Another diet of worms: the applicability of polychaete feeding guilds as a useful conceptual framework and biological variable   总被引：1，自引：0，他引：1  

Paulo Roberto Pagliosa 《Marine Ecology》2005,26(3-4):246-254

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Bioaccumulation and depuration of Zn and Cd in mangrove oysters (Crassostrea rhizophorae, Guilding, 1828) transplanted to and from a contaminated tropical coastal lagoon   总被引：2，自引：0，他引：2  

Rebouças do Amaral MC  de Freitas Rebelo M  Torres JP  Pfeiffer WC 《Marine environmental research》2005,59(4):277-285

In order to study Zn and Cd accumulation and depuration, a set of oysters, Crassostrea rhizophorae, were transplanted to a metal contaminated coastal lagoon and another one was harvested there and transplanted to a non-polluted site. C. rhizophorae oysters and Perna perna mussels native from both sites were collected in order to monitor variability of metal concentration in resident populations. After three months exposure, oysters transplanted to the polluted site accumulated fourfold Zn (307-1319 microgg(-1)) without reaching the concentration level of resident oysters (9770 microgg(-1)). Cadmium concentrations had a slight but significant decrease during the same period (1.25-0.54 microgg(-1)). Oysters transplanted to the non-polluted site, showed threefold Zn depuration (6727-2404 microgg(-1)), while Cd had no significant variation (0.90-1.45 microgg(-1)). Results showed that transplanted oysters do not reach heavy metal concentrations in indigenous populations suggesting transplanted organisms would be better used to evaluate bioavailability instead of environmental concentrations.  相似文献   

Conceptual fuzzy neural network model for water quality simulation     

Paulo Chaves  Toshiharu Kojiri 《水文研究》2007,21(5):634-646

Artificial neural networks (ANNs) have been applied successfully in various fields. However, ANN models depend on large sets of historical data, and are of limited use when only vague and uncertain information is available, which leads to difficulties in defining the model architecture and a low reliability of results. A conceptual fuzzy neural network (CFNN) is proposed and applied in a water quality model to simulate the Barra Bonita reservoir system, located in the southeast region of Brazil. The CFNN model consists of a rationally‐defined architecture based on accumulated expert knowledge about variables and processes included in the model. A genetic algorithm is used as the training method for finding the parameters of fuzzy inference and the connection weights. The proposed model may handle the uncertainties related to the system itself, model parameterization, complexity of concepts involved and scarcity and inaccuracy of data. The CFNN showed greater robustness and reliability when dealing with systems for which data are considered to be vague, uncertain or incomplete. The CFNN model structure is easier to understand and to define than other ANN‐based models. Moreover, it can help to understand the basic behaviour of the system as a whole, being a successful example of cooperation between human and machine. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Science-based and stakeholder-driven marine protected area network planning: A successful case study from north central California     

Mary Gleason  Scott McCreary  Melissa Miller-Henson  John Ugoretz  Evan Fox  Matt Merrifield  Will McClintock  Paulo Serpa  Kathryn Hoffman 《Ocean & Coastal Management》2010,53(2):52-68

The planning process for California's Marine Life Protection Act in north central California represents a case study in the design of a regional component of a statewide network of marine protected areas (MPAs) for improved ecosystem protection. We describe enabling factors, such as a legislative mandate, political will, and adequate capacity and funding that fostered a successful planning process. We identify strategic principles that guided the design of a transparent public planning process that delivered regional MPA network proposals, which both met science guidelines and achieved a high level of support among stakeholders. We also describe key decision support elements (spatial data, planning tools, and scientific evaluation) that were essential for designing, evaluating, and refining alternative MPA network proposals and for informing decision-makers.  相似文献   

Influence of aquifer properties and the spatial and temporal distribution of recharge and abstraction on sustainable yields in semi‐arid regions     

Rui Hugman  Tibor Y. Stigter  José Paulo Monteiro  Luís Nunes 《水文研究》2012,26(18):2791-2801

