Investigation of Aldicarb in Ground Water in Selected Areas of the Central Sand Plain of Wisconsin     

E. R. Rothschild  R. J. Manser  M. P. Anderson 《Ground water》1982,20(4):437-445

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Small channels: Their experimental formation,nature, and significance     

A. J. Moss  Patricia Green  J. Hutka 《地球表面变化过程与地形》1982,7(5):401-415

The manner in which small channels are generated, from plane beds beneath sheet flows, has been experimentally elucidated. On plane, erodible, sand beds, the transition from thin, supercritical sheet flows to the channelled condition was studied over ranges of discharge, slope, and temperature. Secondary flow of the second kind, its action facilitated by steep vertical velocity gradients in the primary flows, caused sheet-flow instability. Along junctions between neighbouring secondary cells, both either raised or lowered elements of the primary flow. In the latter case, fast surface water was lowered to the bed, causing relatively intense, local, longitudinal scour. Dislodged grains were moved divergently to either side, leaving straight, central trenches. Development of positive feedback between cells and trenches led to rapid enlargement of the latter and concomitant growth of paired levees. The resulting structures, ‘protochannels’, were themselves ephemeral, developing two types of instability associated with secondary flow of the first kind. Firstly, small deviations from bilateral symmetry were enhanced, causing evolution into meandering channels. Secondly, headcutting led to multiple tributary development and, at resulting confluences, the action of strong pairs of secondary cells led to the development of braiding channels. Because they are shortlived, protochannels are but rarely seen in nature. Their seeding is markedly temperature-sensitive, reflecting their frictional origin. The erosive power of shallow overland flow largely depends on flow-energy concentration by secondary flow, firstly into channels, then within the channels themselves. Suppression of secondary flow, as by intense raindrop bombardment, can stabilize sheet flows. In deeper water, the effects of secondary flow appear relatively less dramatic. However, even if such motion is weak, bedload divergence from attachment lines can favour entrainment locally and thus affect bed geometry. Analogy between our results and river behaviour appears close and. on continental shelves where water must often flow as sheets, structures resembling giant protochannels evidently persist.  相似文献   

The contribution of throughflow to storm runoff: An evaluation of a chemical mixing model     

M. G. Anderson  T. P. Burt 《地球表面变化过程与地形》1982,7(6):565-574

The contribution of throughflow to storm runoff is examined using a chemical mixing model. The results predict that throughflow is an important component of storm runoff particularly during the period of stream recession. Supporting hydrological data suggests that a major throughflow input occurs coincident with the stream discharge peak. The two sets of results therefore conflict in the predicted timing of the throughflow response.  相似文献   

Southeast and Southern England. The geomorphology of the British Isles | D.K.C. Jones, 1981. Methuen,London, 332 pp.     

M.G. Anderson 《Earth》1982,18(1):79-80

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Concentration,vertical flux,and remineralization of particulate uranium in seawater     

Robert F. Anderson 《Geochimica et cosmochimica acta》1982,46(7):1293-1299

Concentrations and fluxes of particulate U were measured throughout the water column at several locations in the Atlantic and Pacific Oceans with in situ filtration systems and sediment traps. The results indicate that dissolved U is fixed to particles in surface seawater. Organic matter appears to be the carrier phase. Formation of particulate authigenic U below the surface waters could not be detected. Authigenic U is remineralized within the bathypelagic layers at the open ocean sites studied. In the Panama Basin, an upwelling area with high biological productivity, remineralization of authigenic U in the deep water column was not observed. The rate of remineralization of authigenic U in the deep sea is insufficient to produce a measurable concentration gradient between surface and deep waters within the mixing time of the oceans. Formation of authigenic U in the water column in areas such as the Panama Basin is not a significant sink for U on an ocean wide basis.  相似文献   

Petrology of a portion of the Eastern Peninsular Ranges mylonite zone,Southern California     

James R. Anderson 《Contributions to Mineralogy and Petrology》1983,84(2-3):253-271

