scholarly journals Thermal/Optical Methods for Elemental Carbon Quantification in Soils and Urban Dusts: Equivalence of Different Analysis Protocols

PLoS ONE ◽  
2013 ◽  
Vol 8 (12) ◽  
pp. e83462 ◽  
Author(s):  
Yongming Han ◽  
Antony Chen ◽  
Junji Cao ◽  
Kochy Fung ◽  
Fai Ho ◽  
...  
Keyword(s):  
Elemental Carbon ◽  
Optical Methods ◽  
Urban Dusts

scholarly journals Improved measurement of carbonaceous aerosol: evaluation of the sampling artifacts and inter-comparison of the thermal-optical analysis methods

2010 ◽  
Vol 10 (17) ◽  
pp. 8533-8548 ◽  
Author(s):  
Y. Cheng ◽  
K. B. He ◽  
F. K. Duan ◽  
M. Zheng ◽  
Y. L. Ma ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Elemental Carbon ◽  
Correction Method ◽  
Optical Methods ◽  
Carbonaceous Aerosol ◽  
Series Method ◽  
Optical Analysis ◽  
Quartz Filter ◽  
Sampling Artifacts ◽  
In Series

Abstract. The sampling artifacts (both positive and negative) and the influence of thermal-optical methods (both charring correction method and the peak inert mode temperature) on the split of organic carbon (OC) and elemental carbon (EC) were evaluated in Beijing. The positive sampling artifact constituted 10% and 23% of OC concentration determined by the bare quartz filter during winter and summer, respectively. For summer samples, the adsorbed gaseous organics were found to continuously evolve off the filter during the whole inert mode when analyzed by the IMPROVE-A temperature protocol. This may be due to the oxidation of the adsorbed organics during sampling (reaction artifact) which would increase their thermal stability. The backup quartz approach was evaluated by a denuder-based method for assessing the positive artifact. The quartz-quartz (QBQ) in series method was demonstrated to be reliable, since all of the OC collected by QBQ was from originally gaseous organics. Negative artifact that could be adsorbed by quartz filter was negligible. When the activated carbon impregnated glass fiber (CIG) filter was used as the denuded backup filter, the denuder efficiency for removing gaseous organics that could be adsorbed by the CIG filter was only about 30%. EC values were found to differ by a factor of about two depending on the charring correction method. Influence of the peak inert mode temperature was evaluated based on the summer samples. The EC value was found to continuously decrease with the peak inert mode temperature. Premature evolution of light absorbing carbon began when the peak inert mode temperature was increased from 580 to 650 °C; when further increased to 800 °C, the OC and EC split frequently occurred in the He mode, and the last OC peak was characterized by the overlapping of two separate peaks. The discrepancy between EC values defined by different temperature protocols was larger for Beijing carbonaceous aerosol compared with North America and Europe, perhaps due to the higher concentration of brown carbon in Beijing aerosol.

scholarly journals Refining temperature measures in thermal/optical carbon analysis

2005 ◽  
Vol 5 (11) ◽  
pp. 2961-2972 ◽  
Author(s):  
J. C. Chow ◽  
J. G. Watson ◽  
L.-W. A. Chen ◽  
G. Paredes-Miranda ◽  
M.-C. O. Chang ◽  
...  
Keyword(s):  
Elemental Carbon ◽  
Total Carbon ◽  
Sample Temperature ◽  
Optical Methods ◽  
Heating Zone ◽  
Temperature Calibration ◽  
Calibration Standards ◽  
Carbon Fractions ◽  
Thermocouple Temperature ◽  
Carbon Analysis

Abstract. Thermal/optical methods have been widely used for quantifying total carbon (TC), organic carbon (OC), and elemental carbon (EC) in ambient and source particulate samples. Thermally defined carbon fractions have been used for source identification. Temperature precision in thermal carbon analysis is critical to the allocation of carbon fractions. The sample temperature is determined by a thermocouple, which is usually located in the oven near the sample. Sample and thermocouple temperature may differ owing to different thermal properties between the sample filter punch and the thermocouple, or inhomogeneities in the heating zone. Quick-drying temperature-indicating liquids (Tempil Inc., South Plainfield, NJ) of different liquefying points are used as temperature calibration standards. These consist of chemicals that change their appearance at specific temperatures and can be optically monitored to determine the sample temperature. Temperature measures were evaluated for three different models of carbon analyzers. Sample temperatures were found to differ from sensor temperatures by 10 to 50°C. Temperature biases of 14 to 22°C during thermal analysis were found to change carbon fraction measurements. The temperature indicators allow calibration curves to be constructed that relate the sample temperature to the temperature measured by a thermocouple.

scholarly journals Improved measurement of carbonaceous aerosol in Beijing, China: intercomparison of sampling and thermal-optical analysis methods

2010 ◽  
Vol 10 (6) ◽  
pp. 15671-15712
Author(s):  
Y. Cheng ◽  
K. B. He ◽  
F. K. Duan ◽  
M. Zheng ◽  
Y. L. Ma ◽  
...  
Keyword(s):  
Elemental Carbon ◽  
Correction Method ◽  
Optical Methods ◽  
Carbonaceous Aerosol ◽  
Series Method ◽  
Optical Analysis ◽  
Quartz Filter ◽  
Sampling Artifacts ◽  
In Series ◽  
Beijing China

