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Improving a Simple Pressure‐Calcimeter Method for Inorganic Carbon Analysis
Author(s) -
Fonnesbeck Brook B.,
Boettinger Janis L.,
Lawley John R.
Publication year - 2013
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2012.0381
Subject(s) - dolomite , calcite , carbonate , soil water , soil test , mineralogy , dissolution , environmental science , bottle , chemistry , analytical chemistry (journal) , soil science , materials science , chromatography , composite material , organic chemistry
Carbonates are a major component of arid soils and contribute to their chemical properties. Methods have been developed to measure calcite and dolomite, but rapid, accurate, and precise methods measuring carbonate concentrations are needed. Acid dissolution methods that dissolve carbonates and produce CO 2 can be the most rapid, including use of a pressure calcimeter. While common procedures facilitate quick analysis of inorganic carbon (IC) concentrations, problems have been encountered. We propose modifications to improve a simple pressure‐calcimeter method. Soil samples of 1, 2, or 10 g were weighed into a 125‐mL serum bottle. Water was added, acid injected through the septum, and samples allowed to react. Pressure was measured using a transducer attached to a multimeter and compared with a calibration curve. Treatments of <2 vs. <0.25 mm of soil, 2‐ vs. 6‐h reaction times, and sample sizes adjusted by effervescence test were examined. Samples from three sets of soils, (i) Upper Las Vegas Wash, NV; (ii) North American Proficiency Testing Program; and (iii) Uinta Basin, UT, were used to validate our procedure. Sample replicates were analyzed using a paired t test. A 6‐h reaction time, <0.25 mm of soil, and effervescence‐adjusted sample sizes produced the most accurate and precise results. The majority of samples had no significant differences among treatments, but longer reaction produced more IC and lower differences between replicates. Depending on the objectives, nature of the soil, and/or budget, reaction times may be reduced and <2‐mm samples can be used, but IC content and precision may be lower.