scholarly journals A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland

2015 ◽  
Vol 15 (2) ◽  
pp. 799-813 ◽  
Author(s):  
R. Oswald ◽  
M. Ermel ◽  
K. Hens ◽  
A. Novelli ◽  
H. G. Ouwersloot ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Gas Phase Reactions ◽  
Additional Source ◽  
Forest Environment ◽  
Field Station ◽  
Photostationary State ◽  
Unknown Source ◽  
Unidentified Source ◽  
Photolytic Decomposition ◽  
Atmospheric Concentrations

Abstract. Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, significantly exceed the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. This study presents budget calculations of HONO based on simultaneous measurements of all relevant species, including HONO and OH at two different measurement heights, i.e. 1 m above the ground and about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal forest environment. We observed mean HONO concentrations of about 6.5 × 108 molecules cm−3 (26 ppt) during daytime, more than 20 times higher than expected from the PSS of 0.2 × 108 molecules cm−3 (1 ppt). To close the budgets at both heights, a strong additional source term during daytime is required. This unidentified source is at its maximum at noon (up to 1.1 × 106 molecules cm−3 s−1, 160 ppt h−1) and in general up to 2.3 times stronger above the canopy than close to the ground. The insignificance of known gas phase reactions and other processes like dry deposition or advection compared to the photolytic decomposition of HONO at this measurement site was an ideal prerequisite to study possible correlations of this unknown term to proposed HONO sources. But neither the proposed emissions from soils nor the proposed photolysis of adsorbed HNO3 contributed substantially to the unknown source. However, the unknown source was found to be perfectly correlated to the unbalanced photolytic loss of HONO.

scholarly journals Comparison of HONO budgets for two measurement heights at a field station within the boreal forest (SMEAR II – HUMPPA-COPEC 2010)

2014 ◽  
Vol 14 (6) ◽  
pp. 7823-7857 ◽  
Author(s):  
R. Oswald ◽  
M. Ermel ◽  
K. Hens ◽  
A. Novelli ◽  
H. G. Ouwersloot ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Gas Phase Reactions ◽  
Additional Source ◽  
Forest Environment ◽  
Field Station ◽  
Photostationary State ◽  
Unknown Source ◽  
Unidentified Source ◽  
Photolytic Decomposition ◽  
Atmospheric Concentrations

Abstract. Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, normally exceed by far the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. Here, we present budget calculations of HONO based on simultaneous measurements of all relevant species including HONO and OH at two different measurement heights, i.e. 1 m above ground and about 2 to 3 m above canopy (24 m above ground), conducted in boreal forest environment. We observed mean HONO concentrations during daytime of about 6.5 × 108 molecules cm−3 (26 ppt), more than twenty times higher than expected from the PSS, 0.2 × 108 molecules cm−3 (1 ppt). To close the budgets in both heights a strong additional source term during daytime is required. This unidentified source is maximal at noon (up to 1.1 × 106 molecules cm−3 s−1, 160 ppt h−1) and in general up to 2.3 times stronger above the canopy than close to the ground. The insignificance of known gas phase reactions and also other processes like dry deposition or advection compared to the photolytic decomposition of HONO at this measurement site was an ideal prerequisite to study possible correlations of this unknown term to proposed HONO sources. But neither the proposed emissions from soils nor the proposed photolysis of adsorbed HNO3 contributed substantially to the unknown source. However, the unknown source was found to be perfectly correlated to the unbalanced photolytic loss of HONO.

scholarly journals Hygroscopicity, CCN and volatility properties of submicron atmospheric aerosol in a boreal forest environment during the summer of 2010

2013 ◽  
Vol 13 (11) ◽  
pp. 29097-29136 ◽  
Author(s):  
J. Hong ◽  
S. A. K. Häkkinen ◽  
M. Paramonov ◽  
M. Äijälä ◽  
J. Hakala ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Atmospheric Aerosol ◽  
Cloud Condensation Nuclei ◽  
Relative Mass ◽  
Particle Sizes ◽  
Volatile Material ◽  
Differential Mobility ◽  
Forest Environment ◽  
Large Particles ◽  
Aerosol Volume