Abstract. The sampling artifacts (both positive and negative) and the influence of thermal-optical methods (both charring correction method and the peak inert mode temperature) on the split of organic carbon (OC) and elemental carbon (EC) were evaluated in Beijing. The positive sampling artifact constituted 10% and 23% of OC concentration determined by the bare quartz filter during winter and summer, respectively. For summer samples, the adsorbed gaseous organics were found to continuously evolve off the filter during the whole inert mode when analyzed by the IMPROVE-A temperature protocol. This may be due to the oxidation of the adsorbed organics during sampling (reaction artifact) which would increase their thermal stability. The backup quartz approach was evaluated by a denuder-based method for assessing the positive artifact. The quartz-quartz (QBQ) in series method was demonstrated to be reliable, since all of the OC collected by QBQ was from originally gaseous organics. Negative artifact that could be adsorbed by quartz filter was negligible. When the activated carbon impregnated glass fiber (CIG) filter was used as the denuded backup filter, the denuder efficiency for removing gaseous organics that could be adsorbed by the CIG filter was only about 30%. EC values were found to differ by a factor of about two depending on the charring correction method. Influence of the peak inert mode temperature was evaluated based on the summer samples. The EC value was found to continuously decrease with the peak inert mode temperature. Premature evolution of light absorbing carbon began when the peak inert mode temperature was increased from 580 to 650 °C; when further increased to 800 °C, the OC and EC split frequently occurred in the He mode, and the last OC peak was characterized by the overlapping of two separate peaks. The discrepancy between EC values defined by different temperature protocols was larger for Beijing carbonaceous aerosol compared with North America and Europe, perhaps due to the higher concentration of brown carbon in Beijing aerosol.

Intercomparison of Thermal–Optical Methods for the Determination of Organic and Elemental Carbon: Influences of Aerosol Composition and Implications

2011 ◽  
Vol 45 (23) ◽  
pp. 10117-10123 ◽  
Author(s):  
Yuan Cheng ◽  
Feng-kui Duan ◽  
Ke-bin He ◽  
Mei Zheng ◽  
Zhen-yu Du ◽  
...  
Keyword(s):  
Elemental Carbon ◽  
Optical Methods ◽  
Aerosol Composition

Preparation and characterisation of vanadium pentoxide supported rhodium catalyst

1988 ◽  
Vol 46 ◽  
pp. 946-947
Author(s):  
A. Legrouri
Keyword(s):  
Aqueous Solution ◽  
Thermal Decomposition ◽  
Physicochemical Properties ◽  
Surface Area ◽  
Vanadium Pentoxide ◽  
High Purity ◽  
Gas Adsorption ◽  
Rhodium Catalyst ◽  
Optical Methods ◽  
Reducible Oxides

The industrial importance of metal catalysts supported on reducible oxides has stimulated considerable interest during the last few years. This presentation reports on the study of the physicochemical properties of metallic rhodium supported on vanadium pentoxide (Rh/V2O5). Electron optical methods, in conjunction with other techniques, were used to characterise the catalyst before its use in the hydrogenolysis of butane; a reaction for which Rh metal is known to be among the most active catalysts.V2O5 powder was prepared by thermal decomposition of high purity ammonium metavanadate in air at 400 °C for 2 hours. Previous studies of the microstructure of this compound, by HREM, SEM and gas adsorption, showed it to be non— porous with a very low surface area of 6m2/g3. The metal loading of the catalyst used was lwt%Rh on V2Q5. It was prepared by wet impregnating the support with an aqueous solution of RhCI3.3H2O.

Investigation of cluster layers of small netal particles by TEM, SEM, EELS and by photoacoustic spectroscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 250-251
Author(s):  
H. Seiler ◽  
U. Haas ◽  
K.H. Körtje
Keyword(s):  
Bulk Material ◽  
High Vacuum ◽  
Optical Methods ◽  
Metal Particles ◽  
Silver Particles ◽  
Low Loss ◽  
Plasmon Excitation ◽  
First Results ◽  
Diffraction Patterns ◽  
Small Metal Particles

The physical properties of small metal particles reveal an intermediate position between atomic and bulk material. Especially Ag has shown pronounced size effects. We compared silver layers evaporated in high vacuum with cluster layers of small silver particles, evaporated in N2 at a pressure of about 102 Pa. The investigations were performed by electron optical methods (TEM, SEM, EELS) and by Photoacoustic (PA) Spectroscopy (gas-microphone detection).The observation of cluster layers with TEM and high resolution SEM show small silver particles with diameters of about 50 nm (Fig. 1 and Figure 2, respectively). The electron diffraction patterns of homogeneous Ag layers and of cluster layers are similar, whereas the low loss EELS spectra due to plasmon excitation are quite different. Fig. 3 and Figure 4 show first results of EELS spectra of a cluster layer of small silver particles on carbon foil and of a homogeneous Ag layer, respectively.

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