scholarly journals Intercomparison of four different in-situ techniques for ambient formaldehyde measurements in urban air

2005 ◽  
Vol 5 (3) ◽  
pp. 2897-2945 ◽  
Author(s):  
C. Hak ◽  
I. Pundt ◽  
C. Kern ◽  
U. Platt ◽  
J. Dommen ◽  
...  
Keyword(s):  
Regression Line ◽  
Ambient Air ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Measuring Instruments ◽  
Chromatographic Technique ◽  
In Situ Techniques ◽  
Time Period ◽  
The Individual

Abstract. Results from an intercomparison of several currently used in-situ techniques for the measurement of atmospheric formaldehyde (CH2O) are presented. The measurements were carried out at Bresso, an urban site in the periphery of Milan (Italy) as part of the FORMAT-I field campaign. Eight instruments were employed by six independent research groups using four different techniques: Differential Optical Absorption Spectroscopy (DOAS), Fourier Transform Infra Red (FTIR) interferometry, the fluorimetric Hantzsch reaction technique (five instruments) and a chromatographic technique employing C18-DNPH-cartridges (2,4-dinitrophenylhydrazine). White type multi-reflection systems were employed for the optical techniques in order to avoid spatial CH2O gradients and ensure the sampling of nearly the same air mass by all instruments. Between 23 and 31 July 2002, up to 13 ppbv of CH2O were observed. The concentrations lay well above the detection limits of all instruments. The formaldehyde concentrations determined with DOAS, FTIR and the Hantzsch instruments were found to agree within ±11%, with the exception of one Hantzsch instrument, which gave systematically higher values. The two hour integrated samples by DNPH yielded up to 25% lower concentrations than the data of the continuously measuring instruments averaged over the same time period. The consistency between the DOAS and the Hantzsch method was better than during previous intercomparisons in ambient air with slopes of the regression line not significantly differing from one. The differences between the individual Hantzsch instruments could be attributed in part to the calibration standards used. Possible systematic errors of the methods are discussed.

scholarly journals Intercomparison of four different in-situ techniques for ambient formaldehyde measurements in urban air

2005 ◽  
Vol 5 (11) ◽  
pp. 2881-2900 ◽  
Author(s):  
C. Hak ◽  
I. Pundt ◽  
S. Trick ◽  
C. Kern ◽  
U. Platt ◽  
...  
Keyword(s):  
Regression Line ◽  
Ambient Air ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Measuring Instruments ◽  
Chromatographic Technique ◽  
In Situ Techniques ◽  
Time Period ◽  
The Individual

Abstract. Results from an intercomparison of several currently used in-situ techniques for the measurement of atmospheric formaldehyde (CH2O) are presented. The measurements were carried out at Bresso, an urban site in the periphery of Milan (Italy) as part of the FORMAT-I field campaign. Eight instruments were employed by six independent research groups using four different techniques: Differential Optical Absorption Spectroscopy (DOAS), Fourier Transform Infra Red (FTIR) interferometry, the fluorimetric Hantzsch reaction technique (five instruments) and a chromatographic technique employing C18-DNPH-cartridges (2,4-dinitrophenylhydrazine). White type multi-reflection systems were employed for the optical techniques in order to avoid spatial CH2O gradients and ensure the sampling of nearly the same air mass by all instruments. Between 23 and 31 July 2002, up to 13 ppbv of CH2O were observed. The concentrations lay well above the detection limits of all instruments. The formaldehyde concentrations determined with DOAS, FTIR and the Hantzsch instruments were found to agree within ±11%, with the exception of one Hantzsch instrument, which gave systematically higher values. The two hour integrated samples by DNPH yielded up to 25% lower concentrations than the data of the continuously measuring instruments averaged over the same time period. The consistency between the DOAS and the Hantzsch method was better than during previous intercomparisons in ambient air with slopes of the regression line not significantly differing from one. The differences between the individual Hantzsch instruments could be attributed in part to the calibration standards used. Possible systematic errors of the methods are discussed.

scholarly journals Selected In Situ Hybridization Methods: Principles and Application

