Retention of heavy metal ions in bentonites from Grau Region (Northern Peru)   总被引：2，自引：0，他引：2  

J. Ayala  J. L. Vega  R. Alvarez  J. Loredo 《Environmental Geology》2008,53(6):1323-1330

Experimental studies on the retention of metals (Cu, Co, Ni, and Zn) in bentonite samples from the Grau Region (Northern Peru) have been accomplished using monometallic, bimetallic, trimetallic, and tetrametallic solutions. Parameters such as pH and concentration of dissolved metals and organic compounds have been evaluated by means of batch adsorption experiments. Adsorption rates indicate the suitability of these bentonites in the environmental industry for heavy metals retention purposes. In addition to its quality as physical barrier to avoid the dispersion through the environment of polluted leachates, bentonite, due to its high cation exchange capacity, can act also as a chemical barrier, protecting the quality of surface and groundwater systems, while limiting the migration of heavy metals in solid residues or sludge stocked in security landfills. Adsorption rates of tested bentonites were proved to decrease when concentrations of both metal and organic compounds, as well as the number of ionic species, increase in solution; additionally, lower metal removal rates from solution were obtained when extremely acidic conditions were achieved.  相似文献   

Changes in growing season in the Northeastern United States     

Anthony J. Vega  Robert V. Rohli  Elina Wright 《自然地理学》2020,41(4):343-364

ABSTRACT

Changes in growing season length (GSL) are of concern for agricultural, phenological, economic, epidemiological, and bioclimatological reasons. This research identifies spatial and temporal changes over the last several decades in GSL, along with the day-of-year of the last spring freeze and first autumn freeze, for the northeastern United States – a region particularly susceptible to such changes due to the large population and intense economic activities. Results suggest that growing season has significantly increased in length since 1980 as compared to prior to 1980, and both spatial and temporal variation in GSL has decreased for the region over time. Changes to GSL for this region are driven more by a shift in the first autumn freeze date than the last spring freeze date. The areas of greatest increase in GSL in the pre- vs. post-1980 period tend to be in the high elevations, near large water bodies, and near the largest cities. Results will assist environmental planners as they prepare mitigation and adaptation strategies amid a changing environment.  相似文献   

Synoptic climatology of nuisance flooding along the Atlantic and Gulf of Mexico coasts,USA     

Vega  Anthony J.  Miller  Paul W.  Rohli  Robert V.  Heavilin  Jason 《Natural Hazards》2021,105(2):1281-1297

Natural Hazards - Nuisance flooding (NF; also known as high-tide, or “sunny day” flooding) is an increasingly prevalent phenomenon afflicting coastal developments worldwide. NF often...  相似文献   

The Cretaceous–Palaeogene boundary at Gorgonilla Island,Colombia, South America          下载免费PDF全文

Hermann D. Bermúdez  Jenny García  Wolfgang Stinnesbeck  Gerta Keller  José Vicente Rodríguez  Michael Hanel  Jens Hopp  Winfried H. Schwarz  Mario Trieloff  Liliana Bolívar  Francisco J. Vega 《地学学报》2016,28(1):83-90

The discovery of a new Cretaceous/Palaeogene (K/Pg) bathyal marine sequence on Gorgonilla Island, SW Colombia, extends the presence of Chicxulub impact spherule deposits to the Pacific region of northern South America and to the Eastern Pacific Ocean. The Gorgonilla spherule layer is approximately 20 mm thick and consists of extraordinarily well‐preserved glass spherules up to 1.1 mm in diameter. About 70–90% of the spherules are vitrified, and their chemical composition is consistent with Haiti (Beloc) impact glass spherules. Normal size‐grading, delicate spherule textures, welded melt components and an absence of bioturbation or traction transport suggest that the Gorgonilla spherule layer represents an almost undisturbed settling deposit.  相似文献   

Ecosystem-based marine spatial management: Review of concepts, policies, tools, and critical issues   总被引：1，自引：0，他引：1  

