Tracing Carbon Isotope Variations in Lake Sediments Caused by Environmental Factors During the Past Century: A Case Study of Lake Tapeliai, Lithuania

Radiocarbon ◽  
2019 ◽  
Vol 61 (4) ◽  
pp. 885-903 ◽  
Author(s):  
Rūta Barisevičiūtė ◽  
Evaldas Maceika ◽  
Žilvinas Ežerinskis ◽  
Jonas Mažeika ◽  
Laurynas Butkus ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Humic Acids ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Hard Water ◽  
Lake Ecosystem ◽  
Past Century ◽  
Stable Carbon ◽  
Organic Fractions ◽  
Reservoir Age

ABSTRACTIn this study, we examined how land use and urbanization changes in adjacent areas affected biological productivity and carbon cycling in a lake ecosystem over 100 years and how these changes are reflected in carbon isotope variations. We performed radiocarbon (14C) activity and stable carbon isotope ratio analysis in two organic fractions: humin and humic acids of lake sediment. Additionally, we performed pigment and diatom analysis and determined the carbonate and organic matter (OM) content in sediments. Over the last century, the estimated 14C reservoir age in both sediment organic fractions varied from 1136 ± 112 yr to 5733 ± 122 yr. The increase in the reservoir age by 1175 ± 111 yr was related with higher inputs of pre-aged organic carbon and 14C depleted hard water due to the opening of the channel connecting two lakes. Nuclear weapons tests caused an increase in the reservoir age of up to 5421 ± 135 yr and 5733 ± 122 yr in humin and humic acids, respectively. 13C values in the humic acid fraction showed a tendency to decrease, depending on the content of autochthonous versus allochthonous OM in sediments, while changes in the sources of OM had a minor impact on the stable carbon isotope composition in the humin fraction.

scholarly journals Using Stable Carbon Isotopes to Quantify Radiocarbon Reservoir Age Offsets in the Coastal Black Sea

Radiocarbon ◽  
2018 ◽  
Vol 61 (1) ◽  
pp. 309-318 ◽  
Author(s):  
Guillaume Soulet ◽  
Liviu Giosan ◽  
Clément Flaux ◽  
Valier Galy
Keyword(s):  
Carbon Isotope ◽  
Black Sea ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Composition ◽  
The Black Sea ◽  
Stable Carbon ◽  
Stable Carbon Isotope Composition ◽  
Reservoir Age ◽  
Bivalve Shells

AbstractConstraining radiocarbon (14C) reservoir age offsets is critical to deriving accurate calendar-age chronologies from 14C dating of materials which did not draw carbon directly from the atmosphere. The application of 14C dating to such materials is severely limited in hydrologically sensitive environments like the Black Sea because of the difficulty to quantify reservoir age offsets, which can vary quickly and significantly through time, due to the dynamics of the biogeochemical cycling of carbon. Here we reconstruct 14C reservoir age offsets (Rshell-atm) of Holocene bivalve shells from the coastal Black Sea relatively to their contemporaneous atmosphere. We show that the 14C reservoir age offset and the stable carbon isotope composition of bivalve shells are linearly correlated in this region. From a biogeochemical standpoint, this suggests that inorganic stable carbon isotope and 14C compositions of Black Sea coastal waters are controlled by the balance between autochthonous primary productivity and heterotrophic respiration of allochthonous pre-aged terrestrial organic matter supplied by rivers. This provided an important implication for Black Sea geochronology as the reservoir age offset of 14C-dated bivalve shell can be inferred from its stable carbon isotope composition. Our results provide a fundamental and inexpensive geochemical tool which will considerably improve the accuracy of Holocene calendar age chronologies in the Black Sea.

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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