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3874
Author(s):  
Dominika Veselinyová ◽  
Jana Mašlanková ◽  
Katarina Kalinová ◽  
Helena Mičková ◽  
Mária Mareková ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Imaging Techniques ◽  
Cell Communication ◽  
Probe Design ◽  
Rapid Progress ◽  
In Situ Techniques ◽  
Different Types ◽  
Laboratory Procedures ◽  
The Individual

We are experiencing rapid progress in all types of imaging techniques used in the detection of various numbers and types of mutation. In situ hybridization (ISH) is the primary technique for the discovery of mutation agents, which are presented in a variety of cells. The ability of DNA to complementary bind is one of the main principles in every method used in ISH. From the first use of in situ techniques, scientists paid attention to the improvement of the probe design and detection, to enhance the fluorescent signal intensity and inhibition of cross-hybrid presence. This article discusses the individual types and modifications, and is focused on explaining the principles and limitations of ISH division on different types of probes. The article describes a design of probes for individual types of in situ hybridization (ISH), as well as the gradual combination of several laboratory procedures to achieve the highest possible sensitivity and to prevent undesirable events accompanying hybridization. The article also informs about applications of the methodology, in practice and in research, to detect cell to cell communication and principles of gene silencing, process of oncogenesis, and many other unknown processes taking place in organisms at the DNA/RNA level.

Unobtrusive Observation of Cycling Tourists in the Wild

2014 ◽  
Vol 6 (4) ◽  
pp. 22-42
Author(s):  
Benjamin Poppinga ◽  
Martin Pielot ◽  
Wilko Heuten ◽  
Susanne Boll
Keyword(s):  
Field Study ◽  
In Situ Observation ◽  
In Situ Techniques ◽  
In The Wild ◽  
The Individual ◽  
Post Hoc ◽  
Real Challenge ◽  
Unobtrusive Observation

The observation of cycling tourists is a real challenge. Traditional in-situ observation techniques fail as they threaten the intimateness of the experience and often interfere with the users' tasks. In post-hoc studies, like interviews, participants are unable to recap all details of their earlier experience accurately. This paper investigates how a hybrid, i.e., in-situ and post-hoc, observation approach can overcome the individual limitations and thereby provide detailed insights without disturbing the cyclists. The authors demonstrate the approach in a field study, where we observed 11 tourists with three unobtrusive in-situ techniques and used the gathered data to jog their memories in a post-hoc interview. They found that the observation technique allows to get detailed and accurate insights, and the communication between experimenter and participant becomes clearer. The authors conclude that hybrid observation would be valuable in other mobile field study settings.

scholarly journals Spatially resolved measurements of nitrogen dioxide in an urban environment using concurrent multi-axis differential optical absorption spectroscopy

2006 ◽  
Vol 6 (6) ◽  
pp. 12671-12700
Author(s):  
R. J. Leigh ◽  
G. K. Corlett ◽  
U. Frieß ◽  
P. S. Monks
Keyword(s):  
Remote Sensing ◽  
Optical Absorption ◽  
Nitrogen Dioxide ◽  
Urban Environment ◽  
Absorption Spectroscopy ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
High Time Resolution ◽  
In Situ Techniques

Abstract. A novel system using the technique of concurrent multi-axis differential optical absorption spectroscopy system has been developed and applied to the measurement of nitrogen dioxide in an urban environment. Using five fixed telescopes, slant columns of nitrogen dioxide, ozone, water vapour, and the oxygen dimer, O4, are simultaneously retrieved in five vertically separated viewing directions. The application of this remote sensing technique in the urban environment is explored. Through, the application of several simplifying assumptions a tropospheric concentration of NO2 is derived and compared with an urban background in-situ chemiluminescence detector. The remote sensing and in-situ techniques show good agreement. Owing to the high time resolution of the measurements, the ability to image and quantify plumes within the urban environment is demonstrated. The CMAX-DOAS measurements provide a useful measure of overall NO2 concentrations on a city-wide scale.

scholarly journals Tropospheric NO<sub>2</sub> column densities deduced from zenith-sky DOAS measurements in Shanghai, China, and their application to satellite validation

