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41.
《水文科学杂志》2013,58(3)
Abstract The decrease in runoff of the Merguellil basin, Tunisia recorded during the decade 1989–1998 led to the study of several time series derived from daily rainfall. It was found that variability characteristics related to daily rainfall greater than 30 mm are significantly different among successive time periods. In addition, the probability distributions of these rains, recorded at different raingauge sites, are significantly different between the period 1976–1989 and the prior and posterior observation periods. Furthermore, the surface covered by daily rains greater than 30 mm decreased between 1976 and 1989. It was also noted that the probability distributions of the surfaces covered changed significantly after 1976. The combination of human action and pluviometric variability (rainfall increase in the period 1989–1998, notably the increase in the number of days of rainfall greater than 30 mm) may explain the decrease in runoff of Merguellil Wadi. 相似文献
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43.
《水文科学杂志》2013,58(3)
Abstract Abstract Accurate estimates of water losses from mature Sitka spruce (Picea sitchensis) plantations in the UK uplands are required to assess the sustainability of water supply in the event of land-use change. Many investigations have demonstrated that afforestation increases water losses from temperate upland catchments, to up to 40% of annual site rainfall. In a 0.86 km2 upland water supply catchment in southwest Scotland, interception loss in a Sitka spruce-dominated 37-year old plantation, was 52% of annual precipitation (2912 mm), considerably higher than reported in previous studies of similar catchments. From direct measurements of rainfall, cloudwater, discharge and soil evaporation, the catchment water balance was 96–117% complete, within the limits of measurement error. The most probable explanation for the higher forest interception loss reported here is the inclusion of cloudwater measurements. 相似文献
44.
《水文科学杂志》2013,58(5)
Abstract The problem of selecting appropriate objective functions for the identification of a lumped conceptual rainfall–runoff model is investigated, focusing on the value of the model in an operational setting. A probability-distributed soil moisture model is coupled with a linear parallel routing scheme, and conditioned on rainfall–runoff observations from three catchments in the southeast of England. Using an abstraction control problem, which requires accurate simulation of the intermediate flow range, it is shown that using the traditional RMSE fit criterion, produces operationally sub-optimal predictions. This is true in the identification period, when applied to a testing period, and to proxy catchment data. Using a second case study of the Leaf River in Mississippi (USA), where the focus changes to predicting flood peaks over a specified threshold, also suggests that the relevant flood threshold should govern the objective function choice. It is concluded that, due to limitations in the structure of the employed model, it would be counter-productive to try to achieve a good all-round representation of the rainfall–runoff processes, and that a more empirical approach to identification may be preferred for specific forecasting problems. This leaves us with the question of how far hydrological realism should be sacrificed in favour of purpose-driven objective functions. 相似文献
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A. E. SCHEIDEGGER 《水文科学杂志》2013,58(1):109-114
Abstract An investigation is made of the growth of river basins based on the two current models of the structure of such basins: the cyclic model and the random-graph model. Based on the assumption that the networks grow allometrically, the structure of the network that evolves has been calculated based upon the above two models. Nature seems to favor the random-graph model. 相似文献
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用溶胶-凝胶法(sol-gel)制备了纳米荧光粉Y4Al2O9: Eu3+,用X射线粉晶衍射对其进行了物相鉴定,表明在900℃已经得到纯相的Y4Al2O9产物,并用透射电镜对其进行形貌和衍射分析,分析结果证明得到的产物为纳米粉末态晶体,产物Y4Al2O9:Eu3+粒径均匀,大致在20～50nm之间,平均粒径为30nm.并用荧光光度计对其荧光光谱进行了研究,光谱表明Eu3+在Y4Al2O9晶格中占据两种不同的位置.用λ =254nm的紫外光激发Y4Al2O9:Eu3+时,产生两条发光谱带,即由于5 D 0→7 F 1的跃迁产生在峰值λ =590nm处的橙色发光带,和5 D 0→7 F 2跃迁在峰值λ =610nm处的红色发光带. 相似文献
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A survey of soil gas radon concentrations has been carried out at three sites, in the seismic area of Armenia, from 1996 to 1999. The seismicity generates opposed behaviours at the different sites. This heterogeneity is related to the sites locations in the tectonic frame. An increase of radon concentration occurs inside the tectonic micro-blocks during local seismic activity. On the contrary, an abrupt co-seismic decrease is recorded close to the fault area. These variations can be due to ‘pore-collapse’ phenomena which expulse the pore-gas and increases Rn concentration in soil at intra-blocs sites, but also to pore-elastic deformations and microfracturing modifications in the fault area. To cite this article: K. Kharatian et al., C. R. Geoscience 334 (2002) 179–185. 相似文献
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Mercury was determined in thirty‐three international stream sediment and soil reference samples (eleven Chinese soils, GSS‐1 to GSS‐11; twelve Chinese stream sediments, GSD‐1A to GSD‐12; four Canadian stream sediments STSD‐1 to STSD‐4; South African stream sediments, SARM‐42, SARM‐46 and SARM‐47; Japanese stream sediments, JSd‐1 to JSd‐3) by direct mercury analyser. Samples were taken in 500 μl quartz boats, placed in an auto sampler and processed (drying time 60 s at 300 °C; decomposition time 120 s at 850 °C; waiting time 45 s). The instrument was calibrated in the low (0‐50 ng) and high ranges (50‐500 ng) with two reference materials GSS‐5 and GXR‐2 (USGS). Using the calibration line, reference samples were analysed for Hg. The results of the determinations agreed with the recommended values of RMs in all cases except JSd‐1. The RSD calculated for the RMs was found to be within 20%. The detection limit was 1 ng g?1. 相似文献
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Forty‐Nine Major and Trace Element Concentrations Measured in Soil Reference Materials NIST SRM 2586, 2587, 2709a, 2710a and 2711a Using ICP‐MS and Wavelength Dispersive‐XRF 
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下载免费PDF全文 Harris L. Byers Lindsay J. McHenry Timothy J. Grundl 《Geostandards and Geoanalytical Research》2016,40(3):433-445
Excellent agreement was noted in the concentration of major and trace elements in five NIST (National Institute for Science and Technology) soil reference materials (NIST SRM 2586, 2587, 2709a, 2710a and 2711a) between measurement results from wavelength dispersive‐XRF and ICP‐MS from two independent laboratories, and NIST certificate of analysis and literature data. We describe the variability in concentrations of up to forty‐nine elements (plus loss on ignition) and provide values for up to twenty‐one elements previously uncharacterised by NIST in these soil RMs. The additional characterisation provided in this investigation can be utilised to reduce the measurement bias of custom calibration routines and improve the quality of control checks developed using these NIST RMs. 相似文献
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《水文科学杂志》2013,58(4)
Abstract Because the properties of eroded soil affect the deposition phenomena and transport capacity of chemical materials by eroded particles, recent research is trying to link the grain-size distribution of the eroded sediment to that of the original soil in order to explain the enrichment of chemical content of the sediment with the respect to the parent soil. In this study, the spatial distribution of nitrogen, phosphorus and total organic carbon was firstly deduced using the measurements carried out in 47 soil samples distributed over a forested basin together with a kriging interpolation method. Then the load of each chemical was calculated at morphological unit and basin scales using the above-mentioned spatial distributions and sediment yield values calculated by the SEDD (SEdiment Delivery Distributed) model, which couples the universal soil loss equation with a spatial disaggregation criterion of sediment delivery processes. Finally, at basin scale, a new expression of the enrichment ratio of a given chemical was applied. 相似文献