Development of pine needle reference materials for atmospheric mercury biomonitoring

Area of Science:

• Environmental Science
• Analytical Chemistry
• Geochemistry

Background:

• Atmospheric mercury (Hg) biomonitoring is crucial for assessing environmental contamination.
• Accurate measurement of low-concentration mercury samples is increasingly important due to decreasing background levels.
• Reference materials are essential for quality control in environmental monitoring and research.

Purpose of the Study:

• To develop and characterize two new reference materials (RMs) for biomonitoring atmospheric mercury.
• To provide reliable standards for total mercury (THg) and mercury isotope analysis in plant matrices.
• To support accurate quality control in heavy metal and mercury isotope studies.

Main Methods:

• Collection and preparation of first-year pine needles (Pinus thunbergii) from Nara and Ibaraki prefectures.
• Homogenization, sterilization, and rigorous testing for homogeneity and long-term stability of the reference materials.
• Analysis of total mercury (THg) using cold-vapor atomic absorption spectrometry.
• Mercury isotopic analysis using two-stage furnace or microwave-assisted digestion.
• Measurement of various trace element concentrations.

Main Results:

• Two certified reference materials, NIES RM No. 1001 Pine Needle I and NIES RM No. 1002 Pine Needle II, were successfully developed.
• THg concentrations were determined as 5.4 ± 0.4 ng/g for PN I and 22 ± 2 ng/g for PN II.
• Detailed mercury isotopic values (δ²⁰²Hg, Δ¹⁹⁹Hg, Δ²⁰⁰Hg, Δ²⁰¹Hg) were established for both RMs.
• Concentrations of several trace elements were also quantified.

Conclusions:

• The developed pine needle reference materials are suitable for quality control in atmospheric mercury biomonitoring.
• These RMs will aid in precise measurements of total mercury and its isotopes in foliage and similar environmental matrices.
• The availability of these RMs supports advancements in environmental mercury research and regulatory monitoring.