2008 ◽  
Vol 8 (4) ◽  
pp. 16713-16762 ◽  
Author(s):  
D. Chen ◽  
B. Zhou ◽  
S. Beirle ◽  
L. M. Chen ◽  
T. Wagner
Keyword(s):  
Solar Zenith Angle ◽  
Surface Concentration ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Vertical Column ◽  
Satellite Validation ◽  
Tropospheric No2 ◽  
Realistic Information ◽  
Good Agreement

Abstract. Zenith-sky scattered sunlight observations using differential optical absorption spectroscopy (DOAS) technique were carried out in Shanghai, China (31.3° N, 121.5° E) since December 2006. At this polluted urban site, the measurement provided NO2 total columns in the daytime. Here, we present a new method to extract time series of tropospheric vertical column densities (VCD) of NO2 from these observations. The derived tropospheric NO2 VCD is an important quantity for the estimation of emissions and for the validation of satellite observations. Our method makes use of assumptions on the relative NO2 height profiles and on the diurnal variation of the stratospheric NO2 VCD. The influence of these parameters on the retrieved tropospheric NO2 VCD is discussed; for a polluted site like Shanghai, the accuracy of our method is estimated to be <20% for solar zenith angle (SZA) lower than 85°. From simultaneously performed long-path DOAS measurement, the NO2 surface concentration at the same site was observed and the corresponding tropospheric NO2 VCD was estimated using the assumed seasonal NO2 profiles in the planetary boundary layer (PBL). By making a comparison between the tropospheric NO2 VCD from zenith-sky and long-path DOAS measurements, it was found that the former provided more realistic information about total tropospheric pollution than the latter, so it's more suitable for satellite data validation than the in situ measurement. A comparison between the tropospheric NO2 VCD from ground-based zenith-sky measurement and SCIAMACHY was also made. Satellite validation for a strongly polluted area is highly needed, but exhibits also a great challenge. Our comparison showed good agreement, considering in particular the different spatial resolutions between the two measurements.

scholarly journals The development of a nitrogen dioxide sonde

2010 ◽  
Vol 3 (4) ◽  
pp. 2805-2832
Author(s):  
W. W. Sluis ◽  
M. A. F. Allaart ◽  
A. J. M. Piters ◽  
L. F. L. Gast
Keyword(s):  
Boundary Layer ◽  
Nitrogen Dioxide ◽  
Ambient Air ◽  
Measurement Range ◽  
Measuring Instruments ◽  
Chemiluminescent Reaction ◽  
June July ◽  
Good Agreement ◽  
Meteorological Institute

Abstract. A growing number of space-borne instruments measures nitrogen dioxide (NO2) concentrations in the troposphere, but validation of these instruments is hampered by lack of ground-based and in-situ profile measurements. The Royal Netherlands Meteorological Institute (KNMI) has developed a working NO2 sonde. The sonde is attached to a small meteorological balloon and measures a tropospheric NO2 profile. The NO2 sonde has a vertical resolution of 5 m, and a measurement range between 1 and 100 ppbv. The instrument is light in weight (±700 g), cheap (disposable), energy efficient and not harmful to the environment or the person who finds the package after use. The sonde uses the chemiluminescent reaction of NO2 in an aqueous luminol solution. The NO2–luminol reaction produces faint blue/purple light (at about 425 nm), which is detected by an array of silicon photodiodes. The luminol solution is optimised to be specific to NO2. An on-ground comparison with measurements from a Photolytic Analyzer of RIVM shows that both instruments measure similar NO2 variations in ambient air. During the Cabauw Intercomparison campaign of Nitrogen Dioxide measuring Instruments (CINDI) in June/July 2009 six vertical profiles of NO2 from the ground to 5 km altitude were measured, which clearly show that the largest amount of NO2 is measured in the boundary layer. The measured boundary layer heights of the NO2 sonde are in good agreement with boundary layer heights determined by a LD40 Ceilometer at Cabauw.

scholarly journals Autofluorescence of atmospheric bioaerosols: spectral fingerprints and taxonomic trends of pollen

