scholarly journals Hygroscopic growth effect on aerosol light scattering in the urban area of Beijing: a long-term measurement by a wide-range and high-resolution humidified nephelometer system

2018 ◽  
Author(s):  
Pusheng Zhao ◽  
Jing Ding ◽  
Xiang Du ◽  
Jie Su
Keyword(s):  
Light Scattering ◽  
High Resolution ◽  
Urban Area ◽  
Radiation Force ◽  
Water Soluble ◽  
Growth Effect ◽  
Light Extinction ◽  
Hygroscopic Growth ◽  
Particle Size Range ◽  
Wide Range

Abstract. Hygroscopicity is an important feature of ambient aerosols, which is very crucial to the study of light extinction, radiation force, and formation mechanism. The light scattering hygroscopic growth factor (f(RH)) is an important parameter which is usually measured by the humidified nephelometer system and could better describe the aerosol hygroscopicity under wide particle size range and continuous relative humidity (RH). The f(RH) can be applied to the establishment of a parameterization scheme for light extinction, the calculation of hygroscopicity parameter (κ), and also the estimation of aerosol liquid water content (ALWC). However, the humidified nephelometer system in the previous studies could only observe the f(RH) below 90 % due to the larger error of the sensor under high RH (> 90 %). Furthermore, the f(RH) observations in North China Plain needs to be greatly strengthened both in the temporal resolution and the observation duration. In view of this, an improved high-resolution humidified nephelometer system was established to observe the f(RH) of PM2.5 for a wide RH range between 30 %–96 % in the urban area of Beijing over three seasons (winter, summer, and autumn) in 2017. It was found that the f(80 %) at 525 nm of PM2.5 was evidently higher under the polluted conditions and highly correlated with the fractions of all the water-soluble ions. A two-parameter fit equation was selected to fit the observed f(RH) data. For each season, the fitting curve under the very clean condition was lower than that of other conditions. And the f(RH) points of polluted conditions were more concentrated with higher fitting R2 for summer and autumn data. The hygroscopicity of aerosol under higher RH was probably enhanced when compared with the data in the previous study conducted in NCP. In summer, the fitting f(RH) showed a significant dependence on wavelength for each pollution condition. However, there was an opposite performance in the f(RH) curves of different wavelengths for the very clean condition in winter. It was showed that The simulation showed that the maximum uncertainty of f(RH) was less than 10 %.

scholarly journals Impact of relative humidity and particles number size distribution on aerosol light extinction in the urban area of Guangzhou

2013 ◽  
Vol 13 (3) ◽  
pp. 1115-1128 ◽  
Author(s):  
Z. J. Lin ◽  
J. Tao ◽  
F. H. Chai ◽  
S. J. Fan ◽  
J. H. Yue ◽  
...  
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Relative Humidity ◽  
Temporal Variation ◽  
Size Distribution ◽  
Urban Area ◽  
Water Soluble ◽  
Light Extinction ◽  
Hygroscopic Growth ◽  
Number Size Distribution

