scholarly journals Relative humidity anneal effect on hygroscopicity of aerosol particles studied by rapid-scan FTIR-ATR spectroscopy

2008 ◽  
Vol 35 (20) ◽  
Author(s):  
Pei-Dong Lu ◽  
Ting He ◽  
Yun-Hong Zhang
Keyword(s):  
Relative Humidity ◽  
Aerosol Particles ◽  
Rapid Scan ◽  
Atr Spectroscopy

scholarly journals Characterisation of biofluorescent aerosol emissions over winter and summer periods in the United Kingdom

2018 ◽  
Author(s):  
Elizabeth Forde ◽  
Martin Gallagher ◽  
Virginia Foot ◽  
Roland Sarda-Esteve ◽  
Ian Crawford ◽  
...  
Keyword(s):  
United Kingdom ◽  
Relative Humidity ◽  
Aerosol Particles ◽  
Fungal Spores ◽  
Ultra Violet ◽  
Fungal Spore ◽  
Complete Analysis ◽  
Hierarchical Agglomerative Cluster ◽  
The United Kingdom ◽  
Fluorescent Particles

Abstract. Primary biological aerosol particles (PBAP) are an abundant subset of atmospheric aerosol particles which comprise viruses, bacteria, fungal spores, pollen, and fragments such as plant and animal debris. The abundance and diversity of these particles remain poorly constrained, causing significant uncertainties for modelling scenarios and for understanding the potential implications of these particles in different environments. PBAP concentrations were studied at four different sites in the United Kingdom (Weybourne, Davidstow, Capel Dewi, and Chilbolton) using an ultra-violet light induced fluorescence (UV-LIF) instrument, the Wideband Integrated Bioaerosol Spectrometer (WIBS), versions 3 and 4. Using hierarchical agglomerative cluster (HAC) analysis, particles were statistically discriminated between. Fluorescent particles and clusters were then analysed by assessing their diurnal variation and their relationship to the meteorological variables, temperature and relative humidity, and wind speed and direction. Using local land cover types, sources of the suspected fluorescent particles and clusters were then identified. Most sites exhibited a wet discharged fungal spore dominance, with the exception of one site, Davidstow, which had higher concentrations of bacteria, suggested to result from the presence of a local dairy factory. Differences were identified as to the sources of wet discharged fungal spores, with particles originating from arable and horticultural land at Chilbolton, and improved grassland areas at Weybourne. Total fluorescent particles at Capel Dewi were inferred to comprise two sources, with bacteria originating from the broadleaf and coniferous woodland and wet discharged fungal spores from nearby improved grassland areas, similar to Weybourne. The use of HAC and a higher fluorescence threshold (9SD) produced clusters which were considered to be biological following the complete analysis. More knowledge of the reaction of speciated biological particles to differences in meteorology, such as relative humidity and temperature would aid characterisation studies such as this.

A relative humidity processing method for the sampling of aerosol particles with low growth-ability

Tellus B ◽  
1992 ◽  
Vol 44 (5) ◽  
pp. 632-644 ◽  
Author(s):  
BENGT G. MARTINSSON ◽  
HANS-CHRISTEN HANSSON ◽  
LARS ASKING ◽  
SVEN-INGE CEDERFELT
Keyword(s):  
Relative Humidity ◽  
Aerosol Particles ◽  
Processing Method ◽  
Growth Ability

scholarly journals Synergistic effect of water-soluble species and relative humidity on morphological changes of aerosol particles in Beijing mega-city during severe pollution episodes

2018 ◽  
Author(s):  
Xiaole Pan ◽  
Baozhu Ge ◽  
Zhe Wang ◽  
Yu Tian ◽  
Hang Liu ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Synergistic Effect ◽  
Mass Fraction ◽  
Mass Concentration ◽  
Morphological Changes ◽  
Aerosol Particles ◽  
Water Soluble ◽  
Coarse Mode ◽  
Heavy Pollution ◽  
Soluble Species

