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   

Short‐term microscale topographic changes of coastal bedrock on shore platforms     

Wayne J. Stephenson  Anna J. Taylor  Maree A. Hemmingsen  Hidekazu Tsujimoto  Robert M. Kirk 《地球表面变化过程与地形》2004,29(13):1663-1673

We report a series of short‐term (diurnal) rock surface monitoring studies on inter‐ and supra‐tidal shore platforms using a traversing micro‐erosion meter at two sites, Kaikoura Peninsula, New Zealand, and Apollo Bay, Victoria, Australia. Statistically signi?cant day‐to‐day changes were measured. Surface rise and lowering occurred at rates above instrument error, with a maximum range of 3·378 mm between 1·697 mm (lowering) and ‐1·681 mm (rise). Individual measurements showed rises greater than 2 mm. These daily variations reveal that surface lowering and rise occur at a much shorter time scale than previously reported from other studies. The patterns observed suggest wetting and drying is the most likely process causing surface changes at these temporal scales. We argue that traversing micro‐erosion meter studies operating at a short‐term time scale of day‐to‐day provide meaningful results that open new opportunities for studying rock weathering and erosion in a coastal environment. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Geoarchaeological evidence for multidecadal natural climatic variability and ancient Peruvian fisheries     

Daniel H. Sandweiss  Kirk A. Maasch  Fei Chai  C. Fred T. Andrus  Elizabeth J. Reitz 《Quaternary Research》2004,61(3):235-334

Understanding the influence of natural climatic variability on modern fisheries is complicated by over a century of industrial fishing. Archaeological data provide unique opportunities for assessing precolonial and preindustrial fisheries. Records show that anchoveta-vs sardine-dominated fisheries correlate with 20th-century climate change in the Pacific Basin and are linked to multidecadal climatic variability. The “anchovy regime” is characterized by cooler conditions and lower frequency El Niño/Southern Oscillation (ENSO) events, while the “sardine regime” is associated with warmer conditions and higher frequency ENSO. Fish remains excavated at Lo Demás, an Inca-period (ca. A.D. 1480–1540) fishing site at 13°25′S on the Peruvian coast, document a shift from an anchoveta-to a sardine-dominated fishery at about A.D. 1500. This shift correlates with records for increasing ENSO frequency at the same time. Middle and late Holocene sites have archaeofish assemblages that also suggest regime changes. Here we show that changes in fish regimes can result from natural variability and we support the potential role of archaeological assemblages in tracking multidecadal climate change in the Pacific Basin throughout the Holocene (0–11,500 cal yr B.P.).  相似文献   

Regionalizing spain's continuous and discontinuous settlement     

Kirk H Stone 《Geoforum》1971,2(4):9-14

The expected increase of the world's population will be accompanied by a growth of the rural part. Some of the latter will be reflected in expansion of the inhabited area into the uninhabited. To provide knowledge for efficiency of this expansion a classification of the areally continuous and discontinuous settlement of Spain is delineated. The Continuous Settlement Region is in the north, east of a Léon-Bilbao line, north of the latitude of Toledo, and split in two by a NE-SW line through Teruel. The rest is the Discontinuous Settlement Region comprised of four occurrences of Inner Fringe Zone near the country's corners, two of the Middle Fringe Zone, and three of Outer Fringe Zone. Though new rural settling began in Spain in 1907 the principal effort has been during the past two decades under the National Colonization Institute whose work has been concentrated in the Inner Fringe Zone. It is there that continuing study is needed to provide guides for new rural settling elsewhere in the world.  相似文献   

Daily variability in abundance and population characteristics of tidal salt-marsh fauna     

Lyle M. Varnell  Kirk J. Havens  Carl Hershner 《Estuaries and Coasts》1995,18(2):326-334

Nekton and macrocrustacean population levels and characteristics were studied in two similar tidal marsh creeks. Absolute and area-adjusted data were analyzed to determine variability resulting from daily population fluctuations. Two sampling schemes—intensive 3-d seasonal and periodic 1-d—were examined by constructing probability matrices to compare the accuracy of data comparisons resulting from each scheme. The probability of inaccuracies in comparisons of abundance using nonreplicated sampling schemes ranged from 0% to 100%. Significant differences between consecutive day data were observed for population characteristics such as blue crab (Callinectes sapidus) sex ratios, spot (Leiostomus xanthurus) length-weights, killifish: sciaenid ratios, and killifish: blue crab ratios. These data support the need to account for short-term variability when assessing mobile aquatic fauna abundance in estuarine wetlands.  相似文献   

Phytoscreening: A Comparison of In Planta Portable GC‐MS and In Vitro Analyses     

Matt A. Limmer  Gregory D. Martin  Christopher J. Watson  Camilo Martinez  Joel G. Burken 《Ground Water Monitoring & Remediation》2014,34(1):49-56

Phytoscreening has been proven to rapidly delineate subsurface contaminant plumes for semiquantitative site assessment, with minimal impact to property or ecology through the collection and analysis of tree cores. Here, three phytoscreening methods were applied concurrently to identify multiple chlorinated volatile organic compounds (cVOCs) in a phytoremediation treatment system at a contaminated industrial facility. Tree coring, in planta gas chromatography–mass spectrometry (GC‐MS), and in planta passive sampling showed general agreement, with the in planta GC‐MS providing the quickest but least quantitative results. The portable GC‐MS sampling and analysis method identified six cVOCs in the xylem of hybrid poplars (Populus sp.) in the phytoremediation plot. These real‐time data can permit onsite identification and delineation of the contaminants, allowing for adaptive sampling during a single mobilization to a site. The in vitro methods provided quantitative data across two sampling campaigns, as relative cVOC concentrations remained similar between the two trips, despite a decrease in absolute cVOC concentrations from August to October. Overall, this research demonstrates the advantages and limitations of three phytoscreening techniques.  相似文献   

