Articles | Volume 4, issue 12
https://doi.org/10.5194/amt-4-2851-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/amt-4-2851-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
22 Dec 2011
Research article |
| 22 Dec 2011
Effective density of Aquadag and fullerene soot black carbon reference materials used for SP2 calibration
M. Gysel
Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
M. Laborde
Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
J. S. Olfert
Department of Mechanical Engineering, University of Alberta, Edmonton AB T6G 2G8, Canada
R. Subramanian
Droplet Measurement Technologies, Boulder, CO 80301, USA
A. J. Gröhn
Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zurich, Switzerland
Related subject area
Subject: Aerosols | Technique: Laboratory Measurement | Topic: Instruments and Platforms
Quantitative chemical assay of nanogram-level particulate matter using aerosol mass spectrometry: characterization of particles collected from uncrewed atmospheric measurement platforms
An optimised organic carbon ∕ elemental carbon (OC ∕ EC) fraction separation method for radiocarbon source apportionment applied to low-loaded Arctic aerosol filters
Investigating the dependence of mineral dust depolarization on complex refractive index and size with a laboratory polarimeter at 180.0° lidar backscattering angle
Evaluation of a low-cost dryer for a low-cost optical particle counter
Effects of temperature and salinity on bubble-bursting aerosol formation simulated with a bubble-generating chamber
A new hot-stage microscopy technique for measuring temperature-dependent viscosities of aerosol particles and its application to farnesene secondary organic aerosol
Characterization of a modified printed optical particle spectrometer for high-frequency and high-precision laboratory and field measurements
Design and fabrication of an electrostatic precipitator for infrared spectroscopy
Combined application of online FIGAERO-CIMS and offline LC-Orbitrap mass spectrometry (MS) to characterize the chemical composition of secondary organic aerosol (SOA) in smog chamber studies
The AERosol and TRACe gas Collector (AERTRACC): an online measurement controlled sampler for source-resolved emission analysis
High-frequency gaseous and particulate chemical characterization using extractive electrospray ionization mass spectrometry (Dual-Phase-EESI-TOF)
An evaluation of the heat test for the ice-nucleating ability of minerals and biological material
Development, characterization, and application of an improved online reactive oxygen species analyzer based on the Monitor for AeRosols and Gases in ambient Air (MARGA)
Characterization of soot produced by the mini inverted soot generator with an atmospheric simulation chamber
LED-based solar simulator to study photochemistry over a wide temperature range in the large simulation chamber AIDA
Laboratory evaluation of the scattering matrix of ragweed, ash, birch and pine pollen towards pollen classification
Cloud condensation nuclei (CCN) activity analysis of low-hygroscopicity aerosols using the aerodynamic aerosol classifier (AAC)
Characterisation of the Manchester Aerosol Chamber facility
A study on the fragmentation of sulfuric acid and dimethylamine clusters inside an atmospheric pressure interface time-of-flight mass spectrometer
A semi-automated instrument for cellular oxidative potential evaluation (SCOPE) of water-soluble extracts of ambient particulate matter
Utilizing an electrical low-pressure impactor to indirectly probe water uptake via particle bounce measurements
Calibration and evaluation of a broad supersaturation scanning (BS2) cloud condensation nuclei counter for rapid measurement of particle hygroscopicity and cloud condensation nuclei (CCN) activity
Correcting bias in log-linear instrument calibrations in the context of chemical ionization mass spectrometry
Effects of aerosol size and coating thickness on the molecular detection using extractive electrospray ionization
The nano-scanning electrical mobility spectrometer (nSEMS) and its application to size distribution measurements of 1.5–25 nm particles
A dual-droplet approach for measuring the hygroscopicity of aqueous aerosol
A method for liquid spectrophotometric measurement of total and water-soluble iron and copper in ambient aerosols
Efficacy of a portable, moderate-resolution, fast-scanning differential mobility analyzer for ambient aerosol size distribution measurements
Comparative characterization of the performance of bio-aerosol nebulizers in connection with atmospheric simulation chambers
Coupling a gas chromatograph simultaneously to a flame ionization detector and chemical ionization mass spectrometer for isomer-resolved measurements of particle-phase organic compounds
Investigation of structural changes of atmospheric aerosol samples during two thermal–optical measurement procedures (EUSAAR2, NIOSH870)
Development of the drop Freezing Ice Nuclei Counter (FINC), intercomparison of droplet freezing techniques, and use of soluble lignin as an atmospheric ice nucleation standard
Elemental analysis of oxygenated organic coating on black carbon particles using a soot-particle aerosol mass spectrometer
On the calibration of FIGAERO-ToF-CIMS: importance and impact of calibrant delivery for the particle-phase calibration
A single-beam photothermal interferometer for in situ measurements of aerosol light absorption
Aqueous particle generation with a 3D printed nebulizer
A new method for operating a continuous-flow diffusion chamber to investigate immersion freezing: assessment and performance study
Characterization of a non-thermal plasma source for use as a mass specrometric calibration tool and non-radioactive aerosol charger
Application of time-of-flight aerosol mass spectrometry for the real-time measurement of particle-phase organic peroxides: an online redox derivatization–aerosol mass spectrometer (ORD-AMS)
Nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) for investigating hygroscopic properties of sub-10 nm aerosol nanoparticles
Quantification of toxic metals using machine learning techniques and spark emission spectroscopy
A new approach for measuring the carbon and oxygen content of atmospherically relevant compounds and mixtures
An experimental study on light scattering matrices for Chinese loess dust with different particle size distributions
Counting on chemistry: laboratory evaluation of seed-material-dependent detection efficiencies of ultrafine condensation particle counters
Photophoretic spectroscopy in atmospheric chemistry – high-sensitivity measurements of light absorption by a single particle
Laboratory evaluation of particle-size selectivity of optical low-cost particulate matter sensors
Mapping ice formation to mineral-surface topography using a micro mixing chamber with video and atomic-force microscopy
High-humidity tandem differential mobility analyzer for accurate determination of aerosol hygroscopic growth, microstructure, and activity coefficients over a wide range of relative humidity
Development of an improved two-sphere integration technique for quantifying black carbon concentrations in the atmosphere and seasonal snow
Development of the DRoplet Ice Nuclei Counter Zurich (DRINCZ): validation and application to field-collected snow samples
Christopher R. Niedek, Fan Mei, Maria A. Zawadowicz, Zihua Zhu, Beat Schmid, and Qi Zhang
Atmos. Meas. Tech., 16, 955–968, https://doi.org/10.5194/amt-16-955-2023, https://doi.org/10.5194/amt-16-955-2023, 2023
Short summary
Short summary
This novel micronebulization aerosol mass spectrometry (MS) technique requires a low sample volume (10 μL) and can quantify nanogram levels of organic and inorganic particulate matter (PM) components when used with 34SO4. This technique was successfully applied to PM samples collected from uncrewed atmospheric measurement platforms and provided chemical information that agrees well with real-time data from a co-located aerosol chemical speciation monitor and offline data from secondary ion MS.
