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Carbon and oxygen isotope composition of organic matter and carbonates in recent lacustrine sediments

100%

Sensuła B. , Böttger T. , Pazdur A. , Piotrowska N. , Wagner R.

Geochronometria

2006

tom Vol. 25

77-94

The distribution of stable isotopes (18O and 13C) and radiocarbon in organic materials, carbonates and water samples collected from the environment of lacustrine sediments in Gościąż Lake (Central Poland) and Wigry Lake (NE Poland) were investigated. The oxygen and carbon isotopic analysis of terrestrial semi submerged and submerged plants, shells and water samples were compared with the results of the uppermost sediments from lakes. It was found that the concentration of isotopes in different components of organic and carbonate materials in lakes and their environments are reflected in isotope composition averaging of lakes sediments, whereas the isotope composition of plants and carbonate depends on biogeochemical factors. The research carried out revealed significant variations in the distribution of the stable isotopes and 14C in different elements of lacustrine ecosystem. We have analyzed mean values and variations of 14C concentration, δ18O, δ13C of plants, carbonates and the relationship between the total content of carbon and δ13C. In the case of plants, the isotope composition depends also on the physiognomy and the photosynthesis pathway. We noticed variations in δ13C and δ18O within plant tissues, variations in δ13C among whole tissue material and alphacellulose, carbon isotopic composition of photosynthetically fixed carbon and syntaxonomic dependences and then we compared the results of isotope composition of plants and carbonates in Wigry Lake and Gościąż Lake.

Distribution and origin of organic matter in the Baltic Sea sediments dated with 210Pb and 137Cs

88%

Szczepańska A. , Zaborska A. , Maciejewska A. , Kuliński K. , Pempowiak J.

Geochronometria

2012

tom Vol. 39, no. 1

1-9

Organic carbon deposited in marine sediments is an important part of the global carbon cycle. The knowledge concerning the role of shelf seas (including the Baltic Sea) in the carbon cycle has increased substantially, however organic carbon accumulation rates in the Baltic sediments still require clarification. This paper describes methods used for assessing organic carbon and nitrogen accumulation rates in six sediment cores collected in the sediment accumulation areas in the Baltic Sea. Mass sediment accumulation rates were based on 210Pb method validated by 137Cs measurements. The organic carbon accumulation rates ranged from 18 to 75 gźCźm-2źyr-1. The C/N ratios and δ13C were used to access sedimentary organic matter provenance. The C/N ratios in the investigated cores vary in the range from 7.4 to 9.6, while δ13C ranged from -24.4‰ to -26.4‰. Results of the terrestrial organic matter contribution in the sedimentary organic matter were calculated basing on δ13C using the end member approach. Large proportion (41-73%) of the sedimentary organic carbon originates on land. The obtained results indicate the Baltic Sea sediments as an important sink for organic carbon. Substantial fraction of the sedimentary load originates on land.