RESUMO
Because of its small volume, simple structure, low energy consumption, low working temperature, strong ability of sample dissociation/excitation and other significant characteristics, the dielectric barrier discharge is especially suitable for the miniaturization and portable analytical instruments. By now, atomizer or excitation source based on dielectric barrier discharge has applied in atomic absorption spectrometer, atomic fluorescence spectrometer and atomic emission spectrometer successfully, which promoted the development of miniaturization atomic spectrum instrument. This paper reviews DBD's recent progress in atomic spectrum field, emphatically introduces the applications of the DBD-AFS system in different sampling modes and analyses, along with their respective merits and demerits. This paper also introduces the new applications of DBD in vapor generation and direct solid sampling. Due to the DBD's reaction mechanism is still unclear; the study of its subsequent development may be restricted.
RESUMO
The UV-B radiation on the surface of our planet has been enhanced due to gradual thinning of ozone layer. The change of solar spectrum UV-B radiation will cause damage to all kinds of terrestrial plants at certain degree. In this paper, taking breeding sorghum (Sorghum bicolor (L.Moench))variety Longza No.5 as sample, 40 µW·cm-2 UV-B radiation treatment was conducted on sorghum seedlings at two-leaf and one-heart stage and different time courses; then after a 2 d recovering, photosynthetic parameters were measured with a photosynthetic apparatus; the activities of antioxidant enzymes were detected as well. Our results revealed that, as the dosages of UV-B increasing, leaf browning injury was aggravated, plants dwarfing and significantly were reduced fresh weight and dry weight were observed; anthocyanin content was significantly increased; chlorophyll and carotenoid content significantly were reduced and net photosynthetic rate and chlorophyll fluorescence parameters were decreased. Meanwhile, with the increase in UV-B dosages, stomatal conductance, intercellular CO2 concentration and transpiration rate showed "down - up - down" trend; the activities of SOD and GR presented "down - up" changes; activities of POD and CAT demonstrated "down - up - down", and APX, GPX showed an "up - down - up" pattern. It is worth to note that, under the four-dose treatment, a sharp decline in net photosynthesis in sorghum seedlings was observed at 6 h UV-B treatment (equals to 2.4 J·m-2), and an obvious turning point was also found for other photosynthetic parameters and activities of antioxidant enzymes at the same time point. In summary, the results indicated that the enhanced UV-B radiation directly accounted for the damages in photosynthesis system including photosynthetic pigment content, net photosynthetic rate and chlorophyll fluorescence parameters of sorghum; the antioxidant system showed different responses to UV-B radiation below or above 6 h treatment: ASA-GSH cycle was more sensitive to low-dose UV-B radiation, while high-dose UV-B radiation not only undermined the photosynthesis system, but also triggered plant enzymatic and non-enzymatic antioxidant systems, resulting in leaf browning and necrosis,biomass accumulation reduction, plant dwarfing and even death.