2013 ◽  
Vol 6 (12) ◽  
pp. 3369-3392 ◽  
Author(s):  
C. Pöhlker ◽  
J. A. Huffman ◽  
J.-D. Förster ◽  
U. Pöschl
Keyword(s):  
Real Time ◽  
Fungal Spores ◽  
Life Quality ◽  
Principal Component ◽  
Ambient Air ◽  
Allergenic Potential ◽  
The Individual ◽  
Grain Surface

Abstract. Primary biological aerosol particles (PBAP) are important factors in atmospheric cycling, climate, and public health. Pollen is a major fraction of PBAP and is receiving increasing attention due to its high allergenic potential and the associated impacts on personal life quality and economy. Recently, autofluorescence-based techniques have proven to be valuable tools for real time, in situ quantification and classification of PBAP. First studies suggest that the autofluorescence of pollen may be sufficiently selective to be utilized for an automated and real-time monitoring of pollen in ambient air. However, the degree of selectivity autofluorescence can provide is still in question and actively debated. This study addresses the origin, properties, and selectivity of autofluorescence from natural pollen by fluorescence microscopy and spectroscopy measurements along with a systematic synthesis of related literature. We show that dry pollen reveals characteristic and reproducible autofluorescence signatures which are shaped by cell wall associated fluorophores, such as phenolic compounds and carotenoid pigments. In addition, fluorescence signals from proteins and chlorophyll a were observed in some species. The abundance and intensity of the individual fluorescence signals show certain taxonomic trends and allow systematic differentiation from bacteria and fungal spores due to the lack of proteins on the grain surface. Principal component analysis was used to explore the discrimination potential of pollen autofluorescence, in combination with size and shape, revealing a differentiation of pollen on family level. Our results help explore the levels of selectivity that autofluorescence-based techniques can provide to PBAP analysis and will support the development and application of autofluorescence-based detectors for monitoring of allergenic pollen in the atmosphere.

scholarly journals Airborne measurements of oxygen concentration from the surface to the lower stratosphere and pole to pole

2020 ◽  
Author(s):  
Britton B. Stephens ◽  
Eric J. Morgan ◽  
Jonathan D. Bent ◽  
Ralph F. Keeling ◽  
Andrew S. Watt ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Cross Sections ◽  
Vacuum Ultraviolet ◽  
Measurement Techniques ◽  
Ambient Air ◽  
Airborne Measurements ◽  
Stratospheric Dynamics ◽  
Controlled Flow ◽  
The Individual

Abstract. We have developed in situ and flask sampling systems for airborne measurements of variations in the O2/N2 ratio at the part per million level. We have deployed these instruments on a series of aircraft campaigns to measure the distribution of atmospheric O2 from 0–14 km and 87° N to 85° S throughout the seasonal cycle. The NCAR airborne oxygen instrument (AO2) uses a vacuum ultraviolet (VUV) absorption detector for O2 and also includes an infrared CO2 sensor. The VUV detector has a precision in 5 seconds of ±1.25 per meg (1σ) δ(O2/N2), but thermal fractionation and motion effects increase this to ±2.5–4.0 per meg when sampling ambient air in flight. The NCAR/Scripps airborne flask sampler (Medusa) collects 32 cryogenically dried air samples per flight under actively controlled flow and pressure conditions. For in situ or flask O2 measurements, fractionation and surface effects can be important at the required high levels of relative precision. We describe our sampling and measurement techniques, and efforts to reduce potential biases. We also present a selection of observational results highlighting the individual and combined instrument performance. These include vertical profiles, O2 : CO2 correlations, and latitudinal cross sections reflecting the distinct influences of terrestrial photosynthesis, air-sea gas exchange, burning of various fuels, and stratospheric dynamics. When present, we have corrected the flask δ(O2/N2) measurements for fractionation during sampling or analysis, with the use of the concurrent δ(Ar/N2) measurements. We have also corrected the in situ δ(O2/N2) measurements for inlet fractionation and humidity effects by comparison to the corrected flask values. A comparison of Ar/N2-corrected Medusa flask δ(O2/N2) measurements to regional Scripps O2 Network station observations shows no systematic biases over 10 recent campaigns (+0.2 ± 8.2 per meg, mean and standard deviation, n = 86). For AO2, after resolving sample drying and inlet fractionation biases previously on the order of 10–100 per meg, independent AO2 δ(O2/N2) measurements over 6 more recent campaigns differ from coincident Medusa flask measurements by −0.3 ± 7.2 per meg (mean and standard deviation, n = 1361), with campaign-specific means ranging from −5 to +5 per meg.

