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Solar-powered air quality monitor applied under subtropical conditions in Hong Kong: Performance evaluation and application for pollution source tracking
Citation:
Wei, P., Z. Ning, D. Westerdahl, Y. Lam, P. Louie, R. Sharpe, R. Williams, AND G. Hagler. Solar-powered air quality monitor applied under subtropical conditions in Hong Kong: Performance evaluation and application for pollution source tracking. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 214:116825, (2019). https://doi.org/10.1016/j.atmosenv.2019.116825
Impact/Purpose:
This is a manuscript intended for a peer-reviewed journal, summarizing a year-long field test of a compact Village Green Project prototype that was placed on a school rooftop in Hong Kong in collaboration with local universities. This was the first test of the system outside of the United States, in an environment that was subtropical and at higher pollution levels than typically experienced in the United States. This test was important to understand the capability of the instrumentation under more challenging conditions, which represent unique episodes and geographies within the United States as well as evaluating whether the technology would be conducive to international applications. Finally, the analysis of the high time-resolution PM2.5 and wind data incorporated local scale back trajectory modeling, applied to estimate the location of nearby direct emissions.
Description:
Air monitoring is desirable in many places to understand dynamic pollution trends and sources and improve knowledge of population exposure. While highly miniaturized low cost sensor technology is quickly evolving, there is also a need for the advancement of mid-tier systems that are closer to reference-grade technologies in their longevity and performance, but also feature compactness that requires less significant infrastructure. This project evaluated the performance of a prototype solar-powered air monitoring system known as a Village Green Project (VGP) system with wireless data transmission that was deployed on a school rooftop in Hong Kong and operated for over one year. The system provided highly time-resolved and long-term data utilizing mid-tier cost ozone, PM2.5 and meteorological instruments. It operated with very minimal maintenance but shading by a nearby building reduced solar radiation, thus battery run time, over the 16-months measurement period, approximately 330,000 1-min observations were recorded (data completeness of ~62%). The monitoring data were evaluated by comparison with a nearby Hong Kong Environment Protection Department (EPD) station and exhibited good performance for 1-h resolution (R2 = 0.74 for PM2.5 and R2 = 0.76 for ozone). Furthermore as a demonstration, a nonparametric regression (NPR) model was applied for identifying the location of pollution source, combining air pollution and meteorological measurements. In addition, based on the high time-resolution wind data, local-scale back-trajectories were calculated as an input for receptor-oriented Nonparametric Trajectory Analysis (NTA) model. The combination of the VGP air monitoring system and NTA model identified apparent local sources in urban area. The demonstration was largely successful and operational improvements are clearly suggested to insure better siting and configurations to insure adequate power and air flow.
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DOI: Solar-powered air quality monitor applied under subtropical conditions in Hong Kong: Performance evaluation and application for pollution source tracking