A passive sampling method to determine ammonia in ambient air.

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Ecology

Background:

• European ambient ammonia concentrations have risen due to agricultural activities.
• This increase leads to critical load exceedances in sensitive oligotrophic ecosystems like forests and mires.
• Effective source-receptor relationship investigation necessitates continuous monitoring of ammonia levels.

Purpose of the Study:

• To present and evaluate the Zürcher passive sampler, a cost-efficient system for measuring ambient ammonia.
• To assess the performance of the Zürcher passive sampler in determining long-term average ammonia concentrations.

Main Methods:

• The Zürcher passive sampler, a Palmes type diffusive sampler with an acidic absorbent, was deployed.
• Testing was conducted at 46 sites across Switzerland over a one-year period.
• Performance was validated against discontinuous and continuous denuder systems.

Main Results:

• The average ambient air concentration measured was 2.5 µg m⁻³ ± 0.4 µg m⁻³.
• Blank values averaged 0.21 µg m⁻³, with a detection limit of 0.36 µg m⁻³.
• Triplicate measurements showed a mean standard deviation of 9.5%, with deviations less than 10% compared to denuder systems.

Conclusions:

• The Zürcher passive sampler is a user-friendly and economical tool for assessing long-term average ammonia concentrations.
• It is suitable for ambient air monitoring when mean concentrations exceed 1 µg m⁻³ over one- to four-week periods.