scholarly journals Intercomparison of aerosol extinction profiles retrieved from MAX-DOAS measurements

2016 ◽  
Author(s):  
U. Frieß ◽  
H. Klein Baltink ◽  
S. Beirle ◽  
K. Clèmer ◽  
F. Hendrick ◽  
...  
Keyword(s):  
Optimal Estimation ◽  
Optical Absorption Spectroscopy ◽  
Measuring Instruments ◽  
Aerosol Extinction ◽  
Vertical Profiles ◽  
Near Surface ◽  
Aerosol Absorption ◽  
Sun Photometer ◽  
Absorption Measurements

Abstract. A first direct intercomparison of aerosol vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations, performed during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI) in summer 2009, is presented. Five out of 14 participants of the CINDI campaign reported aerosol extinction profiles and aerosol optical thickness (AOT) as deduced from observations of differential slant column densities of the oxygen collision complex (O4) at different elevation angles. Aerosol vertical profiles and AOT are compared to backscatter profiles from a ceilometer instrument and to sun photometer measurements, respectively. Furthermore, the near-surface aerosol extinction coefficient is compared to in-situ measurements of a humidity controlled nephelometer and dry aerosol absorption measurements. The participants of this intercomparison exercise use different approaches for the retrieval of aerosol information, including the retrieval of the full vertical profile using optimal estimation and a parametrised approach with a prescribed profile shape. Despite these large conceptual differences, and also differences in the wavelength of the observed O4 absorption band, good agreement in terms of the vertical structure of aerosols within the boundary layer is achieved between the aerosol extinction profiles retrieved by the different groups and the backscatter profiles observed by the ceilometer instrument. AOT from MAX-DOAS and sun photometer show a good correlation (R > 0.8), but all participants systematically underestimate the AOT. Substantial differences between the near-surface aerosol extinction from MAX-DOAS and from the humidified nephelometer remain largely unresolved.

scholarly journals The development of a nitrogen dioxide sonde

2010 ◽  
Vol 3 (6) ◽  
pp. 1753-1762 ◽  
Author(s):  
W. W. Sluis ◽  
M. A. F. Allaart ◽  
A. J. M. Piters ◽  
L. F. L. Gast
Keyword(s):  
Boundary Layer ◽  
Nitrogen Dioxide ◽  
Ambient Air ◽  
Measurement Range ◽  
Measuring Instruments ◽  
Chemiluminescent Reaction ◽  
June July ◽  
Good Agreement ◽  
Meteorological Institute

Abstract. A growing number of space-borne instruments measures nitrogen dioxide (NO2) concentrations in the troposphere, but validation of these instruments is hampered by the lack of ground-based and in situ profile measurements. The Royal Netherlands Meteorological Institute (KNMI) has developed a working NO2 sonde. The sonde is attached to a small meteorological balloon and measures a tropospheric NO2 profile. The NO2 sonde has a vertical resolution of 5 m and a measurement range between 1 and 100 ppbv. The instrument is light in weight (0.7 kg), cheap (disposable), energy efficient and not harmful to the environment or the person who finds the package after use. The sonde uses the chemiluminescent reaction of NO2 in an aqueous luminol solution. The NO2-luminol reaction produces faint blue/purple light (at about 425 nm), which is detected by an array of silicon photodiodes. The luminol solution is optimised to be specific to NO2. An on-ground comparison with measurements from a Photolytic Analyser of The National Institute for Public Health and the Environment (RIVM) shows that both instruments measure similar NO2 variations in ambient air. During the Cabauw Intercomparison campaign of Nitrogen Dioxide measuring instruments (CINDI) in June/July 2009, six vertical profiles of NO2 from the ground to a 5 km altitude were measured, which clearly show that the largest amount of NO2 is measured in the boundary layer. The measured boundary layer heights of the NO2 sonde are in good agreement with boundary layer heights determined by a LD40 Ceilometer at Cabauw.

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