Semicontinuous determination of anions, cations, and heavy metals in aerosols using PILS-IC-VA

Significance of the Topic

The chemical composition of airborne particulate matter influences respiratory health, ecosystem stability and climate processes.
High time-resolution monitoring is essential to capture transient pollution events that are not detected by traditional filter methods.

Objectives and Study Overview

This work introduces a semi-continuous system coupling Particle-Into-Liquid Sampling with dual-channel ion chromatography and voltammetry (PILS-IC-VA) to measure aerosol anions, cations and trace metals at 60-minute intervals.
Field tests were conducted in Herisau, Switzerland, where air pollution spikes were simulated by burning lead- and cadmium-coated sparklers near the sampler.

Methodology and Instrumentation

The aerosol stream (PM10) was drawn through a cyclone, then through a condensation growth chamber. Supersaturated steam induces droplet formation, and particles are collected by impaction. The liquid sample splits into two streams for ion chromatography and one for voltammetric analysis.

Used Instrumentation

• ADI 2081 Particle-Into-Liquid Sampler (PILS)
• 940 Professional IC Vario TWO/SeS/PP for anion and cation determination
• 797 VA Computrace for anodic stripping voltammetry

Key ion chromatography parameters:

• Anion separation: Metrosep A Supp 5 column at 30 °C, eluent 3.2 mmol/L Na2CO3 with 1.0 mmol/L NaHCO3, flow 0.7 mL/min, 250 μL injection
• Cation separation: Metrosep C 4 column at 30 °C, eluent 2.0 mmol/L HNO3 with 0.7 mmol/L dipicolinic acid, flow 0.9 mL/min, 250 μL injection
• PILS sample conditions: air flow 16.7 L/min, sample streams 0.23 and 1.94 mL/min

Voltammetric analysis:

• Anodic stripping voltammetry for Zn, Cd, Pb and Cu with cathodic enrichment followed by stripping in a single run

Main Results and Discussion

The system achieved a 60-minute time resolution, revealing sharp concentration spikes of nitrate, ammonium and lead during sparkler combustion. Transient increases in chloride, sulfate, sodium and potassium were also observed. Nitrite, calcium, magnesium, copper and cadmium remained below 0.3 μg/m3. Detection limits for heavy metals reached the ng/m3 range, meeting EU directive 2004/107/EG.

Benefits and Practical Applications

• Detection of short-lived pollution events missed by filter-based methods
• Simultaneous quantification of water-soluble ions and trace metals
• Unattended, long-term field deployment in remote or urban sites
• Support for research on aerosol transport, transformation and health impact studies

Future Trends and Applications

The PILS-IC-VA approach can be extended with real-time data analytics and remote access. Future developments may include coupling with mass spectrometry or optical sensors for comprehensive aerosol profiling. Widespread deployment in urban and industrial environments will enhance air quality management and source attribution.

Conclusion

The PILS-IC-VA system demonstrates robust, semi-continuous monitoring of water-soluble aerosol ions and heavy metals with high temporal resolution. Its reliable performance and compliance with regulatory limits establish it as a valuable tool for atmospheric chemistry and air quality research.

Reference

(1) Weber RJ, Orsini DA, Daun Y, Lee YN, Klotz PJ, Brechtel F. A Particle-Into-Liquid Collector for rapid measurement of aerosol bulk chemical composition. Aerosol Sci Technol. 2001;35:718-727.
(2) Emmenegger C, Jansen R, Laeubli M. Determination of anions and cations in aerosols. Pittcon 2008.
(3) Gandhi J, Jones P. Analysis of airborne particulate matter by PILC-IC. Pittcon 2010.