Algal pigment patterns and phytoplankton assemblages in different water masses of the Río de la Plata maritime front     

José I. Carreto  Nora MontoyaRut Akselman  Mario O. CarignanRicardo I. Silva  Daniel A. Cucchi Colleoni 《Continental Shelf Research》2008

The composition of phytoplankton assemblages were studied in three sections across the continental shelf between the Río de la Plata and the oceanic waters of the Subtropical Convergence, during late spring. Algal communities were examined using microscopy and HPLC-derived pigment concentrations. The CHEMTAX program was used to estimate the chlorophyll a (chl a) biomass of different algal classes. Trends in pigment ratios due to phytoplankton photo-adaptation and photo-acclimation were also examined. In order to accommodate the natural diversity of phytoplankton assemblages the original data have been split to represent five ecosystems. In addition, the pigment data for the Brazil Current ecosystem has been split by sample depth.  相似文献   

Fe,Mn, P and S Speciation in Sediments from the Capivara Hydroelectric Dam Lake (Brazil) as an Indicator of Anthropogenic Influences     

Wagner José Barreto  Dilson Norio Ishikawa  Ieda Spacino Scarminio  João de Souza Costa  Paulo dos Santos Nora  Miriam de Fatima Soares  Romilaine Mansano Nicolau  Adriana Celeste Esteves Gonçalves  Sonia Regina Giancoli Barreto 《洁净——土壤、空气、水》2008,36(4):353-359

The conservation of large water resources is essential for the preservation of human life. The quantification and, more importantly, the speciation of chemical substances that indicate the presence of anthropogenic contamination in water resources are of great importance. This paper presents the results of analysis for the determination of organic, inorganic and total phosphorus, pseudo‐sulfur, and iron and manganese, in five fractions, in water sediments collected from the Capivara Hydroelectric Power Plant, Brazil. A study on the seasonal variation of these parameters was conducted, with data having been collected in the winter and in the summer, at two sites along the dam, 5 km apart, close to the city of Primeiro de Maio. Phosphorous was found in sediments and adjacent soil in the organic form (OP), and was used as an indicator of anthropogenic influence on the reservoir banks. Speciation of potentially toxic Mn showed that it is present in the exchangeable fraction of the 0–5 cm depth layer (sediment/water interface), making its transfer to the water column possible. Results from this study showed that domestic and industrial effluent treatment measures are needed for the preservation of the quality of aquatic environments.  相似文献   

Prediction of minesite-drainage chemistry through closure using operational monitoring data     

Kevin A. Morin  Nora M. Hutt 《Journal of Geochemical Exploration》2001,73(2):45

Post-mining drainage chemistry depends strongly on geochemical and hydrologic processes that occur during the operational years. Where routine operational monitoring data are abundant, the dominant processes can often be evaluated with no additional, special studies. Thus, post-mining drainage chemistry can be predicted with confidence based on the operational data. This is referred to here as ‘empirical drainage-chemistry modelling’ (EDCM).This paper presents examples of EDCM using routine monitoring databases from several minesites, each containing thousands of analyses and spanning up to 30 years of mine operation and closure. Simple statistical interpretations in the EDCM can reveal annual cycles and trends that aqueous concentrations display during operation and into closure.A new compilation of 12 EDCM equations for copper versus pH is presented to illustrate similar trends with pH among the sites. However, this compilation also shows that average-annual copper concentrations at a particular pH can vary by three orders of magnitude, reflecting site-specific factors. Also, a new case study comparing actual closure concentrations to those predicted with EDCM in 1991 demonstrates that predictive accuracy is within a factor of two.  相似文献   

Paleontology,sedimentology and paleoenvironment of a new fossiliferous locality of the Jurassic Cañadón Asfalto Formation,Chubut Province,Argentina     

Oscar F. Gallego  Nora G. Cabaleri  Claudia Armella  Wolfgang Volkheimer  Sara C. Ballent  Sergio Martínez  Mateo D. Monferran  Diego G. Silva Nieto  Manuel A. Páez 《Journal of South American Earth Sciences》2011,31(1):54-68

A new Late Jurassic assemblage of “conchostracans”, ostracods, bivalves and caddisfly cases from the locality “Estancia La Sin Rumbo”, Chubut Province (Patagonia, Argentina) is recorded. The fossils occur in the upper part of an outcropping 45 m thick volcaniclastic lacustrine sequence of yellowish tuffs and tuffites of the Puesto Almada Member, which is the upper member of the Cañadón Asfalto Formation with U/Pb age of 161 ± 3 Ma. The sequence represents one sedimentary cycle composed of a (lower) hemicycle of expansion and a (higher) hemicycle of contraction of the water body. The invertebrates lived in small freshwater bodies during the periods of expansion of the lake. The occurrence of a great number of small spinicaudatans, associated with mud-cracks, is evidence of dry climatic conditions and suggests several local mortality events. The spinicaudatan record of the fushunograptid–orthestheriid (component of the Eosestheriopsis dianzhongensis fauna) and the presence of Congestheriella rauhuti Gallego and Shen, suggest a Late Jurassic (Oxfordian to Tithonian) age. Caddisfly cases are recorded for the first time in the Cañadón Asfalto Basin.  相似文献   

