Hydrodynamic dispersion during absorption of water by soil: 1. Model soil-moisture profiles     

D.E Elrick  M.J.L Robin  K.B Laryea 《Journal of Hydrology》1983,65(4):313-331

Solute mixing during sorption of water is analysed for three model soil-water profiles: a step-function profile, an error function complement profile and a curvilinear profile.An analytical solution to the step-function profile was obtained and it was shown that the plane about which salt dispersion occurs is coincident with the plane of separation which assumes that all of the water initially present is pushed ahead by the infiltrating water. Similar results were obtained for the two other model profiles, using numerical analysis. A simplified approach for calculating these planes, based on the delta-function model, is presented for both horizontal and vertical infiltration.Proof is given that the estimate for the plane about which salt dispersion occurs should be made with λ⁰ (defined in the text) rather than with either λ′_c or λ′_θc (also defined in the text). It was also shown that the solute balance is maintained for all values of the dispersion coefficient for the flux-related boundary condition only.  相似文献   

Investigating the multiscale teleconnections of Madden–Julian oscillation and monthly rainfall using time-dependent intrinsic cross-correlation     

Johny  Kavya  Pai  Maya L.  Adarsh  S. 《Natural Hazards》2022,112(2):1795-1822

Natural Hazards - This study proposes a novel ensemble empirical mode decomposition (EEMD) time-dependent intrinsic cross-correlation (TDICC)-coupled framework to investigate the correlation...  相似文献   

Lower mantle diamonds from Rio Soriso (Juina area,Mato Grosso,Brazil)   总被引：4，自引：2，他引：2  

Patrick?C.?Hayman  Maya?G.?KopylovaEmail author  Felix?V.?Kaminsky 《Contributions to Mineralogy and Petrology》2005,149(4):430-445

The morphology, colour, fluorescence, cathodoluminescence, nitrogen content and aggregation state, internal structure and mineral inclusions have been studied for 69 alluvial diamonds from the Rio Soriso (Juina area, Mato Grosso State, Brazil). Nitrogen in most diamonds (53%) is fully aggregated as B centres, but there is also a large proportion of N-free stones (38%). A strong positive correlation between nitrogen and IR-active hydrogen concentrations is observed. The diamonds contain (in order of decreasing abundance) ferropericlase, CaSi-perovskite, magnetite, MgSi-perovskite, pyrrhotite, olivine, SiO₂, perovskite, tetragonal almandine-pyrope phase and some other minerals represented by single grains. The Rio Soriso diamond suite is subdivided into several subpopulations that originated in upper and lower mantle of ultramafic and mafic compositions, with the largest subgroup forming in the ultramafic lower mantle. Analysed ferropericlase grains are enriched in Fe (Mg#=0.43–0.89), which is ascribed to their origin in the lowermost mantle. The Juina kimberlites may be unique in sampling the material from depths below 1,700 km that ascended in a plume formed at the core–mantle boundary.Electronic Supplementary Material  Supplementary material is available for this article at

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Maya G. KopylovaEmail: Phone: +1-604-8220865Fax: +1-604-8226088

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Sequence and eruptive style of the 1783 eruption of Asama Volcano, central Japan: a case study of an andesitic explosive eruption generating fountain-fed lava flow, pumice fall, scoria flow and forming a cone     

Maya Yasui  Takehiro Koyaguchi 《Bulletin of Volcanology》2004,66(3):243-262

The 3-month long eruption of Asama volcano in 1783 produced andesitic pumice falls, pyroclastic flows, lava flows, and constructed a cone. It is divided into six episodes on the basis of waxing and waning inferred from records made during the eruption. Episodes 1 to 4 were intermittent Vulcanian or Plinian eruptions, which generated several pumice fall deposits. The frequency and intensity of the eruption increased dramatically in episode 5, which started on 2 August, and culminated in a final phase that began on the night of 4 August, lasting for 15 h. This climactic phase is further divided into two subphases. The first subphase is characterized by generation of a pumice fall, whereas the second one is characterized by abundant pyroclastic flows. Stratigraphic relationships suggest that rapid growth of a cone and the generation of lava flows occurred simultaneously with the generation of both pumice falls and pyroclastic flows. The volumes of the ejecta during the first and second subphases are 0.21 km³ (DRE) and 0.27 km³ (DRE), respectively. The proportions of the different eruptive products are lava: cone: pumice fall=84:11:5 in the first subphase and lava: cone: pyroclastic flow=42:2:56 in the second subphase. The lava flows in this eruption consist of three flow units (L1, L2, and L3) and they characteristically possess abundant broken phenocrysts, and show extensive "welding" texture. These features, as well as ghost pyroclastic textures on the surface, indicate that the lava was a fountain-fed clastogenic lava. A high discharge rate for the lava flow (up to 10⁶ kg/s) may also suggest that the lava was initially explosively ejected from the conduit. The petrology of the juvenile materials indicates binary mixing of an andesitic magma and a crystal-rich dacitic magma. The mixing ratio changed with time; the dacitic component is dominant in the pyroclasts of the first subphase of the climactic phase, while the proportion of the andesitic component increases in the pyroclasts of the second subphase. The compositions of the lava flows vary from one flow unit to another; L1 and L3 have almost identical compositions to those of pyroclasts of the first and second subphases, respectively, while L2 has an intermediate composition, suggesting that the pyroclasts of the first and second subphases were the source of the lava flows, and were partly homogenized during flow. The complex features of this eruption can be explained by rapid deposition of coarse pyroclasts near the vent and the subsequent flowage of clastogenic lavas which were accompanied by a high eruption plume generating pumice falls and/or pyroclastic flows.Editorial responsibility: T. Druitt  相似文献   

