Groundwater problems in a semiarid area (Low Andarax river,Almeria, Spain)   总被引：1，自引：0，他引：1  

A. Pulido Bosch  F. Sanchez Martos  J. L. Martinez Vidal  F. Navarrete 《Environmental Geology》1992,20(3):195-204

The three aquifer units differentiated in the Low Andarax—detritic, carbonated, and deep aquifers—present problems in water quality. This is made worse during the course of development as a result of the appearance of processes of marine intrusion, dissolution of saline rocks present in the stratigraphic series, overexploitation with considerable increase in the boron content, and the continual recycling of water with a resulting increase in total dissolved solids. All this has resulted in the salinization of the majority of the underlying soils that has led to the abandoning of many cultivated areas—especially areas of citrus growth—and/or the substitution of a farming system that is much more tolerant of the salts.  相似文献   

Ground-Water Age Distribution in Madrid Basin, Spain   总被引：1，自引：0，他引：1  

M. Ramon Llamas  Eugene S. Simpson  Pedro E. Martinez Alfaro 《Ground water》1982,20(6):688-695

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A Re-assessment of Narragansett Bay Benthic Habitat Quality Between 1988 and 2008     

Emily?J.?ShumcheniaEmail author  Marisa?L.?Guarinello  John?W.?King 《Estuaries and Coasts》2016,39(5):1463-1477

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A frequency analysis of the p-mode pulsations of the Ap SrEu(Cr) star HD 119027     

Peter Martinez  C. Koen  & D. J. Sullivan 《Monthly notices of the Royal Astronomical Society》1998,300(1):188-192

We present new high-speed, multisite photometric observations of the rapidly oscillating Ap star HD 119027 acquired over seven nights during 1996. A frequency analysis of these observations reveals the presence of oscillations at 1835, 1875, 1888, 1913, 1940, 1942 and (possibly) 1953 μHz. These frequencies are consistent with a spacing of either 13 or 26 μHz, depending on the reality of the oscillations at 1875 and 1953 μHz. The data in hand do not permit us to discriminate between the two possible spacings. If the smaller value of the spacing is correct, it suggests that HD 119027 is outside the main-sequence band. Two of the frequencies listed above are separated by only 1.95 μHz, suggesting that they are modes of ( n ,ℓ) and ( n  − 1, ℓ + 2), which in roAp stars is a quantity governed by the internal magnetic field.  相似文献   

Discovery of 30-min oscillations in the Ap Sr(EuCr) star HD 75425     

Peter Martinez  R. Medupe 《Astrophysics and Space Science》1998,259(1):57-65

The Ap Sr(CrEu) star HD 75425 is shown to be pulsating with a 30- min period. This is unusually short for a δ Scuti star and about double the period of any known roAp star. The star is shown to be constant at the level of 0.35 mmag in the normal frequency regime of roAp pulsation (900≤ν≤ 2500 μHz). The pulsations in HD 75425 are modulated in amplitude, but the frequencies causing this modulation cannot be identified with the data in hand. HD 75425 is a very close visual double with an insecure Ap classification which needs to be reexamined. If the Ap classification of HD 75425 is correct, and the pulsations can be linked to the peculiar star, then this δ Scuti-like variability is of considerable interest. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Application of Lead Isotopic Ratios in Atmospheric Pollution Studies in the Valley of Mexico     

T. Martinez  J. Lartigue  F. Juarez  P. Avila-Perez  G. Zarazua  C. Marquez  M. P. Orta  V. Alvarez 《Journal of Atmospheric Chemistry》2004,49(1-3):415-424

Lead isotopic studies of airborne particulate matter, gasoline and other environmental samples have been carried out to determine possible sources of lead pollution in the Metropolitan Zone of the Valley of Mexico. ²⁰⁶Pb/²⁰⁷Pb ratio in gasoline was 1.1395 ± 0.0165 and 1.071 ± 0.008 for industrially-derived lead as a mean. Natural lead is more radiogenic with values from 1.2082 ± 0.022 to 1.211 ± 0.108. The measured Pb isotopic signature of airborne particulate matter reflects the relative importance of each of these sources. The ²⁰⁶Pb/²⁰⁷Pb ratio was 1.179 ± 0.105 as a mean. The relative importance of gasoline has decreased, and, therefore, other sources (natural and industrial) can be identified by means of isotopic studies. This is a consequence of the introduction of unleaded gasoline as mandaped by strictest environmental regulation.  相似文献   

Backarc spreading,rifting, and microplate rotation,between transform faults in the Manus Basin   总被引：2，自引：0，他引：2  

Fernando Martinez  Brian Taylor 《Marine Geophysical Researches》1996,18(2-4):203-224

