Diurnal and seasonal variations of UV radiation on the northern edge of the Qinghai-Tibetan Plateau

We monitored UVA, UVB, and solar radiation from August 2001 to 2003 on the northern Qinghai-Tibetan Plateau to characterize the diurnal and seasonal variations of UV radiation on the world's highest plateau. Daily UVB radiation and the ratio of UVB to total solar radiation increased significantly when the atmospheric ozone concentration decreased as estimated by the total ozone mapping spectrometer (TOMS), as well as when cloud coverage decreased. The UVB/UVA ratio also showed a significant increase when the TOMS ozone concentration decreased in the morning. The seasonal variation pattern of UVB, however, was closely correlated with solar elevation but was little affected by the seasonal pattern of the atmospheric ozone amount. Compared to observations from the central plateau, the magnitude of the UVB increase attributed to ozone depletion was smaller at the northern edge. The study suggests that the temporal variation of ground UV radiation is determined by both solar elevation and the ozone amount, but the spatial difference on the plateau is likely to be ascribed mainly to the spatial variation of the ozone amount. (c) 2007 Published by Elsevier B.V.

Identification of phenolics and nucleoside derivatives in Gastrodia elata by HPLC-UV-MS

An HPLC-UV-MS method for simultaneous identification of predominant phenolics and minor nucleoside derivatives in Gastrodia elata was developed, which was based on their UV and MS characteristics summarized through a series of homemade reference standard experiments. Phenolics showed characteristic UV lambda(max) at 267 nm, [M + NH4](+) base peak in positive mode and [M - H](-) base peak in negative mode while nucleosides exhibited UV lambda(max) at 255 nm, [M + H](+), [M - H + 2H(2)O](-) or [M - H + CH3COOH](-). Phenolics conjugates mainly underwent the consecutive loss of gastrodin residue (- 268 U) and the combined loss of H2O and CO2 from the citric acid unit under negative MS/MS conditions whereas nucleosides simply lost the ribose (- 132 U) under positive MS/MS conditions. According to these characteristics, a special pattern under MS/MS conditions and reported compound data for G. elata in the literature, not only 15 phenolics were identified but also 6 nucleoside derivatives were identified. Among these compounds, seven phenolics and three nucleoside derivatives have not been reported yet from G. elata.

Photosynthesis of Saussurea superba and Gentiana straminea is not reduced after long-term enhancement of UV-B radiation

Experiments were conducted in an alpine Kobresia humilis meadow near Haibei Alpine Meadow Ecosystem Research Station (37degrees29'-37degrees45'N, 101degrees12'-101degrees33'E; altitude 3200 m). Effects of enhanced ultraviolet-B (UV-B) radiation on photosynthesis of the alpine plants of Saussurea superba and Gentiana straminea were investigated. Both species were exposed to a UV-B-BE density at 15.80 kJ m(-2) per day, simulating nearly 14% ozone (O-3) reduction during the plant growing season. Neither photosynthetic CO2 uptake rate nor photosynthetic O-2 evolution rate were decreased after a long period of enhanced UV-B radiation treatment. On the contrary, there was a tendency to increase of both parameters in both species. The photosynthetic pigments were also increased, when expressed on a leaf area basis. UV-B absorbing compounds, detected by the absorbance values at 300 mm, had a tendency to increase in both species after enhanced UV-B radiation. After long-term exposure of plants to enhanced UV-B radiation, leaf morphology was also affected. Leaf thickness in both S. superba and G. straminea were increased significantly (P < 0.001). This supports our hypothesis that the increase of leaf thickness in both species after long-term exposure of enhanced UV-B radiation could compensate for the photodestruction of photosynthetic pigments when light passes through the leaf. Therefore, photosynthesis is not reduced in either species when expressed on leaf area basis. (C) 2003 Elsevier B.V. All rights reserved.

Characterization of iron atoms in the framework of MFI-type zeolites by UV resonance Raman spectroscopy

Silicalite-I, ZSM-5, and Fe-ZSM-5 zeolites prepared from two different silicon sources are characterized by UV resonance Raman (UVRR) spectroscopy, X-ray diffraction (XRD), electron spin resonance (ESR), and UV/visible diffuse reflectance spectroscopy (UV/Vis DRS). A new technique for investigating zeolitic structure, UV resonance Raman spectroscopy selectively enhances the Raman bands associated with framework iron atoms incorporated into MFI-type zeolites, and it is very sensitive in identifying the iron atoms in the framework of zeolites, while other techniques such as XRD, ESR, and UV/Vis DRS have failed in uncovering trace amounts of iron atoms in the framework of zeolites. (C) 2000 Academic Press.