Combined Optical and Ionization Measurement Techniques for Inexpensive Characterization of Micrometer and Submicrometer Aerosols

Abstract

This article describes a simple combination ionization chamber and angular scattering sensor and presents the results oflaboratory experiments to define its response to micrometer and submicrometer aerosols as a function of aerosol mass, surface, and diameter. The results of these experiments indicate that a simple theory is adequate to describe the operation of the sensor and presents correlations and techniques that will allow the sensor to be used for measurement and characterization of aerosols over a broad spectrum of possible applications related to ad verse environmental and health consequences. For particles with volume mean diameters in the range of ,...., 150-500 nm, the measured sensor respon ses yielded signal-to-noi se ratios in the range of ,....,25 to > 500 for mass concentrations in the range of 0.50 to 16 mg/nr', INTRODUCTIONMeasurement of micrometer (a few j1m) and submicro meter « 1.0 j1m) aerosol properties such as mass conce ntration, surface area, and diam eter are important in understandin g adverse health effects resultin g from human exposure to aerosols. Curr entl y available techniques and instrum entation necessary to conduct such measurement s are gen erally complex, expensive, and often time-consuming to perform. Such instrum ents and techniques are used routinely in developed co untries in mobile Fundi ng by the Hou sehold Energy and Health Programme of the Shell Foundatio n, UK, to deve lop a low-cost particle mon itor for use in deve lop ing co untries is gratefully acknow ledge d. Commen ts on an earlier draft by Michael Apte, Asho k Gadgil , and Edward (Ted) Ze llers are much apprecia ted.Address co rresponde nce to C harles D. Litto n, Pitt sbu rgh Research Laborator y, NIOS H, C DC, P.O . Box 1807 0, Coc hra ns Mill Rd., Pittsbu rgh , PA 15236, USA . E-mai l: chI3@cdc.gov 1054 laboratorie s and ambient-air mon itoring stations and are wellsuitedfor measurements under controlled laboratory conditions. However, their routine use in real-world environments where better measurements of human exposure rather than ambientair monitoring are needed in order to quantify adverse health effects is often difficult, if not impossible. To add to this difficulty, most applications require multiple measurements using several instruments over extended time periods. In some field measurement s, location s may be remote and electrical power unavailable, so that use of these instrum ent s is not possible. Of particul ar intere st to us in this regard are monitors for use in developin g countries to measure part icle levels in and around household s using solid fuels (bio mass and coa l). Such fuels are co mmonly used for coo king and heating, often resulting in high hum an exposure to part icles and apparen tly contributing significantly to premature mortality and illness (Smi th and Mehta 2003).As particle co ncentrations are much higher in the developing world than average levels in developed countries, the risk attributable to particl es fro m indoor and outdoo r co mbustion of solid fuels is...

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