Abstract. Depolarization ratio (δ) of backscattered light from aerosol particle is an applicable parameter for real-time distinguishing spherical and non-spherical particles, which has been widely adopted by ground-based Lidar observation and satellite remote sensing. From November 2016 to February of 2017, it consecutively suffered from numbers of severe air pollution at Beijing with daily averaged mass concentration of PM2.5 (aerodynamic diameter less than 2.5 μm) larger than 150 μg/m3. We preformed concurrent measurements of water-soluble chemical species and depolarization properties of aerosol particles on the basis of a continuous dichotomous Aerosol Chemical Speciation Analyzer (ACSA-14) and a bench-top optical particle counter with a polarization detection module (POPC). We found that δ value of ambient particles generally decrease as mass concentration of PM2.5 increased at unfavorable meteorological condition. Ratio of mass concentration of nitrate (NO3−) to that of sulfate (SO42−) in PM2.5 was 1.5 ± 0.6, indicating of great importance of NOx in the formation of heavy pollution. Mass concentration of NO3− in PM2.5 (fNO3) was generally an order of magnitude higher than that in coarse mode (cNO3) with a mean fNO3 / cNO3 ratio of 14 ± 10. Relatively high allocation (fNO3/cNO3 = 5) of NO3− in coarse mode could be partially attributed to hygroscopic growth/coagulation of nitrate-rich fine mode particles under higher relative humidity condition. As a result, δ values of particles with Dp = 2 μm (δDp = 2) and 5 μm (δDp = 5) decreased evidently as the mass fraction of water-soluble species (NO3− and SO42−) increase in both PM2.5 and PM2.5–10, respectively. In particular, due to synergistic effect of RH, δDp = 5 value could decrease by 50 % as mass fraction of NO3− in PM2.5–10 increased from 8 % to 23 %. It suggested that alteration of non-sphericity of mineral dust particles was evident owing to coating with pollutants and heterogeneous reactions on the surface of the particle during heavy pollution period. This study brings the attention to great variability of morphological changes of aerosol particles along the transport, which have great complex effects in evaluating their climate and health effect.

scholarly journals A complete parameterisation of the relative humidity and wavelength dependence of the refractive index of hygroscopic inorganic aerosol particles

2017 ◽  
Vol 17 (16) ◽  
pp. 9837-9851 ◽  
Author(s):  
Michael I. Cotterell ◽  
Rose E. Willoughby ◽  
Bryan R. Bzdek ◽  
Andrew J. Orr-Ewing ◽  
Jonathan P. Reid
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Relative Humidity ◽  
Radiative Forcing ◽  
Aerosol Particles ◽  
Measurement Techniques ◽  
Comprehensive Treatment ◽  
Aerosol Optical Properties ◽  
Cavity Ring Down Spectroscopy ◽  
Cavity Ring Down

Abstract. Calculations of aerosol radiative forcing require knowledge of wavelength-dependent aerosol optical properties, such as single-scattering albedo. These aerosol optical properties can be calculated using Mie theory from knowledge of the key microphysical properties of particle size and refractive index, assuming that atmospheric particles are well-approximated to be spherical and homogeneous. We provide refractive index determinations for aqueous aerosol particles containing the key atmospherically relevant inorganic solutes of NaCl, NaNO3, (NH4)2SO4, NH4HSO4 and Na2SO4, reporting the refractive index variation with both wavelength (400–650 nm) and relative humidity (from 100 % to the efflorescence value of the salt). The accurate and precise retrieval of refractive index is performed using single-particle cavity ring-down spectroscopy. This approach involves probing a single aerosol particle confined in a Bessel laser beam optical trap through a combination of extinction measurements using cavity ring-down spectroscopy and elastic light-scattering measurements. Further, we assess the accuracy of these refractive index measurements, comparing our data with previously reported data sets from different measurement techniques but at a single wavelength. Finally, we provide a Cauchy dispersion model that parameterises refractive index measurements in terms of both wavelength and relative humidity. Our parameterisations should provide useful information to researchers requiring an accurate and comprehensive treatment of the wavelength and relative humidity dependence of refractive index for the inorganic component of atmospheric aerosol.

scholarly journals Influence of moisturizer and relative humidity on human emissions of fluorescent biological aerosol particles

Indoor Air ◽  
2016 ◽  
Vol 27 (3) ◽  
pp. 587-598 ◽  
Author(s):  
J. Zhou ◽  
W. Fang ◽  
Q. Cao ◽  
L. Yang ◽  
V. W.-C. Chang ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Aerosol Particles ◽  
Biological Aerosol Particles

Semi-Analytical Study of Aerosol Washout by Rain

2012 ◽  
Author(s):  
Pascal Lemaitre ◽  
Amandine Nuboer ◽  
Arnaud Querel ◽  
Guillaume Depuydt ◽  
Emmanuel Porcheron
Keyword(s):  
Light Scattering ◽  
Relative Humidity ◽  
White Light ◽  
Analytical Approach ◽  
Analytical Study ◽  
Aerosol Particles ◽  
Companion Paper ◽  
Meteorological Conditions ◽  
Internal Diameter ◽  
Special Generator

