Discussion on &quot;Giant versus small porphyry copper deposits of Cenozoic age in northern Chile: adakitic versus normal calc-alkaline magmatism&quot; by Oyarzun et al. (<Emphasis Type="Italic">Mineralium Deposita</Emphasis> 36:794–798, 2001)     

Osvaldo?M.?RabbiaEmail author  Laura?B.?Hernández  Robert?W.?King  Leopoldo?López-Escobar 《Mineralium Deposita》2002,37(8):791-794

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Toxicity of 1,4-dichlorobenzene in sediments to juvenile polychaete worms   总被引：1，自引：0，他引：1  

McPherson CA  Tang A  Chapman PM  Taylor LA  Gormican SJ 《Marine pollution bulletin》2002,44(12):1405-1414

Investigation of sediment contamination associated with a marine sewage outfall in Victoria (BC, Canada) found elevated concentrations of 1,4-dichlorobenzene (1,4-DCB). Juvenile polychaete worm (Neanthes) growth was significantly reduced at or near the outfall, roughly corresponding to elevated 1,4-DCB concentrations. There are few data on 1,4-DCB toxicity to marine organisms and no published literature on its toxicity to benthic marine organisms. To determine whether reduced polychaete growth (measured as dry weight) was due to 1,4-DCB exposure, a laboratory investigation was conducted. Uncontaminated marine sediment was spiked with 1,4-DCB and juvenile Neanthes were exposed in 20-d sublethal toxicity tests. There were no adverse effects on survival at any test concentration; mean survival was 80–100%. Statistically significant decreases in average dry weight only occurred at the highest 1,4-DCB concentration (19,900 μg/kg, dry weight); this represented a 1,4-DCB concentration more than 10 times higher than previously measured at the outfall (1710 μg/kg, dry weight). There were no adverse effects on survival or dry weight at the range of concentrations previously measured in sediments from the vicinity of the outfall.  相似文献   

The SCUBA Half Degree Extragalactic Survey – IV. Radio–mm–FIR photometric redshifts     

Itziar Aretxaga  David H. Hughes  Kristen Coppin  Angela M. J. Mortier  Jeff Wagg  James S. Dunlop  Edward L. Chapin  Stephen A. Eales  Enrique Gaztañaga  Mark Halpern  Rob J. Ivison  Eelco van Kampen  Douglas Scott  Stephen Serjeant  Ian Smail  Thomas Babbedge  rew J. Benson  Scott Chapman  David L. Clements  Loretta Dunne  Simon Dye  Duncan Farrah  Matt J. Jarvis  Robert G. Mann  Alexandra Pope  Robert Priddey  Steve Rawlings  Marc Seigar  Laura Silva  Chris Simpson  Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2007,379(4):1571-1588

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Fermi paradox and alternative strategies for seti programs: The Anthropic Principle and the search for close solar analogs     

Massimo Fracassini  Laura E. Pasinetti Fracassini  Antonio L. Pasinetti 《Astrophysics and Space Science》1988,146(2):321-331

The Anthropic Principle, a new trend of modern cosmology, claims that the origin of life and the development of intelligent beings on the Earth is the result of highly selective biological processes, strictly tuned in the fundamental physical characteristics of the Universe. This principle could account for the failure of some programs of search for extraterrestrial intelligences (SETI) and suggests the search for strict solar analogs as a primary target for SETI strategies. In this connection, we have selected 22 solar analogs and discussed their choice.  相似文献   

Benthic diatom community response to environmental variables and metal concentrations in a contaminated bay adjacent to Casey Station, Antarctica     

Cunningham L  Snape I  Stark JS  Riddle MJ 《Marine pollution bulletin》2005,50(3):264-275

This study examined the effects of anthropogenic contaminants and environmental variables on the composition of benthic diatom communities within a contaminated bay adjacent to an abandoned waste disposal site in Antarctica. The combination of geographical, environmental and chemical data included in the study explained all of the variation observed within the diatom communities. The chemical data, particularly metal concentrations, explained 45.9% of variation in the diatom communities, once the effects of grain-size and spatial structure had been excluded. Of the metals, tin explained the greatest proportion of variation in the diatom communities (28%). Tin was very highly correlated (R2>0.95) with several other variables (copper, iron, lead, and sum of metals), all of which explained similarly high proportions of total variation. Grain-size data explained 23% of variation once the effects of spatial structure and the chemical data had been excluded. The pure spatial component explained only 1.8% of the total variance. The study demonstrates that much of the compositional variability observed in the bay can be explained by concentrations of metal contaminants.  相似文献   

Effects of Soil Composition on Zn Speciation in Drainage Waters from Agricultural Soils     

Hanbin?XueEmail author  Phan?Hong?Nhat  Laura?Sigg 《Aquatic Geochemistry》2005,11(3):303-318

