Remote, Real-Time Monitor for Elemental Speciation of Air Particulates

Air particulates have been identified as sources of primary and secondary health risks. More than 5,000 air particulate monitoring stations have been established in the United States, mostly for measuring total mass and size distribution. Real-time monitoring instruments for mass and size distribution are commercially available today. The network of monitoring stations performing chemical composition measurements is smaller. Samples typically are collected on filters, which then are transported to laboratories for analysis. This particularly is true for the monitoring of heavy metal contamination, predominately performed using energy dispersive x-ray fluorescence (EDXRF) analysis in laboratories. Even with a high-power (water cooling needed), heavy, and expensive laboratory instrument, a long sampling time (typically 24 hours) is needed to achieve reasonable detection sensitivity. X-Ray Optical Systems, Inc., (XOS) proposes to develop a unique EDXRF system for real-time measurement and monitoring of elemental composition, particularly heavy metal contaminants. The use of innovative x-ray optics in the proposed system enables time-resolved measurements with significantly improved detection sensitivity, achieving such performance in a low-power, compact, and automated system. In Phase I, XOS successfully demonstrated the performance of the proposed approach by retrofitting the new x-ray optic technology into an existing particulate monitoring system. Even with the non-optimized prototype, a detection limit of 10 to 40 pg/m3 was achieved for Fe, Cu, Zn, Br, Sr, and Br with a 50 watt x-ray source and 8-hour sampling time. It was estimated that this sensitivity was more than two orders of magnitude higher than that of the conventional EDXRF method. The ultimate objective of this Phase II research project is to develop a prototype system capable of collecting samples and performing composition measurement in a continuous and automatic operating mode. XOS expects to achieve the equivalent detection limit of Phase I with 1-hour time resolution for transition elements with a 50-watt system. The system, which can be configured for PM2.5, PM10, or total suspended particulate, will be packaged as a field-deployable instrument with the size, weight, and power consumption similar to those currently deployed in U.S. Environmental Protection Agency networks. Considering the proposed technology is unique and new, the initial market may be research-oriented. This will provide the opportunity for the PM monitoring community to review the technology and recognize its benefits. Once accepted by the research community, XOS expects systems deploying the technology to be widely distributed both in the United States and internationally.