Using Low Cost Sensors to Measure Ambient Particulate Matter Concentrations and On-Road Emissions Factors

Abstract

Abstract. Air quality is a growing public concern in both developed and developing countries, as is the public interest in having information on air pollutant concentrations within their communities. Quantifying the spatial and temporal variability of ambient fine particulate matter (PM2.5) is of particular importance due to the well-defined health impacts associated with PM2.5. This work evaluates a number of select PM sensors (Shinyei: models PPD42NS, PPD20V, PPD60PV) under a variety of ambient conditions and locations including urban background and roadside sites in Atlanta, GA, as well as a location with substantially higher ambient concentrations in Hyderabad, India. Low cost sensor measurements were compared against reference monitors at all locations. On-road emissions factors were calculated at the Atlanta site by pairing PM2.5 and separately determined black carbon (BC) and carbon dioxide (CO2) measurements. On-road emission factors can vary in different locations and over time for a number of reasons, including vehicle fleet composition and driving patterns and behaviors, and current environmental policy. Emission factors can provide valuable information to inform researchers, citizens, and policy makers. The PPD20V sensors had the highest correlation with the reference environmental beta attenuation monitor (E-BAM) with R2 values above 0.80 at the India site while at the urban background site, the PPD60PV had the highest correlation with the tapered element oscillating microbalance (TEOM) with an R2 value of 0.30. At the roadside site, only the PPD20V was used, with an R2 value against the TEOM of 0.18. Emissions factors at the roadside site were calculated as 0.39 ± 0.10 g PM2.5 per kg fuel and 0.11 ± 0.01g BC per kg fuel, which compare well with other studies and estimates based on other instruments. The results of this work show the potential usefulness of these sensors for high concentration applications in developing countries and for their use in generating emissions factors.

Evaluation of consumer monitors to measure particulate matter

“…Other researchers have also evaluated the OEM sensors used in the Foobot and AirBeam with reference to other commercial photometers. They observed similar results to us for the Foobot (Wang et al, 2015), and AirBeam (Johnson et al, 2016) results. It is not surprising to mention that the pDR-mc bias values were within (salt and ARD) or close (welding fume) to ±10% compared to the three CAMs and that r-values were 0.99 and slopes were 1 ± 0.1 (linear relationship) for all aerosols, since the pDR-mc measurements were gravimetrically adjusted, as is commonly done when using this device.…”

“…Wang et al (2015) observed less favorable agreement (R 2 = 0.89) among output from the Syhitech DSM501A with the SidePak AM510 (TSI, Shoreview, MN, USA) photometer in laboratory conditions. In an urban setting, Johnson, Bergin, Russell, and Hagler (2016) observed poor agreement (R 2 = 0.3) between output from the Shinyei PPD60PV-T2 and an EPA federal equivalent method sampler. To our knowledge, no one has evaluated the Shinyei PPD60PV-T2 for occupational settings.…”

Laboratory Comparison of Low-Cost Particulate Matter Sensors to Measure Transient Events of Pollution

“…In Nyarku et al [34] a mobile phone equipped with PM and Volatile Organic Compounds (VOC) sensors was tested against reference instruments with a range of pollutants, the PM sensor was found to have a linear response at elevated PM concentrations but not at the lower concentrations pertinent to ambient monitoring. The lower accuracy of the sensors at lower concentration has been observed by other studies [35,36]. Particle density and refractive index are assumed in the conversion of sensor signal to a mass of PM so the calibration of a sensor will only be accurate for PM of a specific density, as determined by composition and therefore the sensors must be re-calibrated for different environments [27].…”

“…The DustTrak DRX 8533 Desktop was used as a reference instrument for PM 2.5 concentration. It is an optical instrument based on 90 • light-scattering used by a number of laboratory studies [32,34,36,43,48,50]. It measures particles of diameter ≈0.1-15 µm and is calibrated both for size and particle mass using Arizona Road Dust (ISO 12103-1, A1).…”

“…The great majority of the recent studies investigating the performance of low-cost PM sensors in a laboratory environment, average concentrations over extended periods of time, for example 1 h, are measured, or pollution events which concentration then decreases slowly over several minutes or hours [41]. Other laboratory studies often tested a small number of sensors or sensors from a same manufacturer [32,34,37,[43][44][45][46], and often employed high concentrations of PM, above 100 µg/m 3 that are left to decrease through gravity or particle loss [34,36,44,[46][47][48].…”