Quantitative Analysis of Leaching of Heavy Metals in Soil Using ICP-MS

Significance of the Topic

This study addresses the critical need for precise quantification of heavy metal leaching from contaminated soils, a major pathway for human exposure via groundwater under the Japanese Soil Contamination Countermeasures Act. Ultratrace detection capabilities are essential to ensure public health and regulatory compliance.

Objectives and Study Overview

The primary aim was to evaluate the performance of the Shimadzu ICPMS-2050 system in quantifying arsenic, boron, cadmium, chromium, lead and selenium leached from five types of soil. The work demonstrates sensitivity well below the statutory leaching limits and assesses matrix interference, reproducibility and running costs.

Methodology and Instrumentation

• Sample Selection: Five distinct soil samples (Soil A–E) representing varied contamination profiles.
• Pretreatment:
  1. Mix 10 % soil slurry with ultrapure water.
  2. Shake horizontally at ~200 rpm for 6 h.
  3. Centrifuge, then filter through 0.45 µm membrane.
  4. Acidify 40 mL filtrate with 2 mL HNO3, boil 10 min, dilute to 50 mL.
• Calibration: Seven standard levels (STD1–STD7) prepared from single‐element solutions covering 0 to 1/100 of the regulatory limits; internal standards (Be, Co, In, Tl, Ga) added automatically at 1:9 ratio.
• Instrumentation Configuration:
  Instrument: ICPMS-2050 with DC04 nebulizer, mini-torch, cyclone chamber, nickel sampling/skimmer cones, no cell gas or He/H2 modes for interference reduction.
  RF power: 1.2 kW; gas flows: plasma 9.0 L/min, auxiliary 1.1 L/min, carrier 0.85 L/min.

Key Results and Discussion

Limits of detection (3σ) ranged from 0.0002 to 0.03 µg/L and quantification limits (10σ) from 0.0006 to 0.09 µg/L, all well below soil leachate standards. Measured concentrations for all soils were under regulatory thresholds. Spike recoveries (98–105 %) confirmed minimal matrix effects. A 50-sample stability test at half-standard concentrations yielded 99–104 % reproducibility, and internal standard signals varied between 89–105 %, demonstrating robust long-term performance.

Advantages and Practical Applications

• High sensitivity enabling detection below 1 % of regulatory limits.
• Low matrix interference ensures reliable multi-sample workflows.
• Mini-torch design reduces argon consumption by ~35 %, cutting operational costs.

Future Trends and Potential Applications

As environmental regulations tighten globally, the demand for ultra-trace soil leachate analysis will grow. Future developments may include automated on-site screening, coupling with speciation tools for Cr(VI)/Cr(III) differentiation, and expanded use in remediation monitoring and water quality assessment.

Conclusion

The Shimadzu ICPMS-2050 system, featuring a mini-torch and optimized gas modes, delivers high-sensitivity, low-interference quantification of heavy metals in soil leachates. Its reproducibility and reduced gas consumption make it ideal for routine environmental and regulatory analyses.

References

1. Environment Agency Notification No. 46 “Environmental Standards for Soil Contamination”
2. Environment Notification No. 18 “Determination of Measurement Methods for Soil Elution Test”