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391.
《国际泥沙研究》2020,35(3):287-294
The Suquia River,the largest urban river in Cordoba(Argentina),has been severely polluted for decades.Actions must be taken to restore its environmental quality by managing riparian zones for increased water-self purification.The current study aimed to characterize organic matter(OM) dynamics and humic substances(HS) spectrochemical properties along the lower-middle basin of the Suquia River.Riparian soil(0-20 cm) and sediment(0-10 cm) samples were collected from a reference location(S1)and four polluted sites(S2-S5) during a low-flow period.The contents of soil and sedimentary OM and HS fractions were analyzed by wet oxidation,as well as HS Fourier transform infrared(FT-IR) and ultraviolet-visible(UV-Vis) spectrochemical properties.The OM and HS fractions from riparian soil were high upstream of Cordoba City(S1 and S2,50.2-50.4 g/kg OM) and within a 50 km downstream location(S5,30.9 g/kg OM) owing to a surplus of fresh plant biomass-carbon(C) inputs.Highly heterogeneous sediment samples did not show any significant differences among sites(P 0.05).The lowest values of the ratio of absorbances at 465 and 665 nm(E4/E6)(1.78) and the Δ log K(0.15) coefficient(a measure of HS maturity degree) were obtained downstream of Cordoba City,for both riparian soil and sediment,indicating that HS were enriched by more condensed aromatic structures within highly degraded portions of the river.All samples exhibited similar IR spectra,implying overlapping recalcitrant-C structures at the functional group level,but with different absorbance intensity.Data from the current study constitute a baseline for understanding the chemical nature of HS from sediment and riparian soil along the Suquia River and can be used as a reference for future studies tracking OM compositional changes over time. 相似文献
392.
In this review, we consider the problem of the apparent redshifts of the UV lines in the transition region and review the basic observations made over the last decades, especially the observations of the last few years from satellite observatories. Moreover, we revise the most popular theoretical explanations for the motions in the transition region. This review is a contribution to the understanding of the physical processes in this important layer of the solar atmosphere and it points out the pending problems. 相似文献
393.
394.
A. Richter M. Eisinger A. Ladstätter-weißenmayer J.P. Burrows 《Journal of Atmospheric Chemistry》1999,32(1):83-99
Zenith sky observations of BrO over Bremen (53°N) are reported for the period of September 1994 to January 1996. BrO differential slant columns between 90° and 80° solar zenith angle showed a strong seasonal variation between a winter maximum of 1.9·1014 molec/cm2 and a summer minimum of 0.6·1014 molec/cm2. The seasonal variation in BrO twilight values is shown to be inversely correlated with NO2 columns in agreement with current knowledge of gas phase chemistry of bromine. In contrast to model predictions, no significant difference between morning and evening BrO measurements was observed. During a 6 day polar vortex excursion to mid-latitudes OClO could be measured above Bremen indicating chlorine activation in the vortex air. No significant increase in BrO differential slant columns was detected during this time. 相似文献
395.
H. K. Roscoe P. V. Johnston M. Van Roozendael A. Richter A. Sarkissian J. Roscoe K. E. Preston J-C. Lambert C. Hermans W. DeCuyper S. Dzienus T. Winterrath J. Burrows F. Goutail J-P. Pommereau E. D'Almeida J. Hottier C. Coureul R. Didier I. Pundt L. M. Bartlett C. T. McElroy J. E. Kerr A. Elokhov G. Giovanelli F. Ravegnani M. Premuda I. Kostadinov F. Erle T. Wagner K. Pfeilsticker M. Kenntner L. C. Marquard M. Gil O. Puentedura M. Yela D. W. Arlander B. A. Kastad Hoiskar C. W. Tellefsen K. Karlsen Tornkvist B. Heese R. L. Jones S. R. Aliwell R. A. Freshwater 《Journal of Atmospheric Chemistry》1999,32(2):281-314
In June 1996, 16 UV-visible sensors from 11 institutes measured spectra of the zenith sky for more than 10 days. Spectra were analysed in real-time to determine slant column amounts of O3 and NO2. Spectra of Hg lamps and lasers were measured, and the amount of NO2 in a cell was determined by each spectrometer. Some spectra were re-analysed after obvious errors were found. Slant columns were compared in two ways: by examining regression analyses against comparison instruments over the whole range of solar zenith angles; and by taking fractional differences from a comparison instrument at solar zenith angles between 85° and 91°. Regression identified which pairs of instruments were most consistent, and so which could be used as universal comparison instruments. For O3, regression slopes for the whole campaign agreed within 5% for most instruments despite the use of different cross-sections and wavelength intervals, whereas similar agreement was only achieved for NO2 when the same cross-sections and wavelength intervals were used and only one half-day's data was analysed. Mean fractional differences in NO2 from a comparison instrument fall within ±7% (1-sigma) for most instruments, with standard deviations of the mean differences averaging 4.5%. Mean differences in O3 fall within ±2.5% (1- sigma) for most instruments, with standard deviations of the mean differences averaging 2%. Measurements of NO2 in the cell had similar agreement to measurements of NO2 in the atmosphere, but for some instruments measurements with cell and atmosphere relative to a comparison instrument disagreed by more than the error bars. 相似文献
396.