Martin Rauber, Gary Salazar, Karl Espen Yttri, and Sönke Szidat
Atmos. Meas. Tech., 16, 825–844, https://doi.org/10.5194/amt-16-825-2023, https://doi.org/10.5194/amt-16-825-2023, 2023
Short summary
Short summary
Carbon-containing aerosols from ambient air are analysed for radioactive isotope radiocarbon to determine the contribution from fossil-fuel emissions. Light-absorbing soot-like aerosols are isolated by water extraction and thermal separation. This separation is affected by artefacts, for which we developed a new correction method. The investigation of aerosols from the Arctic shows that our approach works well for such samples, where many artefacts are expected.
Alain Miffre, Danaël Cholleton, Clément Noël, and Patrick Rairoux
Atmos. Meas. Tech., 16, 403–417, https://doi.org/10.5194/amt-16-403-2023, https://doi.org/10.5194/amt-16-403-2023, 2023
Short summary
Short summary
The depolarization ratio of hematite, silica, Arizona and Asian dust is evaluated in a lab with a π-polarimeter operating at lidar 180 ° and at (355, 532) nm wavelengths. The hematite depolarization equals (10±1) % at 355 nm for coarser particles, while that of silica is (33±1) %. This huge difference is explained by accounting for the high imaginary part of the hematite complex refractive index, thus revealing the key role played by light absorption in mineral dust lidar depolarization.
Miriam Chacón-Mateos, Bernd Laquai, Ulrich Vogt, and Cosima Stubenrauch
Atmos. Meas. Tech., 15, 7395–7410, https://doi.org/10.5194/amt-15-7395-2022, https://doi.org/10.5194/amt-15-7395-2022, 2022
Short summary
Short summary
The study evaluates a low-cost dryer to avoid the negative effect of hygroscopic growth and fog droplets in the particulate matter (PM) concentrations of sensors. The results show a reduction in the overestimation of the PM but also an underestimation compared to reference devices. Special care is needed when designing a dryer as high temperatures change the sampled air by evaporating the most volatile particulate species. Low-cost dryers are very promising for different sensor applications.
Svetlana Sofieva, Eija Asmi, Nina S. Atanasova, Aino E. Heikkinen, Emeline Vidal, Jonathan Duplissy, Martin Romantschuk, Rostislav Kouznetsov, Jaakko Kukkonen, Dennis H. Bamford, Antti-Pekka Hyvärinen, and Mikhail Sofiev
Atmos. Meas. Tech., 15, 6201–6219, https://doi.org/10.5194/amt-15-6201-2022, https://doi.org/10.5194/amt-15-6201-2022, 2022
Short summary
Short summary
A new bubble-generating glass chamber design with an extensive set of aerosol production experiments is presented to re-evaluate bubble-bursting-mediated aerosol production as a function of water parameters: bubbling air flow, water salinity, and temperature. Our main findings suggest modest dependence of aerosol production on the water salinity and a strong dependence on temperature below ~ 10 °C.
Kristian J. Kiland, Kevin L. Marroquin, Natalie R. Smith, Shaun Xu, Sergey A. Nizkorodov, and Allan K. Bertram
Atmos. Meas. Tech., 15, 5545–5561, https://doi.org/10.5194/amt-15-5545-2022, https://doi.org/10.5194/amt-15-5545-2022, 2022
Short summary
Short summary
Information on the viscosity of secondary organic aerosols is needed when making air quality, climate, and atmospheric chemistry predictions. Viscosity depends on temperature, so we developed a new method for measuring the temperature-dependent viscosity of small samples. As an application of the method, we measured the viscosity of farnesene secondary organic aerosol at different temperatures.
Sabin Kasparoglu, Mohammad Maksimul Islam, Nicholas Meskhidze, and Markus D. Petters
Atmos. Meas. Tech., 15, 5007–5018, https://doi.org/10.5194/amt-15-5007-2022, https://doi.org/10.5194/amt-15-5007-2022, 2022
Short summary
Short summary
A modified version of a Handix Scientific printed optical particle spectrometer is introduced. The paper presents characterization experiments, including concentration, size, and time responses. Integration of an external multichannel analyzer card removes counting limitations of the original instrument. It is shown that the high-resolution light-scattering amplitude data can be used to sense particle-phase transitions.
Nikunj Dudani and Satoshi Takahama
Atmos. Meas. Tech., 15, 4693–4707, https://doi.org/10.5194/amt-15-4693-2022, https://doi.org/10.5194/amt-15-4693-2022, 2022
Short summary
Short summary
We designed and fabricated an aerosol collector with high collection efficiency that enables quantitative infrared spectroscopy analysis. By collecting particles on optical windows, typical substrate interferences are eliminated. New methods for fabricating aerosol devices using 3D printing with post-treatment to reduce the time and cost of prototyping are described.
Mao Du, Aristeidis Voliotis, Yunqi Shao, Yu Wang, Thomas J. Bannan, Kelly L. Pereira, Jacqueline F. Hamilton, Carl J. Percival, M. Rami Alfarra, and Gordon McFiggans
Atmos. Meas. Tech., 15, 4385–4406, https://doi.org/10.5194/amt-15-4385-2022, https://doi.org/10.5194/amt-15-4385-2022, 2022
Short summary
Short summary
Atmospheric chemistry plays a key role in the understanding of aerosol formation and air pollution. We designed chamber experiments for the characterization of secondary organic aerosol (SOA) from a biogenic precursor with inorganic seed. Our results highlight the advantages of a combination of online FIGAERO-CIMS and offline LC-Orbitrap MS analytical techniques to characterize the chemical composition of SOA in chamber studies.
