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81.
Carbon isotopically based estimates of CO2 levels have been generated from a record of the photosynthetic fractionation of 13C [is equivalent to epsilon(p)] in a central equatorial Pacific sediment core that spans the last approximately 255 ka. Contents of 13C in phytoplanktonic biomass were determined by analysis of C37 alkadienones. These compounds are exclusive products of Prymnesiophyte algae which at present grow most abundantly at depths of 70-90 m in the central equatorial Pacific. A record of the isotopic composition of dissolved CO2 was constructed from isotopic analyses of the planktonic foraminifera Neogloboquadrina dutertrei, which calcifies at 70-90 m in the same region. Values of epsilon(p), derived by comparison of the organic and inorganic delta values, were transformed to yield concentrations of dissolved CO2 [is equivalent to c(e)] based on a new, site-specific calibration of the relationship between epsilon(p) and c(e). The calibration was based on reassessment of existing epsilon(p) versus c(e) data, which support a physiologically based model in which epsilon(p) is inversely related to c(e). Values of PCO2, the partial pressure of CO2 that would be in equilibrium with the estimated concentrations of dissolved CO2, were calculated using Henry's law and the temperature determined from the alkenone-unsaturation index U(K/37). Uncertainties in these values arise mainly from uncertainties about the appropriateness (particularly over time) of the site-specific relationship between epsilon(p) and 1/c(e). These are discussed in detail and it is concluded that the observed record of epsilon(p) most probably reflects significant variations in delta pCO2, the ocean-atmosphere disequilibrium, which appears to have ranged from approximately 110 microatmospheres during glacial intervals (ocean > atmosphere) to approximately 60 microatmospheres during interglacials. Fluxes of CO2 to the atmosphere would thus have been significantly larger during glacial intervals. If this were characteristic of large areas of the equatorial Pacific, then greater glacial sinks for the equatorially evaded CO2 must have existed elsewhere. Statistical analysis of air-sea pCO2 differences and other parameters revealed significant (p<0.01) inverse correlations of delta pCO2 with sea surface temperature and with the mass accumulation rate of opal. The former suggests response to the strength of upwelling, the latter may indicate either drawdown of CO2 by siliceous phytoplankton or variation of [CO2]/[Si(OH)4] ratios in upwelling waters. 相似文献
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研究区域性成矿问题的经验表明,只有根据构造图才能对该问题获得比较有效的解决。关于前寒武纪地层和构造认识的进展,促使成矿方面的许多观点更加明确,并有助于揭示影响矿产的成矿怍用和分布的一些重要因素。作者在编制成矿图时利用了等人的一些科学概念。有关前寒武纪成矿方面的某些新资料是1984年在莫斯科召开的二十七届国际地质会议上提出的。作为编图方法的基础,采用 相似文献
85.
A Monte Carlo-based approach to assess uncertainty in recharge areas shows that incorporation of atmospheric tracer observations (in this case, tritium concentration) and prior information on model parameters leads to more precise predictions of recharge areas. Variance-covariance matrices, from model calibration and calculation of sensitivities, were used to generate parameter sets that account for parameter correlation and uncertainty. Constraining parameter sets to those that met acceptance criteria, which included a standard error criterion, did not appear to bias model results. Although the addition of atmospheric tracer observations and prior information produced similar changes in the extent of predicted recharge areas, prior information had the effect of increasing probabilities within the recharge area to a greater extent than atmospheric tracer observations. Uncertainty in the recharge area propagates into predictions that directly affect water quality, such as land cover in the recharge area associated with a well and the residence time associated with the well. Assessments of well vulnerability that depend on these factors should include an assessment of model parameter uncertainty. A formal simulation of parameter uncertainty can be used to delineate probabilistic recharge areas, and the results can be expressed in ways that can be useful to water-resource managers. Although no one model is the correct model, the results of multiple models can be evaluated in terms of the decision being made and the probability of a given outcome from each model. 相似文献
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Ventura EC Gaelzer LR Zanette J Marques MR Bainy AC 《Marine environmental research》2002,54(3-5):775-779
The initial sampling in the Marine Monitoring Program (MOMAM), coordinated by the Ministry of Marine Affairs (IEAPM), was performed along the southeast coast of Brazil. Orthopristis ruber samples were collected at Guanabara, Sepetiba and Ilha Grande Bays. Microsomal CYP1A levels and cytosolic cholinesterase (ChE), catalase (CAT) and glutathione S-transferase (GST) activities were measured in the liver of these fish according to established procedures. CAT activity and CYP1A content were significantly higher (P < or = 0.05) in fish caught at Guanabara Bay, which might be due to higher levels of peroxisome proliferators and Ah receptor agonists, respectively, at this site compared to the other sites. Also, lower GST activity was observed in fish from this site, which may possibly be related to the presence of oxidative-stress inducing compounds. 相似文献
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Ruoppolo V Vanstreels RE Woehler EJ Heredia SA Adornes AC da Silva-Filho RP Matus R Poleschi C Griot K Kolesnikovas CK Serafini P 《Marine pollution bulletin》2012,64(7):1309-1317
Oil pollution is a significant conservation concern. We examined data from six institutions along the coast of South America: Emergency Relief Team of the International Fund for Animal Welfare, Fundación Mundo Marino, Centro de Recupera??o de Animais Marinhos, Natura Patagonia, Associa??o R3 Animal, and Mar del Plata Aquarium and data from resightings in Argentina, Brazil, Chile and Falkland/Malvinas Islands. From 2000 to 2010, 2183 oiled Magellanic penguins were rehabilitated as part of the routine activities of these institutions or during emergency responses to eight oil spills in which they were involved; all rehabilitated penguins were flipper banded and released. Since their release, 41 penguins were resighted until 31 December 2011. The results demonstrate that, when combined with other prevention strategies, the rehabilitation of Magellanic penguins is a strategy that contributes to the mitigation of adverse effects of oil spills and chronic pollution to the species. 相似文献