Soil carbon determination by thermogravimetrics

Area of Science:

• Soil Science
• Environmental Science
• Analytical Chemistry

Background:

• Accurate soil carbon determination is crucial for agriculture and greenhouse gas offsetting.
• Loss-on-ignition (LOI) is a common but potentially limited method for soil carbon analysis.
• Understanding LOI limitations is key for reliable soil carbon monitoring.

Purpose of the Study:

• To define and understand the limitations of the loss-on-ignition method for soil carbon determination.
• To investigate the potential of thermogravimetric analysis (TGA) for improving soil carbon quantification.
• To evaluate optimal temperature ranges for LOI to accurately measure soil organic carbon.

Main Methods:

• Thermogravimetric analysis (TGA) coupled with mass spectrometry to monitor mass changes during heating.
• Comparative analysis of LOI and TGA data to understand mass-loss patterns.
• Controlled heating experiments to identify optimal temperature ranges for soil carbon analysis.

Main Results:

• Thermogravimetric analysis revealed that LOI methods are best constrained to temperatures between 200°C and 430°C for reliable soil organic carbon determination.
• Exceeding 430°C in LOI leads to increased mass loss from inorganic sources, confounding organic carbon measurements, particularly in high-clay soils.
• Higher temperatures may release more recalcitrant organic matter, potentially associated with minerals.

Conclusions:

• The optimal temperature range for loss-on-ignition to accurately determine soil organic carbon is 200-430°C, especially in clay-rich soils.
• Thermogravimetric analysis provides valuable insights into the limitations of LOI and aids in refining soil carbon quantification methods.
• Accurate soil carbon measurement is essential for effective carbon sequestration strategies and climate change mitigation efforts.