Description and working steps
STEP 1: NaOCl oxidation
3 g of air-dried soil sample were reacted three times with 30 mL of 6 wt% NaOCl adjusted to pH 8.0 during 6h at 25°C.
Samples were then washed twice with 30 mL 1 M NaCl and then with deionized water until the solution was chloride free (i.e. no reaction with AgNO3 occurred). Between each shaking step, the samples were centrifuged and the supernatant discarded. The samples were then dried at 60 °C and homogenized before C measurement on crushed subsamples.
STEP 2: Hydrofluoric acid (HF) hydrolysis
2.25 g of NaOCl-treated dry samples were transferred into pre-weighed centrifuge bottles, and shaken four times with 15 mL 10% HF during 2h, and then washed five times with 15 mL deionized water. Between each shaking step, the samples were centrifuged and the supernatant discarded. The samples were then dried at 60 °C and homogenized before C measurement on crushed subsamples.
Measurements and calculations:
Initial Aim
Separation of fractions according to protection mechanisms (mineral-protected and recalcitrant-C).
Advantages
Disadvantages
References
Mikutta, R., Kleber, M., Torn, M.S., Jahn, R., 2006. Stabilization of soil organic matter: association with minerals or chemical recalcitrance? Biogeochemistry 77, 25-56.