摘要:

The continuing degradation of the Earth's ozone layer by atmospheric pollutants has generated concern about the impact of increased solar ultraviolet-B radiation (UV-B) on aquatic ecosystems. UV-B is a small (less than 1% of total energy) but highly active component of the solar spectrum that can penetrate to biologically significant depths in lakes and oceans. It has the potential to cause wide-ranging effects, including mutagenesis, chronic depression of key physiological processes, and acute physiological stress that may result in death. There are major uncertainties at present about the appropriate time scales and bioassay protocols for assessing such effects. Algal and cyanobacterial cells have four lines of defence against the toxic effects of UV-B. Some species avoid UV exposure by their choice of habitat or by migration strategies. Many species produce sunscreening pigments that filter out UV wavelengths; mycosporine-like amino acids are an especially important and ubiquitous class of such compounds. Most cells have a variety of defences against the toxic end products of UV radiation, such as radical scavenging by carotenoid pigments and superoxide dismutase. Finally, most cells have at least some ability to identify and repair the UV damage of DNA and other biomolecules. There is a large interspecific variability in the extent of each of these defence strategies. Continuing ozone depletion is not likely to cause an abrupt collapse of photosynthetic production, but may result in subtle, community-level responses that could ultimately impact on higher trophic levels.Key words: Arctic, Antarctic, photosynthesis, UV radiation, UV-B, ozone, atmospheric pollutants.

ISSN:1208-6053    

DOI:10.1139/a93-001

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

This is a personal account of the investigation of DDE-induced eggshell thinning and the subsequent use of this information in the legal battle over the banning of DDT. The article focuses on the toxicological effects of DDT on the peregrine falcon,Falco peregrinus, although the effects on other species are briefly considered. The peregrine falcon population crashed throughout the Holarctic region in the 1950s and 1960s. Eggshell thinning was discovered in British peregrines in 1967 and was soon found to be a global phenomenon. The relationship between dichlorodiphenyldichloroethylene (DDE) residues and eggshell thinning was established by the beginning of the 1970s. Information on the effect of DDE on the peregrine falcon formed an important part of the evidence that led to the banning of DDT, and since a ban has been implemented in many countries the peregrine populations have improved in most areas.Key words: peregrine falcon, DDE, eggshell thinning.

ISSN:1208-6053    

DOI:10.1139/a93-002

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Published information concerning the current status of Europe's amphibians is reviewed. A large proportion of species are categorized as endangered or vulnerable. For those species that have been the subject of intensive study, declines are attributed to a diversity of factors, all arising from human destruction or alteration of the habitat. Current evidence does not support the suggestion that amphibians are universally affected by a single common cause.Key words: amphibian, Europe, decline, habitat loss.

ISSN:1208-6053    

DOI:10.1139/a93-003

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Large quantities of mercury are being released into the waters of the Amazon and its tributaries by gold-mining activities. Large releases are also taking place into the air. In this paper, the fate of mercury released to the environment by gold mining in the Brazilian Amazon is reviewed. Mercury contamination is presently widespread in the Amazon region. A major source of mercury in the local environment is the burning of the gold–mercury amalgam, which releases from 30 to 150 t of mercury yearly into the Amazon atmosphere. Air samples collected close to mining sites showed extremely high mercury concentrations (up to 7.5 μg∙m−3). Inside gold-dealers' shops or in amalgam-burning stations, ambient air concentrations may reach 100 μg∙m−3. A secondary source is the discharge of metallic mercury into rivers during the amalgamation process. Sediment concentrations frequently range from 0.3 to 3.0 μg∙g−1in contaminated sites. However, values as high as 19.8 μg∙g−1have been reported in some sites. Waters of many rivers are also contaminated, although reliable data on dissolved mercury concentrations are still lacking. Local carnivorous fishes typically show mercury concentrations higher than 1.0 μg∙g wet wt.−1in contaminated sites and methyl mercury represents over 90% of the total content. Human groups with fish-based diets frequently show evidence of mercury contamination, with high mercury concentrations in hair (up to 70 μg∙g−1). However, a reliable epidemiological study on the affected population still has to be carried out.Key words: mercury, gold mining, Amazon, sediments, aquatic bi