This paper aims to contribute to understanding the importance of four factors on the determination of sustainable yields: (i) aquifer properties; (ii) temporal distribution of recharge; (iii) temporal distribution of groundwater pumping; and (iv) spatial distribution of pumping wells. It is important to comprehend how the present‐day and future vulnerability of groundwater systems to pumping activities depend on these critical factors and what the risks are of considering sustainable yield as a fixed percentage of mean annual recharge (MAR). A numerical model of the Querença–Silves aquifer in Portugal is used to develop hypothetical scenarios with which these factors are studied. Results demonstrate the aquifer properties, particularly the storage coefficient, have an important role in determining the resilience of an aquifer and therefore to which degree it is dependent on the spatial and temporal distribution of abstraction and recharge, as well as the occurrence of extreme events. Sustainable yields are determined for the developed scenarios based on specific criteria rather than a fraction of MAR. Under simplified current recharge and abstraction conditions, the sustainable yield was determined at approximately 73% of MAR or 76 million m³. When considering a concentration of rainfall in time, as predicted by climate scenarios for the region, sustainable yield could drop to ca 70% of MAR. However, a more even distribution of pumping volumes throughout the year could increase this value. The location of the pumping wells is seen to affect the distribution of hydraulic heads in the aquifer, albeit without significant changes in sustainable yield. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

New Method to Predict Crater Depth Obtained in Dynamic Compaction     

de Souza  Tennison Freire  Pasqual  Rodrigo Paulo Strano 《Geotechnical and Geological Engineering》2021,39(5):3981-3993

Geotechnical and Geological Engineering - This article presents a method to estimate dynamic compaction crater depth using empirical equations. As main reference, three physical model studies that...  相似文献   

Hybrid Reconstruction to Derive 3D Height – Time Evolution for Coronal Mass Ejections     

A. Antunes  A. Thernisien  A. Yahil 《Solar physics》2009,259(1-2):199-212

We present a hybrid combination of forward and inverse reconstruction methods using multiple observations of a coronal mass ejection (CME) to derive the three-dimensional (3D) “true” height?–?time plots for individual CME components. We apply this hybrid method to the components of the 31 December 2007 CME. This CME, observed clearly in both the STEREO A and STEREO B COR2 white-light coronagraphs, evolves asymmetrically across the 15-solar-radius field of view within a span of three hours. The method has two reconstruction steps. We fit a boundary envelope for the potential 3D CME shape using a flux-rope-type model oriented to best match the observations. Using this forward model as a constraining envelope, we then run an inverse reconstruction, solving for the simplest underlying 3D electron density distribution that can, when rendered, reproduce the observed coronagraph data frames. We produce plots for each segment to establish the 3D or “true” height?–?time plots for each center of mass as well as for the bulk CME motion, and we use these plots along with our derived density profiles to estimate the CME’s asymmetric expansion rate.  相似文献   

Geochemistry of waters associated with the old mine workings at Fonte Santa (NE of Portugal)     

M.E.P. Gomes  I.M.H.R. Antunes  P.B. Silva  A.M.R. Neiva  F.A.L. Pacheco 《Journal of Geochemical Exploration》2010

The quartz veins containing scheelite from Fonte Santa mine cut the Lower Ordovician quartzites. A muscovite–biotite granite (G1) and a muscovite granite (G2), both S-type, crop out close to the Fonte Santa mine and are related to the Moncorvo–Bemposta shear zone. The most altered samples of G2 show intense muscovitization and microclinization and contain chlorite, columbite–tantalite, wolframite, W-ixiolite and Fe-oxides. The tin-bearing granites contain 18 ppm (G1) and 73 ppm (G2) Sn. The most altered samples of G2 correspond to a tungsten granite. The quartz veins contain muscovite, chlorite, tourmaline, scheelite, pyrrhotite, pyrite, sphalerite, chalcopyrite, galena, arsenopyrite, iron oxides, Fe sulfates, phosphates of Pb, Fe and Al. The Fonte Santa mine area was exploited for W between 1942 and 1982. At the end of November 2006, a flood event damaged the tailings dam of Fonte Santa mine, releasing contaminated material and increasing contaminant levels in water within the area of influence of the mine. The waters related to the Fonte Santa mine are poorly mineralized, with electrical conductivity of < 965 µS/cm, and of a mixed type or HCO₃⁻ and SO₄²⁻ types. Most pH values (5.0−8.5) indicate that there is no significant acidic drainage in the region, as found in other areas. More acidic values (pH = 3.4) were found in the mine's lagoon. Waters associated with mineralized veins and old mine activities have Fe and Mn concentrations that forbid their use for human consumption and agriculture. Natural Na, Mg and K water contents are associated with the alteration of albite, chlorite and muscovite of country rock, while Ca with the W-bearing quartz veins. Weathering agents are carbonic and sulphuric acids and the latter has a strong influence in areas draining fine-grained mine tailings.  相似文献   