Julia Pikmann, Lasse Moormann, Frank Drewnick, and Stephan Borrmann
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2022-206, https://doi.org/10.5194/amt-2022-206, 2022
Revised manuscript accepted for AMT
Short summary
Short summary
Aerosol measured in complex environments is usually a mixture of emissions from different sources. To characterize sources individually, we developed a sampling system for particles and organic trace gases which is coupled to real-time data of physical and chemical aerosol properties, gas concentrations and meteorological variables. Using suitable sampling conditions for individual aerosols which are compared with the real-time data the desired aerosols are sampled separately from each other.
Chuan Ping Lee, Mihnea Surdu, David M. Bell, Josef Dommen, Mao Xiao, Xueqin Zhou, Andrea Baccarini, Stamatios Giannoukos, Günther Wehrle, Pascal André Schneider, Andre S. H. Prevot, Jay G. Slowik, Houssni Lamkaddam, Dongyu Wang, Urs Baltensperger, and Imad El Haddad
Atmos. Meas. Tech., 15, 3747–3760, https://doi.org/10.5194/amt-15-3747-2022, https://doi.org/10.5194/amt-15-3747-2022, 2022
Short summary
Short summary
Real-time detection of both the gas and particle phase is needed to elucidate the sources and chemical reaction pathways of organic vapors and particulate matter. The Dual-EESI was developed to measure gas- and particle-phase species to provide new insights into aerosol sources or formation mechanisms. After characterizing the relative gas and particle response factors of EESI via organic aerosol uptake experiments, the Dual-EESI is more sensitive toward gas-phase analyes.
Martin I. Daily, Mark D. Tarn, Thomas F. Whale, and Benjamin J. Murray
Atmos. Meas. Tech., 15, 2635–2665, https://doi.org/10.5194/amt-15-2635-2022, https://doi.org/10.5194/amt-15-2635-2022, 2022
Short summary
Short summary
Mineral dust and particles of biological origin are important types of ice-nucleating particles (INPs) that can trigger ice formation of supercooled cloud droplets. Heat treatments are used to detect the presence of biological INPs in samples collected from the environment as the activity of mineral INPs is assumed unchanged, although not fully assessed. We show that the ice-nucleating ability of some minerals can change after heating and discuss how INP heat tests should be interpreted.
Jiyan Wu, Chi Yang, Chunyan Zhang, Fang Cao, Aiping Wu, and Yanlin Zhang
Atmos. Meas. Tech., 15, 2623–2633, https://doi.org/10.5194/amt-15-2623-2022, https://doi.org/10.5194/amt-15-2623-2022, 2022
Short summary
Short summary
We introduced an online method to simultaneously determine the content of inorganic salt ions and reactive oxygen species (ROS) in PM2.5 hour by hour. We verified the accuracy and precision of the instrument. And we got the daily changes in ROS and the main sources that affect ROS. This breakthrough enables the quantitative assessment of atmospheric particulate matter ROS at the diurnal scale, providing an effective tool to study sources and environmental impacts of ROS.
Virginia Vernocchi, Marco Brunoldi, Silvia G. Danelli, Franco Parodi, Paolo Prati, and Dario Massabò
Atmos. Meas. Tech., 15, 2159–2175, https://doi.org/10.5194/amt-15-2159-2022, https://doi.org/10.5194/amt-15-2159-2022, 2022
Short summary
Short summary
The performance of a mini inverted soot generator was investigated at a simulation chamber facility by studying the soot generated by ethylene and propane combustion, together with the number, size, optical properties, and EC / OC concentrations. Mass absorption coefficients and Ångström absorption exponents are compatible with the literature, with some differences. The characterization of MISG soot particles is fundamental to design and perform experiments in atmospheric simulation chambers.
Magdalena Vallon, Linyu Gao, Feng Jiang, Bianca Krumm, Jens Nadolny, Junwei Song, Thomas Leisner, and Harald Saathoff
Atmos. Meas. Tech., 15, 1795–1810, https://doi.org/10.5194/amt-15-1795-2022, https://doi.org/10.5194/amt-15-1795-2022, 2022
Short summary
Short summary
A LED-based light source has been constructed for the AIDA simulation chamber at the Karlsruhe Institute of Technology. It allows aerosol formation and ageing studies under atmospherically relevant illumination intensities and spectral characteristics at temperatures from –90 °C to 30 °C with the possibility of changing the photon flux and irradiation spectrum at any point. The first results of photolysis experiments with 2,3-pentanedione, iron oxalate and a brown carbon component are shown.
Danaël Cholleton, Émilie Bialic, Antoine Dumas, Pascal Kaluzny, Patrick Rairoux, and Alain Miffre
Atmos. Meas. Tech., 15, 1021–1032, https://doi.org/10.5194/amt-15-1021-2022, https://doi.org/10.5194/amt-15-1021-2022, 2022
Short summary
Short summary
While pollen impacts public health and the Earth’s climate, the identification of each pollen taxon remains challenging. In this context, a laboratory evaluation of the polarimetric light-scattering characteristics of ragweed, ash, birch and pine pollen, when embedded in ambient air, is here performed at two wavelengths. Interestingly, the achieved precision of the retrieved scattering matrix elements allows unequivocal light scattering characteristics of each studied taxon to be identified.
Kanishk Gohil and Akua A. Asa-Awuku
Atmos. Meas. Tech., 15, 1007–1019, https://doi.org/10.5194/amt-15-1007-2022, https://doi.org/10.5194/amt-15-1007-2022, 2022
Short summary
Short summary
This work develops a methodology and software to study and analyze the cloud-droplet-forming ability of aerosols with an aerodynamic aerosol classifier (AAC). This work quantifies the uncertainties in size-resolved measurements and subsequent uncertainties propagated to cloud droplet parameterizations. Lastly, we present the best practices for AAC cloud droplet measurement.
