Large-scale oil-in-ice experiment in the Barents Sea: monitoring of oil in water and MetOcean interactions     

Faksness LG  Brandvik PJ  Daae RL  Leirvik F  Børseth JF 《Marine pollution bulletin》2011,62(5):976-984

A large-scale field experiment took place in the marginal ice zone in the Barents Sea in May 2009. Fresh oil (7000 L) was released uncontained between the ice floes to study oil weathering and spreading in ice and surface water. A detailed monitoring of oil-in-water and ice interactions was performed throughout the six-day experiment. In addition, meteorological and oceanographic data were recorded for monitoring of the wind speed and direction, air temperature, currents and ice floe movements. The monitoring showed low concentrations of dissolved hydrocarbons and the predicted acute toxicity indicated that the acute toxicity was low. The ice field drifted nearly 80 km during the experimental period, and although the oil drifted with the ice, it remained contained between the ice floes.  相似文献   

Improving benthic monitoring by combining trawl and grab surveys     

Jørgensen LL  Renaud PE  Cochrane SK 《Marine pollution bulletin》2011,62(6):1183-1190

Environmental monitoring is performed on seafloor communities since these organisms are relatively stationary and integrate the environmental conditions over many years. Standard practices involve sampling by grab. Epifaunal taxa, often missed by grab sampling, are likely to have different ecological functions. We investigate how current environmental assessments represent the benthic community as a whole by comparing taxonomic and functional components sampled by grabs and epibenthic trawls. Faunal communities sampled by trawl (filtrating or predator, epifauna) and grab (infaunal, detrivore) differs widely by sampling distinct functional components, and these may be expected to respond to different human-induced stressors. Neither component appears to be a good surrogate for the community as a whole. We suggest a benthic monitoring by combining both techniques. Sustainable ecosystem functioning is intimately tied to the health of both components of the benthic community, and is recognized as an important goal by signatories of the Convention on Biological Diversity.  相似文献   

Influence of multiple stressors on the auto-remediation processes occurring in salt marshes     

Sousa AI  Lillebø AI  Pardal MA  Caçador I 《Marine pollution bulletin》2011,62(7):1584-1587

Due to increasing global population, salt marshes have been subjected to multiple stressors such as increasing nutrient loadings and historical contamination. In order to better understand how does the salt marsh plants auto-remediation capacity (phytoaccumulation of metals) is affected by cultural eutrophication, an experiment was performed under controlled conditions. Plants were exposure to equal metal concentrations (Zn, Cu, and Ni - micronutrients, and Cd - class B metal) simulating historical contamination and three different concentrations of nitrogen (nitrate) simulating steps of cultural eutrophication. According to our study, under the tested concentrations, cultural eutrophication does not seem to affect Zn, Cu and Ni phytoremediation of H. portulacoides, but the ecosystem service of Cd phytoremediation seems to be promoted. Nevertheless, Cd high toxicity and bioaccumulation should be taken into account, as well as the vulnerability of salt marsh ecosystems, whose reduction will have drastic consequences to the ecosystem health.  相似文献   

Complex size-dependent habitat associations in potamodromous fish species     

José Maria Santos  Luís Reino  João Oliveira  Paulo Pinheiro  Pedro Raposo Almeida  Rui Cortes  Maria Teresa Ferreira 《Aquatic Sciences - Research Across Boundaries》2011,73(2):233-245

Knowledge of the distribution of species life stages at multiple spatial scales is fundamental to both a proper assessment of species management and conservation programmes and the ability to predict the consequences of human disturbances for river systems. The habitat requirements of three native cyprinid species—the Iberian barbel Barbus bocagei Steindachner, the Iberian straight-mouth nase Pseudochondrostoma polylepis (Steindachner), and the Northern straight-mouth nase Pseudochondrostoma duriense (Coelho)—were examined at 174 undisturbed or minimally disturbed sites in 8 river catchments across western Iberia, by modelling occurrence and counts of species life stages at two spatial scales—large (regional) and instream (local)—using hurdle models. All the life stages of the barbel showed a negative association with upstream high-gradient river reaches, whereas juvenile P. duriense favoured such areas. Stream width and openness were negatively related with the occurrence of juvenile and small adult barbel, but not with large adults. Juvenile nase, on the other hand, were found to be mainly confined to fast-flowing habitats with high instream cover and coarser substrata. Advanced life stages of the barbel were mainly associated with the “pure” regional and shared components, whereas the purely local attributes accounted for much of the model variation among nases, in particular juveniles, and juvenile barbel. The results of this study are useful for setting or refining management goals, and highlight the need to separately consider life stages when performing conservation-related studies of species distribution.  相似文献   

Geostatistics for radiological evaluation: study of structuring of extreme values   总被引：2，自引：2，他引：0  

Y. Desnoyers  J.-P. Chil��s  D. Dubot  N. Jeann��e  J.-M. Idasiak 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(8):1031-1037