ISSN:1208-6053    

DOI:10.1139/a93-004

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The chemical composition of clouds collected in the eastern United States has been intensely monitored over a 4-year period as part of the Mountain Cloud Chemistry Project. On the basis of these measurements we prepared a climatology for cloud chemistry, using simple statistical analyses tools and incorporating meteorological and cloud physical and chemical information. Five mountain stations have been established for cloud collection covering the northern and southern Appalachian Mountain range: Whiteface Mountain, New York; Mount Moosilauke, New Hampshire; Shenandoah Mountain, Virginia; Whitetop Mountain, Virginia; and Mount Mitchell, North Carolina. This review presents the major result from this 4-year measurement program. Cloud cover and cloud base over the eastern United States were deduced from the global real-time nephanalysis archives produced by the U.S. Air Force, augmented by local observations. Both active and passive cloud collectors were deployed to sample cloud water on an hourly basis, i.e., with sufficient time resolution to resolve synoptic scale phenomena. Chemical analysis of cloud water was performed by a central analytical laboratory with occasional on-site analysis to satisfy quality control procedures. Reliable methods now exist for collecting cloud-water samples in sufficient quantities for detailed chemical analysis. The chemical composition of cloud water varied significantly between sites. However, the differences in cloud-water ion concentration do not necessarily establish a geographic gradient between the sites but rather reflect differences in air-mass trajectories associated with the synoptic air-flow pattern and differences in sample location above cloud base. The dependence of cloud-water ion concentrations on synoptic weather type and observed differences in relative frequencies of warm sector, marine flow, and post-cold frontal synoptic types between northern and southern sites suggest that the north–south differences in cloud-water ion concentrations are related to cloud climatology at the northern sites. When air-mass trajectories shift from southwest to northwest, the concentrations of H+, SO42−, NO3−and NH4+normally decrease but the southern sites continue to receive high concentrations under northwest flow. The height of cloud-water sample collection above cloud base was found to be an additional source of variability in both cloud-water chemistry and liquid-water content. Seasonal variation in cloud-water chemical composition was investigated at one site only. Sulfate levels were found to be significantly lower in supercooled clouds (i.e., during the 'cold' season) than in 'warm' clouds, but nitrate levels remained about the same.Key words: cloud chemistry, cloud frequency, air-mass trajectories,ANOVA.

ISSN:1208-6053    

DOI:10.1139/a93-005

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The pervasive occurrence of contaminated land has become a major issue facing society and involving enormous financial and social implications. Several problems arise at the interface between environmental science and public policy in dealing with future uses of such land. Contaminated sites need to have the nature and magnitude of the contamination identified. Such characterization must deal with the enormous complexity of many common wastes, the selection of appropriate analytical methods, and the heterogeneity of site conditions. Responses to these problems are limited by the capabilities of remediation technologies available. These may be categorized as containment/immobilization, mobilization, or destruction processes. In the last category, bioremediation has shown the most promise and general utility, but a number of specific requirements and constraints must be satisfied. For bioremediation to be feasible, the contaminants must be amenable to biological degradation, an appropriate and active microbial community must be provided, the contaminants must be accessible (bioavailable) to the microbial community, waste-specific constraints must be minimized, and appropriate environmental conditions must be provided for the microbial population. Cleanup criteria are fundamental to any decisions about contaminated sites. The U.S. Superfund approach has avoided developing generic contamination criteria, in contrast with the Canadian approach. Some common problems arise with either approach. There is a trend towards increasing reliance on risk assessment for site remediation decisions. Management challenges facing effective site remediation include the interdisciplinary nature of the issues, communication between laboratory and field personnel, and misrepresentation or inadequate attention to uncertainty. Constructive and positive advances to deal with these problems have been developed and include statistical sampling methods, tiered protocols, integrated toxicity testing procedures, multimedia partitioning models, and uncertainty analyses. Considering all the problems and challenges, there remains overwhelming evidence that prevention of contamination is vastly superior to remediation.Key words: waste characterization, analytical methods, cleanup technologies, bioremediation, cleanup criteria, risk management.

ISSN:1208-6053    

DOI:10.1139/a93-006

出版商:NRC Research Press    

年代:1993

数据来源: NRC