WMO-GAW) states in their 2018 final report that “the fate of the next generation of monitoring stations will be dramatically modified by the breakthroughs of new low-cost sensor (LCS) technologies.”. The development and improvement of low-cost technologies are proving notable applications and today LCSs are already playing a crucial role in fields such as model or emission validation and spatial variability of pollution[1]. Upcoming earth observation programmes, applications, services and support in citizen inclusion in earth monitoring are pushing the European Union (EU) in funding R&D to assess low-cost technologies, thus making the introduction of basic and applied research imperative.<br>PIONEER* aims at establishing a low-cost wireless sensor network (LCS-WSN) for the study of transboundary transport phenomena of air pollutants. Given its highly relevance for the Earth climate, ecosystems, and human health, primary endeavor will be directed towards the study of tropospheric ozone to obtain quantitative, reproducible in-situ measurements. Tropospheric ozone is one of the most important atmospheric gases involved in photochemical reactions[2], it plays a central role in the radiative budget of the atmosphere and it is the third greenhouse gas in the troposphere[3]. Also, surface ozone is a dangerous secondary pollutant causing harm to human health and ecosystems[4]. Since the troposphere is a very complex system the goal is to develop and deploy a reliable LCS-WSN, along the trail Munich-Venice, to be used by scientists as well as citizen engineers in remote areas, where the needs of reliable dense spatial data to model the transport phenomena and Climate Change effects is decisive. <br>PIONEER will exploit the existing open source technologies and commercial low-cost sensors to provide a LCS-WSN systems for long term climate data collection, a cloud-assisted database for time series collection and management, a web portal for uploading, displaying, performing statistical analysis and downloading records and metadata in a fully open access fashion, a comprehensive open source repository with tools, guidelines and application developed. The software will be open-source and released under copyleft license, thus allowing the complete reproducibility of all the developed devices and tools. </p><p>*Individual Global Fellowships granted by the Research Executive Agency. <br>Grant Agreement number: 844526 — PIONEER — H2020-MSCA-IF-2018</p><p>[1] Lewis, Alastair, W. Richard Peltier, and Erika von Schneidemesser. "Low-cost sensors for the measurement of atmospheric composition: overview of topic and future applications." (2018).</p><p>[2] Crutzen, P.J., Lawrence, M.G., Poschl, U.,“On the background photochemistry of tropospheric ozone”, Tellus AB 51, 123–146 (1999).</p><p>[3] Forster, Piers, et al. "Changes in atmospheric constituents and in radiative forcing. Chapter 2." Climate Change 2007. The Physical Science Basis. 2007.</p><p>[4] Cooper, Owen R., et al. "Global distribution and trends of tropospheric ozone: An observation-based review." (2014).</p><p>[5] Young, P. J., et al. "Pre-industrial to end 21st century projections of tropospheric ozone from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)." Atmospheric Chemistry and Physics 13.4 (2013): 2063-2090.</p>

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