A Method for Simultaneous In Situ Measurement in the Vadose Zone of Field-Saturated Hydraulic Conductivity, Sorptivity and the Conductivity-Pressure Head Relationship   总被引：3，自引：0，他引：3  

W. Daniel Reynolds  David E. Elrick 《Ground Water Monitoring & Remediation》1986,6(1):84-95

The Guelph Permeameter (GP) method for simultaneous, in situ measurement in the vadose zone of field-saturated hydraulic conductivity (K_fS), sorptivity (S) and the conductivity-pressure head relationship [K(Ψ)] is described and discussed.
The method involves measuring the steady-state liquid recharge, Q, necessary to maintain a constant depth of water, H, in an uncased, cylindrical well of radius, a, finished above the water table. An "in-hole" Mariotte bottle device is used to maintain H and to measure Q.
Step-by-step procedures with example calculations are given for obtaining K_fS, S and K( Ψ ). Techniques for assessing the results are also given.
Although detailed field verification of the GP method is still incomplete, the studies conducted so far are quite encouraging.
Theoretical and practical advantages afforded by the GP method make it a desirable and cost-effective means for in situ measurement of K_fs, S and K( Ψ ), which are three of the most important parameters governing the flow of water and other wetting liquids in the vadose zone.  相似文献   

C-isotope stratigraphy and paleoenvironmental changes across OAE2 (mid-Cretaceous) from shallow-water platform carbonates of southern Mexico     

Maya Elrick  Roberto Molina-Garza  Robert Duncan  Laura Snow 《Earth and Planetary Science Letters》2009,277(3-4):295-306

The stratigraphic and geochemical record of the mid-Cretaceous (Cenomanian–Turonian) Oceanic Anoxic Event 2 (OAE2) has been studied in numerous Tethyan and proto-Atlantic hemi-pelagic/pelagic successions, but little data comes from nearshore carbonate successions from the proto-Pacific region. Here we present the results of a combined stratigraphic and δ¹³C study of C–T platform carbonates from southern Mexico, which were deposited within the proto-Pacific. Two scales of sedimentary cyclicity are recognized. High-frequency peritidal and subtidal cycles (0.4–8 m) display little evidence of cycle-capping subaerial exposure and are not correlative between sections; these relationships suggest that the amplitudes of high-frequency sea-level changes were minimal during the peak mid-Cretaceous greenhouse. Longer-term transgressive-regressive sequences (18–40⁺ m) are correlated between sections, and using δ¹³C trends, can be correlated with sequences developed in northern Europe and India.The Mexican successions were sampled at a high resolution (~ 10 ky) for stable isotopes (inorganic, organic carbon and oxygen), total organic carbon, insoluble residues, and trace metals. The δ¹³C_carb curve matches global trends (including 6 distinct isotopic stages) permitting identification of OAE2 despite the lack of characteristic anoxic facies. Using the δ¹³C_carb trends, we tie the previously identified ammonite, planktonic foram, and nannofossil biostratigraphy from England and the Western Interior seaway of Colorado into the Mexican sections. The initiation of OAE2, defined by an abrupt positive 3–4‰ δ¹³C shift, coincides with a long-term sea-level rise, though the sedimentary expression of the deepening is no greater than that observed for any of the other sea-level events across the studied interval. OAE2 termination (transition from gradually decreasing to background δ¹³C values) is not associated with a particular sea-level trend. Stratigraphic changes in insoluble residues (proxy for continental sediment discharge) across OAE2 are not correlative between sections and do not show consistent systematic relationships with δ¹³C or sea-level variations, therefore do not support the hypothesis that OAE2 was associated with increased continental-derived nutrient influx. Two peaks in trace metal concentrations coincide with the abrupt increase in δ¹³C ratios (onset of OAE2) and during the transition from elevated-to-decreasing δ¹³C values (near the C–T stage boundary). These trends are similar to those recorded in coeval deposits of the Western Interior seaway, and are consistent with the hypothesis that OAE2 development was related to the release of reduced metals during the short-lived (< 1 My) Caribbean oceanic plateau basalt eruption. In this scenario, oxidation of the metals depleted the existing low dissolved-O₂ concentrations and thermally-buoyant plumes of seawater enriched in biolimiting elements mixed with surface waters, stimulated primary productivity, and further reduced O₂ concentrations leading to widespread anoxia and a large positive δ¹³C shift.  相似文献   

Nutrient Recovery from Domestic Effluent using an Indigenous Strain of Scenedesmus sp.          下载免费PDF全文