On the Basis for the 0.1 mg/L Water Quality Objective for “Taste and Odor” for Diesel in Groundwater          下载免费PDF全文

Dawn A. Zemo  Kirk T. O'Reilly 《Ground Water Monitoring & Remediation》2016,36(3):88-90

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Floating marine debris surface drift: Convergence and accumulation toward the South Pacific subtropical gyre   总被引：2，自引：1，他引：1  

Elodie Martinez  Keitapu Maamaatuaiahutapu  Vincent Taillandier 《Marine pollution bulletin》2009,58(9):1347-1355

Whatever its origin is, a floating particle at the sea surface is advected by ocean currents. Surface currents could be derived from in situ observations or combined with satellite data. For a better resolution in time and space, we use satellite-derived sea-surface height and wind stress fields with a 1/3° grid from 1993 to 2001 to determine the surface circulation of the South Pacific Ocean. Surface currents are then used to compute the Lagrangian trajectories of floating debris. Results show an accumulation of the debris in the eastern-centre region of the South Pacific subtropical gyre ([120°W; 80°W]–[20°S; 40°S]), resulting from a three-step process: in the first two years, mostly forced by Ekman drift, the debris drift towards the tropical convergence zone (30°S). Then they are advected eastward mostly forced by geostrophic currents. They finally reach the eastern-centre region of the South Pacific subtropical gyre from where they could not escape.  相似文献   

Saxicolous and riparian vegetation of a piedmont in central-western Argentina     

E. Martinez Carretero 《Journal of Arid Environments》1999,42(4):305

Four plant communities were determined through floristical and non-metric analysis: a Dolichlasium lagascae community in crevices on sunny rock outcrops; a Cercidium praecox ssp. glaucum community on sunny slopes; an Artemisia mendozana–Adesmia trijuga community on shady slopes; and a Eupatorium buniifolium community on dry riverbanks. The discriminant function analysis showed that the first group corresponds to the sunny rock outcrops discriminated by Na content (r=0·53, p<0·05), the second group is for sunny slopes discriminated by electric conductivity and the third for shady slopes–riparian discriminated by the (Ca+Mg) content (r=0·54, p<0·05). A pattern of primary succession on outcrop surfaces is proposed.  相似文献   

Pre-1991 sulfur transfer between mafic injections and dacite magma in the Mt. Pinatubo reservoir     

Andrea Di Muro  John Pallister  Benoit Villemant  Chris Newhall  Michel Semet  Mylene Martinez  Clarisse Mariet 《Journal of Volcanology and Geothermal Research》2008

Before the 1991–1992 activity, a large andesite lava dome belonging to the penultimate Pinatubo eruptive period (Buag ∼ 500 BP) formed the volcano summit. Buag porphyritic andesite contains abundant amphibole-bearing microgranular enclaves of basaltic–andesite composition. Buag enclaves have lower K₂O and incompatible trace element (LREE, U, Th) contents than mafic pulses injected in the Pinatubo reservoir during the 1991–1992 eruptive cycle. This study shows that Buag andesite formed by mingling of a hot, water-poor and reduced mafic magma with cold, hydrous and oxidized dacite. Depending on their size, enclaves experienced variable re-equilibration during mixing/mingling. Re-equilibration resulted in hydration, oxidation and transfer of mobile elements (LILE, Cu) from the dacite to the mafic melts and prompted massive amphibole crystallization. In Buag enclaves, S-bearing phases (sulfides, apatite) and melt inclusions in amphibole and plagioclase record the evolution of sulfur partition among melt, crystal and fluid phases during magma cooling and oxidation. At high temperature, sulfur is partitioned between andesitic melt and sulfides (Ni-pyrrhotite). Magma cooling, oxidation and hydration resulted in exsolution of a S–Cl–H₂O vapor phase at the S-solubility minimum near the sulfide–sulfate redox boundary. Primary magmatic sulfide (pyrrhotite) and xenocrystic sulfide grains (pyrite), recycled together with olivines and pyroxenes from old mafic intrusives, were replaced by Cu-rich phases (chalcopyrite, cubanite) and, partially, by Ba–Sr sulfate. Sulfides degassed and transformed into residual spongy magnetite in response to fS₂ drop during final magma ascent and decompression. Our research suggests that a complete evaluation of the sulfur budget at Pinatubo must take into account the en route S assimilation from the country rocks. Moreover, this study shows that the efficiency of sulfur transfer between mafic recharges and injected magmas is controlled by the extent and rate of mingling, hydrous flushing and melt oxidation. Vigorous mixing/mingling and transformation of the magmatic recharge into a spray of small enclaves is required in order to efficiently strip their primary S-content that otherwise remains locked in the sulfides. Hydrous flushing increases the magma oxidation state of the recharges and modifies their primary volatile concentrations that cannot be recovered by the study of late-formed mineral phases and melt inclusions. Conversely, S stored in both late-formed Cu-rich sulfides and interstitial rhyolitic melt represents the pre-eruptive sulfur budget immediately available for release from mafic enclaves during their decompression.  相似文献