Isotopic composition of organic carbon and elemental carbon in PM2.5 in Hangzhou, China

2007 ◽  
Vol 52 (17) ◽  
pp. 2435-2437 ◽  
Author(s):  
Gang Liu ◽  
XuXian Zhang ◽  
WeiLin Teng ◽  
Hui Yang
Keyword(s):  
Organic Carbon ◽  
Isotopic Composition ◽  
Elemental Carbon

Ambient organic carbon to elemental carbon ratios: Influence of the thermal–optical temperature protocol and implications

2014 ◽  
Vol 468-469 ◽  
pp. 1103-1111 ◽  
Author(s):  
Yuan Cheng ◽  
Ke-bin He ◽  
Feng-kui Duan ◽  
Zhen-yu Du ◽  
Mei Zheng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Elemental Carbon

scholarly journals Evaluation of a 2-step thermal method for separating organic and elemental carbon for radiocarbon analysis

2014 ◽  
Vol 7 (1) ◽  
pp. 131-169 ◽  
Author(s):  
U. Dusek ◽  
M. Monaco ◽  
M. Prokopiou ◽  
F. Gongriep ◽  
R. Hitzenberger ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Humic Acid ◽  
Organic Carbon ◽  
Organic Compounds ◽  
Strong Evidence ◽  
Elemental Carbon ◽  
Intermediate Temperature ◽  
Thermal Method ◽  
Intermediate Step ◽  
Temperature Step

Abstract. We thoroughly characterized a system for thermal separation of organic carbon (OC) and elemental carbon (EC) for subsequent radiocarbon analysis. Different organic compounds as well as ambient aerosol filter samples were introduced into an oven system and combusted to CO2 in pure O2. The main objective was to test which combustion times and temperatures are best suited to separate OC and EC. The final separation step for OC was combustion at 360 °C for 15 min. Combustion at this temperature proved enough to remove several organic test substances from the filter (including high molecular weight humic acid) but did not remove substantial amounts of EC. For isolation of EC, OC first needs to be completely removed from the filter. This was achieved by water extraction of the filter, followed by combustion of the water insoluble OC at 360 °C and combustion at an intermediate temperature step of 2 min at 450 °C. This last step removed the most refractory OC together with some EC. Finally, the remaining EC was combusted to CO2 at 650 °C. The recovery of black carbon after the intermediate 450 °C step was approximately 80%. Several tests provided strong evidence that OC was removed efficiently during the intermediate temperature step: (i) brown carbon, indicative of refractory OC, was removed; (ii) the fraction modern of EC did not decrease significantly if the temperature of the intermediate step was further increased. Based on tests with various organic compounds, we estimated that charred organic carbon could contribute 4–8% to an elemental carbon sample that was isolated according to our method.

13C discrimination patterns in oceanic phytoplankton: likely influence of CO2 concentrating mechanisms, and implications for palaeoreconstructions

2002 ◽  
Vol 29 (3) ◽  
pp. 323 ◽  
Author(s):  
Edward A. Laws ◽  
Brian N. Popp ◽  
Nicolas Cassar ◽  
Jamie Tanimoto
Keyword(s):  
Growth Rate ◽  
Organic Carbon ◽  
Isotopic Composition ◽  
Active Transport ◽  
Limiting Factor ◽  
Similar Species ◽  
Confounding Factors ◽  
Co2 Concentrations ◽  
Co2 Concentrating Mechanisms ◽  
The Impact

The isotopic composition of organic carbon buried in marine sediments is an appealing proxy for palaeo CO2 concentrations due to the well-documented effect of CO2 concentrations on carbon fractionation by phytoplankton. However, a number of factors, in addition to CO2 concentrations, influence this fractionation. Included among these factors are cell geometry, in particular surface/volume ratios, growth rate, and the presence of CO2 concentrating mechanisms. Other potentially confounding factors are calcification, diagenesis, and the nature of the growth-rate-limiting factor, e.g. light vs nutrients. Because of these confounding factors, palaeoreconstructions based on the isotopic composition of organic carbon (δ13C) will almost certainly have to be based on the isotopic signatures of organic compounds that can be associated with a single species, or group of physiologically similar species. Long-chain alkenones produced by certain species of coccolithophores may provide a suitable diagnostic marker. By combining the δ13C of the alkenone carbon with the δ13C of coccolith carbon and the Sr/Ca ratio of the coccoliths, it is possible to calculate the extent of carbon fractionation (εp) and estimate growth rates. However, active transport of inorganic carbon tends to make εp insensitive to CO2 concentrations when the ratio of growth rate to CO2 concentration exceeds 0.285/rkg mol–1d–1, where r is the effective spherical radius of the cell in microns. Palaeo CO2 concentrations calculated from alkenone and coccolith δ13C data capture the gross features of CO2 concentrations in the Vostok ice core, but explain only 30–35% of the variance in the latter. The absence of a higher correlation may in part reflect the impact of active transport, particularly during glacial times. The impact of active transport may have been less severe prior to the Pleistocene, since CO2 concentrations are believed to have been higher than present-day values during most of Phanerozoic time.

