Performance evaluation of the Alphasense OPC-N3 and Plantower PMS5003 sensor in measuring dust events in the Salt Lake Valley, Utah

As the changing climate expands the extent of arid and semi-arid lands, the number of, severity of, and health effects associated with dust events are likely to increase. However, regulatory measurements capable of capturing dust (PMinline-formula₁₀, particulate matter smaller than 10 inline-formulaµm in diameter) are sparse, sparser than measurements of PMinline-formula_2.5 (PM smaller than 2.5 inline-formulaµm in diameter). Although low-cost sensors could supplement regulatory monitors, as numerous studies have shown for PMinline-formula_2.5 concentrations, most of these sensors are not effective at measuring PMinline-formula₁₀ despite claims by sensor manufacturers. This study focuses on the Salt Lake Valley, adjacent to the Great Salt Lake, which recently reached historic lows exposing 1865 kminline-formula² of dry lake bed. It evaluated the field performance of the Plantower PMS5003, a common low-cost PM sensor, and the Alphasense OPC-N3, a promising candidate for low-cost measurement of PMinline-formula₁₀, against a federal equivalent method (FEM, beta attenuation) and research measurements (GRIMM aerosol spectrometer model 1.109) at three different locations. During a month-long field study that included five dust events in the Salt Lake Valley with PMinline-formula₁₀ concentrations reaching 311 inline-formulaµg minline-formula⁻³, the OPC-N3 exhibited strong correlation with FEM PMinline-formula₁₀ measurements (inline-formulaR² inline-formula= 0.865, RMSE inline-formula= 12.4 inline-formulaµg minline-formula⁻³) and GRIMM (inline-formulaR² inline-formula= 0.937, RMSE inline-formula= 17.7 inline-formulaµg minline-formula⁻³). The PMS exhibited poor to moderate correlations (inline-formulaR² inline-formula< 0.49, RMSE inline-formula= 33–45 inline-formulaµg minline-formula⁻³) with reference or research monitors and severely underestimated the PMinline-formula₁₀ concentrations (slope inline-formula< 0.099) for PMinline-formula₁₀. We also evaluated a PM-ratio-based correction method to improve the estimated PMinline-formula₁₀ concentration from PMSs. After applying this method, PMS PMinline-formula₁₀ concentrations correlated reasonably well with FEM measurements (inline-formulaR² inline-formula> 0.63) and GRIMM measurements (inline-formulaR² inline-formula> 0.76), and the RMSE decreased to 15–25 inline-formulaµg minline-formula⁻³. Our results suggest that it may be possible to obtain better resolved spatial estimates of PMinline-formula₁₀ concentration using a combination of PMSs (often publicly available in communities) and measurements of PMinline-formula_2.5 and PMinline-formula₁₀, such as those provided by FEMs, research-grade instrumentation, or the OPC-N3.