Geostatistics applied to radiological evaluation of nuclear premises provides sound methods to estimate radiological activities, together with their uncertainty. Quantification and risk analysis of contaminated areas are initially performed by applying geostatistical methods relying on the multi-Gaussian assumption. However, the application of the classical bi-Gaussian model for disjunctive kriging proves sub-optimal due to the spatial structuring of high and low values. The beta model which pertains to the class of Hermitian isofactorial models is potentially better suited to radiological evaluation as it allows a continuous evolution from a mosaic to a pure diffusive model. In the test case, disjunctive kriging estimates are obtained by applying in turn the beta model and the pure diffusive model. The comparison of estimation outcomes shows rather limited differences, primarily located in and around the homogeneous contaminated areas.  相似文献   

Active surface faulting or landsliding in the Lower Tagus Valley (Portugal)? A solved controversy concerning the Vila Chã de Ourique site     

João Manuel Cabral  Fernando Marques  Paula Figueiredo  Luís Matias 《Journal of Seismology》2011,15(2):215-234

The Lower Tagus Valley has experienced significant (M 6–7) historical seismicity, evidencing the presence of seismogenic faults. These are still deficiently known due to the low strain rates and the recent alluvial sedimentation of the Tagus River that buries most of the structures, though Paleoseismic evidence was allegedly found by a research team in the Tagus valley, at a site 60 km N of Lisbon, near Vila Chã de Ourique (VCO). According to this team, trenching at the VCO site exposed an active thrust fault, evidencing the surface rupture of a large earthquake that occurred in 1531. Our studies performed at this site, comprising field observations with a reappraisal of the trench outcrops previously excavated, borehole drilling, soil mechanics laboratory testing, and seismic reflection acquisition, pointed to the alternative interpretation that the outcropping structures are gravitational and not of tectonic origin. The interpretation of new outcrops crosscutting the structures exposed at the trenches, as well as newly acquired high-resolution seismic reflection data, definitely exclude the active thrust fault explanation and support a gravitational slip model for all the observed structures. Gravitational slip in the river bank slope was promoted by low shear strength clays and high pore water pressure coupled with slope toe river erosion. Gravitational slides must have occurred prior to development of the present sedimentation level of the Tagus alluvial plain, which was attained in the last few thousand years as indicated by borehole data and estimations of sedimentation rates.  相似文献   

Changing compositions in the Iceland plume; Isotopic and elemental constraints from the Paleogene Faroe flood basalts     

Nina Søager  Paul Martin Holm 《Chemical Geology》2011,280(3-4):297-313

Elemental and Sr, Nd, Hf and high precision Pb isotopic data are presented from 59 low-Ti and high-Ti lavas from the syn-break up part of the Faroe Flood Basalt Province. The depleted MORB-like low-Ti lavas erupted in the rift zone between the Faroe Islands and central East Greenland around the time of break up of the North Atlantic have isotopic end-member compositions different from the depleted Iceland lavas. We suggest that the main low-Ti mantle component is NAEM (North Atlantic End-Member (Ellam and Stuart, 2000, J. Petrol. 41, 919) and that the ²⁰⁷Pb/²⁰⁴Pb value of the component should be 15.35 and ε_Hf = + 16.5. NAEM is the main depleted component in the early Iceland plume. This is supported by high mantle potential temperatures (up to 1550 °C) calculated for the source of the low-Ti basalts. The unique mantle isotopic composition of NAEM with low ²⁰⁶Pb/²⁰⁴Pb (17.5) and Δ7/4Pb (? 3.8) precludes a derivation from recycled MORB lithosphere. Instead we suggest that NAEM represents a plume component of recycled depleted Archean lithospheric mantle that was further depleted ~ 500 Ma ago, possibly in connection with the recycling process. Two other isotopic end-members are required to explain the variation of the Faroe low-Ti basalts: (1) The Faroe depleted component (FDC), with ⁸⁷Sr/⁸⁶Sr = 0.7025, ε_Nd = + 11, ε_Hf = + 19.5, ²⁰⁶Pb/²⁰⁴Pb = 18.2, ²⁰⁷Pb/²⁰⁴Pb = 15.454 and ²⁰⁸Pb/²⁰⁴Pb = 37.75, which is similar in composition to some Atlantic MORB and is regarded as a local upper mantle source. (2) An enriched EM-type component similar in geochemistry to the Icelandic Öræfajökull lavas. This component is believed to be recycled pelagic sediments in the plume but it can alternatively be a local crustal or lithospheric mantle component. The enriched Faroe high-Ti lavas erupted inland from the rift have isotopic compositions very similar to the enriched Icelandic neo-volcanics and these lava suites apparently share the two enriched plume end-members IE1 and IE2 (Geochim. Cosmochim. Acta 68, 2, 2004). The lack of mixing between high and low-Ti melts at the time of break up, is explained by a zoned plume where only low-Ti sources were present beneath the rift zone surrounded by high-Ti sources on both sides of the rift. The enriched plume components in the high-Ti lava sequences on the Faroe Islands and central East Greenland changed rapidly on a ka-scale which implies, from geophysical modelling, that this area was positioned above the center of the plume, and that the Iceland plume was centered under the Atlantic ridge already from the Paleocene.  相似文献   

