Acid fumigation of soils to remove carbonates prior to total organic carbon or CARBON‐13 isotopic analysis

• Published in: Soil Science Society of America journal Vol. 65; no. 6; pp. 1853 - 1856
• Main Authors: Harris, David, Horwáth, William R., Kessel, Chris
• Format: Journal Article
• Language: English
• Published: Madison Soil Science Society 01-11-2001; Soil Science Society of America; American Society of Agronomy
• Subjects: Agronomy. Soil science and plant productions; Analysis; Biological and medical sciences; Carbon; Carbon 13; Carbonates; Chemical, physicochemical, biochemical and biological properties; Earth sciences; Earth, ocean, space; Exact sciences and technology; Field capacity; Fumigation; Fundamental and applied biological sciences. Psychology; Geochemistry; Isotopes; Organic carbon; Organic chemistry; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil and rock geochemistry; Soil science; Soils; Isotopic analysis; Organic carbon; Hydrogen Chlorides; Organic matter; Fumigation; Chemical method; Carbon Isotopes; Isotopic composition; Laboratory measurement; Decarbonation; Carbon content; Soil science; Chemical composition; Carbonates; Pretreatment; Acid medium; Method study; Analytical chemistry; Nuclear method; Etching reagent; Experimental study; Mineral matter; Carbon cycle; Organic chemistry; Soils; Biogeochemistry; Analysis method
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj2001.1853

The use of 13C natural abundance (δ13C) to follow C input to soil has gained widespread acceptance. However, inorganic C present in the soil as carbonates will interfere with the measurement of soil organic 13C unless removed or excluded from measurement. We report a simple and convenient HCl‐fumigation method to remove inorganic C from soil. Soil samples are weighed in Ag‐foil capsules, arranged on a microtiter plate, wetted with water to approximately field capacity, and placed in a desiccator containing a beaker with concentrated (12 M) HCl. The carbonates are released as CO2 by the acid treatment in 6 to 8 h. The soil samples are then dried at 60°C prior to isotope determination. The advantages of the HCl‐fumigation method to remove inorganic C from the soil are that: (i) no water soluble C will be lost from the soil; (ii) a large number of samples can be processed simultaneously; (iii) the removal of inorganic C is rapid and complete; and (iv) the method could also be used to determine both organic and inorganic C content in the soil. A potential disadvantage, however, is that the HCl fumigation changed the 15N natural abundance of soil N.