TiO 2 nanofibers that are loaded with 1 wt % Pt metal that is introduced at different stages of the wet impregnation procedure have very different photocatalytic activities. Two photocatalysts prepared using different procedures were denoted as PtHTN and PtB catalysts. The former was prepared by impregnating hydrogen trititanate nanofibers (H 2 Ti 3 O 7 , abbreviated as HTN) directly with H 2 PtCl 6 , before calcining between 573 and 873 K and then reducing at 423 K in flowing hydrogen. The latter was prepared by initially calcining HTN nanofiber between 573 and 873 K to yield TiO 2 nanofiber, and then impregnating this TiO 2 support with H 2 PtCl 6 ; the support was then calcined and reduced as PtHTN to produce PtB catalysts. Although most of their physical properties such as surface area, pore volume, crystalline phase composition and crystallinity, capability to absorb UV light, and band gap energy are quite similar, the optimized H 2 yield over PtB catalyst in the photocatalytic dehydrogenation of neat ethanol was 1.86 times that over PtHTN catalyst. XPS and subambient temperature temperature-programmed reduction indicated that the stronger photocatalytic activity of PtB was associated with its higher surface Pt concentration and better reducibility and electron conductivity. The specific Pt impregnation order generated in the PtHTN catalyst a strong interaction between the Pt nanoparticles and the TiO 2 nanofiber surface that was not present in the PtB catalyst. This interaction was revealed by the particular microstructure at the Pt-nanofiber interface, as observed by HRTEM, which was responsible for the marked difference between the electronic properties and the photocatalytic activities of the two catalysts.

The formulation of watershed management strategies to protect water resources threatened by soil erosion and sedimentation requires a thorough understanding of sediment sources and factors that drive soil movement in the watershed. This paper describes a study of medium-term water-driven soil erosion rates in a mountainous watershed of the Shihmen Reservoir in Taiwan. A total of 60 sampling sites were selected along a hillslope. At each sampling site, the inventory 137 Cs activity was determined and then calculated with the diffusion and migration model to derive soil erosion rates. The rates are one to two orders of magnitude lower than estimates using the Universal Soil Loss Equation, a soil erosion model often used in Taiwan. Results of multiple regression analysis indicate that the spatial variability of soil erosion rates is associated with the relative position of a sampling site to the nearest ridge and soil bulk densities (r 2 = 0.33, p \ 0.01). Finally, the patterns of soil redistribution rates on the hillslope follow the 137 Cs hillslope model as soil erosion increases in the downslope direction. No deposition site is found at footslope because soil deposition is swept away by regular flooding along the stream channel. This study is an important first step in using 137 Cs as a tracer of soil redistribution in mountainous watersheds of Taiwan.

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