A new protocol to detect light elements in estuarine sediments by X-ray microanalysis (SEM/EDS)

Area of Science:

• Geochemistry
• Mineralogy
• Analytical Chemistry

Background:

• Standard scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM/EDS) faces challenges in detecting light elements, such as carbon.
• Accurate identification of light elements is crucial for mineralogical and geochemical analyses.

Purpose of the Study:

• To develop and validate a novel SEM/EDS protocol for the reliable detection of calcium carbonate (CaCO3).
• To apply this protocol to analyze sediments from the Jaguaribe River estuary, NE Brazil.

Main Methods:

• Utilized handmade gold mounting discs (Au stubs) for sample support.
• Employed inexpensive glue (Loctite Super_Bonder) or direct sample disposal on Au stubs.
• Used CaCO3 and NaCl as controls, validating the method's efficiency for light element detection.

Main Results:

• The developed SEM/EDS protocol effectively detected calcium carbonate in sediment samples.
• Sediments contained diverse particle morphologies, with clay minerals and silica being predominant.
• Biological and non-biological calcium carbonates, including nanoparticles, were identified across all core depths.
• X-ray emissions from the gold stubs did not interfere with CaCO3 analysis.

Conclusions:

• The proposed SEM/EDS protocol offers an efficient method for identifying calcium carbonate in geological samples.
• This technique overcomes limitations in detecting light elements, enhancing mineralogical analysis of sediments.