Yunqi Shao, Yu Wang, Mao Du, Aristeidis Voliotis, M. Rami Alfarra, Simon P. O'Meara, S. Fiona Turner, and Gordon McFiggans
Atmos. Meas. Tech., 15, 539–559, https://doi.org/10.5194/amt-15-539-2022, https://doi.org/10.5194/amt-15-539-2022, 2022
Short summary
Short summary
A comprehensive description and characterisation of the Manchester Aerosol Chamber (MAC) was conducted. The MAC has good temperature and relative humidity homogeneity, fast mixing times, and comparable losses of gases and particles with other chambers. The MAC's bespoke control system allows improved duty cycles and repeatable experiments. Moreover, the effect of contamination on performance was also investigated. It is highly recommended to regularly track the chamber's performance.
Dina Alfaouri, Monica Passananti, Tommaso Zanca, Lauri Ahonen, Juha Kangasluoma, Jakub Kubečka, Nanna Myllys, and Hanna Vehkamäki
Atmos. Meas. Tech., 15, 11–19, https://doi.org/10.5194/amt-15-11-2022, https://doi.org/10.5194/amt-15-11-2022, 2022
Short summary
Short summary
To study what is happening in the atmosphere, it is important to be able to measure the molecules and clusters present in it. In our work, we studied an artifact that happens inside a mass spectrometer, in particular the fragmentation of clusters. We were able to quantify the fragmentation and retrieve the correct concentration and composition of the clusters using our dual (experimental and theoretical) approach.
Sudheer Salana, Yixiang Wang, Joseph V. Puthussery, and Vishal Verma
Atmos. Meas. Tech., 14, 7579–7593, https://doi.org/10.5194/amt-14-7579-2021, https://doi.org/10.5194/amt-14-7579-2021, 2021
Short summary
Short summary
Oxidative potential (OP) of particulate matter (PM) is an important indicator of PM toxicity. However, no automated instrument has ever been developed to provide a rapid high-throughput analysis of cell-based OP measurements. Here, we developed a semi-automated instrument, the first of its kind, for measuring oxidative potential using rat alveolar cells. We also developed a dataset on the intrinsic cellular OP of several compounds commonly known to be present in ambient PM.
Kevin B. Fischer and Giuseppe A. Petrucci
Atmos. Meas. Tech., 14, 7565–7577, https://doi.org/10.5194/amt-14-7565-2021, https://doi.org/10.5194/amt-14-7565-2021, 2021
Short summary
Short summary
The viscosity of organic particles in atmospheric aerosol is sometimes correlated to bounce factor. It is generally accepted that more viscous particles will be more likely to bounce following acceleration toward and impaction on a surface. We demonstrate that use of multi-stage low-pressure impactors for this purpose may result in measurement artifacts that depend on chemical composition, particle size, and changing relative humidity. A hypothesis for the observed effect is presented.
Najin Kim, Yafang Cheng, Nan Ma, Mira L. Pöhlker, Thomas Klimach, Thomas F. Mentel, Ovid O. Krüger, Ulrich Pöschl, and Hang Su
Atmos. Meas. Tech., 14, 6991–7005, https://doi.org/10.5194/amt-14-6991-2021, https://doi.org/10.5194/amt-14-6991-2021, 2021
Short summary
Short summary
A broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of supersaturation simultaneously, can measure a broad range of CCN activity distribution with a high time resolution. We describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve. Intercomparison experiments between typical DMA-CCN and BS2-CCN measurements to evaluate the BS2-CCN system showed high correlation and good agreement.
Chenyang Bi, Jordan E. Krechmer, Manjula R. Canagaratna, and Gabriel Isaacman-VanWertz
Atmos. Meas. Tech., 14, 6551–6560, https://doi.org/10.5194/amt-14-6551-2021, https://doi.org/10.5194/amt-14-6551-2021, 2021
Short summary
Short summary
Calibration techniques have been recently developed to log-linearly correlate analyte sensitivity with CIMS operating conditions particularly for compounds without authentic standards. In this work, we examine the previously ignored bias in the log-linear-based calibration method and estimate an average bias of 30 %, with 1 order of magnitude for less sensitive compounds in some circumstances. A step-by-step guide was provided to reduce and even remove the bias.
Chuan Ping Lee, Mihnea Surdu, David M. Bell, Houssni Lamkaddam, Mingyi Wang, Farnoush Ataei, Victoria Hofbauer, Brandon Lopez, Neil M. Donahue, Josef Dommen, Andre S. H. Prevot, Jay G. Slowik, Dongyu Wang, Urs Baltensperger, and Imad El Haddad
Atmos. Meas. Tech., 14, 5913–5923, https://doi.org/10.5194/amt-14-5913-2021, https://doi.org/10.5194/amt-14-5913-2021, 2021
Short summary
Short summary
Extractive electrospray ionization mass spectrometry (EESI-MS) has been deployed for high throughput online detection of particles with minimal fragmentation. Our study elucidates the extraction mechanism between the particles and electrospray (ES) droplets of different properties. The results show that the extraction rate is likely affected by the coagulation rate between the particles and ES droplets. Once coagulated, the particles undergo complete extraction within the ES droplet.
Weimeng Kong, Stavros Amanatidis, Huajun Mai, Changhyuk Kim, Benjamin C. Schulze, Yuanlong Huang, Gregory S. Lewis, Susanne V. Hering, John H. Seinfeld, and Richard C. Flagan
Atmos. Meas. Tech., 14, 5429–5445, https://doi.org/10.5194/amt-14-5429-2021, https://doi.org/10.5194/amt-14-5429-2021, 2021
Short summary
Short summary
We present the design, modeling, and experimental characterization of the nano-scanning electrical mobility spectrometer (nSEMS), a recently developed instrument that probes particle physical properties in the 1.5–25 nm range. The nSEMS has proven to be extremely powerful in examining atmospheric nucleation and the subsequent growth of nanoparticles in the CERN CLOUD experiment, which provides a valuable asset to study atmospheric nanoparticles and to evaluate their impact on climate.
Jack M. Choczynski, Ravleen Kaur Kohli, Craig S. Sheldon, Chelsea L. Price, and James F. Davies
Atmos. Meas. Tech., 14, 5001–5013, https://doi.org/10.5194/amt-14-5001-2021, https://doi.org/10.5194/amt-14-5001-2021, 2021
Short summary
Short summary
Relative humidity (RH) and hygroscopicity play an important role in regulating the physical, chemical, and optical properties of aerosol. In this work, we develop a new method to characterize hygroscopicity using particle levitation. We levitate two droplets with an electrodynamic balance and measure their size with light-scattering methods using one droplet as a probe of the RH. We demonstrate highly accurate and precise measurements of the RH and hygroscopic growth of a range of samples.
