Compact High-Performance Sulfur Dioxide Monitor

Sulfur dioxide (SO2) is one of the six "criteria" pollutants listed in the Clean Air Act that are regulated under the EPA National Ambient Air Quality Standards (NAAQS). SO2 is the most abundant anthropogenic sulfur compound in the troposphere, and is mainly emitted through coal and petroleum combustion, petroleum refining, and metal smelting operations. Although national ambient air quality trend for SO2 shows 90% decline over the last four decades, certain regional trends are still above the National Primary Standard (75 ppb SO2). Therefore, continuing efforts on measurement and control of sulfur dioxide emissions are needed. There are regulatory-grade SO2 monitors that meet the measurement performance requirements. However, these monitors are typically higher cost systems that are not easily portable and are typically operated in permanent air monitoring shelters. There is a need in SO2 measurement instrumentation that would support supplemental ambient monitoring needs in the United States, which may include short-term measurements at multiple locations to understand spatial variability of SO2 concentrations and exploratory monitoring to determine siting of an air monitoring shelter. For these types of applications, an accurate measurement of SO2 is still needed, however other design factors such as portability and miniaturization are desirable. Mesa Photonics proposes to develop a fast, sensitive and selective sulfur dioxide optical monitor. The compact, lightweight and low-power instrument will be designed specifically to target these primary EPA applications. Other potential markets include industrial SO2 monitoring and volcanic research. Our approach has important advantages over existing methods for continuous SO2 monitoring such as exceptional selectivity, limit of detection of 5 ppb or better, and reduced calibration requirements with the potential of self-calibrating capability. The low power draw will allow battery and solar powered operation. The objectives of the Phase I study are to demonstrate the feasibility of the proposed spectroscopic approach to sensitive and selective sulfur dioxide monitoring, evaluate the calibration requirements and outline the optical and mechanical layout of the Phase II prototype instrument. Successful completion of the Phase I project will provide the critical design information needed to build a compact standalone SO2 monitor for evaluation and testing in Phase II and commercialization in Phase III.