Designing air ticket taxes for climate change mitigation: insights from a Swedish valuation study     

Jonas Sonnenschein  Nora Smedby 《Climate Policy》2019,19(5):651-663

Research on air travellers’ willingness to pay (WTP) for climate change mitigation has focussed on voluntary emissions offsetting so far. This approach overlooks policy relevant knowledge as it does not consider that people may value public goods higher if they are certain that others also contribute. To account for potential differences, this study investigates Swedish adults’ WTP for a mandatory air ticket surcharge both for short- and long-distance flights. Additionally, policy relevant factors influencing WTP for air travel emissions reductions were investigated. The results suggest that mean WTP is higher in the low-cost setting associated with short-distance flights (495 SEK/ tCO₂; 50 EUR/ tCO₂) than for long-distance flights (295 SEK/ tCO₂; 30 EUR/t CO₂). The respondents were more likely to be willing to pay the air ticket tax if they were not frequent flyers, if they were women, had a left political view, if they had a sense of responsibility for their emissions and if they preferred earmarking revenues from the tax for climate change mitigation and sustainable transport projects.

Key policy insights

• A mandatory air ticket tax is a viable policy option that might receive majority support among the population.

• While a carbon-based air ticket tax promises to be an effective tool to generate revenues, its potential steering effect appears to be lower for low cost contexts (short-distance flights) than for high cost contexts (long-distance flights).

• Policy consistency regarding the tax base and its revenue use may increase public acceptability of (higher) air ticket taxes. Earmarking revenues is clearly preferred to tax recycling or general budget use.

• Insights about the personal drivers behind WTP for emissions reductions from air travel can help to inform targeting and segmentation of policy interventions.

  相似文献   

Hepatic biomarkers of sediment-associated pollution in juvenile turbot, Scophthalmus maximus L     

Hartl MG  Kilemade M  Sheehan D  Mothersill C  O'Halloran J  O'Brien NM  van Pelt FN 《Marine environmental research》2007,64(2):191-208

Hatchery-reared turbot (Scophthalmus maximus L.) were exposed for 3 weeks, under laboratory conditions, to sediment collected from polluted sites in Cork Harbour and a reference site at Ballymacoda, Co. Cork, Ireland. The potential of surficial sediment for inducing hepatic biomarkers was assessed at two levels of biological organisation: expression of cytochrome P450 [Western blotting analysis and 7-ethoxy-resorufin O-dealkylase (EROD), 7-benzoxy resorufin O-dealkylase (BROD), 7-methoxy resorufin O-dealkylase (MROD), 7-pentoxy-resorufin O-dealkylase (PROD) activities] and DNA integrity (Comet assay). Positive controls were generated, either by exposing turbot to cadmium chloride-spiked seawater (Comet assay) or to beta-naphthaflavone by intraperitoneal injection (cytochrome P450 induction). The induction of cytochrome P450 activity (EROD, MROD and PROD) in animals following a 7-day exposure to contaminated sediments was significantly higher than those exposed to reference site sediment and remained elevated thereafter; BROD was not induced. DNA single-strand breaks were also significantly higher following exposure to contaminated sediments throughout the experiment. Although no direct correlation between induction of alkoxyresorufin O-dealkylase activities and a particular chemical class was established, the induction of MROD and PROD activities in fish exposed to sediments containing complex contaminant mixtures, appeared to be more sensitive than conventional EROD activity assays. We conclude from the present laboratory study that S. maximus is a suitable sentinel species for the assessment of moderately contaminated sediments and therefore allows for the further development of this model for future, ecologically relevant, field studies.  相似文献   

A computer modelling study of the interaction of organic adsorbates with fluorapatite surfaces     

Donald Mkhonto  Phuti E. Ngoepe  Timothy G. Cooper  Nora H. de Leeuw 《Physics and Chemistry of Minerals》2006,33(5):314-331

