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1.
Modelling the impact of within-storm variability of rainfall on the loading of solutes to preferential flow pathways 总被引:1,自引:1,他引:1
Rainfall variability within a storm can have a significant impact on the amount of chemical transported by surface runoff and preferential flow. Previously, studies have evaluated only a few slowly varying rainfall patterns and related sorption capacities. We use a bounded random cascade approach to generate 50 000 realizations of realistic rainfall intensity patterns within a single storm event (96 minutes duration, mean intensity of 18.75 mm hour?1) to explore the effects on the partitioning of rainfall and linearly sorbing solutes between fast preferential flow (loading) and slow flow in the soil matrix for a silt loam and a sandy clay. Loading and infiltration are modelled by a near‐surface mixing model and Green–Ampt infiltration. The statistical properties of loading were evaluated from these simulations. For this storm the mean total of resident solute mixing from the soil to preferential flow reached a maximum for a retardation factor R ~ 5. Much smaller loadings occurred for more weakly sorbing and more strongly sorbing solutes. The variability of loading tended to decrease with increasing R. Ensemble averaged rainfall patterns were derived which related to the magnitude of loading. The patterns of rainfall generating large preferential flows did not necessarily lead to large solute loading. Early peaking, mid‐storm peaking and late peaking rainfall contributed to large solute loadings, depending upon soil and chemical properties. These patterns result from a balance between the amount of preferential flow generated and the amount of solute available when preferential flow is triggered. The results suggest that the use of R as a measure of the mobility of resident solutes depends on the flow pathway considered. In addition, characterization of flux distributions in soil with weakly sorbing, resident tracers, may underestimate the potential for rapid transport of strongly sorbing solutes subject to natural variations in rainfall. 相似文献
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Ryll M Christensen H Bisgaard M Christensen JP Hinz KH Köhler B 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2001,48(7):537-546
A total of 44 bacterial strains obtained from 49 clinically healthy ducklings of different ages originating from four different farms were identified as members of the species Riemerella anatipestifer (RA) using conventional biochemical test methods. Numerical analysis of the whole-cell fatty acid patterns of these isolates resulted in two different clusters, one of which showed a similar pattern to that of the type strain of RA. Strains having a different fatty acid methyl esters (FAME)-profile (cluster II) were designated R. anatipestifer-like (RA-like). Sequencing of 16S rRNA genes of RA-like field isolates revealed 99% identity to RA. The significance of these observations are discussed. The present findings document for the first time that RA seems to represent a normal part of the pharyngeal flora of healthy Pekin ducks. 相似文献
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Krause O Rieke GH Birkmann SM Le Floc'h E Gordon KD Egami E Bieging J Hughes JP Young ET Hinz JL Quanz SP Hines DC 《Science (New York, N.Y.)》2005,308(5728):1604-1606
Two images of Cassiopeia A obtained at 24 micrometers with the Spitzer Space Telescope over a 1-year time interval show moving structures outside the shell of the supernova remnant to a distance of more than 20 arc minutes. Individual features exhibit apparent motions of 10 to 20 arc seconds per year, independently confirmed by near-infrared observations. The observed tangential velocities are at roughly the speed of light. It is likely that the moving structures are infrared echoes, in which interstellar dust is heated by the explosion and by flares from the compact object near the center of the remnant. 相似文献
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Maćerak Anita Leovac Ivančev-Tumbas Ivana Börnick Hilmar Ilić Gordana Isakovski Marijana Kragulj Maletić Snežana 《Journal of Soils and Sediments》2019,19(2):964-972
Journal of Soils and Sediments - This study utilizes column tests to investigate the retardation of certain herbicides with different hydrophobicities (atrazine, alachlor and trifluralin) during... 相似文献