The accidents of Chernobyl and Fukushima have shown the necessity to better understand all the mechanisms implied in the scavenging of aerosol particles released to the atmosphere during a nuclear accident. Among all the phenomena involved in the deposition of aerosol particles, we focus here on the aerosol particles scavenging by the raindrops below the clouds, also called washout (as opposed to the rainout, which concerns scavenging inside the clouds). The strategy of IRSN to enhance the knowledge and the modelling of any mechanism involved in the washout of aerosol particles by rain spans from environmental studies, to analytical ones. The semi-analytical approach chosen here is halfway between these two modes of reasoning. A companion paper is also submitted to the conference to present the microphysical approach chosen at IRSN. In order to perform this study, aerosol particles were dispersed in the TOSQAN chamber, which is a large cylindrical enclosure (4.8 m height with 1.5 m internal diameter). The aerosol particles once dispersed, synthetic rains of different kinds (from stratiform to convective rains) can be activated. Finally, the instantaneous spectral scavenging coefficients are determined from the spectral decrease of aerosol particles concentration in the chamber as a function of time. In order to be able to produce synthetic rains representative of any tropospheric events, a special generator has been designed; it is based on a vibro-rotative disk. This generator is able to produce monodispersed rains at the top of the TOSQAN chamber with rainfall rates from 7 to 15 mm/h and drops diameters from 0.5 to 2.5 mm injected at velocities close to their terminal one. During these tests, the spectral aerosol concentration is measured in line with the help of a Welas granulometer. This instrument is based on white light scattering. The results of these experiments highlight the influence of “meteorological” conditions inside the chamber on the washout of the chamber atmosphere, especially when the relative humidity is reaching saturation.

Hygroscopic Growth of Multicomponent Aerosol Particles Influenced by Several Cycles of Relative Humidity

2008 ◽  
Vol 112 (11) ◽  
pp. 2378-2385 ◽  
Author(s):  
Thomas Rosenoern ◽  
Julie C. Schlenker ◽  
Scot T. Martin
Keyword(s):  
Relative Humidity ◽  
Aerosol Particles ◽  
Hygroscopic Growth

scholarly journals Effects of relative humidity on aerosol light scattering in the Arctic

2010 ◽  
Vol 10 (8) ◽  
pp. 3875-3890 ◽  
Author(s):  
P. Zieger ◽  
R. Fierz-Schmidhauser ◽  
M. Gysel ◽  
J. Ström ◽  
S. Henne ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Light Scattering ◽  
Relative Humidity ◽  
Aerosol Particles ◽  
Aerosol Size Distribution ◽  
Hygroscopic Growth ◽  
Scattering Coefficients ◽  
Dry Conditions ◽  
Hygroscopic Particles

Abstract. Aerosol particles experience hygroscopic growth in the ambient atmosphere. Their optical properties – especially the aerosol light scattering – are therefore strongly dependent on the ambient relative humidity (RH). In-situ light scattering measurements of long-term observations are usually performed under dry conditions (RH>30–40%). The knowledge of this RH effect is of eminent importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. This study combines measurements and model calculations to describe the RH effect on aerosol light scattering for the first time for aerosol particles present in summer and fall in the high Arctic. For this purpose, a field campaign was carried out from July to October 2008 at the Zeppelin station in Ny-Ålesund, Svalbard. The aerosol light scattering coefficient σsp(λ) was measured at three distinct wavelengths (λ=450, 550, and 700 nm) at dry and at various, predefined RH conditions between 20% and 95% with a recently developed humidified nephelometer (WetNeph) and with a second nephelometer measuring at dry conditions with an average RH<10% (DryNeph). In addition, the aerosol size distribution and the aerosol absorption coefficient were measured. The scattering enhancement factor f(RH, λ) is the key parameter to describe the RH effect on σsp(λ) and is defined as the RH dependent σsp(RH, λ) divided by the corresponding dry σsp(RHdry, λ). During our campaign the average f(RH=85%, λ=550 nm) was 3.24±0.63 (mean ± standard deviation), and no clear wavelength dependence of f(RH, λ) was observed. This means that the ambient scattering coefficients at RH=85% were on average about three times higher than the dry measured in-situ scattering coefficients. The RH dependency of the recorded f(RH, λ) can be well described by an empirical one-parameter equation. We used a simplified method to retrieve an apparent hygroscopic growth factor g(RH), defined as the aerosol particle diameter at a certain RH divided by the dry diameter, using the WetNeph, the DryNeph, the aerosol size distribution measurements and Mie theory. With this approach we found, on average, g(RH=85%) values to be 1.61±0.12 (mean±standard deviation). No clear seasonal shift of f(RH, λ) was observed during the 3-month period, while aerosol properties (size and chemical composition) clearly changed with time. While the beginning of the campaign was mainly characterized by smaller and less hygroscopic particles, the end was dominated by larger and more hygroscopic particles. This suggests that compensating effects of hygroscopicity and size determined the temporal stability of f(RH, λ). During sea salt influenced periods, distinct deliquescence transitions were observed. At the end we present a method on how to transfer the dry in-situ measured aerosol scattering coefficients to ambient values for the aerosol measured during summer and fall at this location.

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