Field Measurement of Acid Gases and Soluble Anions in Atmospheric Particulate Matter Using a Parallel Plate Wet Denuder and an Alternating Filter-Based Automated Analysis System

Abstract

We present a new fully automated instrument for the measurement of acid gases and soluble anionic constituents of atmospheric particulate matter. The instrument operates in two independent parallel channels. In one channel, a wet denuder collects soluble acid gases; these are analyzed by anion chromatography (IC). In a second channel, a cyclone removes large particles and the aerosol stream is then processed by another wet denuder to remove potentially interfering gases. The particles are then collected by one of two glass fiber filters which are alternately sampled, washed, and dried. The washings are preconcentrated and analyzed by IC. Detection limits of low to subnanogram per cubic meter concentrations of most gaseous and particulate constituents can be readily attained. The instrument has been extensively field-tested; some field data are presented. Results of attempts to decipher the total anionic constitution of urban ambient aerosol by IC-MS analysis are also presented.

Semicontinuous PM2.5and PM10Mass and Composition Measurements in Lindon, Utah, during Winter 2007

“…Anion analysis is performed using an IonPac AG11-HC guard column and an IonPac AS11-AC column with 30-min chromatographic cycles largely following protocols described previously. 19,20 The system can collect particles down to 100-nm aerodynamic diameter with high efficiency. This technology was field tested in Philadelphia, PA, in the summer of 2001; in Tampa, FL, in the summer of 2002; and in Fresno, CA, in the winter of 2003.…”

What Have We Learned from Highly Time-Resolved Measurements during EPA’s Supersites Program and Related Studies?

“…The temporal patterns of their concentrations, available with highly time-resolved instruments, can elucidate atmospheric transport and transformation processes that are key to their dynamics. Boring et al 15 simultaneously measured nitric acid (HNO 3 ), nitrous acid (HONO), and SO 2 at the Atlanta and Houston Supersites observing HONO peaks at night 180°out of phase with HNO 3 peaks in the daytime. Genfa et al 16 further analyzed these data, observing many weekdays with double HONO peaks, but less so on weekends; the morning peak is thought to be due to direct emission from vehicles during rush hour whereas the evening peak is thought to arise from the afternoon rush plus atmospheric reaction pathways.…”

Monitoring and Source Apportionment of Fine Particulate Matter at Lindon, Utah

“…For the instrument used in this study, the air sample was first passed through a cyclone with a 50% cutpoint at 2.5 µm flowing at 5 L/min and then proceeded through a parallel plate wet denuder using 0.5 mM H 2 O 2 as the scrubber liquid; this removed soluble gases, notable SO 2 , HNO 3 , and NH 3 (Boring et al 2002). Air exiting the denuder enters the annular channel of a concentric nozzle, the center tube consists of a capillary that draws deionized water up by Venturi action.…”