Abstract. In the urban area of Guangzhou, observations on aerosol light extinction effect were conducted at a monitoring site of the South China Institute of Environmental Sciences (SCIES) during April 2009, July 2009, October 2009 and January 2010. The main goal of these observations is to recognise the impact of relative humidity (RH) and particles number distribution on aerosol light extinction. PM2.5 was sampled by Model PQ200 air sampler; ions and OC/EC in PM2.5 were identified by the Dionex ion chromatography and the DRI model 2001 carbon analyser, respectively; particles number size distribution was measured by TSI 3321 APS, while total light scattering coefficient was measured by TSI 3563 Nephelometer. Chemical composition of PM2.5 was reconstructed by the model ISORROPIA II. As a result, possible major components in PM2.5 were (NH4)2SO4, Na2SO4, K2SO4, NH4NO3, HNO3, water, POM and EC. Regarding ambient RH, mass concentration of PM2.5 ranged from 26.1 to 279.1 μg m−3 and had an average of 94.8, 44.6, 95.4 and 130.8 μg m−3 in April, July, October and January, respectively. With regard to the total mass of PM2.5, inorganic species, water, POM, EC and the Residual accounted for 34–47%, 19–31%, 14–20%, 6–8% and 8–17%, respectively. Under the assumption of "internal mixture", optical properties of PM0.5–20 were estimated following the Mie Model. Optical refractive index, hygroscopic growth factor and the dry aerosol density required by the Mie Model were determined with an understanding of chemical composition of PM2.5. With these three parameters and the validated particles number size distribution of PM0.5–20, the temporal variation trend of optical property of PM0.5–20 was estimated with good accuracy. The highest average of bep,pm0.5–20 was 300 Mm−1 in April while the lowest one was 78.6 Mm−1 in July. Regarding size distribution of bep,pm0.5–20, peak value was almost located in the diameter range between 0.5 and 1.0 μm. Furthermore, hygroscopic growth of optical properties of PM0.5–20 largely depended on RH. As RH increased, bep,pm0.5–20 grew and favoured a more rapid growth when aerosol had a high content of inorganic water-soluble salts. Averagely, fbep,pm0.5–20 enlarged 1.76 times when RH increased from 20% to 90%. With regard to the temporal variation of ambient RH, fbep,pm0.5–20 was 1.29, 1.23, 1.14 and 1.26 on average in April, July, October and January, respectively.

scholarly journals Aerosol hygroscopicity in the marine atmosphere: a closure study using high-resolution, size-resolved AMS and multiple-RH DASH-SP data

2008 ◽  
Vol 8 (4) ◽  
pp. 16789-16817
Author(s):  
S. P. Hersey ◽  
A. Sorooshian ◽  
S. M. Murphy ◽  
R. C. Flagan ◽  
J. H. Seinfeld
Keyword(s):  
High Resolution ◽  
Water Soluble ◽  
High Time Resolution ◽  
Marine Atmosphere ◽  
Hygroscopic Growth ◽  
Aerosol Mass Spectrometer ◽  
Central California ◽  
Aerosol Mass ◽  
Soluble Organic Fraction ◽  
Aerosol Hygroscopicity

Abstract. We have conducted the first closure study to couple high-resolution aerosol mass spectrometer (AMS) composition data with size-resolved, multiple-RH, high-time-resolution hygroscopic growth factor (GF) measurements from the differential aerosol sizing and hygroscopicity spectrometer probe (DASH-SP). These data were collected off the coast of Central California during seven of the 16 flights carried out during the MASE-II field campaign in July 2007. Two of the seven flights were conducted in airmasses that originated over the continental United States. These flights exhibited elevated organic volume fractions (VForganic=0.46±0.22, as opposed to 0.24±0.18 for all other flights), corresponding to significantly suppressed GFs at high RH (1.61±0.14 at 92% RH, as compared with 1.91±0.07 for all other flights), more moderate GF suppression at intermediate RH (1.53±0.10 at 85%, compared with 1.58±0.08 for all other flights, and no measurable GF suppression at low RH (1.31±0.06 at 74%, compared with 1.31±0.07 for all other flights). Organic loadings were slightly elevated in above-cloud aerosols, as compared with below-cloud aerosols, and corresponded to a similar trend of significantly suppressed GF at high RH, but more moderate impacts at lower values of RH. A hygroscopic closure based on a volume-weighted mixing rule provided excellent agreement with DASH-SP measurements (R2=0.79). Minimization of root mean square error between observations and predictions indicated mission-averaged organic GFs of 1.20, 1.43, and 1.46 at 74, 85, and 92% RH, respectively. These values agree with previously reported values for water-soluble organics such as dicarboxylic and multifunctional acids, and correspond to a highly oxidized, presumably water-soluble, organic fraction (O:C=0.92±0.33). Finally, a backward stepwise linear regression revealed that, other than RH, the most important predictor for GF is VForganic, indicating that a simple emperical model relating GF, RH, and the relative abundance of organic material can provide accurate predictions of hygroscopic growth in the marine atmosphere.

scholarly journals Assessment of NAAPS-RA performance in Maritime Southeast Asia during CAMP<sup>2</sup>Ex

