Improved atmospheric sampling of hexavalent chromium

Area of Science:

• Environmental Science
• Analytical Chemistry
• Air Quality Monitoring

Background:

• Hexavalent chromium (Cr(VI)) is a toxic air pollutant linked to various health issues, including cancer and respiratory illnesses.
• Accurate measurement of ambient Cr(VI) is challenging due to potential oxidation state changes during sampling.
• Current sampling methods, like the National Air Toxics Trends Stations (NATTS) sampler, face limitations in preserving Cr(VI) integrity.

Purpose of the Study:

• To design, construct, and field-test a novel Cr(VI) sampler (Clarkson sampler) for improved ambient air sampling.
• To address the challenge of Cr(VI) reduction during sampling by controlling particle deliquescence.
• To compare the performance of the Clarkson sampler against the existing NATTS Cr(VI) sampler.

Main Methods:

• Developed the Clarkson sampler based on reducing relative humidity below the deliquescence relative humidity (DRH) of ambient particles.
• Conducted side-by-side field testing of the Clarkson and NATTS samplers in Elizabeth, NJ, during winter and summer 2012.
• Collected total suspended particles (TSP) and analyzed Cr(VI) recovery rates after 24-hour sampling intervals.

Main Results:

• The Clarkson sampler demonstrated higher average Cr(VI) recovery rates (57% summer, 72% winter) compared to the NATTS sampler (46% both seasons).
• Field testing indicated that preventing aerosol deliquescence is crucial for improving Cr(VI) sampling accuracy.
• The Clarkson sampler showed a significant improvement in preserving Cr(VI) integrity during ambient air sampling.

Conclusions:

• The Clarkson sampler offers a more effective method for accurately measuring ambient Cr(VI) concentrations.
• Controlling relative humidity to prevent particle deliquescence is a key factor in successful Cr(VI) sampling.
• This new approach enhances the reliability of air toxics monitoring data for public health protection.