Yuhan Yang, Dong Gao, and Rodney J. Weber
Atmos. Meas. Tech., 14, 4707–4719, https://doi.org/10.5194/amt-14-4707-2021, https://doi.org/10.5194/amt-14-4707-2021, 2021
Short summary
Short summary
Iron and copper are commonly found in ambient aerosols and have been linked to adverse health effects. We describe a relatively simple benchtop instrument that can be used to quantify these metals in aqueous solutions and verify the method by comparison with inductively coupled plasma mass spectrometry. The approach is based on forming light-absorbing metal–ligand complexes that can be measured with high sensitivity utilizing a long-path liquid waveguide capillary cell.
Stavros Amanatidis, Yuanlong Huang, Buddhi Pushpawela, Benjamin C. Schulze, Christopher M. Kenseth, Ryan X. Ward, John H. Seinfeld, Susanne V. Hering, and Richard C. Flagan
Atmos. Meas. Tech., 14, 4507–4516, https://doi.org/10.5194/amt-14-4507-2021, https://doi.org/10.5194/amt-14-4507-2021, 2021
Short summary
Short summary
We assess the performance of a highly portable mobility analyzer, the Spider DMA, in measuring ambient aerosol particle size distributions, with specific attention to its moderate sizing resolution (R=3). Long-term field testing showed excellent correlation with a conventional mobility analyzer (R=10) over the 17–500 nm range, suggesting that moderate resolution may be sufficient to obtain key properties of ambient size distributions, enabling smaller instruments and better counting statistics.
Silvia G. Danelli, Marco Brunoldi, Dario Massabò, Franco Parodi, Virginia Vernocchi, and Paolo Prati
Atmos. Meas. Tech., 14, 4461–4470, https://doi.org/10.5194/amt-14-4461-2021, https://doi.org/10.5194/amt-14-4461-2021, 2021
Short summary
Short summary
Experiments conducted inside confined artificial environments, such as atmospheric simulation chambers (ASCs), where atmospheric conditions and composition are controlled, can provide valuable information on bio-aerosol viability, dispersion, and impact. We focus here on the reproducible aerosolization and injection of viable microorganisms into an ASC, the first and crucial step of any experimental protocol to expose bio-aerosols to different atmospheric conditions.
Chenyang Bi, Jordan E. Krechmer, Graham O. Frazier, Wen Xu, Andrew T. Lambe, Megan S. Claflin, Brian M. Lerner, John T. Jayne, Douglas R. Worsnop, Manjula R. Canagaratna, and Gabriel Isaacman-VanWertz
Atmos. Meas. Tech., 14, 3895–3907, https://doi.org/10.5194/amt-14-3895-2021, https://doi.org/10.5194/amt-14-3895-2021, 2021
Short summary
Short summary
Measurement techniques that can achieve molecular characterizations are necessary to understand the differences of fate and transport within isomers produced in the atmospheric oxidation process. In this work, we develop an instrument to conduct isomer-resolved measurements of particle-phase organics. We assess the number of isomers per chemical formula in atmospherically relevant samples and examine the feasibility of extending the use of an existing instrument to a broader range of analytes.
Theresa Haller, Eva Sommer, Thomas Steinkogler, Christian Rentenberger, Anna Wonaschuetz, Anne Kasper-Giebl, Hinrich Grothe, and Regina Hitzenberger
Atmos. Meas. Tech., 14, 3721–3735, https://doi.org/10.5194/amt-14-3721-2021, https://doi.org/10.5194/amt-14-3721-2021, 2021
Short summary
Short summary
Structural changes of carbonaceous aerosol samples during thermal–optical measurement techniques cause a darkening of the sample during the heating procedure which can influence the attribution of the carbonaceous material to organic and elemental carbon. We analyzed structural changes of atmospheric aerosol samples occurring during the EUSAAR2 and NIOSH870 measurement protocols with Raman spectroscopy. We found that the darkening of the sample is not necessarily caused by graphitization.
Anna J. Miller, Killian P. Brennan, Claudia Mignani, Jörg Wieder, Robert O. David, and Nadine Borduas-Dedekind
Atmos. Meas. Tech., 14, 3131–3151, https://doi.org/10.5194/amt-14-3131-2021, https://doi.org/10.5194/amt-14-3131-2021, 2021
Short summary
Short summary
To characterize atmospheric ice nuclei, we present (1) the development of our home-built droplet freezing technique (DFT), which involves the Freezing Ice Nuclei Counter (FINC), (2) an intercomparison campaign using NX-illite and an ambient sample with two other DFTs, and (3) the application of lignin as a soluble and commercial ice nuclei standard with three DFTs. We further compiled the growing number of DFTs in use for atmospheric ice nucleation since 2000 and add FINC.
Mutian Ma, Laura-Hélèna Rivellini, YuXi Cui, Megan D. Willis, Rio Wilkie, Jonathan P. D. Abbatt, Manjula R. Canagaratna, Junfeng Wang, Xinlei Ge, and Alex K. Y. Lee
Atmos. Meas. Tech., 14, 2799–2812, https://doi.org/10.5194/amt-14-2799-2021, https://doi.org/10.5194/amt-14-2799-2021, 2021
Short summary
Short summary
Chemical characterization of organic coatings is important to advance our understanding of the physio-chemical properties and atmospheric processing of black carbon (BC) particles. This work develops two approaches to improve the elemental analysis of oxygenated organic coatings using a soot-particle aerosol mass spectrometer. Analyzing ambient data with the new approaches indicated that secondary organics that coated on BC were likely less oxygenated compared to those externally mixed with BC.
Arttu Ylisirniö, Luis M. F. Barreira, Iida Pullinen, Angela Buchholz, John Jayne, Jordan E. Krechmer, Douglas R. Worsnop, Annele Virtanen, and Siegfried Schobesberger
Atmos. Meas. Tech., 14, 355–367, https://doi.org/10.5194/amt-14-355-2021, https://doi.org/10.5194/amt-14-355-2021, 2021
Short summary
Short summary
FIGAERO-ToF-CIMS enables online volatility measurements of chemical compounds in ambient aerosols. Previously published volatility calibration results however differ from each other significantly. In this study we investigate the reason for this discrepancy. We found a major source of error in the widely used syringe deposition method and propose a new method for volatility calibration by using atomized calibration compounds.