The Manus Basin in the eastern Bismarck Sea is a fastopening backarc basin behind the New Britain arc-trench system. Within the basin, motion between the Pacific and Bismarck plates about a pole located at 11° S, 145° E, occurs along three major leftlateral transform faults and a variety of extensional segments. We interpret SeaMARC II sidescan and other geophysical data to show that a Brunhes age plate reorganization created new extensional boundaries and a microplate between the NW-trending Willaumez, Djaul, and Weitin transforms. Two linked spreading segments formed in backarc basin crust between the Willaumez and Djaul transforms: the ESE-trending extensional transform zone (ETZ) in the west and the Manus spreading center (MSC) in the east. Positively magnetized crust on the MSC forms a wedge varying in width from 72 km at its southwest end to zero at its northeast tip, with corresponding Brunhes spreading rates varying from 92 mm/yr to zero. The MSC forms the northwestern boundary of the 100 km-scale Manus microplate and opens at 51°/m.y. about a pole near its apex at 3°02S, 150°32E. Opposite the MSC, bordering the arc margin of New Britain, the microplate is bound by a zone of broadly distributed strike slip motion, extension, and volcanism. Within this area, the Southern Rifts contain a series of grabens partially floored by lava flows. Left-lateral motion between the Pacific and Bismarck plates appears to drive the counterclockwise pivoting motion of the Manus microplate and the complementary wedge-like opening of the MSC and the Southern Rifts. The pivoting motion of the microplate has resulted in compressional areas along its NE and SW boundaries with the Pacific and Bismarck plates respectively. East of the microplate, between the Djaul and Weitin transforms and within the arc margin of New Ireland, another zone of broad extension referred to as the Southeast Rifts takes up opening in a pull-apart basin. There, en echelon volcanic ridges may be the precursors of spreading segments, but erupted lavas include calcalkaline volcanics. Kinematic modeling and marine geophysical observations indicate that the responses to similar amounts of extension in the eastern Manus Basin have varied as a function of the different types of pre-existing crust: arc crust tectonically stretched over a broad area whereas backarc crust underwent relatively little stretching before accommodating extension by seafloor spreading.  相似文献   

RAPD typing of north-east Atlantic minke whale (Balaenoptera acutorostrata)     

Martinez  I.; Elvevoll  E. O.; Haug  T. 《ICES Journal of Marine Science》1997,54(3):478-484

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Pito Rift: How a large-offset rift propagates     

David F. Naar  Fernando Martinez  R. N. Hey  Thomas B. Reed IV  Seth Stein 《Marine Geophysical Researches》1991,13(4):287-309

The Pito Rift area is the site of actively deforming oceanic lithosphere that has been primarily under extension for at least the past million years, based on kinematic reconstructions. The major morphologic features, Pito Deep and Pito Seamount, are aligned toward the Euler pole for relative motion between the Easter and Nazca plates. SeaMARC II side-scan and bathymetry data indicate that there are two general modes of faulting currently active in the Pito Rift area. One is associated with incipient rifting of old (3 Ma) Nazca lithosphere by large NW-SE normal faults, and the other is associated with a broad area of right-lateral transform shear between the Nazca and Easter plates. This transform shear is distributed over a broad region because of the northward growth of the East Rift and parallel tectonic rifting within the Pito Rift area. The majority of the Pito Rift area is composed of preexisting blocks of Nazca plate that are back-tilted away from Pito Deep and strike perpendicular to present and previous relative plate motions. This observation suggests that block-faulting and back-tilting are the primary mechanisms responsible for the distributed lithospheric extension, in agreement with gravity and magnetic analyses (Martinez et al., this issue).The only recent volcanic flows observed in side-scan data are from the Pito Seamount area and to the outside of the outer pseudofault of the East Rift. The significance of the young flows near the outer pseudofault is not understood. We interpret the flows extending northwest from the Pito Seamount as representing a newly formed seafloor spreading axis within the Pito Rift area. Gravity and magnetic analyses (Martinez et al., this issue) together with SeaMARC II bathymetry and side-scan data support this interpretation.Based on the tectonic evolution of the Easter microplate, we propose an evolutionary model for the formation of the Pito Rift area, where new tectonic grabens form immediately west of the previous graben and with slightly more counterclockwise orientation. The duration and history of tectonic activity for each graben are not well constrained.  相似文献   

Using beryllium-7 to evaluate soil erosion processes in agricultural lands in semiarid regions of Central Argentina     

Juan Pablo de Rosas  Alexander Dario Esquivel  Diego Martinez Heimann  Agustin E. Negri  Flavia Lohaiza  Diego Leonardo Valladares  Alejandro I. Zavala  Hugo Huck  Jimena Juri Ayub 《Environmental Earth Sciences》2018,77(16):587

This work presents the results of a soil erosion study using the ⁷Be technique. This technique estimates the water erosion/deposition from the comparison between ⁷Be soil content of a reference site and an eroded or sedimented site. The soil samples were collected from an agricultural area of the semiarid region of Argentina near San Luis City, which has a marked rainfall season. The area has been used for crop cultivation, being subjected to plowing practices. The ⁷Be in the Reference Site was in the first centimeter of soil, showing the typical exponential decreasing of ⁷Be soil content with depth, with the ⁷Be inventories value being 340?±?50 Bq m^?2 for the dry season and 571?±?48 Bq m^?2 for the rainy season. The ⁷Be technique was applied to a potential eroded site subjected to traditional tillage practices (plowing). A net soil erosion value of 13.5 t ha^?1 (1.35 kg m^?2) was obtained. From the assumptions of the applied technique, we can draw the inference that this erosion was caused by rains produced in the month prior to the date of soil sampling.  相似文献