2021 ◽  
Author(s):  
Eva-Lou Edwards ◽  
Jeffrey S. Reid ◽  
Peng Xian ◽  
Sharon P. Burton ◽  
Anthony L. Cook ◽  
...  
Keyword(s):  
Southeast Asia ◽  
Cloud Condensation Nuclei ◽  
Particle Mass ◽  
High Spectral Resolution ◽  
Light Extinction ◽  
Aerosol Extinction ◽  
Hygroscopic Growth ◽  
Extinction Coefficients ◽  
Wide Range ◽  
Aerosol Properties

Abstract. Monitoring and modeling aerosol particle lifecycle in Southeast Asia (SEA) is challenged by high cloud cover, complex meteorology, and the wide range of aerosol species, sources, and transformations found throughout the region. Satellite observations are limited, and there are few in situ observations of aerosol extinction profiles, aerosol properties, and environmental conditions. Therefore, accurate aerosol model outputs are crucial for the region. This work evaluates the Navy Aerosol Analysis and Prediction System Reanalysis (NAAPS-RA) aerosol optical thickness (AOT) and light extinction products using airborne aerosol and meteorological measurements from the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex) in SEA. Modeled AOTs and extinction coefficients were compared to those retrieved with a High Spectral Resolution Lidar (HSRL-2). Correlations were highest for AOT in the mixed layer (AOTML; R2 = 0.83, bias = 0.00, root mean square error [RMSE] = 0.03) compared to total AOT (R2 = 0.68, bias = 0.01, RMSE = 0.14), although the correlations between the observations and 1° × 1° degree NAAPS-RA outputs were weaker in regions with strong gradients in aerosol properties, such as near areas of active convection. Correlations between simulated and retrieved aerosol extinction coefficients were highest from 145–500 m (R2 = 0.75, bias = 0.01 km−1, RMSE = 0.08 km−1) and decreased with increasing altitude (R2 = 0.69 and 0.26, bias = 0.00 and 0.00 km−1, RMSE = 0.09 and 0.00 km−1 for 500–1500 m and > 1500 m, respectively), which was likely a result of the use of bulk cloud mixing parameterizations. We also investigated the role of possible relative humidity (RH) errors in extinction simulations. Despite negative biases in modeled RH (−4.9, −7.7, and −2.3 % for altitudes < 500 m, 500–1500 m, and > 1500 m, respectively), AOT and extinction agreement with the HSRL-2 did not change significantly at any altitude when RHs from dropsondes were substituted into the model. Improvements may have been stunted due to errors in how NAAPS-RA modeled physics of particle hygroscopic growth, dry particle mass concentrations, and/or dry mass extinction efficiencies, especially when combined with AOT corrections from data assimilation. Specifically, the model overestimated the hygroscopicity of (i) smoke particles from biomass burning in the Maritime Continent (MC), and (ii) anthropogenic emissions transported from East Asia. This work provides insight into how certain environmental and microphysical properties influence AOT and extinction simulations, which can then be interpreted in the context of modeling global concentrations of particle mass and cloud condensation nuclei (CCN).

scholarly journals Impact of relative humidity and particles size distribution on aerosol light extinction in urban area of Guangzhou

2012 ◽  
Vol 12 (6) ◽  
pp. 15639-15674 ◽  
Author(s):  
Z. J. Lin ◽  
J. Tao ◽  
F. H. Chai ◽  
S. J. Fan ◽  
J. H. Yue ◽  
...  
Keyword(s):  
Light Scattering ◽  
Relative Humidity ◽  
Size Distribution ◽  
Extinction Coefficient ◽  
Light Extinction ◽  
Inorganic Salts ◽  
Hygroscopic Growth ◽  
Light Extinction Coefficient ◽  
Particles Size Distribution ◽  
Total Light

