Comparison of Formaldehyde Measurements by HANTZSCH, CRDS and DOAS instruments in the SAPHIR Chamber

2020 ◽  
Author(s):  
Marvin Glowania ◽  
Hendrik Fuchs ◽  
Franz Rohrer ◽  
Hans-Peter Dorn ◽  
Frank Holland ◽  
...  
Keyword(s):  
Measurement Techniques ◽  
Chemical Conversion ◽  
Ambient Air ◽  
Optical Absorption Spectroscopy ◽  
Base Line ◽  
Fluorescence Measurement ◽  
Gas Stripping ◽  
Gas Source ◽  
Acid Titration ◽  
Good Agreement

<p>Three instruments using different measurement techniques were used to measure formaldehyde (HCHO) concentrations during experiments in the atmopshere simulation chamber SAPHIR at the Forschungszentrum Juelich. An AL4021 instrument by Aero Laser GmbH uses the wet-chemical Hantzsch reaction for efficient gas stripping, chemical conversion and fluorescence measurement. An internal permeation gas source provides daily calibrations characterized by sulfuric acid titration. A G2307 analyzer by PICARRO INC. uses Cavity Ring-Down Spectroscopy (CRDS) technique to determine concentrations of HCHO, water and methane. A high-resolution laser differential optical absorption spectroscopy (DOAS) instrument provided HCHO measurements along the central chamber axis using an optical multiple reflection cell. The measurements were conducted from June to December 2019 in experiments when ambient air was flowed through the chamber and also in photochemical experiments in synthetic air with mixtures of different reactants, water vapour, nitrogen oxides, and ozone concentrations. Results demonstrate the importance for a linear base line interpolation between zero measurements for the Hantzsch instrument. In addition, a strong water dependence of the baseline of CRDS measurements was found. After correction for the baselines, the correlation analysis of measurements demonstrate good agreement (R > 0.98) between the instruments.</p>

scholarly journals Replacing the AMOR by the miniDOAS in the ammonia monitoring network in the Netherlands

2017 ◽  
Author(s):  
A. J. C. Stijn Berkhout ◽  
Daan P. J. Swart ◽  
Hester Volten ◽  
Lou F. L. Gast ◽  
Marty Haaima ◽  
...  
Keyword(s):  
The Netherlands ◽  
Monitoring Network ◽  
Ambient Air ◽  
Automatic Monitoring ◽  
Quality Monitoring ◽  
Optical Absorption Spectroscopy ◽  
Fast Time ◽  
Air Quality Monitoring ◽  
Process Studies ◽  
Good Agreement

Abstract. In this paper we present the continued development of the miniDOAS, an active differential optical absorption spectroscopy (DOAS) instrument to measure ammonia concentrations in ambient air. The miniDOAS has been adapted for use in the Dutch National Air Quality Monitoring Network. The miniDOAS replaces the life-expired continuous-flow denuder ammonia monitor (AMOR). From September 2014 to December 2015, both instruments measured in parallel before the change from AMOR to miniDOAS was made. The instruments were deployed on six monitoring stations throughout the Netherlands. We report on the results of this intercomparison. Both instruments show a good uptime of ca. 90 %, adequate for an automatic monitoring network. Although both instruments produce minute values of ammonia concentrations, a direct comparison on short timescales such as minutes or hours does not give meaningful results, because the AMOR response to changing ammonia concentrations is slow. Comparisons between daily and monthly values show a good agreement. For monthly averages, we find a small average offset of 0.65 ± 0.28 µg m−3 and a slope of 1.034 ± 0.028, with the miniDOAS measuring slightly higher than the AMOR. The fast time resolution of the miniDOAS makes the instrument not only suitable for monitoring but also for process studies.

scholarly journals Replacing the AMOR with the miniDOAS in the ammonia monitoring network in the Netherlands

