A Mathematical View of Water Table Fluctuations in a Shallow Aquifer in Brazil          下载免费PDF全文

Dagmar C. Neto  Hung K. Chang  Martinus Th. van Genuchten 《Ground water》2016,54(1):82-91

Detailed monitoring of the groundwater table can provide important data about both short‐ and long‐term aquifer processes, including information useful for estimating recharge and facilitating groundwater modeling and remediation efforts. In this paper, we presents results of 4 years (2002 to 2005) of monitoring groundwater water levels in the Rio Claro Aquifer using observation wells drilled at the Rio Claro campus of São Paulo State University in Brazil. The data were used to follow natural periodic fluctuations in the water table, specifically those resulting from earth tides and seasonal recharge cycles. Statistical analyses included methods of time‐series analysis using Fourier analysis, cross‐correlation, and R/S analysis. Relationships could be established between rainfall and well recovery, as well as the persistence and degree of autocorrelation of the water table variations. We further used numerical solutions of the Richards equation to obtain estimates of the recharge rate and seasonable groundwater fluctuations. Seasonable soil moisture transit times through the vadose zone obtained with the numerical solution were very close to those obtained with the cross‐correlation analysis. We also employed a little‐used deep drainage boundary condition to obtain estimates of seasonable water table fluctuations, which were found to be consistent with observed transient groundwater levels during the period of study.  相似文献   

Angola seismicity     

Francisco António Pereira Neto  George Sand França  Cristobal Condori  Giuliano Sant’Anna Marotta  Cristiano Naibert Chimpliganond 《Journal of Seismology》2018,22(5):1113-1126

This work describes the development of the Angolan earthquake catalog and seismicity distribution in the Southwestern African Plate, in Angola. This region is one of the least seismically active, even for stable continental regions (SCRs) in the world. The maximum known earthquake had a magnitude of 6.0 M_s, while events with magnitudes of 4.5 have return period of about 10 years. Events with magnitude 5 and above occur with return period of about 20 years. Five seismic zones can be confirmed in Angola, within and along craton edges and in the sedimentary basins including offshore. Overall, the exposed cratonic regions tend to have more earthquakes compared to other regions such as sedimentary basins. Earthquakes tend to occur in Archaic rocks, especially inside preexisting weakness zones and in tectonic-magmatic reactivation zones of Mesozoic and Meso-Cenozoic, associated with the installation of a wide variety of intrusive rocks, strongly marked by intense tectonism. This fact can be explained by the models of preexisting weakness zones and stress concentration near intersecting structures. The Angolan passive margin is also a new region where seismic activity occurs. Although clear differences are found between different areas along the passive margin, in the middle near Porto Amboim city, seismic activity is more frequent compared with northwestern and southwestern regions.  相似文献   

Assessing drought in the drylands of northeast Brazil under regional warming exceeding 4 °C     

Marengo  Jose A.  Cunha  Ana Paula M. A.  Nobre  Carlos A.  Ribeiro Neto  Germano G.  Magalhaes  Antonio R.  Torres  Roger R.  Sampaio  Gilvan  Alexandre  Felipe  Alves  Lincoln M.  Cuartas  Luz A.  Deusdará  Karinne R. L.  Álvala  Regina C. S. 《Natural Hazards》2020,103(2):2589-2611

Natural Hazards - Historically, during periods of extreme drought, food security in the drylands of the semiarid region of Northeast Brazil (NEB) is under severe risk due to agricultural collapse....  相似文献   

Short‐term dynamics in fish assemblage structure on a sheltered sandy beach in Guanabara Bay,Southeastern Brazil     

Ruan Managna Vasconcellos  Francisco Gerson Araújo  Joaquim Neto De Sousa Santos  Márcio De Araújo Silva 《Marine Ecology》2010,31(3):506-519

Short‐term dynamics in juvenile fish assemblage structure were studied to test whether the most abundant species show temporal segregation, in order to assess whether selected environmental variables could predict species groupings, and to examine the stability of sunset–day–sunrise–night differences. Samplings were collected at 3‐h intervals over 48 h on a seasonal basis between spring 2005 and winter 2006. Fish species richness and abundance were higher in spring, and the lowest values occurred in winter. Harengula clupeola occurred mainly in spring, whereas Atherinella brasiliensis peaked in summer and autumn. On the other hand, Trachinotus carolinus, Umbrina coroides and Mugil liza were abundant in winter. Although temperature, salinity and dissolved oxygen were not found to have a strong effect on the abundance patterns of most species, they did appear to have a significant influence on assemblage groupings, according to canonical correspondence analysis and Spearman rank correlation. There is no consistency of diel usage patterns by a given species across seasons. The relative abundance differed between the time of day, which differed among the seasons; this further complicates an understanding of the dynamics of an assemblage. Studies of diel changes that pooled the sampling period as day or night can miss important changes that occur in a short time scale, such as a 3‐h period.  相似文献   

Coupled use of carbon isotopes and noble gas isotopes in the Potiguar basin (Brazil): Fluids migration and mantle influence   总被引：1，自引：0，他引：1  

Alain Prinzhofer  Eugenio Vaz Dos Santos Neto  Anne Battani 《Marine and Petroleum Geology》2010

