Real Time Cascade Impactor Based On Surface Acoustic Wave Delay Lines for PM10 and PM2.5 Mass Concentration Measurement.

Virginie Blondeau-Patissier,Meddy Vanotti,Lyes Djoumi

doi:10.3390/s18010255

Abstract

In this research, Surface Acoustic Wave (SAW) sensors are combined with a cascade impactor to perform real time PM10 and PM2.5 mass concentration measurements. The SAW sensors consist of 125 MHz delay lines based on Love waves propagating on an AT-cut quartz substrate. The Love waves are guided on the substrate’s surface using a silica layer. SAW sensors themselves are not capable to discriminate particles by their size, therefore, particle separation based on aerodynamic diameter is achieved using a 3 Lpm dedicated cascade impactor. The latter was designed to integrate the SAW sensors which are monitored using a phase shift measurement. The collected particles impact on the acoustic sensor’s surface inducing a gravimetric effect that modifies the acoustic wave propagation conditions. The resulted phase shift allows the measurement of the mass deposited on the sensitive zone. The novel cascade impactor with SAW sensors as particle collecting stages is exposed to different aerosols in the 0–150 μg/m3 concentration range and proved to be able to detect and differentiate particles based on their size in real time. The system’s response was compared to a commercial optical counter based on light scattering technology and was found to be in good agreement with it.

Highlights

During the last few years, environmental pollution has become a big concern
The phase measurement is performed in a differential mode, which means that each sensor contains a couple of identical Surface Acoustic Wave (SAW) delay lines: one receives the particles to measure and the other stays free of particles and works as a reference
We developed an original device for airborne particulate matter concentration monitoring

Summary

Introduction

During the last few years, environmental pollution has become a big concern. In particular, fine particulate matter (PM) often reaches dangerous levels in the atmosphere of big cities around the world. Particulate matter having an aerodynamic diameter (AED) smaller than 10 μm and 2.5 μm, respectively PM10 and PM2.5, are a major threat on human health as they can penetrate the human lungs. These particles can cause cardiovascular diseases leading to death for extreme, cases [1,2,3,4]. The current trend is going toward high reliability, low cost and low maintenance instruments allowing access to data in real time This permits the use of a large number of instruments simultaneously and to obtain large geographical coverage [5,6,7]

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