2017 ◽  
Vol 10 (11) ◽  
pp. 4099-4120 ◽  
Author(s):  
Augustinus J. C. Berkhout ◽  
Daan P. J. Swart ◽  
Hester Volten ◽  
Lou F. L. Gast ◽  
Marty Haaima ◽  
...  
Keyword(s):  
The Netherlands ◽  
Monitoring Network ◽  
Ambient Air ◽  
Automatic Monitoring ◽  
Quality Monitoring ◽  
Optical Absorption Spectroscopy ◽  
Fast Time ◽  
Air Quality Monitoring ◽  
Process Studies ◽  
Good Agreement

Abstract. In this paper we present the continued development of the miniDOAS, an active differential optical absorption spectroscopy (DOAS) instrument used to measure ammonia concentrations in ambient air. The miniDOAS has been adapted for use in the Dutch National Air Quality Monitoring Network. The miniDOAS replaces the life-expired continuous-flow denuder ammonia monitor (AMOR). From September 2014 to December 2015, both instruments measured in parallel before the change from AMOR to miniDOAS was made. The instruments were deployed at six monitoring stations throughout the Netherlands. We report on the results of this intercomparison. Both instruments show a good uptime of ca. 90 %, adequate for an automatic monitoring network. Although both instruments produce 1 min values of ammonia concentrations, a direct comparison on short timescales such as minutes or hours does not give meaningful results because the AMOR response to changing ammonia concentrations is slow. Comparisons between daily and monthly values show good agreement. For monthly averages, we find a small average offset of 0.65 ± 0.28 µg m−3 and a slope of 1.034 ± 0.028, with the miniDOAS measuring slightly higher than the AMOR. The fast time resolution of the miniDOAS makes the instrument suitable not only for monitoring but also for process studies.

scholarly journals Comparison of formaldehyde measurements by Hantzsch, CRDS and DOAS in the SAPHIR chamber

2021 ◽  
Vol 14 (6) ◽  
pp. 4239-4253
Author(s):  
Marvin Glowania ◽  
Franz Rohrer ◽  
Hans-Peter Dorn ◽  
Andreas Hofzumahaus ◽  
Frank Holland ◽  
...  
Keyword(s):  
Water Vapour ◽  
Organic Compounds ◽  
Limit Of Detection ◽  
Linear Regression Analysis ◽  
Ambient Air ◽  
Optical Absorption Spectroscopy ◽  
Fluorescence Measurement ◽  
Good Precision ◽  
Mixing Ratio ◽  
Mixing Ratios

Abstract. Three instruments that use different techniques to measure gaseous formaldehyde (HCHO) concentrations were compared in experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich. One instrument (AL4021, Aero-Laser GmbH) detects HCHO using the wet-chemical Hantzsch reaction (for efficient gas-phase stripping), chemical conversion and fluorescence measurement. An internal HCHO permeation source allows for daily calibrations. This instrument was characterized by sulfuric acid titration (overall accuracy 8.6 %) and yields measurements with a time resolution of 90 s and a limit of detection (3σ) of 0.3 ppbv. In addition, a new commercial instrument that makes use of cavity ring-down spectroscopy (CRDS) determined the concentrations of HCHO, water vapour, and methane (G2307, Picarro, Inc.). Its limit of detection (3σ) is specified as 0.3 ppbv for an integration time of 300 s, and its accuracy is limited by the drift of the zero signal (manufacturer specification 1.5 ppbv). A custom-built high-resolution laser differential optical absorption spectroscopy (DOAS) instrument provided HCHO measurements with a limit of detection (3σ) of 0.9 ppbv and an accuracy of 7 %​​​​​​​ using an optical multiple reflection cell. The measurements were conducted from June to December 2019 in experiments in which either ambient air flowed through the chamber or the photochemical degradation of organic compounds in synthetic air was investigated. Measured HCHO concentrations were up to 8 ppbv. Various mixtures of organic compounds, water vapour, nitrogen oxides and ozone were present in these experiments. Results demonstrate the need to correct the baseline in measurements performed by the Hantzsch instrument to compensate for drifting background signals. Corrections were equivalent to HCHO mixing ratios in the range of 0.5–1.5 ppbv. The baseline of the CRDS instrument showed a linear dependence on the water vapour mixing ratio with a slope of (-11.20±1.60) ppbv %−1 below and (-0.72±0.08) ppbv %−1 above a water vapour mixing ratio of 0.2 %. In addition, the intercepts of these linear relationships drifted within the specification of the instrument (1.5 ppbv) over time but appeared to be equal for all water mixing ratios. Regular zero measurements are needed to account for the changes in the instrument zero. After correcting for the baselines of measurements by the Hantzsch and the CRDS instruments, linear regression analysis of measurements from all three instruments in experiments with ambient air indicated good agreement, with slopes of between 0.98 and 1.08 and negligible intercepts (linear correlation coefficients R2>0.96). The new small CRDS instrument measures HCHO with good precision and is accurate if the instrument zero is taken into account. Therefore, it can provide measurements with similar accuracy to the DOAS instrument but with slightly reduced precision compared to the Hantzsch instrument.