We used the carbon isotope ratios of hydrocarbons and CO₂, and the proportions of noble gas isotopes of associated gases from several geological provinces of the Potiguar Basin (Brazil) for gas/source rock correlation, and to determine maturity, post-genetic processes (migration, leakage, biodegradation), and to assess the possible interactions between hydrocarbons and surrounding waters. Barriers of permeability at the basin scale, the amount of water interacting with the accumulated hydrocarbons, proportion of meteoric water, and contamination of the fluids by the mantle were quantified for the distinct petroleum systems defined in this basin.  相似文献   

Effect of exposure time on the bioaccumulation of Cd, Mg, Mn and Zn in Cystoseira abies-marina samples subject to shallow water hydrothermal activity in São Miguel (Azores)     

Francisco M. Wallenstein  Daniel F. Torrão  Ana I. Neto  Martin Wilkinson  & Armindo S. Rodrigues 《Marine Ecology》2009,30(S1):118-122

Shallow water hydrothermal vents can be compared to polluted places due to high concentrations of heavy metals, and are thus good models for bioaccumulation studies. The present study intended to estimate the time of exposure required for the accumulation of certain elements to stabilize in specimens of Cystoseira abies-marina , to be used as a reference in future work. Cystoseira abies-marina intertidal specimens were transplanted from Mosteiros (a non-hydrothermal and pristine site) to Ferraria (with hydrothermal activity) and left there. Transplanted samples were collected after 1, 2, 4 and 8 weeks and the concentrations of Cd, Mg, Mn and Zn were measured through flame atomic absorption spectrophotometry. Although further studies with increased periods of exposure are needed because the concentration of these elements never stabilized in the collected samples, there is strong evidence that increased time of exposure led to increased concentrations of Cd, Mg, Mn, but not Zn. These results are consistent with the assumption that C. abies-marina is bioaccumulating some of the heavy metals and can thus be a good indicator for polluted waters.  相似文献   

Occurrence and distribution of humpback whales (Megaptera novaeangliae) on the north coast of the State of Bahia, Brazil, 2000-2006     

Rossi-Santos  Marcos R.; Neto  Elitieri S.; Baracho  Clarencio G.; Cipolotti  Sergio R.; Marcovaldi  Enrico; Engel  Marcia H. 《ICES Journal of Marine Science》2008,65(4):667-673

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Modern sedimentation processes in a wave-dominated coastal embayment: Espírito Santo Bay,southeast Brazil     

Alex Cardoso Bastos  Daphnne Moraes Costa Moscon  Dannilo Carmo  José Antonio Baptista Neto  Valéria da Silva Quaresma 《Geo-Marine Letters》2015,35(1):23-36

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P–T-Fluid evolution and graphite deposition during retrograde metamorphism in Ribeira Fold Belt,SE Brazil: Oxygen fugacity,fluid inclusions and C–O–H isotopic evidence     

Telmo M. Bento dos Santos  José M.U. Munhá  Colombo C.G. Tassinari  Fernando M. Noronha  Alexandra Guedes  Paulo E. Fonseca  Coriolano Dias Neto  Armanda Dória 《Journal of South American Earth Sciences》2011,31(1):93-109

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Accretion of Grenvillian terranes to the southwestern border of the R��o de la Plata craton, western Argentina     

Ricardo Varela  Miguel A. S. Basei  Pablo D. Gonz��lez  Ana M. Sato  Maximiliano Naipauer  Mario Campos Neto  Carlos A. Cingolani  Vinicius T. Meira 《International Journal of Earth Sciences》2011,100(2-3):243-272

A comprehensive review of the geological, geochronological, and isotopic features of the Mesoproterozoic Grenvillian terranes attached to the southwest of the Río de la Plata craton in Early Paleozoic times is presented in this paper. They are grouped into the northern (sierras de Umango, Maz and del Espinal and surroundings), central (Sierra de Pie de Palo, southern Precordillera and Frontal Cordillera), and southern (San Rafael and Las Matras Blocks) segments. The Mesoproterozoic basement consists mainly of arc related, intermediate to acidic and mafic?Cultramafic rocks of 1,244?C1,027?Ma, with juvenile, Laurentian affinity. Exception to it is the Maz Group, with a protracted history and reworked character. They are affected by 846?C570?Ma, extensional magmatism in the northern and central segments, which represents the Neoproterozoic breakup of the Rodinia supercontinent. Successive passive margin sedimentation is registered in Late Neoproterozoic (~640?C580?Ma) and Cambro-Ordovician (~550?C470?Ma) times. The southern segment is noted for the younger sedimentation alone, and for showing the exclusive primary unconformable relationship between the Mesoproterozoic basement and Early Ordovician cover. The effects of Early Paleozoic Famatinian orogeny, associated with the collisions of Cuyania and Chilenia terranes, are recorded as main phase (480?C450?Ma), late phase (440?C420?Ma), and Chanic phase (400?C360?Ma). Among them, the tectonothermal climax is the Ordovician main phase, to which klippe and nappe structures typical of collisional orogens are related in the northern and central segments. Preliminary data allow us to suggest a set of paired metamorphic belts, with an outboard high-P/T belt, and an inboard Barrowian P/T belt.  相似文献