Abstract. The Volatility-Hygroscopicity Tandem Differential Mobility Analyzer (VH-TDMA) was applied to study the hygroscopicity and volatility properties of submicron atmospheric aerosol in a boreal forest environment in Hyytiälä, Finland during the summer of 2010. Aitken and accumulation mode particles (50 nm, 75 nm and 110 nm) were investigated. The results suggest that the particles were internally mixed at all sizes. Hygroscopicity was found to increase with size. The relative mass fraction of organics and SO42− is probably the major contributor to the fluctuation of the hygroscopicity for all particle sizes. The Cloud Condensation Nuclei counter (CCNc)-derived hygroscopicity parameter κ was slightly higher than κ calculated from VH-TDMA data under sub-saturated conditions, which can be explained by the fact that particulate organics have a different degree of dissolution in sub- and supersaturated conditions. Also, the size-resolved volatility properties of particles were investigated. Upon heating, small particles evaporated more compared to large particles. There was a significant amount of aerosol volume (non-volatile material) left even at heating temperatures above 280 °C. Using size resolved volatility-hygroscopicity analysis, we concluded that there was always hygroscopic material remaining in the particles of different sizes at all different heating temperatures, even above 280 °C. This indicates that the observed non-volatile aerosol material was not consisting solely of black carbon.

scholarly journals Observation of 2-methyltetrols and related photo-oxidation products of isoprene in boreal forest aerosols from Hyytiälä, Finland

2005 ◽  
Vol 5 (10) ◽  
pp. 2761-2770 ◽  
Author(s):  
I. Kourtchev ◽  
T. Ruuskanen ◽  
W. Maenhaut ◽  
M. Kulmala ◽  
M. Claeys
Keyword(s):  
Boreal Forest ◽  
Atmospheric Chemistry ◽  
Unsaturated Fatty Acids ◽  
Oxidation Products ◽  
Conifer Forest ◽  
Aerosol Formation ◽  
Summer Period ◽  
Forest Environment ◽  
Photo Oxidation ◽  
Pinic Acid

Abstract. Oxidation products of isoprene including 2-methyltetrols (2-methylthreitol and 2-methylerythritol), 2-methylglyceric acid and triol derivatives of isoprene (2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and 3-methyl-2,3,4-trihydroxy-1-butene) have been detected in boreal forest PM1 aerosols collected at Hyytiälä, southern Finland, during a 2004 summer period, at significant atmospheric concentrations (in total 51 ng m−3 in summer versus 0.46 ng m−3 in fall). On the basis of these results, it can be concluded that photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol formation during summer in this conifer forest ecosystem. In addition to isoprene oxidation products, malic acid, which can be regarded as an intermediate in the oxidation of unsaturated fatty acids, was also detected at high concentrations during the summer period (46 ng m−3 in summer versus 5.2 ng m−3 in fall), while levoglucosan, originating from biomass burning, became relatively more important during the fall period (29 ng m−3 in fall versus 10 ng m−3 in summer). Pinic acid, a major photo-oxidation product of α-pinene in laboratory experiments, could only be detected at trace levels in the summer samples, suggesting that further oxidation of pinic acid occurs and/or that different oxidation pathways are followed. We hypothesize that photo-oxidation of isoprene may participate in the early stages of new particle formation, a phenomenon which has been well documented in the boreal forest environment.

scholarly journals Relating the hygroscopic properties of submicron aerosol to both gas- and particle-phase chemical composition in a boreal forest environment

2015 ◽  
Vol 15 (11) ◽  
pp. 15511-15541
Author(s):  
J. Hong ◽  
J. Kim ◽  
T. Nieminen ◽  
J. Duplissy ◽  
M. Ehn ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Growth Factor ◽  
Boreal Forest ◽  
Gas Phase ◽  
Mixing Rule ◽  
Particle Phase ◽  
Hygroscopic Growth ◽  
Forest Environment ◽  
Composition Data

