Accurate Measurement of Heavy Metals in Soil Using SC-LIBS

Environmental pollution is mostly a consequence of human activity. It threatens the Earth’s delicate ecosystems, which could lead to deleterious outcomes for living organisms. Environmental pollution can manifest in many forms—air, water, soil, noise, and light (1).

Spectroscopy plays a vital role in helping to address environmental pollution, specifically. Because of increased urbanization and manufacturing, the release of toxic chemicals, plastics, and heavy metals often find their way into the soil, presenting a severe risk to human health (1). Detecting and determining the amounts of heavy metalsis where atomic spectroscopy could be used to help preserve the environment. Notable heavy elements found in soil include lead, mercury, arsenic, and cadmium (2).

Read More: Energy Dispersive XRF in Soil Analysis for the Agrifood Sector

A recent study published in the Journal of Analytical Atomic Spectroscopy explored how to use atomic spectroscopy to improve accuracy when determining heavy metal contents in soil. The research team, led by Shixiang Ma from China, introduced a novel method involving laser-induced breakdown spectroscopy (LIBS) for this purpose (3).

LIBS is a powerful analytical technique used for elemental analysis of materials. It involves focusing a high-energy laser pulse onto a sample surface, which causes rapid heating and vaporization of the material, creating a microplasma or plasma plume. This plasma emits characteristic wavelengths of light as the excited atoms and ions return to lower energy states, a process known as atomic emission.

Despite its advantages, LIBS encounters challenges when analyzing soil because of matrix effects caused by variations in soil particle sizes. These effects can hinder the precision of measurements if the soil is not adequately preprocessed (3).

To tackle this issue, Ma and the team developed a novel approach integrating solid-phase conversion (SC) with LIBS (3). Using SC-LIBS contributed to the stability of measurements of heavy metals in soil. The comparative analysis with direct measurement and tableting methods revealed promising results (3).

Read More: Monitoring Soil Quality Using MIR and NIR Spectral Models: An Interview with Felipe Bachion de Santana

The study demonstrated that the relative standard deviations (RSD) for lead (Pb) and chromium (Cr) contents determined by SC-LIBS were notably lower, with reductions of 71.4% and 53.4% respectively, compared to conventional methods (3). Additionally, the root mean square errors (RMSE) for SC-LIBS were substantially reduced for both lead and chromium, further indicating enhanced accuracy (3).

One of the significant findings of the research was the improvement in detection limits. SC-LIBS achieved detection limits of 9.34 mg/kg for Pb and 3.60 mg/kg for Cr, setting a new standard for sensitivity in soil analysis techniques (3).

Ma and the team's findings suggest that SC-LIBS not only effectively mitigates matrix effects, but that it also significantly enhances the accuracy and stability of heavy metal determination in soil. This research holds promise for future environmental monitoring efforts and underscores the importance of innovative analytical techniques in safeguarding human health and the environment.

This article was written with the help of artificial intelligence and has been edited to ensure accuracy and clarity. You can read more about our policy for using AI here.

References

(1) Gaur, N.; Sharma, S.; Yadav, N. Chapter 2 - Environmental Pollution. In Garg, V. K.; Yadav, A.; Mohan, C.; Yadav, S.; Kumari, N., Eds. Advances in Green and Sustainable Chemistry: Green Chemistry Approaches to Environmental Sustainability; Elsevier: 2024; pp 23–41. DOI: 10.1016/B978-0-443-18959-3.00010-0.

(2) Yao, Z.; Li, J.; Xie, H.; Yu, C. Review on Remediation Technologies of Soil Contaminated by Heavy Metals. Procedia Environ. Sci. 2012, 16, 722–729. DOI: 10.1016/j.proenv.2012.10.099

(3) Song, C.; Lin, P.; Ma, S.; et al. Decreasing the Effect of Soil Particle Size on Heavy Metal Measurement Stability Using a Method Involving Laser-induced Breakdown Spectroscopy and Solid-phase Conversion. JAAS 2024, ASAP. DOI: 10.1039/D3JA00361B