Abstract. In urban area of Guangzhou, an experiment was conducted at the monitoring site of SCIES in order to recognize the impact of relative humidity (RH) and particles size distribution on aerosol light extinction during 2009 to 2010. Water-soluble ions and OC/EC in daily PM2.5 samples was determined by the Dionex ion chromatography and the DIR model 2001 carbon analyzer, respectively; particles size distribution was measured by TSI 3321 APS; and total light scattering coefficient was measured by TSI 3565 Nephelometer. Inorganic salts that constitute PM2.5 were recognized under an assumption of the electrical charge neutrality, while chemical components as POM, EC and water content were determined by means of hygroscopic growth calculation and chemical mass closure. As a result, (NH4)2SO4, NaNO3, POM, EC and water content were found to be the major components. By the Mie Model, light scattering and absorption coefficient of PM0.5–2.5 were estimated on the basis of the chemical composition of PM2.5 and the size distribution of number concentration of PM0.5–2.5. This estimation was evaluated by results from Nephelometer measurement and proved to have high accuracy. With the knowledge of hygroscopic growth of some inorganic salts, it was realized that optical properties of PM2.5 greatly depended on relative humidity, while light extinction was enhanced averagely 1.23, 1.38 and 1.75 times at 70%, 80% and 90% RH, respectively. Moreover, light extinction coefficient of PM0.5–2.5 increased averagely 1.24 to 1.28 times during wet days while merely 1.04 times in dry days. Furthermore, combined results from Nephelometer, the knowledge of relation between EC and aerosol light absorption and the Mie Model estimation, size distribution of total light extinction coefficient was determined. PM1 contributed averagely 76%, 85%, 94% and 93% to light extinction in spring, summer, autumn and winter, respectively, while the contributions from PM2.5 were 94% at least.

Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

Three-fold astigmatism: An important TEM aberration

1993 ◽  
Vol 51 ◽  
pp. 972-973 ◽  
Author(s):  
O.L. Krivanek ◽  
M.L. Leber
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Field Emission ◽  
Azimuthal Angle ◽  
Hollow Cone ◽  
Small Probe ◽  
Wide Range ◽  
High Resolution Images ◽  
Image Position

Three-fold astigmatism resembles regular astigmatism, but it has 3-fold rather than 2-fold symmetry. Its contribution to the aberration function χ(q) can be written as:where A3 is the coefficient of 3-fold astigmatism, λ is the electron wavelength, q is the spatial frequency, ϕ the azimuthal angle (ϕ = tan-1 (qy/qx)), and ϕ3 the direction of the astigmatism.Three-fold astigmatism is responsible for the “star of Mercedes” aberration figure that one obtains from intermediate lenses once their two-fold astigmatism has been corrected. Its effects have been observed when the beam is tilted in a hollow cone over a wide range of angles, and there is evidence for it in high resolution images of a small probe obtained in a field emission gun TEM/STEM instrument. It was also expected to be a major aberration in sextupole-based Cs correctors, and ways were being developed for dealing with it on Cs-corrected STEMs.

Scanning tunneling microscopy of polymers: A status report

1989 ◽  
Vol 47 ◽  
pp. 330-331
Author(s):  
P.E. Russell ◽  
I.H. Musselman
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscopy ◽  
Sample Surface ◽  
Atomic Scale ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Status Report ◽  
Tunneling Microscopy ◽  
Research Issues ◽  
Wide Range

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.

Microsponges: An Overview

2017 ◽  
Vol 4 (4) ◽  
Author(s):  
Hamid Hussain ◽  
Divya Juyal ◽  
Archana Dhyani
Keyword(s):  
Controlled Release ◽  
Delivery System ◽  
Oral Delivery ◽  
Active Agent ◽  
Topical Delivery ◽  
Water Soluble ◽  
Wide Range ◽  
Porous Beads

Microsponge and Nanosponge delivery System was originally developed for topical delivery of drugs can also be used for controlled oral delivery of drugs using water soluble and bioerodible polymers. Microsponge delivery system (MDS) can entrap wide range of drugs and then release them onto the skin over a time by difussion mechanism to the skin. It is a unique technology for the controlled release of topical agents and consists of nano or micro porous beads loaded with active agent and also use for oral delivery of drugs using bioerodible polymers.

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