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61.
The use of coefficients, derived from cross-sectional mortality studies, for air pollution risk assessment is quite controversial. In this study, the major limitations of cross-sectional studies are reviewed. The consistency of results from the major recent cross-sectional studies is examined, and the sensitivity of results to model specification is analyzed. Finally, the implications for risk assessment of our inquiries are discussed. 相似文献
62.
The effects of pathway configuration, landmarks and stress on environmental cognition 总被引:1,自引:0,他引:1
Gary W. Evans Mary Anne Skorpanich Tommy Grling Kendall J. Bryant Brian Bresolin 《Journal of environmental psychology》1984,4(4):323-335
The results of this study indicate that manipulations of the pathway grid configuration and landmark placement in a setting cause changes in environmental knowledge. These experimental manipulations were accomplished using a realistic, dynamic simulation technique at the Berkeley Environmental Simulation Laboratory. Measures of environmental knowledge include: memory for incidental information along the simulated urban route, accuracy of route maps, relocation memory for scenes along the route, and questionnaire measures. Data are also presented showing both positive and negative effects of stress from noise on the processes of environmental cognition. 相似文献
63.
M. E. Evans 《Die Naturwissenschaften》1983,70(10):485-494
Two distinct types of motion are commonly attributed to the geomagnetic poles — polar wander and dipole wobble. But two or three decades of intensive effort have failed to provide a sound understanding of either. Why? Polar wander is a very slow phenomenon associated with time scales of 107 to 108 years and thus intimately connected with the drift of the continents arising from plate tectonics. While there is no question of the validity of relative movements between the continents and the pole, the possibility of independent polar motion remains debatable. Dipole wobble is a more rapid phenomenon, most likely associated with time scales of 106 years or less. Currently the geomagnetic axis diverges from the Earth's spin axis by 11 1/2°, but paleomagnetic data indicate that, when averaged over a million years or so, the two coincide. Dipole wobble is the supposed mechanism responsible. The main difficulty here is one of isolating any dipole effects from perturbations of similar magnitude arising from the non-dipole fraction of the geomagnetic field — the so-called secular variation. Recent studies have significantly advanced our understanding of the secular variation, but the dipole wobble remains enigmatic. 相似文献
64.
Identification of metal toxicity in sewage sludge leachate 总被引:1,自引:0,他引:1
Sewage sludge is a source of organic matter and nutrients with the potential for being used as a fertilizer. However, metals in sewage sludge might accumulate in soil after repeated sludge applications, and metal concentrations might reach concentrations that are toxic to microorganisms, soil organisms and/or plants. This toxicity might change with time due to kinetic factors or abiotic factors such as freezing, drying or rainfall. The objective of this study was to determine toxicity of sewage sludge leachate from a lysimeter with 50 cm of sludge applied. Attempts were also made to identify the cause of toxicity of the sludge leachate by toxicity identification and evaluation (TIE) techniques. Sludge leachate was collected monthly during 1 experimental year (August 2001 to August 2002). Metal concentrations were analysed, and the toxicity was determined with Daphnia magna (48-h immobility). The effect of EDTA or sodium thiosulphate addition, filtration through a CM-resin or a Millex-resin on toxicity was also tested. The results showed that toxicity of the sludge leachate apparently varied during the year, and that filtration through the CM-resin reduced most of the toxicity followed by the addition of EDTA. None of the other treatments reduced the toxicity of the sludge leachate. This indicated that one or more metals were responsible for the observed toxicity. Further calculations of toxic units (TU) suggested that Zn contributed most to the toxicity. Results also indicated that Ca concentrations in the sludge leachate reduced the toxicity of Zn. 相似文献
65.
66.
Although choristoderes have a good Lower Cretaceous record in Asia, they have never previously been recorded from Jurassic
deposits. Here we describe fragmentary vertebral material referable to Choristodera indet. from the Middle Jurassic Balabansai
Svita of the Fergana Valley, Kyrgyzstan. This provides a significant range extension for the group in Asia and shows that
choristoderes already had a Pan-Laurasian distribution in the Jurassic. 相似文献
67.
Risk-based regulation assumes that risk assessment can evaluate risks against policy objectives. However, policy goals are often ambiguous and require risk assessors to interpret them for use in risk assessment. This risk assessment-policy gap stems partly from normative and imprecise policy language but is rooted more fundamentally in society's uncertain expectations for the environment. Until this uncertainty is resolved, the democratic and regulatory effectiveness of risk regulation will be undermined by ad hoc policy decisions abdicated to risk assessors. 相似文献
68.
Dave Niyam Varadavenkatesan Thivaharan Singh Ram Sharan Giri Balendu Shekher Selvaraj Raja Vinayagam Ramesh 《Environmental science and pollution research international》2021,28(42):58857-58871
Environmental Science and Pollution Research - Green macroalgae comprise significant amount of structural carbohydrates for their conversion to liquid biofuels. However, it generally relies on... 相似文献
69.
Dyfed Evans 《Environmental geochemistry and health》1991,13(2):84-92
This study investigates contemporary fluvial contamination of stream sediments by Pb, Zn and Cu from a mine near Aberystwyth, Wales. Of particular interest is the association between metal cations and particulate substrates and which is investigated using a selective extraction procedure. Emphasis is also placed on the difference between adsorptive phases depending on particle size. As particle size decreases the labile phase becomes dominant, with the easily and moderately reducible fraction being the major scavenging agent of soluble cations. Zinc and copper are largely held as residual rock or ore particles and are therefore expected to have a longer residence time in sediments. Recent floodplain development is difficult to interpret due to reworking of upstream metal-rich alluvium. However evidence is presented to suggest that once silt and clay size particles enter the main channel they are largely removed from the system. 相似文献
70.
Mauricio Rodriguez-Lanetty Elisha M. Wood-Charlson Lea L. Hollingsworth Dave A. Krupp Virginia M. Weis 《Marine Biology》2006,149(4):713-719
The obligate symbiotic relationship between dinoflagellates, Symbiodinium spp. and reef building corals is re-established each host generation. The solitary coral Fungia scutaria Lamarck 1801 harbors a single algal strain, Symbiodinium ITS2 type C1f (homologous strain) during adulthood. Previous studies have shown that distinct algal ITS2 types in clade C correlate with F. scutaria—Symbiodinium specificity during the onset of symbiosis in the larval stage. The present study examined the early specificity events in the onset of symbiosis between F. scutaria larvae and Symbiodinium spp., by looking at the temporal and spatial infection dynamics of larvae challenged with different symbiont types. The results show that specificity at the onset of symbiosis was mediated by recognition events during the initial symbiont—host physical contact before phagocytosis, and by subsequent cellular events after the symbionts were incorporated into host cells. Moreover, homologous and heterologous Symbiodinium sp. strains did not exhibit the same pattern of localization within larvae. When larvae were infected with homologous symbionts (C1f), ~70% of the total acquired algae were found in the equatorial area of the larvae, between the oral and aboral ends, 21 h after inoculation. In contrast, no spatial difference in algal localization was observed in larvae infected with heterologous symbionts. This result provides evidence of functional differences among gastrodermal cells, during development of the larvae. The cells in the larval equator function as nutritive phagocytes, and also appear to function as a region of enhanced symbiont acquisition in F. scutaria. 相似文献