Method for the quantification and characterization of carbon in soils

A method of characterizing and quantifying carbon present in a superficial deposit, from a sample representative of the superficial deposit, comprising:

• A. heating the sample according to a first heating sequence in an inert atmosphere, and continuously measuring a quantity of hydrocarbon compounds, a quantity of CO and a quantity of CO2 released during the first heating sequence, the first heating sequence in an inert atmosphere comprising at least one isothermal stage of predetermined duration at an initial temperature followed by a thermal gradient in order to reach a final temperature, the initial pyrolysis temperature temperature ranging between 80° C. and 200° C., the final pyrolysis temperature ranging between 600° C. and 650° C.;
• B. heating a residue of the sample from the first heating sequence according to a second heating sequence in an oxidizing atmosphere, and measuring a quantity of CO and a quantity of CO2 released during the second heating sequence, the second heating sequence in an oxidizing atmosphere starting at an initial temperature ranging between 150° C. and 300° C., and ending at a final temperature ranging between 850° C. and 1200° C., following a thermal gradient;
• C. determining a value of a parameter SCmin representative of a mineral carbon proportion in relation to total carbon of the sample, from a ratio between a quantity of CO2 released by the residue of the sample above an intermediate temperature of the second heating sequence ranging between 620° C. and 680° C., and the quantity of CO2 released by the residue during the second heating sequence;
• D. from the measurements of the quantities of HC, CO and CO2 released during the first and second heating sequences, determining parameters defined with formulas of a type:
• TOC
• =
• [
• S
• ⁢
• 2
• *
• 0
• .
• 0
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• 8
• ⁢
• 3
• ]
• +
• [
• S
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• 3
• *
• 1
• ⁢
• 2
• 4
• ⁢
• 4
• ⁢
• 0
• ]
• +
• [
• (
• S
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• 3
• ⁢
• C
• ⁢
• O
• +
• S
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• 3
• ′
• ⁢
• C
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• O
• 2
• )
• *
• 1
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• 2
• 1
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• 8
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• 0
• ]
• +
• [
• S
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• 4
• ⁢
• CO
• 2
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• 1
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• 2
• 4
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• 4
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• 0
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• +
• [
• S
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• 4
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• CO
• *
• 1
• ⁢
• 2
• 2
• ⁢
• 8
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• 0
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• Min
• ⁢
• C
• =
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• S
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• 3
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• 1
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• 2
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• 4
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• 0
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• +
• [
• S
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• 3
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• C
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• O
• 2
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• 1
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• 2
• 2
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• 8
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• 0
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• +
• [
• S
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• 5
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• 1
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• 2
• 4
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• 4
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• 0
• ]
• where S2 represents the quantity of HC released during the first heating sequence, S3 and S3′ represent the quantities of CO2 released during the first heating sequence respectively up to and above a first intermediate temperature of the first heating sequence ranging between 370° C. and 430° C., S3CO and S3′CO represent the quantities of CO released during the first heating sequence respectively up to and above a second intermediate temperature of the first heating sequence ranging between 520° C. and 580° C., S4CO2 and S4CO represent the quantities respectively of CO2 and CO released during the second heating sequence up to the intermediate temperature of the second heating sequence, and S5 represents the quantity of CO2 released during the second heating sequence above the intermediate temperature of the second heating sequence;
• E. quantifying at least one of an organic carbon content and a mineral carbon content of the sample by a determination:
• i. if the value of the parameter SCmin is less than or equal to a predefined threshold value of the parameter SCmin, the mineral carbon content is zero and the organic carbon content is equal to a sum of the parameters TOC and MinC;
• ii. if the value of the parameter SCmin is greater than the predefined threshold value of the parameter SCmin:
• the mineral carbon content Cmin is determined according to a formula:
• Cmin=MinC−kxTOC;
• and
• the organic carbon content Corg is determined according to a formula:
• Corg=TOC+kxTOC, where k is a correction factor ranging between 0.04 and 0.12.