Radin Maya Saphira Radin Mohamed  Adel Al‐Gheethi  Ramlah Buyong  Nor Haslina Hashim  Hazel Monica Matias‐Peralta  Amir‐Hashim Mohd‐Kassim 《洁净——土壤、空气、水》2018,46(8)

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Integrating value-chain approach with participatory multicriteria analysis for sustainable planning of a niche crop in Indian Himalayas     

Sudeshna Maya SEN  Arun KANSAL 《山地科学学报》2019,(10)

The value-chain approach(VCA)was used for exploring how a niche crop,namely large cardamom(Amomum subulatum Roxb.),can be developed sustainably to increase incomes and enhance rural livelihoods in the mountains.Large cardamom is a high-value,agro-climatically suitable,and non-perishable spice crop grown in the Himalayan region.Originating in Sikkim,the crop is important to the local economy and is sold in both domestic and international markets;however,its production in India has been declining significantly in recent years.Using VCA and participatory methods of data collection the study helped elicit value chain actors'perspectives on various reasons for the decline as well as potential strategies to improve the cardamom value chain.The results present the multiple environmental and climatic(e.g.water stress),social(e.g.women participation)and institutional(e.g.lack of trust between actors)challenges and corresponding upgrading strategies.Through participatory multi-criteria analysis(MCA),the strategies were prioritized based on the overall preferences of multiple stakeholders.The analysis considered eight criteria and 25 options,or strategies,and found that that marketability and profitability were the most important criteria,and increasing cardamom production,the most important optiontrait.Stakeholder discussions along with sensitivity analysis also showed how these options could be implemented and revealed how criteria preferences can change with expert inputs.This combination of VCA and MCA,because it supports participatory decision-making and balances multiple dimensions of sustainable development,can be effectively deployed in planning for agricultural development in the mountains.  相似文献   

Numerical Simulations of the Microscale Heterogeneities of Turbulence Observed on a Complex Site     

Hanane Zaïdi  Eric Dupont  Maya Milliez  Luc Musson-Genon  Bertrand Carissimo 《Boundary-Layer Meteorology》2013,147(2):237-259

We simulate the microscale heterogeneities of turbulent variables observed at a complex site for different wind directions. The atmospheric computational fluid dynamics (CFD) results are compared with an ensemble of 36 months of data collected at the experimental site SIRTA “Site Instrumental de Recherche par Télédétection Atmosphérique”, located near Paris (France) in a semi-urban environment. The experimental data show that the normalized turbulent kinetic energy (TKE) k/U ² (where k is TKE and U is the wind speed) at 10-m height, for two different locations, is highly dependent on wind direction and strongly influenced by trees. These measurements show a strong increase of the normalized TKE downstream of the forest canopies with a large variability within the 36-month period in part due to the variation of the tree foliage. The numerical simulations are carried out using the CFD code Code_Saturne with the standard k?ε closure, in neutral stratification. The buildings are taken into account explicitly in the mesh and the forested areas are modelled with two approaches: the classical roughness wall law and a drag porosity. A comparison has been performed between the calculated values and the median of measured values of the normalized TKE and the normalized friction velocity, for each wind sector of 10°. A very good agreement is obtained with the drag porosity model, whereas the classical roughness law leads to a strong underestimation downstream of the forested areas. However, this large improvement of the results using the drag porosity model can only be obtained with a refinement of the grid, especially in forested areas, and an accurate land-use map.  相似文献   

The Coastal Springs of Southern Kerala,SW India – Hydrology and Water Quality Assessment     

K. Maya  Prasenjit Das  K. Sreelash  K. Narendra Babu 《Journal of the Geological Society of India》2018,92(5):616-625

Spring water is a reliable source of potable water in many parts of the world. Uplifted coasts of the Southern Kerala host many high yielding cold water springs which emerge from the sand - clay interface of the Neogene outcrops. Lack of adequate studies on the hydrological and water quality aspects of these springs is challenging the wise use and management of these springs. Therefore, an attempt has been made to map the locations and study the water quality of the free-falling type of springs emerging from the Neogene outcrops exposed on the cliffed coasts of Southern Kerala, especially falling within the jurisdiction of Kollam and Thiruvananthapuram districts. A total of 31 springs from four distinct geomorphic settings has been located in our survey conducted in 2008–2009 period. But, our recent survey carried out in March 2017 revealed that about 10 % of the springs were dried out due to various reasons. The total spring water discharge during 2017 was about 450 liters/minute against the total discharge of 800 liters/minute in 2007–08 period. In general, the hydrochemistry of spring waters is dominated by alkali and strong acids, i.e. alkali-chloride type. Most of the hydrochemical parameters exhibit a great degree of seasonal and spatial variations and are well within the permissible limits (with the exception of pH) for all four groups of springs. The low mineral contents may be attributed to minimal weathering from silicate-rich rocks and insignificant leaching from soil due to infiltration from anthropogenic activities. The spring water quality in all the four groups of the study area is bacteriologically contaminated and therefore proper disinfection is required before human consumption. Most of the spring water samples are classified to be “excellent to good” for irrigation and is not expected to cause any salinity hazard.  相似文献