Determination of organic and inorganic carbon, δ13C,and nitrogen in soils containing carbonates after acid fumigation with HCl |
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Authors: | Lorenz Walthert Ursula Graf Adrian Kammer Jörg Luster Daniele Pezzotta Stephan Zimmermann Frank Hagedorn |
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Affiliation: | Swiss Federal Institute for Forest, Snow, and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland |
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Abstract: | In carbonate‐containing soils a reliable determination of organic C requires a method that effectively separates organic and inorganic C without altering the organic matter. This study was conducted to determine whether HCl vapor completely removes carbonates even in dolomite‐rich soils and to what extent a widely used acid‐fumigation method has to be modified for humus‐rich soils. Furthermore, it was tested whether HCl fumigation alters organic‐C content. Since C and N parameters are often analyzed simultaneously we also tested the influence of acid‐vapor treatment on N content and on δ13C of soil organic matter. We applied fumigation with 37% HCl for 8 and 32 h using 9 carbonate‐containing soil samples. Inorganic C ranged from 7 to 124 and organic C from 9 to 267 g kg–1. The maximum contents of dolomite and calcite were 940 and 640 g kg–1, respectively. A time of 8 h was enough to completely remove all carbonates. Neither the content nor the δ13C of organic C were significantly affected by fumigation. In contrast, N contents were altered by acid treatment. Based on these results and on our experience in analyzing more than 1000 soil samples, a recommended procedure for acid fumigation of carbonate‐containing soils with a wide range of organic‐ and inorganic‐C contents was derived. Samples pretreated in this way can be analyzed reliably for their organic‐C content and δ13C. Furthermore, N and inorganic‐C contents can be determined with a quality sufficient for many purposes. |
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Keywords: | carbonate removal acid treatment dolomite soil organic matter dry combustion forest soils |
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