Metal measurement in aquatic environments by passive sampling methods: Lessons learning from an in situ...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Water Quality Monitoring

Background:

• Passive sampling devices (PS) are essential for water pollutant monitoring.
• Estimating measurement uncertainties associated with PS has been historically limited.
• Understanding key parameters influencing PS metal measurements is critical for reliable data.

Purpose of the Study:

• To identify key parameters affecting passive sampling measurements of metals.
• To assess the uncertainties in time-weighted average (TWA) metal concentrations using diffusive gradient in thin films (DGT).
• To compare the performance of DGT with traditional spot sampling methods.

Main Methods:

• Conducted an in situ intercomparison study of diffusive gradient in thin films (DGT) in surface waters.
• Involved 10 participating laboratories analyzing ultra-trace metal concentrations.
• Analyzed data dispersion and identified sources of uncertainty in TWA concentration calculations.

Main Results:

• Achieved satisfactory interlaboratory uncertainties for TWA concentrations (28% to 112%) despite ultra-trace levels.
• Identified DGT handling and analytical procedures as primary sources of data dispersion.
• Demonstrated that DGT significantly lowers the limit of quantification (LOQ) compared to spot sampling.

Conclusions:

• DGT handling, including assembly and dismantling, is critical for accurate metal analysis (e.g., Cd, Cr, Zn) and requires stringent clean conditions.
• Accurate data calculation methods are essential for reliable passive sampling results.
• DGT offers a significant advantage in lowering LOQ for metal monitoring in aquatic environments.