Abstract. Measurements of the hygroscopicity of 15–145 nm particles in a boreal forest environment were conducted using two Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) systems during the Pan-European Gas-AeroSOIs-climate interaction Study (PEGASOS) campaign in spring 2013. Measurements of the chemical composition of non-size segregated particles were also performed using a High-Resolution Aerosol Mass Spectrometer (HR-AMS) in parallel with hygroscopicity measurements. On average, the hygroscopic growth factor (HGF) of particles was observed to increase from the morning until afternoon. In case of accumulation mode particles, the main reasons for this behavior were increases in the ratio of sulfate to organic matter and oxidation level (O : C ratio) of the organic matter in the particle phase. Using an O : C dependent hygroscopic growth factor of organic matter (HGForg), fitted using the inverse Zdanovskii–Stokes–Robinson (ZSR) mixing rule, clearly improved the agreement between measured HGF and that predicted based on HR-AMS composition data. Besides organic oxidation level, the influence of inorganic species was tested when using the ZSR mixing rule to estimate the hygroscopic growth factor of organics in the aerosols. While accumulation and Aitken mode particles were predicted fairly well by the bulk aerosol composition data, the hygroscopicity of nucleation mode particles showed little correlation. However, we observed them to be more sensitive to the gas phase concentration of condensable vapors: the more there was sulfuric acid in the gas phase, the more hygroscopic the nucleation mode particles were. No clear dependence was found between the extremely low-volatility organics (ELVOCs) concentration and the HGF of particles of any size.

scholarly journals Transformation of marine air masses in the Fennoscandian Boreal forest – changes in aerosol, humidity, and clouds

2021 ◽  
Author(s):  
Meri Räty ◽  
Larisa Sogacheva ◽  
Helmi-Marja Keskinen ◽  
Veli-Matti Kerminen ◽  
Tuukka Petäjä ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Water Vapour ◽  
Cloud Condensation Nuclei ◽  
Source Region ◽  
Cloud Formation ◽  
Condensation Nuclei ◽  
Forest Environment ◽  
Transport Time ◽  
Air Mass ◽  
Air Masses

<p>Fennoscandian boreal forest is a region with commonly occurring particle formation, which benefits from the abundance of biogenic volatile organic compounds emitted by the vegetation. The same vegetation also regulates the exchange of water vapour between the ecosystem and the atmosphere. Thus, as the forest has the potential to provide the two components needed in cloud formation, i.e. condensation nuclei and humidity, there is reason to suspect consequent changes in air masses that are influenced by the forest below.</p><p>We investigated the link between boreal forest air mass transport and cloud related properties in air masses that arrived to the SMEAR II station (61°10’N, 24°17’E, 170m a.s.l.), Finland, from between western and norther directions. These selected air masses were originally marine and travelled only across a land area with relatively minor anthropogenic emissions sources, allowing us to focus on biogenic influences. The source region and the time each air mass spent above land before arrival, were determined from 96-hour long air mass back trajectories. We used a long-term comprehensive data sets, spanning up to 11 growing seasons (April-September, 2006-2016).</p><p>Air masses with short transport times over the forest, often coincided with measurements of particles in smaller size ranges. Higher numbers of larger cloud condensation nuclei sized particles became more common in air masses with longer transport times over the forest. Similarly, air masses that spent little time over land, were often relatively cool and carried less water vapour. Whereas, higher specific humidities were more likely in air masses with longer times spent over land, as associated warming had most likely facilitated an increased uptake of water vapour from plant evapotranspiration. We also observed corresponding moderate increases in satellite observed cloud optical thickness and in-situ measured precipitation. Air masses with very short transport times over land were an exception, as these fast-moving air masses are likely to be connected to weather fronts and therefore also have a high probability for clouds and precipitation. The reported differences between air masses more or less disappeared when the transport time over land reached approximately 60 hours, and any further increase in land transport time no longer caused a substantial change. This appears to be the time scale in which most of the forest environment’s influence on these cloud related properties is realised and a balance is reached.</p>

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