A laboratory investigation of the relative humidity dependence of light extinction by organic compounds from lignin combustion

Abstract. Reduced visibility is an indicator of poor air quality. Moreover, degradation in visibility can be hazardous to human safety; for example, low visibility can lead to road, rail, sea and air accidents. In this paper, we explore the combined influence of atmospheric aerosol particle and gas characteristics, and meteorology, on long-term visibility. We use visibility data from eight meteorological stations, situated in the UK, which have been running since the 1950s. The site locations include urban, rural and marine environments. Most stations show a long-term trend of increasing visibility, which is indicative of reductions in air pollution, especially in urban areas. Additionally, the visibility at all sites shows a very clear dependence on relative humidity, indicating the importance of aerosol hygroscopicity on the ability of aerosol particles to scatter radiation. The dependence of visibility on other meteorological parameters, such as wind speed and wind direction, is also investigated. Most stations show long-term increases in temperature which can be ascribed to climate change, land-use changes (e.g. urban heat island effects) or a combination of both; the observed effect is greatest in urban areas. The impact of this temperature change upon local relative humidity is discussed. To explain the long-term visibility trends and their dependence on meteorological conditions, the measured data were fitted to a newly developed light-extinction model to generate predictions of historic aerosol and gas scattering and absorbing properties. In general, an excellent fit was achieved between measured and modelled visibility for all eight sites. The model incorporates parameterizations of aerosol hygroscopicity, particle concentration, particle scattering, and particle and gas absorption. This new model should be applicable and is easily transferrable to other data sets worldwide. Hence, historical visibility data can be used to assess trends in aerosol particle properties. This approach may help constrain global model simulations which attempt to generate aerosol fields for time periods when observational data are scarce or non-existent. Both the measured visibility and the modelled aerosol properties reported in this paper highlight the success of the UK's Clean Air Act, which was passed in 1956, in cleaning the atmosphere of visibility-reducing pollutants.

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Silicon Carbide Field Effect Transistors for Detection of Ultra-Low Concentrations of Hazardous Volatile Organic Compounds

Materials Science Forum ◽

10.4028/www.scientific.net/msf.778-780.1067 ◽

2014 ◽

Vol 778-780 ◽

pp. 1067-1070 ◽

Cited By ~ 6

Author(s):

Donatella Puglisi ◽

Jens Eriksson ◽

Christian Bur ◽

Andreas Schütze ◽

Anita Lloyd Spetz ◽

...

Keyword(s):

Silicon Carbide ◽

Volatile Organic Compounds ◽

Relative Humidity ◽

Organic Compounds ◽

Field Effect ◽

Field Effect Transistors ◽

Long Term Stability ◽

Volatile Organic ◽

Recovery Times ◽

Response And Recovery

Gas sensitive silicon carbide field effect transistors with nanostructured Ir gate layers have been used for the first time for sensitive detection of volatile organic compounds (VOCs) at part per billion level for indoor air quality applications. Formaldehyde, naphthalene, and benzene have been used as typical VOCs in dry air and under 10% and 20% relative humidity. A single VOC was used at a time to study long-term stability, repeatability, temperature dependence, effect of relative humidity, sensitivity, response and recovery times of the sensors.

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Humidity effects on the detection of soluble and insoluble nanoparticles in butanol operated condensation particle counters

Atmospheric Measurement Techniques ◽

10.5194/amt-12-3659-2019 ◽

2019 ◽

Vol 12 (7) ◽

pp. 3659-3671 ◽

Cited By ~ 7

Author(s):

Christian Tauber ◽

Sophia Brilke ◽

Peter Josef Wlasits ◽

Paulus Salomon Bauer ◽

Gerald Köberl ◽

...

Keyword(s):

Sodium Chloride ◽

Relative Humidity ◽

Ambient Conditions ◽

Expansion Chamber ◽

Aerosol Composition ◽

Neutral Particles ◽

Charge Dependence ◽

A Charge ◽

Humidity Dependence ◽

The Impact

Abstract. In this study the impact of humidity on heterogeneous nucleation of n-butanol onto hygroscopic and nonabsorbent charged and neutral particles was investigated using a fast expansion chamber and commercial continuous flow type condensation particle counters (CPCs). More specifically, we measured the activation probability of sodium chloride (NaCl) and silver (Ag) nanoparticles by using n-butanol as condensing liquid with the size analyzing nuclei counter (SANC). In addition, the cutoff diameters of regular butanol-based CPCs for both seed materials under different charging states were measured and compared to SANC results. Our findings reveal a strong humidity dependence of NaCl particles in the sub-10 nm size range since the activation of sodium chloride seeds is enhanced with increasing relative humidity. In addition, negatively charged NaCl particles with a diameter below 3.5 nm reveal a charge-enhanced activation. For Ag seeds this humidity and charge dependence was not observed, underlining the importance of molecular interactions between seed and vapor molecules. Consequently, the cutoff diameter of a butanol-based CPC can be reduced significantly by increasing the relative humidity. This finding suggests that cutoff diameters of butanol CPCs under ambient conditions are likely smaller than corresponding cutoff diameters measured under clean (dry) laboratory conditions. At the same time, we caution that the humidity dependence may lead to wrong interpretations if the aerosol composition is not known.

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60 years of UK visibility measurements: impact of meteorology and atmospheric pollutants on visibility

10.5194/acp-2016-738 ◽

2016 ◽

Cited By ~ 2

Author(s):

Ajit Singh ◽

William J. Bloss ◽

Francis D. Pope

Keyword(s):

Relative Humidity ◽

Aerosol Particle ◽

Urban Areas ◽

Land Use Changes ◽

Gas Absorption ◽

Atmospheric Pollutants ◽

Light Extinction ◽

The Impact ◽

Aerosol Hygroscopicity

Abstract. Reduced visibility is an indicator of poor air quality. Moreover, degradation in visibility can be hazardous to human safety; for example, low visibility can lead to road, rail, sea and air accidents. In this paper, we explore the combined influence of atmospheric aerosol particle and gas characteristics, and meteorology, on long-term visibility. We use visibility data from eight meteorological stations, situated in the UK, which have been running since the 1950s. The site locations include urban, rural and marine environments. Most stations show a long term trend of increasing visibility which is indicative of reductions in air pollution, especially in urban areas. Additionally, the visibility at all sites show a very clear dependence on relative humidity indicating the importance of aerosol hygroscopicity on the ability of aerosol particles to scatter radiation. The dependence of visibility on other meteorological parameters, such as wind speed and wind direction is also investigated. Most stations show long term increases in temperature which can be ascribed to either climate change, land-use changes (e.g. urban heat island effects) or a combination of both; the observed effect is greatest in urban areas. The impact of this temperature change upon local relative humidity is discussed. To explain the long term visibility trends and their dependence on meteorological conditions, the measured data were fitted to a newly developed light extinction model to generate predictions of historic aerosol and gas scattering and absorbing properties. In general, an excellent fit was achieved between measured and modelled visibility for all 8 sites. The model incorporates parameterizations of aerosol hygroscopicity, particle concentration, particle scattering, and particle and gas absorption. This new model should be applicable and is easily transferrable to other data sets worldwide. Hence, historical visibility data can be used to assess trends in aerosol particle properties. This approach may help constrain global model simulations which attempt to generate aerosol fields for time periods when observational data are scarce or non-existent. Both the measured visibility and the modelled aerosol properties reported in this paper highlight the success of the UK’s Clean Air Act, which was passed in 1956, in cleaning the atmosphere of visibility reducing pollutants.

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