Proposal Title: Development of a Compact, High Sensitivity Sensor for In Situ Measurements of Atmospheric SO2
We propose to develop a compact, lightweight, rugged sensor for in situ measurement of atmospheric sulfur dioxide (SO2). The proposed methodology will exploit very recent advances in fiber lasers and associated technologies to make possible instrumentation that is significantly smaller, lighter, more efficient (reduced power consumption and no cooling requirements), and less expensive than is allowed by current technology.
SO2 plays an important role in the chemistry of the troposphere and stratosphere, in the biogeochemical sulfur cycle, and in the formation of atmospheric aerosols. Sulfate aerosols derived from oxidation of SO2 are a major contributor to radiative forcing of the climate system, play a critical role in cloud formation, and provide a substrate for heterogeneous reactions that regulate the abundance of ozone. In situ measurements of SO2 are required to address several outstanding questions, but no high-sensitivity, fast-response SO2 instrument currently exists. We propose to develop fiber-laser-based laser-induced fluorescence (LIF) for detection of atmospheric SO2. In this technique, a near-infrared fiber laser is frequency converted to the deep-UV spectral region, providing the tunable, narrow-bandwidth radiation required for LIF detection of SO2 (and a number of other molecules).
LIF is a highly specific spectroscopic technique and, based on the results of a pilot study, the SO2 detection limit is calculated to be<1 ppt for a 1 sec integration time, a factor of>100 higher sensitivity than was previously attainable. LIF detection of small molecules is common in the laboratory, but the complexity, size, weight, power requirements, and cost of existing UV laser systems have prevented wide application of this technique for atmospheric field measurements. The proposed approach addresses all of these issues, providing exceptional flexibility in choice of deployment platform.