scholarly journals Comparison of formaldehyde measurements by Hantzsch, CRDS and DOAS in the SAPHIR chamber

2021 ◽  
Author(s):  
Marvin Glowania ◽  
Franz Rohrer ◽  
Hans-Peter Dorn ◽  
Andreas Hofzumahaus ◽  
Frank Holland ◽  
...  
Keyword(s):  
Water Vapour ◽  
Organic Compounds ◽  
Limit Of Detection ◽  
Ambient Air ◽  
Optical Absorption Spectroscopy ◽  
Fluorescence Measurement ◽  
Good Precision ◽  
Mixing Ratio ◽  
Instrument Making ◽  
Mixing Ratios

Abstract. Three instruments using different techniques measuring gaseous formaldehyde (HCHO) concentrations were compared in experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich. One instrument detected HCHO by using the wet-chemical Hantzsch reaction for efficient gas-phase stripping, chemical conversion and fluorescence measurement (AL4021, Aero Laser GmbH). An internal permeation HCHO source allows for daily calibrations. It was characterized by sulfuric acid titration (overall accuracy 8.5 %). Measurements have a time resolution of 90 s with a limit of detection (3 σ) of 0.3 ppbv. In addition, a new commercial instrument making use of cavity ring-down spectroscopy (CRDS) determined concentrations of HCHO, water, and methane (G2307, Picarro Inc.). The limit of detection (3 σ) is specified as 0.3 ppbv for an integration time of 300 s and the accuracy is limited by the drift of the zero signal (manufacturer specification 1.5 ppbv). A custom-built, high-resolution laser differential optical absorption spectroscopy (DOAS) instrument provided HCHO measurements with a limit of detection (3 σ) of 0.9 ppbv and an accuracy of 6 % using an optical multiple reflection cell. The measurements were conducted from June to December 2019 in experiments in which either ambient air was flowed through the chamber or the photochemical degradation of organic compounds in synthetic air was investigated. Measured HCHO concentrations were up to 8 ppbv. Various mixtures of organic compounds, water vapour, nitrogen oxides, and ozone concentrations were present in these experiments. Results demonstrate the need to correct the baseline in the measurements of the Hantzsch instrument to compensate for drifting background signals. Corrections were equivalent to HCHO mixing ratios in the range of 0.5 to 1.5 ppbv. The baseline of the CRDS instrument showed a linear dependence on the water-vapour mixing ratio with different slopes of (−11.20 ± 1.60) ppbv %−1 and (−0.72 ± 0.08) ppbv %−1 above and below 0.2 % water vapour mixing ratio, respectively. In addition, the intercept of these linear relationships drifted with time within the specification of the instrument (1.5 ppbv), but appeared to be equal for all water mixing ratios. Regular zero measurements are required to account for the changes in the instrument zero. After correcting for the baselines of measurements by the Hantzsch and the CRDS instruments, a linear regression analysis of measurements from all three instruments in experiments with ambient air results in a good agreement with slopes between 0.93 and 1.07 with negligible intercepts (linear correlation coefficients R2 > 0.96). The new, small-sized CRDS instrument measures HCHO with a good precision and is accurate, if the instrument zero is taken into account. Therefore, it can provide accurate and calibration-free measurements like the DOAS instrument with a slightly reduced precision compared to the Hantzsch instrument.