Bradley Visser, Jannis Röhrbein, Peter Steigmeier, Luka Drinovec, Griša Močnik, and Ernest Weingartner
Atmos. Meas. Tech., 13, 7097–7111, https://doi.org/10.5194/amt-13-7097-2020, https://doi.org/10.5194/amt-13-7097-2020, 2020
Short summary
Short summary
Here we report on the development of a novel single-beam photothermal interferometer and its use in the measurement of aerosol light absorption. We demonstrate how light-absorbing gases can be used to calibrate the instrument and how this absorption is automatically subtracted during normal operation. The performance of the instrument is compared to a standard filter-based instrument using a black carbon test aerosol. The 60 s detection limit is found to be less than 10 Mm-1.
Michael Rösch and Daniel J. Cziczo
Atmos. Meas. Tech., 13, 6807–6812, https://doi.org/10.5194/amt-13-6807-2020, https://doi.org/10.5194/amt-13-6807-2020, 2020
Short summary
Short summary
The need for a simple atomizer with a high-output stability combined with the capabilities of CAD software and high-resolution 3D printing has allowed for the design, production and testing of the PRinted drOpleT Generator (PROTeGE) to generate liquid particles from solutions. The size and number concentrations of the generated particles have been characterized with different ammonium sulfate and PSL solutions. PROTeGE is easy to operate, requires minimal maintenance and is cost-effective.
Gourihar Kulkarni, Naruki Hiranuma, Ottmar Möhler, Kristina Höhler, Swarup China, Daniel J. Cziczo, and Paul J. DeMott
Atmos. Meas. Tech., 13, 6631–6643, https://doi.org/10.5194/amt-13-6631-2020, https://doi.org/10.5194/amt-13-6631-2020, 2020
Short summary
Short summary
This study presents a new continuous-flow-diffusion-chamber-style operated ice chamber (Modified Compact Ice Chamber, MCIC) to measure the immersion-freezing efficiency of atmospheric particles. MCIC allowed us to obtain maximum droplet-freezing efficiency at higher time resolution without droplet breakthrough ambiguity. Its evaluation was performed by reproducing published data from the recent ice nucleation workshop and past laboratory data for standard and airborne ice-nucleating particles.
Christian Tauber, David Schmoll, Johannes Gruenwald, Sophia Brilke, Peter Josef Wlasits, Paul Martin Winkler, and Daniela Wimmer
Atmos. Meas. Tech., 13, 5993–6006, https://doi.org/10.5194/amt-13-5993-2020, https://doi.org/10.5194/amt-13-5993-2020, 2020
Short summary
Short summary
In this paper we show that a commercially available plasma charger with nitrogen as the working gas can enhance the charging probability for sub-12 nm particles. In addition, the charger ion mobilities and the chemical composition have been examined using an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF MS), and comparison of the experimental results revealed that the generated neutralizer ions are not dependent on the charging mechanism.
Marcel Weloe and Thorsten Hoffmann
Atmos. Meas. Tech., 13, 5725–5738, https://doi.org/10.5194/amt-13-5725-2020, https://doi.org/10.5194/amt-13-5725-2020, 2020
Short summary
Short summary
Aerosol mass spectrometers (AMSs) are frequently applied in atmospheric aerosol research in connection with climate, environmental or health-related projects. The paper describes a new real-time technique for the measurement of organic peroxides, which play an important role in new particle formation and as
reactive oxygen speciesin aerosol–health-related aspects of atmospheric aerosols.
Ting Lei, Nan Ma, Juan Hong, Thomas Tuch, Xin Wang, Zhibin Wang, Mira Pöhlker, Maofa Ge, Weigang Wang, Eugene Mikhailov, Thorsten Hoffmann, Ulrich Pöschl, Hang Su, Alfred Wiedensohler, and Yafang Cheng
Atmos. Meas. Tech., 13, 5551–5567, https://doi.org/10.5194/amt-13-5551-2020, https://doi.org/10.5194/amt-13-5551-2020, 2020
Short summary
Short summary
We present the design of a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) apparatus that enables high accuracy and precision in hygroscopic growth measurements of aerosol nanoparticles with diameters less than 10 nm. We further introduce comprehensive methods for system calibration and validation of the performance of the system. We then study the size dependence of the deliquescence and the efflorescence of aerosol nanoparticles for sizes down to 6 nm.
Seyyed Ali Davari and Anthony S. Wexler
Atmos. Meas. Tech., 13, 5369–5377, https://doi.org/10.5194/amt-13-5369-2020, https://doi.org/10.5194/amt-13-5369-2020, 2020
Short summary
Short summary
Traditional instruments for detection and quantification of toxic metals in the atmosphere are expensive. In this study, we have designed, fabricated, and tested a low-cost instrument, which employs cheap components to detect and quantify toxic metals. Advanced machine learning (ML) techniques have been used to improve the instrument's performance. This study demonstrates how the combination of low-cost sensors with ML can address problems that traditionally have been too expensive to be solved.
James F. Hurley, Nathan M. Kreisberg, Braden Stump, Chenyang Bi, Purushottam Kumar, Susanne V. Hering, Pat Keady, and Gabriel Isaacman-VanWertz
Atmos. Meas. Tech., 13, 4911–4925, https://doi.org/10.5194/amt-13-4911-2020, https://doi.org/10.5194/amt-13-4911-2020, 2020
Short summary
Short summary
The chemical composition of aerosols has implications for human and ecosystem health. Current methods for determining chemical composition are expensive and require highly trained personnel. Our method is promising for moderate-cost, low-maintenance measurements of oxygen / carbon ratios, a key chemical parameter, and other elements may also be studied. In this work, we coupled two commonly used detectors to assess O / C ratios in a variety of compounds and mixtures within an acceptable error.
