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 a succession of at least six isothermal stages of predetermined duration, the succession of the at least six isothermal stages comprising a first isothermal stage at a first temperature ranging between 80° C. and 200° C. (T0), a second isothermal stage at a second temperature ranging between 340° C. and 380° C. (T1), a third isothermal stage at a third temperature ranging between 400° C. and 440° C. (T2), a fourth isothermal stage at a fourth temperature ranging between 450° C. and 490° C. (T3), a fifth isothermal stage at a fifth temperature ranging between 500° C. and 540° C. (T4), and a sixth isothermal stage at a sixth temperature ranging between 580° C. and 650° C. (T5), the isothermal stages being connected by a thermal gradient;
• 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 a minimum temperature ranging between 150° C. and 300° C., and ending at a maximum 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 a quantity of CO2 released by the residue during the second heating sequence;
• D. quantifying at least one of an organic carbon content and a mineral carbon content of the sample by:
• 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 depends on a totality of the quantities of HC, CO and CO2 released during the first heating sequence, and on quantities of CO and CO2 released during the second heating sequence up to an intermediate temperature of the second heating sequence;
• ii. if the value of the parameter SCmin is greater than the predefined threshold value of the parameter SCmin:
• a quantity of CO2 released by thermal cracking of the organic matter of the sample during the first heating sequence above the third temperature (T2) is estimated from the quantity of CO2 released during the first heating sequence up to the third temperature (T2) of the first heating sequence, multiplied by at least a predefined factor k;
• and
• the organic carbon content and the mineral carbon content are determined according to the quantities of HC, CO and CO2 released during the first heating sequence and to the quantities of CO and CO2 released during the second heating sequence up to the intermediate temperature of the second heating sequence, and by accounting for the estimated quantity of CO2 released by thermal cracking of the organic matter of the sample during the first heating sequence above the third temperature (T2).