Quantification of total carbon in soil using laser-induced breakdown spectroscopy: a method to correct interference...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Geoscience

Background:

• The carbon (C) cycle in Brazilian forests is vital for climate change and soil management.
• Accurate in situ soil C measurements are needed for improved climate and soil models, especially in remote rainforest regions.
• Traditional methods of soil C analysis are costly and time-consuming due to sample collection and transport.

Purpose of the Study:

• To develop and validate a Laser-Induced Breakdown Spectroscopy (LIBS) method for in situ soil carbon quantification in Brazilian forest soils.
• To address and correct spectral interferences, specifically aluminum (Al), affecting carbon (C) emission lines in LIBS measurements.
• To assess the feasibility of using a low-resolution LIBS apparatus for rapid, on-site soil C analysis.

Main Methods:

• Investigated two Brazilian forest soils (spodosol and oxisol) rich in aluminum.
• Utilized a low-resolution LIBS apparatus to measure carbon emission line intensities at 193.03 nm and 247.86 nm.
• Developed and applied a correction method to resolve Al interference with the 193.03 nm C line, using the 247.86 nm line for model validation.

Main Results:

• Identified significant spectral interferences for both evaluated carbon lines (247.86 nm with Fe/Si, 193.03 nm with Al).
• Successfully developed a correction method to mitigate Al interference on the 193.03 nm carbon emission line.
• Achieved a strong correlation (Pearson's R=0.91) between LIBS measurements and the reference dry combustion method, validating the proposed technique.

Conclusions:

• The developed LIBS method, with the proposed correction for Al interference, is a valid and promising technique for in situ soil carbon analysis in Brazilian forests.
• This approach offers a cost-effective and rapid alternative to traditional methods, facilitating better soil C dynamics assessment for climate and land management.
• The study highlights the potential of portable LIBS for environmental monitoring in challenging field conditions.