Stelios Katsanevakis  Vanessa Stelzenmüller  Andy South  Thomas Kirk Sørensen  Peter J.S. Jones  Sandy Kerr  Fabio Badalamenti  Christos Anagnostou  Patricia Breen  Guillem Chust  Giovanni D’Anna  Mike Duijn  Tatiana Filatova  Fabio Fiorentino  Helena Hulsman  Kate Johnson  Aristomenis P. Karageorgis  Ingrid Kröncke  Simone Mirto  Carlo Pipitone  Susan Portelli  Wanfei Qiu  Henning Reiss  Dimitris Sakellariou  Maria Salomidi  Luc van Hoof  Vassiliki Vassilopoulou  Tomás Vega Fernández  Sandra Vöge  Anke Weber  Argyro Zenetos  Remment ter Hofstede 《Ocean & Coastal Management》2011,54(11):807-820

Conventional sectoral management and piecemeal governance are considered less and less appropriate in pursuit of sustainable development. Ecosystem based marine spatial management (EB-MSM) is an approach that recognizes the full array of interactions within an ecosystem, including human uses, rather than considering single issues, species, or ecosystem services in isolation. Marine spatial planning and ocean zoning are emerging concepts that can support EB-MSM. EB-MSM is driven by high-level goals that managers aim to achieve through the implementation of measures. High-level goals and objectives need to be translated into more operational objectives before specific targets, limits and measures can be elaborated.Monitoring, evaluation and adaptation are necessary to ensure that marine management measures are both effective and efficient. Solid monitoring frameworks are the foundation of adaptive management, as they provide the necessary information to evaluate performance and the effectiveness of management actions. Marine protected areas (MPAs) - possibly set up in networks - constitute a key component in EB-MSM policies and practises and have been applied as a cornerstone in conservation of marine biodiversity, management of fish populations, development of coastal tourism, etc. Moreover, MPA experiences have provided methods and concepts (such as zoning) to a wider EB-MSM context. The assignment of values to biophysical features of the marine environment allows the direct assessment of related management choices and may assist EB-MSM.A range of monetary valuation techniques have been proposed to reduce attributes of goods and services to a single metric. However, in the marine environment such an approach is often over simplistic, and thus less reductive techniques may be necessary. Rather than producing a single metric, the results of non-monetary assessments guide policy allowing weight to be given as necessary to potential areas of conflict and consensus.Strategies to take into account climate change effects and geohazard risks in EB-MSM have been applied or proposed worldwide. EB-MSM regimes must be alert to such risks and flexible to account for changes.  相似文献   

Flux predictions of high-energy neutrinos from pulsars     

Bennett Link  Fiorella Burgio 《Monthly notices of the Royal Astronomical Society》2006,371(1):375-379

Young, rapidly rotating neutron stars could accelerate ions from their surfaces to energies of ∼1 PeV. If protons reach such energies, they will produce pions (with low probability) through resonant scattering with X-rays from the stellar surface. The pions subsequently decay to produce muon neutrinos. Here, we calculate the energy spectrum of muon neutrinos, and estimate the event rates at Earth. The spectrum consists of a sharp rise at ∼50 TeV, corresponding to the onset of the resonance, above which the flux drops with neutrino energy as  ε⁻²_ν  up to an upper energy cut-off that is determined by either kinematics or the maximum energy to which protons are accelerated. We estimate event rates as high as 10–100 km⁻² yr⁻¹ from some candidates, a flux that would be easily detected by IceCube. Lack of detection would allow constraints on the energetics of the poorly understood pulsar magnetosphere.  相似文献   

Risk of metal mobility in soils from a Pb/Zn depleted mine (Lugo,Spain)     

D. Arenas-Lago  M. Lago-Vila  A. Rodríguez-Seijo  M. L. Andrade  F. A. Vega 《Environmental Earth Sciences》2014,72(7):2541-2556

