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ENVIRONMENTAL APPLICATIONS OF RAMAN SPECTROSCOPY TO AQUEOUS SYSTEMS
Citation:
Williams, T. L. AND T W. Collette. ENVIRONMENTAL APPLICATIONS OF RAMAN SPECTROSCOPY TO AQUEOUS SYSTEMS. Chapter 17, Lewis, I.R. and H.G.M. Edwards (ed.), Handbook of Raman Spectroscopy. Marcel Dekker Incorporated, New York, NY, , 683-731, (2001).
Impact/Purpose:
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
Description:
The aim of this chapter is to demonstrate the great potential that the Raman spectroscopic technique offers for environmental applications, particularly to aqueous systems. We demonstrate the benefits of the technique relative to other information-rich spectroscopic techniques, in light of the immense advances that have taken place in Raman instrumentation in the decade preceding this writing. Also, we provide our perspective on the current limitations of the technique and offer suggestions for potentially fruitful avenues of research and development for increasing the value of Raman spectroscopy (RS) for environmental applications.
We will demonstrate the benefits of the technique by reviewing environmental applications of RS to aqueous systems. The most recent reviews that cover this area were published in the early 1980s by Lynch and Brown [1], Gracile et al. [2], and Van Haverbeke and Brown [3]. Since that time, instrumentation for RS has undergone much development and improvement, and this is reflected in the resurgence of this technique to addressing environmental problems in aqueous systems. Our discussion and review of research in this area includes normal Raman spectroscopy (NRS), resonance Raman spectroscopy (RRS), surface-enhanced Raman spectroscopy (SERS), and the coupling of these methods to various separation techniques.
Typically, environmental analysis is categorized according to the media in which the analysis is made, namely air, water, and soil. Although the advantages of RS are perhaps most important for aqueous systems, the technique has also been widely applied to air analysis, especially in the remote analysis of pollutants, with a range of up to several kilometers. In fact, approximately 150 articles devoted to this topic have been published since 1990. Many of these studies involve Raman-based light detection and ranging (LIDAR). In particular, smoke-stack emission studies have been an area of considerable
potential for these techniques and much of the work has involved simple inorganic species (e.g., NO, S02,NO,, C02, and HS). Due to the extent of work in this area and the focus on the analysis of a limited set of simple inorganic chemical species, Raman-based LIDAR has developed into a mature field somewhat apart from the development of the general- purpose Raman spectrometer. For this reason, we have chosen -to omit the development and application of Raman-based LIDAR (and related techniques) from our literature review and focus, instead, on aqueous systems. Moreover, LIDAR and related techniques have been reviewed thoroughly in recent years (e.g., see Panne et al. [4]). However, many of our comments that follow regarding the benefits of Raman (e.g., tolerance of water and high information content) apply to ambient-air analysis as well. Also, it should be noted that we have omitted nonlinear Raman techniques from our review and discussion. Al- though some of these techniques [most notably coherent anti-Stokes Raman spectroscopy (CARS) e.g., Refs. 5-8] show promise for environmental applications, progress in this has been slow.