Jia Liu, Qixing Zhang, Yinuo Huo, Jinjun Wang, and Yongming Zhang
Atmos. Meas. Tech., 13, 4097–4109, https://doi.org/10.5194/amt-13-4097-2020, https://doi.org/10.5194/amt-13-4097-2020, 2020
Short summary
Short summary
Angular behaviors of light scattering properties for loess dust sampled from the Chinese Loess Plateau were investigated using a self-developed apparatus. Two samples with different size distributions were used to represent dust that can or cannot be transported over long ranges. Analyses of optical simulation results showed that differences of measurements are mainly caused by different sizes. This study is useful for the development of optical models of loess dust during transportation.
Peter Josef Wlasits, Dominik Stolzenburg, Christian Tauber, Sophia Brilke, Sebastian Harald Schmitt, Paul Martin Winkler, and Daniela Wimmer
Atmos. Meas. Tech., 13, 3787–3798, https://doi.org/10.5194/amt-13-3787-2020, https://doi.org/10.5194/amt-13-3787-2020, 2020
Short summary
Short summary
In this paper we show that chemical similarities between the seed particle material and the working fluid have an impact on the detection efficiency of commonly used CPCs. A remarkable set of CPCs, including the newly developed V-WCPC 3789, was tested. Among others, reproducibly generated organic seeds based on beta-caryophyllene were used. Theoretical simulations of supersaturation profiles were successfully linked to measured data.
Nir Bluvshtein, Ulrich K. Krieger, and Thomas Peter
Atmos. Meas. Tech., 13, 3191–3203, https://doi.org/10.5194/amt-13-3191-2020, https://doi.org/10.5194/amt-13-3191-2020, 2020
Short summary
Short summary
Light-absorbing organic particles undergo transformations during their exposure in the atmosphere. The role these particles play in the global radiative balance is uncertain. This study describes high-sensitivity and high-precision measurements of light absorption by a single particle levitated in an electrodynamic balance. This high level of sensitivity enables future studies to explore the major processes responsible for changes to the particle's light absorptivity.
Joel Kuula, Timo Mäkelä, Minna Aurela, Kimmo Teinilä, Samu Varjonen, Óscar González, and Hilkka Timonen
Atmos. Meas. Tech., 13, 2413–2423, https://doi.org/10.5194/amt-13-2413-2020, https://doi.org/10.5194/amt-13-2413-2020, 2020
Short summary
Short summary
Particle-size-dependent detection ranges of low-cost particulate matter sensors were evaluated in a laboratory experiment. Six different sensor models were evaluated altogether. The results showed that none of the sensor models adhered to the technical specifications provided by the manufacturers, and thus a high risk of sensor misuse is posed. It is paramount that the limitations regarding the particle size discrimination of low-cost sensors are acknowledged properly.
Raymond W. Friddle and Konrad Thürmer
Atmos. Meas. Tech., 13, 2209–2218, https://doi.org/10.5194/amt-13-2209-2020, https://doi.org/10.5194/amt-13-2209-2020, 2020
Short summary
Short summary
An obstacle to predicting ice content in mixed-phase clouds is the inability to directly view atmospheric ice nucleation at the nanoscale, where this process occurs. Here we show how a cloud-like environment can be created in a small atomic-force microscopy (AFM) sample cell. By colocating video microscopy of ice formation with high-resolution AFM images, we quantitatively show how the surface topography, down to nanometer-length scales, can determine the preferential locations of ice formation.
Eugene F. Mikhailov and Sergey S. Vlasenko
Atmos. Meas. Tech., 13, 2035–2056, https://doi.org/10.5194/amt-13-2035-2020, https://doi.org/10.5194/amt-13-2035-2020, 2020
Short summary
Short summary
Here we present the high-humidity tandem differential hygroscopicity analyzer (HHTDMA) and a new method to measure the hygroscopic growth of aerosol particles with in situ restructuring to minimize the influence of particle shape. Our results demonstrate that the HHTDMA system described in this work allows us to determine the thermodynamic characteristics of aqueous solutions with an accuracy close to that obtained by bulk methods.
Xin Wang, Xueying Zhang, and Wenjing Di
Atmos. Meas. Tech., 13, 39–52, https://doi.org/10.5194/amt-13-39-2020, https://doi.org/10.5194/amt-13-39-2020, 2020
Short summary
Short summary
We developed an improved two-sphere integration (TSI) technique to quantify black carbon (BC) concentrations in the atmosphere and seasonal snow. The major advantage of this system is that it combines two distinct integrated spheres to reduce the scattering effect due to light-absorbing particles and thus provides accurate determinations of total light absorption from BC collected on Nuclepore filters.
Robert O. David, Maria Cascajo-Castresana, Killian P. Brennan, Michael Rösch, Nora Els, Julia Werz, Vera Weichlinger, Lin S. Boynton, Sophie Bogler, Nadine Borduas-Dedekind, Claudia Marcolli, and Zamin A. Kanji
Atmos. Meas. Tech., 12, 6865–6888, https://doi.org/10.5194/amt-12-6865-2019, https://doi.org/10.5194/amt-12-6865-2019, 2019
Short summary
Short summary
Here we present the development and applicability of the DRoplet Ice Nuclei Counter Zurich (DRINCZ). DRINCZ allows for ice nuclei in the immersion mode to be quantified between 0 and -25 °C with an uncertainty of ±0.9 °C. Furthermore, we present a new method for assessing biases in drop-freezing apparatuses and cumulative ice-nucleating-particle concentrations from snow samples collected in the Austrian Alps at the Sonnblick Observatory.
Cited articles
Cross, E. S., Onasch, T. B., Ahern, A., Wrobel, W., Slowik, J. G., Olfert, J., Lack, D. A., Massoli, P., Cappa, C. D., Schwarz, J. P., Spackman, J. R., Fahey, D. W., Sedlacek, A., Trimborn, A., Jayne, J. T., Freedman, A., Williams, L. R., Ng, N. L., Mazzoleni, C., Dubey, M., Brem, B., Kok, G., Subramanian, R., Freitag, S., Clarke, A., Thornhill, D., Marr, L. C., Kolb, C. E., Worsnop, D. R., and Davidovits, P.: Soot particle studies – Instrument inter-comparison – project overview, Aerosol Sci. Technol., 44, 592–611, https://doi.org/10.1080/02786826.2010.482113, 2010.
DeCarlo, P. F., Slowik, J. G., Worsnop, D. R., Davidovits, P., and Jimenez, J. L.: Particle morphology and density characterization by combined mobility and aerodynamic diameter measurements. Part 1: Theory, Aerosol Sci. Technol., 38, 1185–1205, 2004.