397.
398.
Peter J. Valbracht Thomas Staudacher Alex Malahoff Claude J. Allgre 《Earth and Planetary Science Letters》1997,150(3-4):399-411
We report new noble gas fusion and crushing data for six pillow rim glasses, recovered between 3 and 5 km water depth on the south rift zone of Loihi Seamount, Hawaii. Helium abundances of the glasses vary from 0.3 to 2.3 μcc/g, with 4He/3He ratios between 30000 and 27000 (24–27 RA), similar to previously reported values. The neon data form a correlation line which is similar to the Loihi-Kilauea line reported by Honda et al. [1], but extends to much higher ratios, up to 12.9 and 0.0382 for the 20Ne/22Ne and 21Ne/22Ne ratios, respectively. This provides conclusive evidence for the suggestion that the Hawaiian plume, thought to originate in the lower mantle, has a solar-like 20Ne/22Ne composition [1], but a slightly higher 21Ne/22Ne ratio. 40Ar/36Ar ratios of the deep rift-zone glasses are as high as 2600, and show a positive correlation with neon isotopic ratios. In contrast to neon and argon, all xenon isotopic compositions are isotopically indistinguishable from air, which either suggests preferential atmospheric contamination of xenon, or could indicate an atmospheric xenon isotopic composition for the lower mantle. 相似文献
399.
Helium and neon isotopes in the Imnaha Basalt, Columbia River Basalt Group: Evidence for a Yellowstone plume source 总被引:3,自引:0,他引:3
Allen Dodson B. Mack Kennedy Donald J. DePaolo 《Earth and Planetary Science Letters》1997,150(3-4):443-451
Helium, neon, and argon isotopic compositions were measured in two flows of the Columbia River flood basalt. The Imnaha Basalt has a 3He/4He ratio of 11.4 times atmospheric and 20Ne/22Ne and 21Ne/22Ne ratios characteristic of a plume component. The measured 3He/4He is a lower limit, due to possible preferential 3He loss and/or addition of radiogenic 4He. A Wanapum Basalt flow, erupted approximately 2 Ma later in the waning stages of volcanism, has more MORB-like noble gases. The He, Nd and Sr isotopic compositions of these lavas suggest that the Columbia River basalts were derived from the Yellowstone plume head which contained both ‘high-helium’ plume material and entrained depleted mantle. As the eruptions progressed the plume component in the melting region was gradually diluted or replaced. 相似文献
400.
多波长线性回归--紫外分光光度法测定壳聚糖的脱乙酰度 总被引:1,自引:0,他引:1
以不同浓度的N-乙酰基-D-葡萄糖胺溶液在波长200,201,202,203nm处的吸光度值对波长作图得到线性关系良好的1组直线,其斜率与对应溶液的浓度成正比,线性范围为0.002 5~0.040 0mg/mL,回归方程为κ=-2.252 c-0.002 7,相关系数r=0.999 95(n=6).不同批号壳聚糖样品测定结果的相对标准偏差0.20%~0.52% (n=5),回收率在100.2%~101.6%之间.本法解决了单波长紫外分光光度法中共存物吸收干扰问题,并简化了紫外一阶导数法中导数值的求法.实验结果表明,该法测定壳聚糖的脱乙酰度准确度高,重现性好,试样无须特殊处理,适用于可溶性壳聚糖脱乙酰度的测定. 相似文献