| 1. |
- Dusek, U., et al.
(författare)
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Water uptake by biomass burning aerosol at sub- and supersaturated conditions: closure studies and implications for the role of organics
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 11, s. 9519-9532
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the CCN activity of freshly emitted biomass burning particles and their hygroscopic growth at a relative humidity (RH) of 85%. The particles were produced in the Mainz combustion laboratory by controlled burning of various wood types. The water uptake at sub- and supersaturations is parameterized by the hygroscopicity parameter, κ (c.f. Petters and Kreidenweis, 2007). For the wood burns, κ is low, generally around 0.06. The main emphasis of this study is a comparison of κ derived from measurements at sub- and supersaturated conditions (κG and κCCN), in order to see whether the water uptake at 85% RH can predict the CCN properties of the biomass burning particles. Differences in κGand κCCN can arise through solution non-idealities, the presence of slightly soluble or surface active compounds, or non-spherical particle shape. We find that κG and κCCN agree within experimental uncertainties (of around 30%) for particle sizes of 100 and 150 nm; only for 50 nm particles is κCCN larger than κG by a factor of 2. The magnitude of this difference and its dependence on particle size is consistent with the presence of surface active organic compounds. These compounds mainly facilitate the CCN activation of small particles, which form the most concentrated solution droplets at the point of activation. The 50 nm particles, however, are only activated at supersaturations higher than 1% and are therefore of minor importance as CCN in ambient clouds. By comparison with the actual chemical composition of the biomass burning particles, we estimate that the hygroscopicity of the water-soluble organic carbon (WSOC) fraction can be represented by a κWSOC value of approximately 0.2. The effective hygroscopicity of a typical wood burning particle can therefore be represented by a linear mixture of an inorganic component with κ ≅ 0.6, a WSOC component with κ ≅ 0.2, and an insoluble component with κ = 0.
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| 2. |
- Fors, Erik, et al.
(författare)
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Hygroscopic properties of Amazonian biomass burning and European background HULIS and investigation of their effects on surface tension with two models linking H-TDMA to CCNC data
- 2010
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 10:12, s. 5625-5639
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Tidskriftsartikel (refereegranskat)abstract
- HUmic-LIke Substances (HULIS) have been identified as major contributors to the organic carbon in atmospheric aerosol. The term "HULIS" is used to describe the organic material found in aerosol particles that resembles the humic organic material in rivers and sea water and in soils. In this study, two sets of filter samples from atmospheric aerosols were collected at different sites. One set of samples was collected at the K-puszta rural site in Hungary, about 80 km SE of Budapest, and a second was collected at a site in Rondonia, Amazonia, Brazil, during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) biomass burning season experiment. HULIS were extracted from the samples and their hygroscopic properties were studied using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) at relative humidity (RH) < 100%, and a cloud condensation nucleus counter (CCNC) at RH > 100%. The H-TDMA measurements were carried out at a dry diameter of 100 nm and for RH ranging from 30 to 98%. At 90% RH the HULIS samples showed diameter growth factors between 1.04 and 1.07, reaching values of 1.4 at 98% RH. The cloud nucleating properties of the two sets of aerosol samples were analysed using two types of thermal static cloud condensation nucleus counters. Two different parameterization models were applied to investigate the potential effect of HULIS surface activity, both yielding similar results. For the K-puszta winter HULIS sample, the surface tension at the point of activation was estimated to be lowered by between 34% (47.7 mN/m) and 31% (50.3 mN/m) for dry sizes between 50 and 120 nm in comparison to pure water. A moderate lowering was also observed for the entire water soluble aerosol sample, including both organic and inorganic compounds, where the surface tension was decreased by between 2% (71.2 mN/m) and 13% (63.3 mN/m).
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| 3. |
- Massling, A., et al.
