Applications of Time-Resolved Laser Fluorescence Spectroscopy to the Environmental Biogeochemistry of Actinides.

Time-resolved laser fluorescence spectroscopy ( TRLFS) is a useful means of identifying certain actinide species resulting from various biogeochemical processes. In general, TRLFS diff erentiates chemical species of a fl uorescent metal ion through analysis of diff erent excitation and emission spectra and decay lifetimes. Although this spectroscopic technique has largely been applied to the analysis of actinide and lanthanide ions having fl uorescence decay lifetimes on the order of microseconds, such as UO(2)(2+), Cm(3+), and Eu(3+), continuing development of ultra-fast and cryogenic TRLFS systems off ers the possibility to obtain speciation information on metal ions having room-temperature fl uorescence decay lifetimes on the order of nanoseconds to picoseconds. Th e main advantage of TRLFS over other advanced spectroscopic techniques is the ability to determine in situ metal speciation at environmentally relevant micromolar to picomolar concentrations. In the context of environmental biogeochemistry, TRLFS has principally been applied to studies of ( i) metal speciation in aqueous and solid phases and ( ii) the coordination environment of metal ions sorbed to mineral and bacterial surfaces. In this review, the principles of TRLFS are described, and the literature reporting the application of this methodology to the speciation of actinides in systems of biogeochemical interest is assessed. Signifi cant developments in TRLFS methodology and advanced data analysis are highlighted, and we outline how these developments have the potential to further our mechanistic understanding of actinide biogeochemistry. © American Society of Agronom