n-alkane distribution coupled with organic carbon isotope composition in the shell bar section, Qarhan paleolake, Qaidam basin, NE Tibetan Plateau

2009 ◽  
Vol 3 (3) ◽  
pp. 327-335 ◽  
Author(s):  
Yang Pu ◽  
Hucai Zhang ◽  
Guoliang Lei ◽  
Fengqin Chang ◽  
Mingsheng Yang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Organic Carbon ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Qaidam Basin ◽  
Carbon Isotope Composition ◽  
Organic Carbon Isotope ◽  
Ne Tibetan Plateau ◽  
Shell Bar Section ◽  
Shell Bar

scholarly journals AMS Dating on the Shell Bar Section from Qaidam Basin, Ne Tibetan Plateau, China

Radiocarbon ◽  
2008 ◽  
Vol 50 (2) ◽  
pp. 255-265 ◽  
Author(s):  
H C Zhang ◽  
H F Fan ◽  
F Q Chang ◽  
W X Zhang ◽  
G L Lei ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Organic Carbon ◽  
Stable Carbon Isotopes ◽  
Qaidam Basin ◽  
Sampling Site ◽  
Organic Carbon Content ◽  
Ams Dating ◽  
Ne Tibetan Plateau ◽  
Shell Bar Section ◽  
Shell Bar

Radiocarbon dating by accelerator mass spectrometry (AMS) of the shell bar section of Qaidam Basin, NE Tibetan Plateau, shows that this section was formed between ~39.7 and ~17.5 14C kyr BP and represented the highest paleolake development period since the Late Pleistocene. It was difficult to obtain reliable dates due to the low organic carbon content, which was formed mainly by authochtonous algae-bacteria (Zhang et al. 2007a). In order to improve the dating, 14C ages of both the alkali residual and acid-soluble components of the organic carbon were measured to check the consistency of the dating results. Total organic carbon (TOC) content and stable carbon isotopes (δ13Corg) might also be used as critical references for checking the reliability of dates. For example, in our study of the shell bar section from Qaidam Basin, we found that when the TOC content was higher than 0.15% and/or δ13Corg was lower than −23, the AMS dates were reliable. AMS dating of fossil shells demonstrated that they could provide valuable age information. The ages given by fossil shells are comparable to those of bulk carbonate from a similar sampling site, and are about 15~18 kyr older than the ages given by organic matter. Due to the U/Th dating requirements and open nature of the system, we concluded that U/Th dating results are unreliable and that this technique is unsuitable for dating halite deposits from Qaidam Basin.

scholarly journals High time-resolved measurement of stable carbon isotope composition in water-soluble organic aerosols: method optimization and a case study during winter haze in East China

2018 ◽  
Author(s):  
Wenqi Zhang ◽  
Yan-Lin Zhang ◽  
Fang Cao ◽  
Yankun Xiang ◽  
Yuanyuan Zhang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Organic Aerosols ◽  
Carbon Isotope Composition ◽  
Water Soluble ◽  
High Time ◽  
Stable Carbon ◽  
Air Mass

Abstract. Water soluble organic carbon (WSOC) is a significant fraction of organic carbon (OC) in atmospheric aerosols. WSOC is of great interest due to its significant effects on atmospheric chemistry, the Earth’s climate and human health. Stable carbon isotope (δ13C) can be used to track the potential sources and investigate atmospheric processes of organic aerosols. In this study, a method of simultaneously measuring the mass concentration and δ13C values of WSOC from aerosol samples is established by coupling the Gas Bench II preparation device with isotopic ratio mass spectrometry. The precision and accuracy of isotope determination is better than 0.17 ‰ and 0.5 ‰, respectively, for samples containing carbon larger than 5 μg. This method is then applied for the high time-resolution aerosol samples during a severe wintertime haze period in Nanjing, East China. WSOC varies between 3–32 μg m−3, whereas δ13C-WSOC ranges from −26.24 ‰ to −23.35 ‰. Three different episodes (e.g., namely the Episode 1, the Episode 2, the Episode 3) are identified in the sampling period, showing a different tendency of δ13C-WSOC with the accumulation process of WSOC aerosols. The increases in both the WSOC mass concentrations and the δ13C-WSOC values in the Episode 1 indicate that WSOC is subject to a substantial photochemical aging during the air mass transport. In the Episode 2, the decline of the δ13C-WSOC is accompanied by the increase in the WSOC mass concentrations, which is associated with regional-transported biomass burning emissions. In the Episode 3, heavier isotope (13C) is exclusively enriched in total carbon (TC) compares to WSOC aerosols. This suggests that water-insoluble carbon may contain 13C-enriched components such as dust carbonate which is supported by the enhanced Ca2+ concentrations and air mass trajectories analysis. The present study provides a novel method to determine stable carbon isotope composition of WSOC and it offers a great potential to better understand the source emission, the atmospheric aging and the secondary production of water soluble organic aerosols.

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