Technical noteMeasurement of particle sulfate from micro-aethalometer filters

- Particle sulfate is measured from micro-aethalometer filters.
- The AE51 sulfate agrees reasonably with the filterpack results.
- Quantifying personal exposures to both sulfate and BC using AE 51 is available.

The micro-aethalometer (AE51) was designed for high time resolution black carbon (BC) measurements and the process collects particles on a filter inside the instrument. Here we examine the potential for saving these filters for subsequent sulfate (SO42−) measurement. For this purpose, a series lab and field blanks were analyzed to characterize blank levels and variability and then collocated 24-h aerosol sampling was conducted in Beijing with the AE51 and a dual-channel filterpack sampler that collects fine particles (PM2.5). AE51 filters and the filters from the filterpacks sampled for 24 h were extracted with ultrapure water and then analyzed by Ion Chromatography (IC) to determine integrated SO42− concentration. Blank corrections were essential and the estimated detection limit for 24 h AE51 sampling of SO42− was estimated to be 1.4 μg/m3. The SO42− measured from the AE51 based upon blank corrections using batch-average field blank SO42− values was found to be in reasonable agreement with the filterpack results (R2 > 0.87, slope = 1.02) indicating that it is possible to determine both BC and SO42− concentrations using the AE51 in Beijing. This result suggests that future comparison of the relative health impacts of BC and SO42− could be possible when the AE51 is used for personal exposure measurement.