Helium irradiation study on zircon     

Lutz Nasdala  Dieter Grambole  Jens Götze  Ulf Kempe  Tamás Váczi 《Contributions to Mineralogy and Petrology》2011,161(5):777-789

Synthetic ZrSiO₄ and (mildly to strongly radiation-damaged) natural zircon samples were irradiated with 8.8 MeV ⁴He²⁺ ions (fluences in the range 1 × 10¹³–5 × 10¹⁶ ions/cm²). For comparison, an additional irradiation experiment was done with 30 MeV ¹⁶O⁶⁺ ions (fluence 1 × 10¹⁵ ions/cm²). The light-ion irradiation resulted in the generation of new (synthetic ZrSiO₄) or additional (mildly to strongly metamict natural samples) damage. The maximum extent of the damage is observed in a shallow depth range approximately 32–33 μm (8.8 MeV He) and ~12 μm (30 MeV O) below the sample surface, i.e. near the end of the ion trajectories. These depth values, and the observed damage distribution, correspond well to defect distribution patterns as predicted by Monte Carlo simulations. The irradiation damage is recognised from the notable broadening of Raman-active vibrational modes, lowered interference colours (i.e. decreased birefringence), and changes in the optical activity (i.e. luminescence emission). At very low damage levels, a broad-band yellow emission centre is generated whereas at elevated damage levels, this centre is suppressed and samples experience a general decrease in their emission intensity. Most remarkably, there is no indication of notable structural recovery in pre-damaged natural zircon as induced by the light-ion irradiation, which questions the relevance of alpha-assisted annealing of radiation damage in natural zircon.  相似文献   

Zooplankton succession during extraordinary drought–flood cycles: A case study in a South American floodplain lake     

Griselda Chaparro  María Cristina Marinone  Ruben J. Lombardo  María Romina Schiaffino  Alice de Souza Guimarães  Inés O’Farrell 《Limnologica》2011,41(4):371-381

We examined the zooplankton abundance and composition of Laguna Grande, a floodplain wetland of the Lower Paraná Basin (Argentina), during an extraordinary drought–flood cycle that affected both the environment and the biological conditions of the lake. Low waters were characterised by remarkably high conductivities and pH values, and high phytoplankton and bacterioplankton abundances with cyanobacterial blooms, while high waters showed opposite features. In relation to zooplankton, the mean abundances of all the taxonomic groups (rotifers, cladocerans, copepods, ciliates, and heterotrophic nanoflagellates) were slightly higher at low waters. Major changes were observed in the specific composition of metazooplankton: the euryhaline species assemblage that dominated in the dry warm period was replaced by several oligohaline littoral and planktonic species characteristic of the Paraná River Basin, when the water level rose. Mean species richness values at high waters doubled those of low waters and were directly correlated to water depth. Most of the rotifers of the genus Brachionus and the cladoceran Moina micrura switched from parthenogenetic to sexual reproduction during low waters, as a response to a harsh environment and crowding. We suggest that the main changes in the environmental conditions in this eutrophic floodplain lake are driven by the hydrology, which regulates the zooplankton succession. The herein described shifts in the zooplankton structure and dynamics of Laguna Grande over an extraordinary drought–flood cycle contribute to the understanding of the processes that might occur under the scenarios predicted by climate change models.  相似文献   

Innovating resource regimes: Water, wastewater, and the institutional dynamics of urban hydraulic reach in northwest Mexico     

Christopher A. Scott  Nicolás Pineda Pablos 《Geoforum》2011,42(4):439-450

The twin facets of urban hydraulic reach - cities’ appropriation of water from surrounding regions and irrigation use of urban wastewater over a growing rural footprint - form an emerging global policy challenge, especially as democratizing societies seek institutional means to address both urban growth and water scarcity. A central concern of this paper is to demonstrate that policy regionalism, as a process-based understanding of institutions and decision-making, better explains the causes, forms, and outcomes of hydraulic reach than do more structural approaches. Hermosillo, Mexico presents an unfolding case of rural-urban tension for control over rivers and aquifers as well as the infrastructure for water capture, storage, conveyance, and wastewater release. The analysis employs process documentation of water transfer and wastewater negotiations through interviews, review of primary documents, and field observations. Hermosillo’s recourse to negotiated agreements and quasi-market transactions, led by an emerging group of public sector innovators, advances understanding of water policy in Mexico by moving beyond prevailing concerns with the water reform’s neoliberal underpinnings to exploration of rapidly changing urban-centered experimentation. We conclude that evolving urban-rural power disparities and water resource landscapes of urban growth will drive continued expansion of hydraulic reach in water-scarce regions globally.  相似文献