STATISTICAL METHODS FOR THE ASSESSMENT OF AIR POLLUTION OF JHANSI CITY, UTTAR PRADESH, INDIA

2018 ◽  
Vol 24 (1) ◽  
Author(s):  
V. S. CHAUHAN ◽  
BHANUMATI SINGH ◽  
SHREE GANESH ◽  
JAMSHED ZAIDI
Keyword(s):  
Air Pollution ◽  
Uttar Pradesh ◽  
Ambient Air ◽  
Ambient Air Pollution ◽  
Base Line ◽  
Multivariate Statistical ◽  
Large Cities ◽  
Governmental Organizations ◽  
Non Governmental Organizations ◽  
The Status

Studies on air pollution in large cities of India showed that ambient air pollution concentrations are at such levels where serious health effects are possible. This paper presents overview on the status of air quality index (AQI) of Jhansi city by using multivariate statistical techniques. This base line data can help governmental and non-governmental organizations for the management of air pollution.

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

2009 ◽  
Vol 9 (11) ◽  
pp. 3641-3662 ◽  
Author(s):  
D. Chen ◽  
B. Zhou ◽  
S. Beirle ◽  
L. M. Chen ◽  
T. Wagner
Keyword(s):  
Satellite Data ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Vertical Column ◽  
Error Sources ◽  
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 measurements provided NO2 total columns in the daytime. Here, we present a new method to extract time series of tropospheric vertical column densities (VCDs) of NO2 from these observations. The derived tropospheric NO2 VCDs are important quantities 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 the diurnal variation of stratospheric NO2 VCDs. The main error sources arise from the uncertainties in the estimated stratospheric slant column densities (SCDs) and the determination of tropospheric NO2 air mass factor (AMF). For a polluted site like Shanghai, the accuracy of our method is conservatively estimated to be <25% for solar zenith angle (SZA) lower than 70°. From simultaneously performed long-path DOAS measurements, the NO2 surface concentrations at the same site were observed and the corresponding tropospheric NO2 VCDs were estimated using the assumed seasonal NO2 profiles in the planetary boundary layer (PBL). By making a comparison between the tropospheric NO2 VCDs from zenith-sky and long-path DOAS measurements, it is found that the former provides more realistic information about total tropospheric pollution than the latter, so it's more suitable for satellite data validation. A comparison between the tropospheric NO2 VCDs from ground-based zenith-sky measurements and SCIAMACHY was also made. Satellite validation for a strongly polluted area is highly needed, but exhibits also a great challenge. Our comparison shows good agreement, considering in particular the different spatial resolutions between the two measurements. Remaining systematic deviations are most probably related to the uncertainties of satellite data caused by the assumptions on aerosol properties as well as the layer heights of aerosols and NO2.

Field intercomparison of measurement techniques for total NH4+ and total NO3− in ambient air

1988 ◽  
Vol 22 (10) ◽  
pp. 2275-2281 ◽  
Author(s):  
M. Ferm ◽  
H. Areskoug ◽  
J.-E. Hanssen ◽  
G. Hilbert ◽  
H. Lättilä
Keyword(s):  
Measurement Techniques ◽  
Ambient Air ◽  
Field Intercomparison

Pollution potential of oil-contaminated soil on groundwater resources in Kuwait

2003 ◽  
Vol 47 (7-8) ◽  
pp. 259-265 ◽  
Author(s):  
P. Literathy ◽  
M. Quinn ◽  
M. Al-Rashed
Keyword(s):  
Drinking Water ◽  
Crude Oil ◽  
Groundwater Resources ◽  
Measurement Techniques ◽  
Soil Layer ◽  
Soil Survey ◽  
Total Petroleum Hydrocarbons ◽  
Fluorescence Measurement ◽  
Groundwater Aquifer ◽  
Freshwater Resource