Ehara, K., Hagwood, C., and Coakley, K. J.: Novel method to classify aerosol particles according to their mass-to-charge ratio – Aerosol particle mass analyser, J. Aerosol Sci., 27, 217–234, https://doi.org/10.1016/0021-8502(95)00562-5, 1996.
Gelencsér, A.: Carbonaceous Aerosol, vol. 30 of \em Atmospheric and Oceanographic Sciences Library\/, Springer Netherlands, Dordrecht, https://doi.org/10.1007/978-1-4020-2887-8, 2004.
Knutson, E. and Whitby, K. T.: Aerosol classification by electric mobility: Apparatus, theory, and applications, J. Aerosol Sci., 6, 443–451, https://doi.org/10.1016/0021-8502(75)90060-9, 1975.
Kondo, Y., Sahu, L., Moteki, N., Khan, F., Takegawa, N., Liu, X., Koike, M., and Miyakawa, T.: Consistency and traceability of black carbon measurements made by laser-induced incandescence, thermal-optical transmittance, and filter-based photo-absorption techniques, Aerosol Sci. Technol., 45, 295–312, https://doi.org/10.1080/02786826.2010.533215, 2011.
Laborde, M., Gysel, M., and the SOOT11 TEAM: Calibration and intercomparison study of 6 SP2 investigating different types of soot particles and black carbon reference materials, manuscript in preparation, 2011{a}.
Laborde, M., Mertes, P., Zieger, P., Dommen, J., Baltensperger, U., and Gysel, M.: Sensitivity of the Single Particle Soot Photometer to different black carbon types, Atmos. Meas. Tech. Discuss., submitted, 2011{b}.
Laden, F., Neas, L. M., Dockery, D. W., and Schwartz, J.: Association of fine particulate matter from different sources with daily mortality in six US cities, Environ. Health Perspect., 108, 941–947, 2000.
Moteki, N. and Kondo, Y.: Effects of mixing state on black carbon measurements by laser-induced incandescence, Aerosol Sci. Technol., 41, 398–417, https://doi.org/10.1080/02786820701199728, 2007.
Moteki, N. and Kondo, Y.: Dependence of laser-induced incandescence on physical properties of black carbon aerosols: measurements and theoretical interpretation, Aerosol Sci. Technol., 44, 663–675, https://doi.org/10.1080/02786826.2010.484450, 2010.
Moteki, N., Kondo, Y., Takegawa, N., and Nakamura, S.: Directional dependence of thermal emission from nonspherical carbon particles, J. Aerosol Sci., 40, 790–801, https://doi.org/10.1016/j.jaerosci.2009.05.003, 2009.
Moteki, N., Kondo, Y., and Nakamura, S.: Method to measure refractive indices of small nonspherical particles: Application to black carbon particles, J. Aerosol Sci., 41, 513–521, https://doi.org/10.1016/j.jaerosci.2010.02.013, 2010.
Olfert, J. S. and Collings, N.: New method for particle mass classification - the Couette centrifugal particle mass analyzer, J. Aerosol Sci., 36, 1338–1352, https://doi.org/10.1016/j.jaerosci.2005.03.006, 2005.
Olfert, J. S., Symonds, J. P. R., and Collings, N.: The effective density and fractal dimension of particles emitted from a light-duty diesel vehicle with a diesel oxidation catalyst, J. Aerosol Sci., 38, 69–82, https://doi.org/10.1016/j.jaerosci.2006.10.002, 2007.
Ramanathan, V. and Carmichael, G.: Global and regional climate changes due to black carbon, Nat. Geosci., 1, 221–227, https://doi.org/10.1038/ngeo156, 2008.
Scheckman, J. H., McMurry, P. H., and Pratsinis, S. E.: Rapid characterization of agglomerate aerosols by in situ mass-mobility measurements, Langmuir, 25, 8248–8254, https://doi.org/10.1021/la900441e, 2009.
Schwarz, J. P., Gao, R. S., Fahey, D. W., Thomson, D. S., Watts, L. A., Wilson, J. C., Reeves, J. M., Darbeheshti, M., Baumgardner, D. G., Kok, G. L., Chung, S. H., Schulz, M., Hendricks, J., Lauer, A., Kärcher, B., Slowik, J. G., Rosenlof, K. H., Thompson, T. L., Langford, A. O., Loewenstein, M., and Aikin, K. C.: Single-particle measurements of midlatitude black carbon and light-scattering aerosols from the boundary layer to the lower stratosphere, J. Geophys. Res., 111, D16207, https://doi.org/10.1029/2006JD007076, 2006.
Schwarz, J. P., Spackman, J. R., Gao, R. S., Watts, L. A., Stier, P., Schulz, M., Davis, S. M., Wofsy, S. C., and Fahey, D. W.: Global-scale black carbon profiles observed in the remote atmosphere and compared to models, Geophys. Res. Lett., 37, L18812, https://doi.org/10.1029/2010GL044372, 2010.
Slama, R., Morgenstern, V., Cyrys, J., Zutavern, A., Herbarth, O., Wichmann, H. E., Heinrich, J., and Group, L. S.: Traffic-related atmospheric pollutants levels during pregnancy and offspring's term birth weight: a study relying on a land-use regression exposure model, Environ. Health Perspect., 115, 1283–1292, https://doi.org/10.1289/ehp.10047, 2007.
Slowik, J. G., Cross, E. S., Han, J.-H., Davidovits, P., Onasch, T. B., Jayne, J. T., Williams, L. R., Canagaratna, M. R., Worsnop, D. R., Chakrabarty, R. K., Moosmüller, H., Arnott, W. P., Schwarz, J. P., Gao, R.-S., Fahey, D. W., Kok, G. L., and Petzold, A.: An inter-comparison of instruments measuring black carbon content of soot particles, Aerosol Sci. Technol., 41, 295–314, https://doi.org/10.1080/02786820701197078, 2007.
Stephens, M., Turner, N., and Sandberg, J.: Particle identification by laser-induced incandescence in a solid-state laser cavity, Appl. Opt., 42, 3726–3736, https://doi.org/10.1364/AO.42.003726, 2003.
