Analysis of airborne particulate matter by PILS-IC

Significance of the Topic

Airborne particulate matter smaller than 2.5 μm poses significant health and environmental risks. Rapid and accurate quantification of water-soluble aerosol ions such as nitrate, sulfate and chloride is essential for air quality assessment and regulatory compliance.

Objectives and Overview of the Study

This study evaluated the performance of an automated Particle-Into-Liquid Sampler (PILS) coupled to ion chromatography (IC) against conventional filter-based manual extraction and IC analysis. The comparison covered daily measurements over a 30-day period in Teddington, UK, focusing on PM2.5 anion mass balance.

Methodology

Air was sampled through a PM2.5 cyclone followed by a carbonate-coated denuder to remove acidic gases. In the PILS-IC setup, aerosols were grown into droplets via steam condensation and collected for near-continuous IC analysis with a 19-minute cycle. Parallel manual sampling employed a Thermo Partisol®-Plus Model 2025 to collect daily 47 mm quartz filter samples, subsequently extracted and analyzed offline by IC.

Used Instrumentation

• ADI 2018 Particle-Into-Liquid Sampler (PILS) with PM2.5 cyclone and steam condensation chamber
• Carbonate-coated denuder for gas removal
• Impactor droplet collector with LiBr carrier solution
• Metrohm ion chromatography system with 100 μL injection volume and 19-minute analysis cycle
• Thermo Partisol®-Plus Model 2025 sequential air sampler with quartz filters

Main Results and Discussion

PILS-IC daily concentrations of nitrate, sulfate and chloride correlated well with the manual filter method (R values of 0.93, 0.86 and 0.87, respectively). High temporal resolution PILS-IC data captured nitrate and sulfate trends that aligned closely with water-soluble PM2.5 during pollution events, notably the May 13–16 episode. Chloride measurements showed deviations, likely due to reactive halide transformations not detected by PILS-IC.

Benefits and Practical Applications

The PILS-IC approach offers real-time or near-real-time monitoring of aerosol ionic composition, reducing labor and sample handling. Its unattended operation over extended periods enables detection of rapid concentration changes essential for environmental surveillance, source attribution and validation of air quality models.

Future Trends and Potential Applications

Expected developments include coupling PILS-IC with advanced spectroscopic or mass spectrometric detectors for expanded analyte coverage, miniaturization for mobile or distributed sensor networks, and integration with meteorological data streams. Such enhancements will improve spatial–temporal resolution of aerosol composition in urban and remote environments.

Conclusion

Automated PILS-IC provides robust, high-resolution measurements of key water-soluble aerosol ions that compare favorably with traditional filter-based methods. Its capability for continuous, unattended operation makes it an indispensable tool for modern atmospheric chemistry research and air quality monitoring.

References

1. Weber RJ, Orsini DA, Daun Y, Lee Y-N, 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. Orsini DA, Ma Y, Sullivan A, Sierau B, Baumann K, Weber RJ. Refinements to the particle-into-liquid sampler (PILS) for ground and airborne measurements of water-soluble aerosol composition. Atmos Environ. 2003;37:1243-1259.
3. Emmenegger C, Jansen R, Laeubli M. Determination of anions and cations in aerosols. Pittcon 2008; Metrohm Product Note 8.000.6014EN.