Field performance evaluation of a newly developed PM₂.₅ sampler at IIT Kanpur

In order to meet the challenges of growing air pollution for a developing nation and to measure the ambient fine particles (PM₂.₅, particles having aerodynamic diameter less than 2.5 μm) on routine basis an air sampler was designed, developed and evaluated in the field. The impactor removes particles greater than 2.5 μm from the air stream via impacting them onto a vacuum grease substrate and finer particles get eventually collected on a backup filter. Various impactor nozzles with conical geometry were designed based on the published theoretical design equations. A detail parametric investigation was carried out which resulted in the optimum impactor nozzle design. For this exercise, a novel dry aerosol generator was employed in addition to the well known time-of-flight instrument, APS (Aerodynamic Particle Sizer, Model 3021, TSI Inc.). The average particle losses for the impactor nozzle as well as the sampler body were below 10% and the overall pressure drop (including a backup 47 mm filter) through the PM₂.₅ sampler was only 2 in. of H₂O. This developed PM₂.₅ sampler operates at a flow rate of 15 LPM. Field performance of this sampler was evaluated through co-located sampling with a high volume PM₂.₅ reference sampler (HVS, GEM-BLI Model 2360, Tisch Environment Instrument) within the IIT Kanpur campus. The sampling period was 10 h long and it was carried out on six different days. The entire sets of filters were analyzed gravimetrically followed by their chemical analysis for elemental and anionic analyses. The particle mass, elemental, and anionic concentrations obtained with this newly developed PM₂.₅ sampler as well as those from the reference HVS sampler showed moderate to good correlation.