Development and Laboratory Performance Evaluation of a Variable Configuration PM1/PM2.5 Impaction-Based Sampler

ABSTRACT

This study presents the design and lab evaluation of a compact medium flow multiple round nozzle-based inertial impactor with variable head for collecting particulate matter (PM). The impactor operates at a flow rate of 175 LPM and consists of two different sets of circular acceleration nozzles designed for PM_2.5 (particle aerodynamic diameter < 2.5 µm) and PM₁ (particle aerodynamic diameter < 1 µm), either of them could be used at a time as per the objective of sampling. High vacuum grade silicone grease is used as an impaction substrate. Lab experiments were performed using a poly-disperse dolomite powder as test aerosol. The nozzle configurations selected were such that the first one provides a 50% cutpoint at 2.50 µm (aerodynamic diameter) with a pressure drop of 0.35 kPa while the second one produces a 50% cutpoint at 1.06 µm (aerodynamic diameter) with a pressure drop of 1.07 kPa. Particle losses through the nozzles were low for particle diameter upto 5.0 µm. Particle bounce-off and re-entrainment losses were found to be insignificant. Owing to its higher flow rate, it has an advantage of collecting appreciable quantity of particles (and higher number of samples) in a relatively smaller time frame as compared to other low flow rate samplers. The samples can be analyzed to obtain finely time-resolved aerosol composition which can help in a better understanding of the role of various physico-chemical processes active during different meteorological conditions (extreme dust and foggy events) that affect fate and transport of PM, especially in the Indo-Gangetic plain (IGP).