Total Mercury in Soils

Importance of the Topic

This application note describes a reliable approach for determining total mercury concentration in soil samples. Monitoring mercury levels in soils is critical due to the element’s toxicity, persistence, and potential to bioaccumulate. Accurate quantification supports environmental risk assessments, remediation efforts, and regulatory compliance.

Study Objectives and Overview

The main goals of the study are to establish a straightforward calibration and analysis procedure for soil matrices using thermal decomposition atomic absorption spectrometry, to validate the method with standard reference materials, and to demonstrate reproducibility across a range of mercury concentrations found in soils.

Methodology and Instrumentation

Samples are weighed into nickel boats and analyzed directly by thermal decomposition at controlled temperature and time intervals, eliminating chemical digestion. The protocol includes:

• Blank determination to purge residual mercury.
• Calibration using certified reference materials covering the target dynamic range.
• Automated sample loading and analysis sequence.
• Quality control by re-analysis of calibration checks.

Used Instrumentation

• LECO AMA254 Mercury Analyzer.
• Small nickel boats (pre-baked at 400 °C).
• Temperature program: drying 60 s, decomposition 200 s, cuvette clear 45 s.
• Auto-select cell configuration and peak area quantification via Quicksilver Windows software (version 2.0).

Key Results and Discussion

Validation with NIST 2709 Soil Reference yielded an average mercury content of 1.44 ppm (RSD 1.4%). Analysis of two unknown soils produced average values of 0.22 ppm (RSD 1.96%) and 7.00 ppm (RSD 3.7%). The method demonstrated:

• High precision across low to moderate mercury levels.
• No significant interference from soil matrix components due to direct thermal decomposition.
• Minimal sample preparation reducing risk of contamination.

Benefits and Practical Applications

The described method offers rapid, accurate mercury determination without wet chemistry, increasing laboratory throughput and safety. It is suitable for environmental monitoring, site characterization, and routine quality control in industries handling contaminated soils.

Future Trends and Potential Applications

Advances may include integration with autosamplers to further boost productivity, expansion of calibration libraries for diverse soil types, and coupling with speciation techniques to distinguish inorganic and organic mercury forms. Emerging portable analyzers could enable on-site screening in real time.

Conclusion

The LECO AMA254 method for total mercury in soils is efficient, precise, and user-friendly. It minimizes sample handling and delivers reproducible results across a broad concentration range, making it a valuable tool for environmental laboratories.

Reference

LECO Corporation. Total Mercury in Soils: Application Note, Form No. 203-821-112, Rev 4, 2010.