³⁶Cl, a new tool to assess soil carbon dynamics

Area of Science:

• Environmental Science
• Geochemistry
• Radiochemistry

Background:

• Soil organic carbon (SOC) is crucial for mitigating anthropogenic CO₂ emissions.
• Accurate assessment of SOC age is vital for understanding sequestration potential.
• Current methods like carbon-14 (¹⁴C) and carbon-13 (¹³C) show inconsistencies in estimating SOC age.

Purpose of the Study:

• To introduce and validate cosmogenic chlorine-36 (³⁶Cl) as an independent method for determining SOC age.
• To quantify ³⁶Cl retention fraction and duration in soils.
• To compare ³⁶Cl-derived estimates with existing modeling and isotopic approaches.

Main Methods:

• Utilizing the cosmogenic chlorine nuclide, ³⁶Cl, as a tracer for soil organic matter.
• Quantifying the fraction and duration of ³⁶Cl retained in soil organic matter.
• Analyzing ³⁶Cl retention time in relation to soil depth.

Main Results:

• ³⁶Cl retention time increases with soil depth, ranging from 20 to 322 years.
• These retention times align with estimates from modeling and ¹³C approaches.
• ³⁶Cl appears to provide more consistent SOC age estimations compared to ¹⁴C.

Conclusions:

• ³⁶Cl retention duration serves as a reliable proxy for soil organic carbon age.
• This method offers a promising, independent approach to assess soil carbon sequestration potential.
• ³⁶Cl can help refine climate change mitigation strategies by improving SOC stock estimations.