Mid-infrared spectroscopy tracing of channel erosion in highly erosive catchments on the Chinese Loess Plateau.

Whether channel erosion or topsoil erosion constitutes the dominant erosion process throughout in the hilly region of the Chinese Loess Plateau (CLP), which suffers perhaps the most severe soil erosion in the world, had been controversial for a long time. The present article attempts to use the mid-infrared (MIR) spectroscopy fingerprinting method to trace sediment sources within nine small catchments in the hilly region of the CLP. Two major categories of sediment sources are identified: channel sediment and topsoil. Sediments trapped by check dams are used as the final sediment transferred by soil erosion. Discriminant analysis shows that MIR spectroscopy can differentiate between the two kinds of source sediments very well. The contributions of channel sediment and topsoil to the total final sediment are quantified using partial least squares regression (PLSR) analyses of MIR spectra to compare the trapped sediment samples with experimental models. The results of the root mean square error of calibration, root mean square error of validation and coefficient of determination for 18 models all show that the MIR-PLSR models boast very high prediction abilities in the nine catchments. A comparison between the geochemical fingerprinting method and the MIR spectroscopy method in one catchment reveals that although the two methods agree well on the channel sediment contributions, the two methods produce a significant difference (R2 = 0.4). Overall, the MIR-PLSR results show that channel sediments contribute 19% to 66% of the total sediment with an average of 33 ±â€¯16% in the nine small catchments. Our results indicate that although channel bank sediment is important, topsoil erosion is the predominant process in small dam-controlled catchments on the CLP. Furthermore, the MIR spectroscopy fingerprinting method can provide a useful, non-destructive, rapid and inexpensive tool for tracing sediment sources from different kinds of loess.

Effects of tobacco smoking on human ocular smooth pursuit.

OBJECTIVE: Test the hypothesis that nicotine-induced nystagmus results in reduced ocular smooth performance and pupil diameter in tobacco smokers. METHODS: Twenty nonsmokers (age range, 20 to 45 years; mean age +/- SE, 31.5 +/- 1.7 years) and 14 smokers (age range, 17 to 50 years; mean age +/- SE, 30.6 +/- 2.6 years) were studied after a minimum of 2 hours of tobacco abstinence. Subjects were studied before and immediately after they inhaled air through a sham cigarette or after they smoked one of their preferred brand of cigarettes, respectively. RESULTS: A very small, consistent, and statistically significant increase in smooth pursuit was found with both eyes to a 15 degrees per second moving target after one tobacco cigarette was smoked. This was due to improvement in left and not right eye smooth pursuit. The nonsmokers had no significant change in 15 degrees per second pursuit after sham smoking. Nonsmokers and smokers did not differ in left eye 6 degrees per second smooth pursuit before or after sham or tobacco smoking. The changes in right eye 6 degrees per second smooth pursuit were inconsistent and differed at various times between the two groups. During the smooth pursuit task the pupil diameter of the nonsmokers increased, but there was no change in the tobacco smokers. Black subjects had smaller baseline pupils than white subjects, unrelated to smoking status. CONCLUSIONS: Contrary to the hypothesis, tobacco smokers had a very small but significant improvement in left eye pursuit but no change in pupil diameter. Race-related differences in baseline pupil diameter were similar in both nonsmokers and smokers.