Computer modelling techniques were employed to investigate the adsorption of a selection of organic surfactant molecules to a range of fluorapatite surfaces, and new interatomic potential models for the apatite/adsorbate interactions are presented. The adsorbates coordinate mainly to the surfaces through interaction between their oxygen (or nitrogen) atoms to surface calcium ions, followed by hydrogen-bonded interactions to surface oxygen ions and, to a much lesser extent, surface fluorides. Bridging between two surface calcium ions is the preferred mode of adsorption, when the geometry of the adsorbates allows it, and multiple interactions between surfaces and adsorbate molecules lead to the largest adsorption energies. All adsorbates containing carbonyl and hydroxy groups interact strongly with the surfaces, releasing energies between approximately 100 and 215 kJ mol⁻¹, but methylamine containing only the –NH₂ functional group adsorbs to the surfaces to a much lesser extent (25–95 kJ mol⁻¹). Both hydroxy methanamide and hydroxy ethanal prefer to adsorb to some surfaces in an eclipsed conformation, which is a requisite for these functional groups. Sorption of the organic material by replacement of pre-adsorbed water at different surface features is calculated to be mainly exothermic for methanoic acid, hydroxy methanamide and hydroxy ethanal molecules, whereas methyl amine would not replace pre-adsorbed water at the fluorapatite surfaces. The efficacy of the surfactant molecules is calculated to be hydroxy aldehydes > alkyl hydroxamates > carboxylic acids ≫ alkyl amines. The results from this study suggest that computer simulations may provide a route to the identification or even design of particular organic surfactants for use in mineral separation by flotation.  相似文献   

Preliminary studies on methane fluxes in Hainan mangrove communities     

卢昌义  黄玉山  谭凤仪  叶勇  崔胜辉  林鹏 《中国海洋湖沼学报》1998,16(1):64-71

INTRODUCTIONChrbondioxideandInehanearethetwomostabundantabosphericcarbonspedes.Methane'sconcenhati0nintheboposphereinonsesO.7-l.l%peryearraasmussenandKhaili,l98l,BlakeandRowand,l988,Scheeetal.,l989).Ihauseofmethne'sforpaCtontheearth'sclirnateandthechernistryoftheatInosphere,thebudgetofabosphericmethanehasmivedconsiderableattchti0n.Wetlandsareestirnataltobeoneofthelamptsoimofabosphericmethane,aocountingforab0ut4O%to5O%0ftheglobalInehanesoonannually(Cforneand0reInland,l988,WhitingandC…  相似文献   

Vegetation analysis of a typical mangrove swamp—Lai Chi Wo coast of Hong Kong     

Lu Chang-yi  Wong Yuk-shan  F. Y. Tam Nora  Berry Richard 《中国海洋湖沼学报》1998,16(1):72-77

A vegetation analysis reveals that the Lai Chi Wo mangrove swamp in Hong Kong has 10 mangrove species comprising 76.9% of the total number of mangrove species in Hong Kong. This swamp is a mixed community dominated byAegiceras corniculatum, Heritiera littoralis, Excoecaria agallocha, Kandelia candel, Bruguiera gymnorrhiza, with importance values of 37.88, 28.19, 14.33, 11.33 and 8.27 respectively. The community’s mangrove species diversity and evenness, as based on the Shannon-Wiener Function, were 1.44 and 62.01%, which were lower than those of the south su-tropical evergreen broad-leaf forest community but its ecological dominance (0.26) was higher. The correlation information field (CIF) method, a useful analytical method for complex forest community, was adopted in the present mangrove analysis. The species correlation information was:Aegiceras corniculatum (0.268)>Heritiera littoralis (0.250)>Kandelia candel (0.220)>Excoecaria agallocha (0.169)>Bruguiera gymnorrhiza (0.101). The correlation information of the mangrove community was 1.008. This work was financially supported by the Agriculture and Fisheries Department of The Hong Kong Government and The Hong Kong University of Science & Technology.  相似文献   

Post-Wisconsinian paleoenvironments at Salinas del Bebedero basin, San Luis, Argentina     

Miguel A. González  Nora I. Maidana 《Journal of Paleolimnology》1998,20(4):353-368

We present a climatic reconstruction of Holocene lacustrine episodes in the Salinas del Bebedero basin (Argentina), based on geological and diatom information.Morphological, sedimentological and diatom evidence between 11600 ± 140 yr BP and 325 ± 95 yr BP, allowed us to interpret the paleoenvironments of the basin. Episodes of high energy (sandy levels) are linked to large inflow of meltwater through the Desaguadero River, related to development of glaciers on the Andes. This inflow is characterized by peaks of relative abundance of the brackish water diatom Cyclotella choctawatcheeana Prasad. The values of C. choctawatcheeana decrease in deposits of low energy (clay levels), where it co-dominates with oligohalobous Fragilaria and Epithemia spp.To the last two peaks of large inflow of meltwater, radiocarbon dates corrected to sidereal ages, are AD 1280/1420 and AD 1443/1656. These ages agree with two cold episodes clearly recorded in dendrological studies from the Patagonian Andes and were correlated to the Little Ice Age. Thus, older Holocene episodes of large inflow of water to the basin were correlated with the Neoglacial Advances defined by Mercer (1976) for the Andes.  相似文献