scholarly journals High contributions of fossil sources to more volatile organic aerosol

2019 ◽  
Vol 19 (15) ◽  
pp. 10405-10422 ◽  
Author(s):  
Haiyan Ni ◽  
Ru-Jin Huang ◽  
Junji Cao ◽  
Wenting Dai ◽  
Jiamao Zhou ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Elemental Carbon ◽  
Organic Aerosol ◽  
Formation Mechanisms ◽  
Formation Processes ◽  
Combustion System ◽  
Relative Contribution ◽  
Custom Made ◽  
Volatile Organic ◽  
Volatile Carbon

Abstract. Sources of particulate organic carbon (OC) with different volatility have rarely been investigated, despite the significant importance for better understanding of the atmospheric processes of organic aerosols. In this study we develop a radiocarbon-based (14C) approach for source apportionment of more volatile OC (mvOC) and apply to ambient aerosol samples collected in winter in six Chinese megacities. mvOC is isolated by desorbing organic carbon from the filter samples in helium (He) at 200 ∘C in a custom-made aerosol combustion system for 14C analysis. Evaluation of this new isolation method shows that the isolated mvOC amount agrees very well with the OC1 fraction (also desorbed at 200 ∘C in He) measured by a thermal–optical analyzer using the EUSAAR_2 protocol. The mvOC, OC and elemental carbon (EC) of 13 combined PM2.5 samples in six Chinese cities are analyzed for 14C to investigate their sources and formation mechanisms. The relative contribution of fossil sources to mvOC is 59±11 %, consistently larger than the contribution to OC (48±16 %) and smaller than that to EC (73±9 %), despite large differences in fossil contributions in different cities. The average difference in the fossil fractions between mvOC and OC is 13 % (range of 7 %–25 %), similar to that between mvOC and EC (13 %, with a range 4 %–25 %). Secondary OC (SOC) concentrations and sources are modeled based on the 14C-apportioned OC and EC and compared with concentrations and sources of mvOC. SOC concentrations (15.4±9.0 µg m−3) are consistently higher than those of mvOC (3.3±2.2 µg m−3), indicating that only a fraction of SOC is accounted for by the more volatile carbon fraction desorbed at 200 ∘C. The fossil fraction in SOC is 43 % (10 %–70 %), lower than that in mvOC (59 %, with a range of 45 %–78 %). Correlation between mvOC and SOC from nonfossil sources (mvOCnf vs. SOCnf) and from fossil sources (mvOCfossil vs. SOCfossil) is examined to further explore sources and formation processes of mvOC and SOC.

scholarly journals Sources of PM<sub>2.5</sub> carbonaceous aerosol in Riyadh, Saudi Arabia

2017 ◽  
Author(s):  
Qijing Bian ◽  
Badr Alharbi ◽  
Mohammed M. Sharee ◽  
Tahir Husai ◽  
Mohammad J. Pasha ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Air Quality ◽  
Organic Carbon ◽  
Pollution Control ◽  
Elemental Carbon ◽  
Control Strategies ◽  
Continuous Method ◽  
Carbonaceous Aerosol ◽  
Abstract Knowledge ◽  
The City

Abstract. Knowledge of the sources of carbonaceous aerosol affecting air quality in Riyadh, Saudi Arabia is limited, but needed for the development of pollution control strategies. We conducted sampling of PM2.5 from April to September, 2012 at various sites in the city, and used a thermo-optical semi-continuous method to quantify the organic carbon (OC) and elemental carbon (EC) concentrations. The average OC and EC concentrations were 4.7 ± 4.4 and 2.1 ± 2.5 μg  m

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