The risk of Pb, Zn and Cd mobility is evaluated in soils from a depleted mine at Rubiais (Lugo, Spain). This area is under special protection because of its outstanding natural value. Soils from nine different areas were selected: at the mining zone (R1, R2, R3), at minespoils (R4, R5, R6) and soils developed on the settling pond (R7, R8, R9). A control soil (RC) was sampled outside the mine. The objectives are (i) to study the characteristics of soils with high influence on metal retention, (ii) to determine the content of Pb, Zn and Cd comparing it with the generic reference levels, and (iii) to evaluate the distribution and the interactions between the metals and the soil geochemical phases by means of sequential chemical extraction, X-ray diffraction, field emission scanning electron microscopy/energy-dispersive X-ray spectroscopy (FE-SEM/EDS) and time of flight secondary ion mass spectrometry (TOF–SIMS). The concentration of Pb, Zn and Cd ranges 850–6,761, 1,754–32,287 and 1.8–43.7 mg kg^?1, respectively, and the highest proportion is in the residual fraction. The Mn oxides highly influence the retention of Cd while Pb retention is mainly influenced by Fe oxides. Zn is uniformly distributed amongst the residual fraction and the Fe and Mn oxides. TOF–SIMS and SEM/EDS techniques confirm the fractionation results, showing how Pb and Zn are as sulphide and associated with Fe and Mn oxides. Nevertheless, care should be taken since oxides and sulphides could suffer sulphide oxidation processes or alteration of the oxides causing leaching and the contamination of the protected ecosystem.  相似文献   

GPR survey to confirm the location of ancient structures under the Valencian Cathedral (Spain)     

Vega Prez Gracia  Jos Antonio Canas  Lluis G. Pujades  Jaume Claps  Oriol Caselles  Francesc García  Raul Osorio 《Journal of Applied Geophysics》2000,43(2-4)

This paper describes the ground-penetrating radar (GPR) survey performed inside the Cathedral of Valencia, Spain. It is part of historical studies performed in the Cathedral in order to add information to old maps and documents in the Cathedral Archives and also to analyze the extent and importance of potentially destructive moisture areas that were appearing on the floor. The construction of the Cathedral of Valencia occurred in three stages, all of which are well-documented in the Cathedral Archives with detailed drawings, maps, and charts. The radar data were successful in locating crypts, ossuaries, sepulchers, and graves, and the location of ancient walls that existed before the final Cathedral expansion. Three cultural layers corresponding to the three periods of construction were also identified corresponding to the Roman, Arabian and Middle Age Epochs. Measurements of relative sub-floor moisture were obtained by comparing dielectric permittivity changes and radar velocity differences between materials in humid and non-humid areas.  相似文献   

Extraterrestrial microspherules from Bajada del Diablo,Chubut, Argentina     

M.J. Orgeira  L.N. Castro  G.A. Goldmann  C.B. Prezzi  E. Sileo  D.R. Vega  C. Franzosi  R.D. Acevedo  O. Martínez  J. Rabassa  J.F. Ponce  O.R. Tófalo 《地学前缘(英文版)》2017,8(1):137-149

The Quaternary infilling of a circular structure located in Bajada del Diablo, Chubut Province, Argentina has been proposed as a crater strewn field in previous studies. Here we report the finding of about 65 microspherules collected in a trench excavated in the center of the structure. The majority of hand-picked specimens are single, but some of them exhibit compound forms. The single specimens are spherical with a mean size of 137 μm, whereas the more complex samples show peduncles and drop shapes. Dendritic crystal growth is recognized in the internal structure of some broken microspherules. Preliminary chemical composition from the surface and center of microspherules was determined by energy dispersive spectrometry employing EDS. Quantitative EMPA and XRD analysis indicate that the microspherules are mainly composed of Fe and O with magnetite, Fe0 with subordinate wüstite. Following consideration of possible anthropogenic and volcanic origins, these spherulites are ascribed to an extraterrestrial input. An accumulation rate of 47 microspherules per m²/yr is estimated for the studied sediments. This value is two orders of magnitude higher than the reference flux for cosmic dust estimated for the last 1 Ma in the Transantarctic Mountains. The microspherules might have been generated as a byproduct of asteroid entry in the atmosphere.  相似文献   

