Nitrogen Speciation Monitoring at Bondville, IL

In an effort to better understand fine particle formation in the upper Midwest, the Midwest RPO is sampling gas-phase and particle-phase nitrogen species at Bondville, Illinois.  The Midwest experiences wintertime episodes of high PM2.5 and low visibility when nitrate is a large fraction of PM2.5 and the primary contributor to light extinction.  In addition, nitrogen deposition (both dry and wet) in the form of ammonium and nitrate is the highest in the country across the central part of Iowa, Illinois, Indiana, and Ohio. 

Under contract to LADCO, the Illinois State Water Survey is collecting gas- and particle-phase data on the major precursors of PM-fine:  ammonia, nitric acid, nitrous acid, sulfur dioxide, nitrate, sulfate, and ammonium.  An ion chromatograph has been specially designed for this project by Purnendu Dasgupta at Texas Tech University.  The instrument collects and analyzes gas and particle samples every 15 minutes.  Shown at left is the particle collector.  This humidified chamber 'grows' the particles by humidification and collects them in a liquid stream that then flows to the ion chromatograph .

The denuder for collecting gases is shown at left (the long rectangular object below the particle collector).  A continuous stream of eluent, added at the top of the denuder, keeps the walls of the denuder constantly wetted.  The sample air stream is passed thru the denuder with a countercurrent flow.  The gases of interest (ammonia, nitric acid, sulfur dioxide) are highly soluble and are absorbed into the liquid eluent, which is collected at the bottom of the denuder and routed to the chromatograph for concentration and analysis.

These measurements collected at Bondville with the IC, as well as some high sensitivity photolytic NO2, NOy, and denuders, will be used to support thermodynamic models of particle formation and help determine when conditions for particle formation are limited by nitric acid and ammonia. 

Some interesting early results from the particle IC data showing that PM2.5 at Bondville is generally fully neutralized during the early morning hours, but becomes slightly acidic over the course of the day.  For more details, see the draft paper from Allen Williams et al., to be presented at this summer's annual AWMA conference.

Our intrepid crew, outside the trailer at Bondville during IC installation, January 2003. 

From left to right, Rida Al Hour, TTU; Allen Williams, ISWS, Mike Caughey, ISWS, Zhining Tao, ISWS, Rahmat Ullah, TTU,Donna Kenski, LADCO

LADCO Home