LED-Based Photoacoustic Particle Optical Absorption Monitor

Measuring the radiative forcing of aerosols is currently the focus of the Department of Energy Atmospheric Sciences Program. Aerosol particles affect the radiative balance of the earth directly, by scattering and absorbing solar and terrestrial radiation, and indirectly, by acting as cloud condensation nuclei. It is now recognized that the atmospheric loading of aerosols generated through human activities can exert an influence on the earths radiation budget comparable in magnitude with greenhouse gases. Measurement of particle optical absorption at present requires comparatively expensive instrumentation which limits its level of use. We propose the development of a particle optical absorption monitor that employs a photoacoustic spectrometer based on a 3-wavelength (RGB) LED module rather than solid state lasers. The result is a far more robust, less power hungry, lighter and far less expensive instrument than any currently available. Furthermore, the range of wavelength is only limited by the availability of reasonably powerful LEDs, which now range from the near ultraviolet to the near-IR regions of the spectrum. Commercial Applications and Other Benefits: Successful development and marketing of this monitor will yield a significant level of direct commercial sales from the atmospheric sciences and environmental pollution research and development communities. The comparatively low cost and ease of use of this sensor will allow almost routine measurement of the absorption properties of atmospheric aerosols, something precluded by the cost and complexity of current instrumentation.