Interaction of wind and cold-season hydrologic processes on erosion from complex topography following wildfire in sagebrush steppe     

Samantha P. Vega  C. Jason Williams  Erin S. Brooks  Frederick B. Pierson  Eva K. Strand  Peter R. Robichaud  Robert E. Brown  Mark S. Seyfried  Kathleen A. Lohse  Kayla Glossner  Jennifer L. Pierce  Clay Roehner 《地球表面变化过程与地形》2020,45(4):841-861

Wildfire is a natural component of sagebrush (Artemisia spp.) steppe rangelands that induces temporal shifts in plant community physiognomy, ground surface conditions, and erosion rates. Fire alteration of the vegetation structure and ground cover in these ecosystems commonly amplifies soil losses by wind- and water-driven erosion. Much of the fire-related erosion research for sagebrush steppe has focused on either erosion by wind over gentle terrain or water-driven erosion under high-intensity rainfall on complex topography. However, many sagebrush rangelands are geographically positioned in snow-dominated uplands with complex terrain in which runoff and sediment delivery occur primarily in winter months associated with cold-season hydrology. Current understanding is limited regarding fire effects on the interaction of wind- and cold-season hydrologic-driven erosion processes for these ecosystems. In this study, we evaluated fire impacts on vegetation, ground cover, soils, and erosion across spatial scales at a snow-dominated mountainous sagebrush site over a 2-year period post-fire. Vegetation, ground cover, and soil conditions were assessed at various plot scales (8 m² to 3.42 ha) through standard field measures. Erosion was quantified through a network of silt fences (n = 24) spanning hillslope and side channel or swale areas, ranging from 0.003 to 3.42 ha in size. Sediment delivery at the watershed scale (129 ha) was assessed by suspended sediment samples of streamflow through a drop-box v-notch weir. Wildfire consumed nearly all above-ground live vegetation at the site and resulted in more than 60% bare ground (bare soil, ash, and rock) in the immediate post-fire period. Widespread wind-driven sediment loading of swales was observed over the first month post-fire and extensive snow drifts were formed in these swales each winter season during the study. In the first year, sediment yields from north- and south-facing aspects averaged 0.99–8.62 t ha⁻¹ at the short-hillslope scale (~0.004 ha), 0.02–1.65 t ha⁻¹ at the long-hillslope scale (0.02–0.46 ha), and 0.24–0.71 t ha⁻¹ at the swale scale (0.65–3.42 ha), and watershed scale sediment yield was 2.47 t ha⁻¹. By the second year post fire, foliar cover exceeded 120% across the site, but bare ground remained more than 60%. Sediment yield in the second year was greatly reduced across short- to long-hillslope scales (0.02–0.04 t ha⁻¹), but was similar to first-year measures for swale plots (0.24–0.61 t ha⁻¹) and at the watershed scale (3.05 t ha⁻¹). Nearly all the sediment collected across all spatial scales was delivered during runoff events associated with cold-season hydrologic processes, including rain-on-snow, rain-on-frozen soils, and snowmelt runoff. Approximately 85–99% of annual sediment collected across all silt fence plots each year was from swales. The high levels of sediment delivered across hillslope to watershed scales in this study are attributed to observed preferential loading of fine sediments into swale channels by aeolian processes in the immediate post-fire period and subsequent flushing of these sediments by runoff from cold-season hydrologic processes. Our results suggest that the interaction of aeolian and cold-season hydrologic-driven erosion processes is an important component for consideration in post-fire erosion assessment and prediction and can have profound implications for soil loss from these ecosystems. © 2019 John Wiley & Sons, Ltd.  相似文献