Atmospheric Measurement Techniques | 2019
Understanding the ability of low-cost MOx sensors to quantify ambient VOCs
Abstract
Abstract. Volatile organic compounds (VOCs) present a unique challenge in air quality\nresearch given their importance to human and environmental health, and their\ncomplexity to monitor resulting from the number of possible sources and\nmixtures. New technologies, such as low-cost air quality sensors, have the\npotential to support existing air quality measurement methods by providing\ndata in high time and spatial resolution. These higher-resolution data could\nprovide greater insight into specific events, sources, and local variability.\nFurthermore, given the potential for differences in selectivities for\nsensors, leveraging multiple sensors in an array format may even be able to\nprovide insight into which VOCs or types of VOCs are present. During the\nFRAPPE and DISCOVER-AQ monitoring\ncampaigns, our team was able to co-locate two sensor systems, using metal\noxide (MOx) VOC sensors, with a proton-transfer-reaction quadrupole mass\nspectrometer (PTR-QMS) providing speciated VOC data. This dataset provided\nthe opportunity to explore the ability of sensors to estimate specific VOCs\nand groups of VOCs in real-world conditions, e.g., dynamic temperature and\nhumidity. Moreover, we were able to explore the impact of changing VOC\ncompositions on sensor performance as well as the difference in selectivities\nof sensors in order to consider how this could be utilized. From this\nanalysis, it seems that systems using multiple VOC sensors are able to\nprovide VOC estimates at ambient levels for specific VOCs or groups of VOCs.\nIt also seems that this performance is fairly robust in changing VOC\nmixtures, and it was confirmed that there are consistent and useful\ndifferences in selectivities between the two MOx sensors studied. While this\nstudy was fairly limited in scope, the results suggest that there is the\npotential for low-cost VOC sensors to support highly resolved ambient\nhydrocarbon measurements. The availability of this technology could enhance\nresearch and monitoring for public health and communities impacted by air\ntoxics, which in turn could support a better understanding of exposure and\nactions to reduce harmful exposure.