How to determine the organic carbon content of reclaimed tideland soils containing inorganic carbon?

Reclaimed tideland (RTL) soils, which are created in the coastal area may play a sink role of atmospheric CO 2 with cultivation due to their low soil organic carbon (SOC) content.The wet oxidation method with an oxidizing reagent (e.g., K 2 Cr 2 O 7 ) and the dry combustion method using elemental analyzers are conventionally used to determine the SOC content of RTL soils.The RTL soils are characterized by the presence of inorganic carbonate and chloride (Cl -), which may potentially interfere with the SOC analysis.In this study, we explored the potential limitation of SOC determination using these methods to suggest a suitable method for the determination of SOC of RTL soils.Using wet oxidation, SOC is specifically determined by ruling out the potential interference of carbonate.However, Cl -is also oxidized to Cl 2 by consuming the oxidizing reagent, leading to an overestimation of SOC.Therefore, the removal of Cl via precipitation with Ag 2 SO 4 is required.Dry combustion is a quick and simple method for the analysis of SOC.However, not only SOC but also inorganic C is combusted to CO 2 , resulting in an overestimation of SOC.Although several methods for the removal of carbonate using acids are proposed, the procedure is time-consuming and inaccurate, and the residual acid may cause instrument failure.Most critically, acid treatment may deteriorate SOC to cause an underestimation of SOC.Given the advantages and disadvantages of the methods, we suggest that the wet oxidation after the removal of Cl -interference is the most suitable procedure for the determination of SOC for RTL soils.