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In order to reduce the uncertainty of aerosol radiative forcing in global climate models, we need to better understand natural aerosol sources which are important to constrain the current and pre-industrial climate. Here, we analyze Particle Number Size Distributions (PNSD) collected during a year (2015) across four coastal and inland Antarctic research bases (Halley, Marambio, Concordia/Dome C and King Sejong). We find that the four Antarctic locations have striking differences in PNSD, stressing multiple aerosol sources and processes likely exist. We utilise k-means cluster analysis to separate the PNSD data into six main categories. Nucleation and Bursting PNSDs occur 28-48% of the time between sites, most commonly at coastal sites Marambio and King Sejong where air masses mostly come from the west and travel over extensive regions of sea ice, marginal ice, and open ocean, and likely arise from new particle formation. Aitken high, Aitken low, and bimodal PNSDs occur 37-68% of the time, most commonly at Concordia/Dome C on the Antarctic Plateau, and likely arise from atmospheric transport and aging from aerosol originating likely in both coastal boundary layer and free troposphere. Pristine PNSDs with low aerosol concentrations occur 12-45% of the time, most common at Halley located at low altitudes and far from the coastal melting ice, and influenced by air masses from the west. The Antarctic Atmospheric circulation has a strong control on the air mass origin type. Most of the time Marambio and King Sejong stations are affected by Easterly air masses, whereas Halley gets air masses mainly from the Weddell sea marginal and consolidated pack ice. Not only the sea spray primary aerosols and gas to particle secondary aerosols sources, but also the different air masses impacting the research stations should be kept in mind when deliberating upon different aerosol precursors sources across research stations. We provide evidence that both primary and secondary components from pelagic and sympagic regions strongly contribute to the annual seasonal cycle of Antarctic aerosols which add insight on the possible sources of aerosol production/activity in the whole Antarctic region. Our simultaneous aerosol measurements stress the importance of the variation in atmospheric biogeochemistry across the Antarctic region. [ABSTRACT FROM AUTHOR]

The absorption of shortwave irradiance in snow depends on the physical properties of snow (e.g., snow grain size and shape, liquid water content, etc.) and light-absorbing particles (LAP). Originating from natural and anthropogenic sources, LAP has been reported to accelerate snowmelt significantly in different regions globally. Yet, our process-level understanding of LAP after deposition onto snow remains rather limited. Here we investigate the impacts of artificial deposition of different LAP onto snow surfaces in an outdoor environment of northern Finland. Following LAP dry deposition into a custom-made tent standing on top of the snowpack, the albedo was followed along with the properties of snow in snow pit measurements throughout the spring season. The results showed that the albedo decay at the end of the season for the different spots were linked to the initial amount and type of LAP that were deposited onto the snowpack. Measured snow temperature profiles from LAP doped snow versus natural reference snow illustrated that the LAP affected snow had higher temperatures in the subsurface snow layers. Collected snow samples analyzed for size distribution of soot particles revealed no apparent agglomeration of soot particles during thaw-freezing events taking place during the experiment. Despite the relatively large perturbation of the experimentally deposited LAP, their impact on the season length was only up to 3 days. Additional experiments are, nevertheless, needed to better constrain the effects of LAP on snow albedo, melt rate, and other associated processes. [ABSTRACT FROM AUTHOR]

Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon (BrC) to the total particulate light absorption in the wavelength range of 370–950 nm (BrC 370–950) and the particulate absorption Ångström exponents (AAE 470/950) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC 370–950 was estimated to be from 1 % to 21 % for wood log stoves and 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC / EC) and BrC 370–950 indicated that a one-unit increase in OC / EC corresponded to approximately a 14 % increase in BrC 370–950. Additionally, BrC 370–950 was clearly influenced by the fuel moisture content and the combustion efficiency, while the effect of the combustion appliance type was less prominent. AAE 470/950 of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE 470/950 and OC / EC, an AAE 470/950 close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE 470/950 of 1.02, with BrC contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC from residential wood combustion with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for northern European wood stove emissions with relatively high OC / EC ratios. [ABSTRACT FROM AUTHOR]

Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the Earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon to the total particulate light absorption in the wavelength range of 370 to 950 nm (BrC370-950)and the particulate absorption Ångström exponents (AAE470/950) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC370-950 was estimated to be from 1 % to 21 % for wood log stoves and was primarily influenced by fuel moisture content and minimally affected by combustion appliance type. The BrC370-950 contribution was 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC/EC) and BrC indicated that a one unit increase in OC/EC corresponded to approximately a 14 % increase in BrC370-950. Additionally, BrC370-950 increased with decreasing combustion efficiency. AAE470/950 of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE470/950 and OC/EC, an AAE470/950 close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE470/950 of 1.02, with BrC370-950 contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC370-950 of RWC emissions with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for Northern European wood stove emissions with relatively high OC/EC ratios. [ABSTRACT FROM AUTHOR]

ABSTRACT A simple method for correcting for the loading effects of aethalometer data is presented. The formula [BC.sub.CORRECTED] = (1 + k x ATN) x [BC.sub.NONCORRECTED], where ATN is the [...]

Photoacoustic detection is a sensitive method for measurement of light-absorbing particles directly in the aerosol phase. In this article, we demonstrate a new sensitive technique for photoacoustic aerosol absorption measurements using a cantilever microphone for the detection of the photoacoustic signal. Compared to conventional diaphragm microphones, a cantilever offers increased sensitivity by up to two orders of magnitude. The measurement setup uses a photoacoustic cell from Gasera PA201 gas measurement system, which we have adapted for aerosol measurements. Here we reached a noise level of 0.013 Mm−1 (one standard deviation) with a sampling time of 20 s, using a simple single-pass design without a need for a resonant acoustic cell. The sampling time includes 10 s signal averaging time and 10 s sample exchange, since the photoacoustic cell is designed for closed cell operation. We demonstrate the method in measurements of size-selected nigrosin particles and ambient black carbon. Due to the exceptional sensitivity, the technique shows great potential for applications where low detection limits are required, for example size-selected absorption measurements and black carbon detection in ultra clean environments. [ABSTRACT FROM AUTHOR]