(författare)
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Results and recommendations from an intercomparison of six Hygroscopicity-TDMA systems
- 2011
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 4:3, s. 485-497
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Tidskriftsartikel (refereegranskat)abstract
- The performance of six custom-built Hygrocopicity-Tandem Differential Mobility Analyser (H-TDMA) systems was investigated in the frame of an international calibration and intercomparison workshop held in Leipzig, February 2006. The goal of the workshop was to harmonise H-TDMA measurements and develop recommendations for atmospheric measurements and their data evaluation. The H-TDMA systems were compared in terms of the sizing of dry particles, relative humidity (RH) uncertainty, and consistency in determination of number fractions of different hygroscopic particle groups. The experiments were performed in an air-conditioned laboratory using ammonium sulphate particles or an external mixture of ammonium sulphate and soot particles. The sizing of dry particles of the six H-TDMA systems was within 0.2 to 4.2% of the selected particle diameter depending on investigated size and individual system. Measurements of ammonium sulphate aerosol found deviations equivalent to 4.5% RH from the set point of 90% RH compared to results from previous experiments in the literature. Evaluation of the number fraction of particles within the clearly separated growth factor modes of a laboratory generated externally mixed aerosol was done. The data from the H-TDMAs was analysed with a single fitting routine to investigate differences caused by the different data evaluation procedures used for each H-TDMA. The differences between the H-TDMAs were reduced from +12/-13% to +8/-6% when the same analysis routine was applied. We conclude that a common data evaluation procedure to determine number fractions of externally mixed aerosols will improve the comparability of H-TDMA measurements. It is recommended to ensure proper calibration of all flow, temperature and RH sensors in the systems. It is most important to thermally insulate the aerosol humidification unit and the second DMA and to monitor these temperatures to an accuracy of 0.2 degrees C. For the correct determination of external mixtures, it is necessary to take into account size-dependent losses due to diffusion in the plumbing between the DMAs and in the aerosol humidification unit.
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| 4. |
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| 5. |
- Kivekäs, Niku, et al.
(författare)
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Contribution of ship traffic to aerosol particle concentrations downwind of a major shipping lane
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:16, s. 8255-8267
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Tidskriftsartikel (refereegranskat)abstract
- Particles in the atmosphere are of concern due to their toxic properties and effects on climate. In coastal areas, ship emissions can be a significant anthropogenic source. In this study we investigated the contribution from ship emissions to the total particle number and mass concentrations at a remote location. We studied the particle number concentration (12 to 490 nm in diameter), the mass concentration (12 to 150 nm in diameter) and number and volume size distribution of aerosol particles in ship plumes for a period of 4.5 months at Hovsore, a coastal site on the western coast of Jutland in Denmark. During episodes of western winds, the site is about 50 km downwind of a major shipping lane and the plumes are approximately 1 hour old when they arrive at the site. We have used a sliding percentile-based method for separating the plumes from the measured background values and to calculate the ship plume contribution to the total particle number and PM0.15 mass concentration (mass of particles below 150 nm in diameter, converted from volume assuming sphericity) at the site. The method is not limited to particle number or volume concentration, but can also be used for different chemical species in both particle and gas phase. The total number of analyzed ship plumes was 726, covering on average 19% of the time when air masses were arriving at the site over the shipping lane. During the periods when plumes were present, the particle concentration exceeded the background values on average by 790 cm(-3) by number and 0.10 gm(-3) by mass. The corresponding daily average values were 170 cm-3 and 0.023 gm-3, respectively. This means that the ship plumes contributed between 11 and 19% to the particle number concentration and between 9 and 18% to PM0.15 during days when air was arriving over the shipping lane. The estimated annual contribution from ship plumes, where all wind directions were included, was in the range of 5-8% in particle number concentration and 4-8% in PM0.15.
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| 6. |
- Roldin, Pontus, et al.
(författare)
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Aerosol ageing in an urban plume - implication for climate
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 11:12, s. 5897-5915
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Tidskriftsartikel (refereegranskat)abstract
- The climate effects downwind of an urban area resulting from gaseous and particulate emissions within the city are as yet inadequately quantified. The aim of this work was to estimate these effects for Malmo city in southern Sweden (population 280 000). The chemical and physical particle properties were simulated with a model for Aerosol Dynamics, gas phase CHEMistry and radiative transfer calculations (ADCHEM) following the trajectory movement from upwind of Malmo, through the urban background environment and finally tens and hundreds of kilometers downwind of Malmo. The model results were evaluated using measurements of the particle number size distribution and chemical composition. The total particle number concentration 50 km (similar to 3 h) downwind, in the center of the Malmo plume, is about 3700 cm(-3) of which the Malmo contribution is roughly 30%. Condensation of nitric acid, ammonium and to a smaller extent oxidized organic compounds formed from the emissions in Malmo increases the secondary aerosol formation with a maximum of 0.7-0.8 mu gm(-3) 6 to 18 h downwind of Malmo. The secondary mass contribution dominates over the primary soot contribution from Malmo already 3 to 4 h downwind of the emission sources and contributes to an enhanced total surface direct or indirect aerosol shortwave radiative forcing in the center of the urban plume ranging from -0.3 to -3.3 Wm(-2) depending on the distance from Malmo, and the specific cloud properties.
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