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901.
Environmental contamination with ionic chromium has been identified as a problem at numerous Superfund and RCRA Corrective Action sites. In many cases, contamination of groundwater to levels above existing standards or criteria may be a potential problem both for direct consumption of groundwater and for transport of mobile forms of chromium to areas such as basements where it can becontacted. In the environment, chromium occurs in two forms: trivalent and hexavalent. The trivalent form is generally immobile and nontoxic; hexavalent chromium is generally mobile and toxic. This article first presents the extent of the chromium problem, reviews the environmental chemistry literature on chromium, and reviews existing treatment technology for chromium immobilization in the nontoxic trivalent state. Finally, we present a case study where immobilization of chromium occurred through natural processes allowing a modified no-action scenario for site remediation. 相似文献
902.
903.
The geographic distribution of the animals of Venezuela was analyzed as a basis for a series of guidelines to help develop strategies for their conservation. A total of 313 animal taxa is distributed among 24 geographic units, corresponding to the political divisions of the country. Three different criteria were considered in analyzing these data: (1) the number and density of threatened taxa were used to define a ranking system for geographic units; (2) "hotspots" were identified using the distribution of threatened endemics, and (3) a "critical faunas analysis" was used to determine the minimum number of geographic units needed to maximize the number of sampled taxa. The first two criteria emphasize the importance of protecting habitat in the northern portion of the country, where most human intervention has already taken place. But the southern portion of the country is where most of the undisturbed habitat remains. We suggest that the conservation of the animals of Venezuela must follow a mixed strategy, based on two principles: one, aimed mainly at threatened endemics, should focus on the protection of critical habitat north of the Orinoco river, the second, aimed at all threatened animals— particularly high-risk taxa—should focus on assuring the long-term persistence of the pristine habitat in the south. 相似文献
904.
Ester van der Voet René Kleijn Lauran van Oers Reinout Heijungs Ruben Huele Paul Mulder 《Environmental science and pollution research international》1995,2(2):89-89
In the tradition of the study of materials flows through society, the Substance Flow Analysis (SFA) method and its software tool SFINX are presented. SFA aims at providing the relevant information for a country’s overall management strategy regarding single substances or coherent groups of substances. Three modelling techniques and their possibilities and limitations are discussed: Bookkeeping, static modelling, and dynamic modelling. The computer program SFINX can be used for varoius purposes: (1) to obtain an overview of stocks and flows of a substance in, out and through a nation’s economy and environment for a specific year, (2) to trace the origins of specific pollution problems, and (3) to estimate the effectiveness of certain abatement measures. Each application has its own requirements with regard to data and modelling. 相似文献
905.
Paul Stephen Corn 《Conservation biology》2003,17(2):622-625
906.
907.
Benthic ecology of the high arctic deep sea 总被引:2,自引:0,他引:2
An analysis is made of 75 quantitative benthic samples collected by Mini-LUBS, and 28 qualitative benthic samples collected with the small biological trawl, from Fletcher's Ice Island, T-3, while it was drifting over the Alpha Cordillera region of the High Arctic Ocean during October, 1969 through February, 1970 and in March, 1972. The depth range was 1000 to 2500 m. Benthic foraminiferans account for about 53%, bivalves for 27%, sponges for 7%, and polychaetes for 5% of the total biomass. Other groups make up the remaining 8%. The weight ratio of macro- to meiofauna is 1:1. Numerically, excluding Foraminifera, polychaetes comprise 42%, nematodes 16%, sponges 11%, and bivalves 8% of the total fauna. The remaining 23% is composed of 13 other taxa. Biomass in the Amerasian Basin at depths of 1000 to 2000 m is extremely low (0.04 g/m); it is comparable to depths of 5000 to 6000 m in the oligotrophic red-clay area of the mid-Pacific Ocean, and is 40 times less than biomass at comparable depths from Antarctica and off Peru. Diversity, as calculated by the Shannon-Weaver method, is low, suggesting that the Arctic ecosystem is young, as reported in earlier studies (Dunbar, 1968; Menzies et al., 1973). Although the H' values are low, no biocoenoses of oligomixity in the deep Arctic are revealed, contrary to previous statements and beliefs. There may be fewer major benthic groups in the Arctic Ocean than in other parts of the world oceans. Following the conventional terminology of Petersen (1913) and Thorson (1957), we have called the High Arctic biocoenoses of the Alpha Cordillera region a Thenea abyssorum-Spirorbis granulatus community. 相似文献
908.
Paul Ramdohr 《Die Naturwissenschaften》1971,58(12):613-615
The iron of the Mundrabilla meteorite contains graphite in very exceptional needle-like forms, obviously in many different polytypes. They are similar to graphite in the iron of the Khairpur meteorite. Here the needles || thec-axis form cross-like twins or thrillings with base faces of ~ 90°. Further growth can fill the interstices to form the cube-like “cliftonite”. 相似文献
909.
Christel Thauvin-Robinet Thierry Rousseau Christine Durand Nicole Laurent Catherine Maingueneau Laurence Faivre Paul Sagot Annie Nivelon-Chevallier 《黑龙江环境通报》2001,21(6):466-470
Porencephaly is a rare central nervous system (CNS) abnormality that can be caused by an intraparenchymal destructive process or a developmental defect. Here we report on a prenatal ultrasound diagnosis of complex CNS abnormalities including agenesis of the corpus callosum, agenesis of the cerebellar vermis, bilateral hydrocephaly, and bilateral porencephaly in fetus at 33 weeks' gestation. The diagnosis of familial orofaciodigital syndrome type I (OFD I) was raised after fetal autopsy, clinical examination of the family, and the X-linked dominant inheritance pattern. This is the fourth report of porencephaly in association with OFD I. We discuss the difficulties in genetic counselling since OFD I shows variable expressivity of the phenotypic features. Furthermore, we emphasize the importance of a detailed ultrasound examination after a prenatal diagnosis of porencephaly. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
910.
Julia Tomei Stella Semino Helena Paul Lilian Joensen Mario Monti Erling Jelsøe 《Mitigation and Adaptation Strategies for Global Change》2010,15(4):371-394
With the rising emphasis on biofuels as a potential solution to climate change, this paper asks whether certification schemes, developed to promote sustainable feedstock production, are able to deliver genuine sustainability benefits. The Round Table on Responsible Soy (RTRS) is a certification scheme that aims to promote responsible soy production through the development of principles and criteria. However, can and does this initiative address the negative impacts associated with the intensive production of soy? Taking the example of soy biodiesel produced in Argentina, this paper asks whether the social and environmental impacts of soybean production can be mitigated by the RTRS. It concludes that at present certification schemes are unlikely to be able to address either the institutional challenges associated with their implementation or the detrimental impacts of the additional demand generated by biofuels. 相似文献