The influence of Zn speciation on Zn transport by drainage from different soils to surface water is examined in a stream catchment in an agricultural area. Drainage waters were collected from two types of soils, a mineral soil (MS) and a soil rich in organic matter (OS) by means of artificial drainage pipes. The speciation of dissolved Zn in the stream and the drainage waters was determined using ligand-exchange and voltammetry. About 50–95% of dissolved Zn is bound in strong complexes, and the free Zn²⁺ ion concentration is in the range of 1–16% of dissolved Zn. A substantial part of Zn is present in weaker organic or inorganic complexes. The simulated Zn speciation using the WHAM VI model is compared to the determined speciation. Free Zn²⁺ concentrations predicted by the WHAM VI model are generally higher than the analytically determined free Zn²⁺, but are mostly within the same order of magnitude. Effects of different soil organic matter content on Zn speciation and transport are discussed. Zn speciation in the drainage at the OS site is influenced by the distribution of organic matter between the solid and solution phase. The abundant organic Zn complexes in solution contribute to facilitate Zn transport from soil into surface waters, through the drainage at the OS site. Drainage from the OS site contributes about twice as much Zn input to the receiving water as the MS soil, as related to specific area. The mineral soil contains much lower organic matter, and a part of Zn bound with inorganic phases can hardly be released by dissolved organic ligands, leading to much higher Zn retention at the MS site.  相似文献   

The influence of flushing rates, terrestrial input and low salmon escapement densities on paleolimnological reconstructions of sockeye salmon (Oncorhynchus nerka) nutrient dynamics in Alaska and British Columbia   总被引：3，自引：2，他引：1  

Anita J. Holtham  Irene Gregory-Eaves  Marlow G. Pellatt  Daniel T. Selbie  Laura Stewart  Bruce P. Finney  John P. Smol 《Journal of Paleolimnology》2004,32(3):255-271

Recent advances in paleolimnology have enabled reconstructions of past sockeye salmon (Oncorhynchus nerka) dynamics using a number of proxy-indicators, including diatoms and stable isotopes. Thus far, studies have focused on nursery lakes with high escapement densities and low flushing rates, ensuring that levels of salmon-derived nutrients (SDN) are high and are incorporated into the food chain. This study examines three oligotrophic sockeye salmon nursery lakes in Alaska (Afognak and Saltery lakes) and British Columbia (Hobiton Lake) to determine if sockeye salmon populations can be tracked in nursery systems with lower salmon escapement densities, higher flushing rates and/or higher terrestrial input. We adopted a multi-proxy approach using diatoms, stable isotopes (¹⁵N), organic carbon to nitrogen (C/N) ratios and pollen to draw inferences from ²¹⁰Pb-dated sediment cores. ¹⁵N showed little response to historic variation in sockeye salmon populations, even in Saltery Lake, which has a very high escapement density, and in Afognak Lake, in which average escapement is known to have increased. Dilution effects due to high flushing rates were likely partly responsible for the low ¹⁵N and minimal variation throughout the cores, although very high terrestrial input in Hobiton Lake also dampened the salmon signal. Small changes in diatom species assemblages, however, were evident in all three lakes and may be in response to fluctuating loads of salmon-derived nutrients. Most notably, increases of mesotrophic diatom taxa, such as Asterionella formosa and Aulacoseira subarctica, corresponded to increased salmon production in Alaskan lakes as a result of enhancement (fertilization) activities and climatic changes. Changes in the relative abundance of Cyclotella pseudostelligera in Hobiton Lake may also be in response to a significant decline in sockeye salmon populations off the west coast of Vancouver Island in the 1970s. Other factors, however, such as logging and lake fertilization may also have influenced diatom species composition. These results confirm that, while salmon-derived nutrients may be of key importance in juvenile salmonid development in some lakes, this may not be the case in all systems, especially those in which flushing rates are high. Further, in these systems, diatom communities appear to respond more sensitively to fluctuations in salmon populations (and therefore nutrients) than stable isotope methods, provided that other changes in trophic status are minor.  相似文献   

Some aspects of seismic hazard assessment when comparing different approaches     

Laura Peruzza  Dario Slejko 《Natural Hazards》1994,9(1-2):273-273

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Estimates of the γ-ray flux from Sagittarius A     

Laura Maraschi  Massimo Tarenghi  Aldo Treves 《Astrophysics and Space Science》1970,8(1):12-19

Analysis of the anisotropy of the -ray background observed by Clarket al. (1968) has lead to the suggestion that part of the anisotropy be due to a source at the Galactic Centre. The complex structure of radio and infrared emission of the region of Sgr A is considered. The -ray flux arising from Compton scattering and ₀ decay is calculated. For a value of the magnetic field H10^–4 Gauss, corresponding to equipartition, the -ray flux above 100 MeV at Earth from the Sgr A source is expected to lie between 10^–6 and 10^–5 gamma/cm² sec. Such a source should be detectable in the near future.  相似文献   

Book reviews     

Fakhry A. Assaad  Laura Stafford  Philip E. LaMoreaux 《Environmental Geology》2005,48(8):1149-1150

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