Laser microprobe technique for stable carbon isotope analyses of organic carbon in sedimentary rocks.

Abstract. In order to determine the origins of dissolved organic matter (DOM) occurring in the seawater of Sihwa Lake, we measured the stable carbon isotope ratios of dissolved organic carbon (DOC-δ13C) and the optical properties (absorbance and fluorescence) of DOM in two different seasons (March 2017 and September 2018). Sihwa Lake is enclosed by a dike along the western coast of South Korea, and the water is exchanged with the Yellow Sea twice a day through the sluice gates. The DOC concentrations were generally higher in lower-salinity waters in both periods, and excess of DOC was also observed in 2017 in high-salinity waters. Here, the excess DOC represents any DOC concentrations higher than those in the incoming open-ocean seawater. The excess DOC occurring in the lower-salinity waters originated mainly from marine sediments of tidal flats, based on the DOC-δ13C values (-20.7±1.2 ‰) and good correlations among the DOC, humic-like fluorescent DOM (FDOMH), and NH4+ concentrations. However, the origins of the excess DOC observed in 2017 appear to be from two different sources: one mainly from marine sources such as biological production based on the DOC-δ13C values (−19.1 ‰ to −20.5 ‰) and the other mainly from terrestrial sources by land–seawater interactions based on its depleted DOC-δ13C values (−21.5 ‰ to −27.8 ‰). This terrestrial DOM source observed in 2017 was likely associated with DOM on the reclaimed land, which experienced extended exposure to light and bacterial degradation as indicated by the higher spectral slope ratio (SR) of light absorbance and no concurrent increases in the FDOMH and NH4+ concentrations. Our study demonstrates that the combination of these biogeochemical tools can be a powerful tracer of DOM sources and characteristics in coastal environments.

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The stable carbon isotope composition of soil organic carbon and pedogenic carbonates along a bioclimatic gradient in the Palouse region, Washington State, USA

Geoderma ◽

10.1016/j.geoderma.2004.03.006 ◽

2005 ◽

Vol 124 (1-2) ◽

pp. 37-47 ◽

Cited By ~ 102

Author(s):

B.A. Stevenson ◽

E.F. Kelly ◽

E.V. McDonald ◽

A.J. Busacca

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Carbon Isotope ◽

Isotope Composition ◽

Stable Carbon Isotope ◽

Washington State ◽

Carbon Isotope Composition ◽

Stable Carbon ◽

Stable Carbon Isotope Composition ◽

Pedogenic Carbonates

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Correlation of stable carbon isotope, reflectance, and total organic carbon that help provide a new stratigraphic framework for defining Desmoinesian and Atokan sediments in the Denver and Cherokee basins in the Mid-continent United States

Methods and Applications in Petroleum and Mineral Exploration and Engineering Geology ◽

10.1016/b978-0-323-85617-1.00004-7 ◽

2021 ◽

pp. 39-63

Author(s):

Steven A. Tedesco

Keyword(s):

United States ◽

Organic Carbon ◽

Total Organic Carbon ◽

Carbon Isotope ◽

Stable Carbon Isotope ◽

Stable Carbon ◽

Stratigraphic Framework

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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

10.5194/acp-2018-1056 ◽

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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