Peraluminous and metaluminous plutonic rocks of the Peninsular Ranges batholith near Borrego Springs in southern California were mylonitized in the large shear zone known as the eastern Peninsular Ranges mylonite zone (EPRMZ). Accompanying mylonitization in this portion of the EPRMZ was metamorphism at intermediate-low-pressure amphibolite-facies conditions. Deformation in the zone overlapped in time with Cretaceous intrusion of the batholith. In the San Ysidro Mountain — Pinyon Ridge area, four north-south trending zones of differing intensity of deformation have been defined; from east to west the degree and style of deformation gradually change from undeformed or weakly deformed rocks to strongly mylonitized rocks. Electron microprobe analysis shows that recrystallized hornblende, biotite, and plagioclase are variable in composition, probably reflecting a range of metamorphic conditions accompanying deformation. Comparison of mineral compositions with those from mafic schists of Vermont suggests conditions ranged from andalusite-staurolite through sillimanite-muscovite grades as defined for pelitic rocks. Stability of muscovite+quartz in mylonite assemblages and lack of remelting of granitic rocks indicate that temperature did not exceed about 650° C during mylonitization and lithostatic pressure did not exceed about 5 kbar. Over time, any given rock volume experienced a range of temperature, lithostatic pressure, and perhaps fluid pressure and differential stress. Mineral reactions in the zone involved hydration, requiring introduction of water. The possibility of large-scale migration of K and Fe is suggested by whole-rock chemical data. Brittle and ductile deformation features are closely associated in one part of the EPRMZ. The combined evidence suggests the presence of a pore fluid with fluid pressure close to lithostatic pressure. Short periods of low fluid pressure and possible high differential stress cannot be ruled out.  相似文献   

Alteration of oceanic crust and geologic cycling of chlorine and water   总被引：1，自引：0，他引：1  

Emi Ito  David M Harris  Alfred T Anderson 《Geochimica et cosmochimica acta》1983,47(9):1613-1624

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Autoxidation of N(III), S(IV), and other Species in Frozen Solution – A Possible Pathway for Enhanced Chemical Transformation in Freezing Systems     

Eric A. Betterton  Darcy J. Anderson 《Journal of Atmospheric Chemistry》2001,40(2):171-189

The chemistry of glycolaldehyde (hydroxyacetaldehyde) relevant to the troposphere has been investigated using UV absorption spectrometry and FTIR absorption spectrometry in an environmental chamber. Quantitative UV absorption spectra have been obtained for the first time. The UV spectrum peaks at 277 nm with a maximum cross section of (5.5± 0.7)×10^–20 cm² molecule^–1. Studies of the ultraviolet photolysis of glycolaldehyde ( = 285 ± 25 nm) indicated that the overall quantum yield is > 0.5 in one bar of air, with the major products being CH₂OH and HCO radicals. Rate coefficients for the reactions of Cl atoms and OH radicals with glycolaldehyde have been determined to be (7.6± 1.5)×10^–11 and (1.1± 0.3)×10^–11 cm³ molecule^–1 s^–1, respectively, in good agreement with the only previous study. The lifetime of glycolaldehyde in the atmosphere is about 1.0 day for reaction with OH, and > 2.5 days for photolysis, although both wet and dry deposition should also be considered in future modeling studies.  相似文献   

Glacial refugium of <Emphasis Type="Italic">Pinus pumila</Emphasis> (Pall.) Regel in northeastern Siberia     

N. A. Shilo  A. V. Lozhkin  P. M. Anderson  T. A. Brown  A. Yu. Pakhomov  T. B. Solomatkina 《Doklady Earth Sciences》2007,412(1):122-124

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Paleolimnological assessment of human impacts on an urban South African lake     

F. García-Rodríguez  C. R. Anderson  J. B. Adams 《Journal of Paleolimnology》2007,38(3):297-308

North End Lake is a polluted and eutrophic freshwater system located in Port Elizabeth, South Africa. Since the lake is expected to be used for recreational/tourist purposes by 2010, a rehabilitation program will have to be designed. For this reason, we retrieved a sediment core from the central region of the lake to decipher the effect of historical human impacts on the water body. Pre-disturbance paleolimnological inferences indicate that the lake was likely mesotrophic. After ∼1831, when sheep farming activities were undertaken in the catchment, increases in trophic state and changes in sediment composition were observed. After ∼1937, increases in trace metal levels, organic matter, spheroidal carbonaceous particles (SCP) and changes in sediment composition were recorded. The system became eutrophic as indicated by the dominance of the diatom Actinocyclus normanii, a cosmopolitan species often observed in systems where water quality has been dramatically degraded. The conditions worsened after 1986 because of the construction of a storm-water retention system, which intentionally channeled storm-water runoff into the lake. Because of this, extremely high values of fecal coliforms (i.e. 2 × 10⁶ every 100 ml) have been measured in the water column. The paleolimnological information identified the sharp increase in organic content in the uppermost section of the core, and this could be correlated to the operation of the storm-water retention system. Therefore, as an immediate management measure, we suggest that the storm-water retention system should either no longer be utilized, or the storm-water runoff should be treated before disposal into the lake. In addition, an effective sewage system has to be constructed.  相似文献