Kimberlitic sources of super-deep diamonds in the Juina area,Mato Grosso State,Brazil     

Felix V. Kaminsky  Sergei M. Sablukov  Elena A. Belousova  Paulo Andreazza  Mousseau Tremblay  William L. Griffin 《Lithos》2010,114(1-2):16-29

The Juina diamond field, in the 1970–80s, was producing up to 5–6 million carats per year from rich placer deposits, but no economic primary deposits had been found in the area. In 2006–2007, Diagem Inc. discovered a group of diamondiferous kimberlitic pipes within the Chapadão Plateau (Chapadão, or Pandrea cluster), at the head of a drainage system which has produced most of the alluvial diamonds mined in the Juina area. Diamonds from placer deposits and newly discovered kimberlites are identical; they have super-deep origins from the upper-mantle and transition zone. Field observations and petrographic studies have identified crater-facies kimberlitic material at seven separate localities. Kimberlitic material is represented by tuffs, tuffisites and various epiclastic sediments containing chrome spinel, picroilmenite, manganoan ilmenite, zircon and diamond. The diamond grade varies from 0.2–1.8 ct/m³. Chrome spinel has 30–61 wt.% Cr₂O₃. Picroilmenite contains 6–14 wt.% MgO and 0.2–4 wt.% Cr₂O₃. Manganoan ilmenite has less than 3 wt.% MgO and 0.38–1.41 wt.% MnO. The ¹⁷⁶Hf/¹⁷⁷Hf ratio in kimberlitic zircons is 0.028288–0.28295 with ε_Hf = 5.9–8.3, and lies on the average kimberlite trend between depleted mantle and CHUR. The previously known barren and weakly diamondiferous kimberlites in the Juina area have ages of 79–80 Ma. In contrast, zircons from the newly discovered Chapadão kimberlites have a mean ²⁰⁶Pb/²³⁸U age of 93.6 ± 0.4 Ma, corresponding to a time of magmatic activity related to the opening of the southern part of the Atlantic Ocean. The most likely mechanism of the origin of kimberlitic magma is super-deep subduction process that initiated partial melting of zones in lower mantle with subsequent ascent of proto-kimberlitic magma.  相似文献   

Ground-based measurements of the methane distribution on Titan     

Paulo F. Penteado  Caitlin A. Griffith 《Icarus》2010,206(1):345-7996

Using spectra taken with NIRSPEC (Near Infrared Spectrometer) and adaptive optics on the Keck II telescope, we resolved the latitudinal variation of the 3ν₂ band of CH₃D at 1.56 μm. As CH₃D is less abundant than CH₄ by a factor of 50±10×10^-5, these CH₃D lines do not saturate in Titan’s atmosphere, and are well characterized by laboratory measurements. Thus they do not suffer from the large uncertainties of the CH₄ lines that are weak enough to be unsaturated in Titan. Our measurements of the methane abundance are confined to the latitude range of 32°S-18°N and longitudes sampled by a 0.04″ slit centered at ∼195°W. The methane abundance below 10 km is constant to within 20% in the tropical atmosphere sampled by our observations, consistent with the low surface insolation and lack of surface methane [Griffith, C.A., McKay, C.P., Ferri, F., 2008. Astrophys. J. 687, L41-L44].  相似文献