The only natural freshwater resource of Kuwait occurs as lenses floating on the saline groundwater in the northern part of the country, near to the oil fields. Rainwater is the only means of recharge of this limited groundwater resource. This groundwater is used as bottled drinking water and the fresh groundwater aquifer is considered as a strategic drinking water reserve for Kuwait. As a result of the 1991 Gulf War, the upper soil layer has been widely contaminated with crude oil and crude oil combustion products, which are potential pollutants likely affecting the groundwater resources. Significant efforts have been made to assess this pollution. These included: (a) a soil survey for assessing the soil contamination, and (b) leaching experiments to characterise the mobilization of the soil-associated pollutants. Fluorescence measurement techniques were used during field surveys as well as for laboratory testing. In addition, determination of the total extractable matter (TEM), total petroleum hydrocarbons (TPH), and GC/MS measurement of polyaromatic hydrocarbons (PAHs) were performed for the assessments. The laser induced fluorescence (LIF) measurement, having good correlation with the other laboratory measurements, was proved to provide necessary information for the assessment of the oil-contamination level in the desert soil. The subsequent leaching test with water demonstrated the mobilization of the fluorescing compounds (e.g. PAHs), and the alteration in the leaching characteristics of the contamination during the long-term environmental weathering of the oil.

scholarly journals Comparison of continuous in-situ CO<sub>2</sub> observations at Jungfraujoch using two different measurement techniques

2014 ◽  
Vol 7 (7) ◽  
pp. 7053-7084
Author(s):  
M. F. Schibig ◽  
M. Steinbacher ◽  
B. Buchmann ◽  
I. T. van der Laan-Luijkx ◽  
S. van der Laan ◽  
...  
Keyword(s):  
Materials Science ◽  
Measurement Techniques ◽  
Ambient Air ◽  
Pollution Monitoring ◽  
Smooth Transition ◽  
Research Station ◽  
Short Term ◽  
Technical Problems ◽  
Two Systems ◽  
Data Coverage

Abstract. Since 2004, atmospheric carbon dioxide (CO2) is measured at the High Altitude Research Station Jungfraujoch by the division of Climate and Environmental Physics at the University of Bern (KUP) using a nondispersive infrared gas analyzer (NDIR) in combination with a paramagnetic O2 analyzer. In January 2010, CO2 measurements based on cavity ring down spectroscopy (CRDS) as part of the Swiss National Air Pollution Monitoring Network have been added by the Swiss Federal Laboratories for Materials Science and Technology (Empa). To ensure a smooth transition – a prerequisite when merging two datasets e.g. for trend determinations – the two measurement systems run in parallel for several years. Such a long-term intercomparison also allows identifying potential offsets between the two datasets and getting information about the compatibility of the two systems on different time scales. A good agreement of the seasonality as well as for the short-term variations was observed and to a lesser extent for trend calculations mainly due to the short common period. However, the comparison revealed some issues related to the stability of the calibration gases of the KUP system and their assigned CO2 mole fraction. It was possible to adapt an improved calibration strategy based on standard gas determinations, which lead to better agreement between the two data sets. By excluding periods with technical problems and bad calibration gas cylinders, the average hourly difference (CRDS − NDIR) of the two systems is −0.03 ppm ± 0.25 ppm. Although the difference of the two datasets is in line with the compatibility goal of ±0.1 ppm of the World Meteorological Organization (WMO), the standard deviation is still too high. A significant part of this uncertainty originates from the necessity to switch the KUP system frequently (every 12 min) for 6 min from ambient air to a working gas in order to correct short-term variations of the O2 measurement system. Allowing additionally for signal stabilization after switching the sample, an effective data coverage of only 1/6 for the KUP system is achieved while the Empa system has a nearly complete data coverage. Additionally, different internal volumes and flow rates between the two systems may affect observed differences.

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