The influence of sample drying procedures on mercury concentrations analyzed in soils

Area of Science:

• Environmental Science
• Analytical Chemistry
• Geochemistry

Background:

• Standard soil sample preparation methods may compromise mercury (Hg) analysis.
• Volatile Hg species can be lost during drying at elevated temperatures.
• Accurate Hg measurement is crucial for environmental monitoring and risk assessment.

Purpose of the Study:

• To evaluate the impact of different drying methods on mercury (Hg) concentrations in soil.
• To compare Hg loss in natural soils versus reference materials.
• To highlight the importance of sample preparation for reliable Hg analysis.

Main Methods:

• Tested freeze-drying, air-drying (25°C), and oven-drying (105°C) on two Hg-contaminated soils and three standard reference materials.
• Quantified Hg concentrations using a validated analytical method.
• Compared Hg concentrations across different drying treatments.

Main Results:

• Air-drying caused a 24% decrease and oven-drying a 3% decrease in Hg concentrations in contaminated soils compared to freeze-drying.
• Oven-drying at 105°C resulted in 5%-8% Hg loss from reference materials.
• Differences in Hg loss between natural soils and sterilized materials suggest microbiological activity influences results.

Conclusions:

• High-temperature drying methods (air and oven) lead to significant mercury (Hg) loss in soil samples.
• Freeze-drying is the preferred method for preserving Hg integrity in soil samples for accurate analysis.
• Microbiological activity in natural soils plays a role in mercury (Hg) retention during sample preparation.