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31.
Previous work has shown that the breeding density of a bird characteristic of upland streams, the dipper Cinclus cinclus, is markedly reduced at low pH in both Wales and Scotland. Populations also declined when streams became more acidic. Evidence of causal explanation for these relationships is that: (1) Food quantity is reduced in acidic streams, and important prey, including those rich in calcium, are scarce; (2) Blood chemistry in pre-breeding birds differs between acid and circumneutral streams, with plasma calcium reduced in those breeding at low pH. Skeletal sources of calcium are probably limited; (3) The time spent foraging by pre-breeding birds on acidic streams is markedly increased, even though overall energy costs on acidic and circumneutral streams are similar. Body condition is inferior to birds on circumneutral streams; (4) Egg laying is significantly delayed on acidic streams irrespective of an effect on laying of altitude, and clutch and brood sizes are significantly reduced; (5) Eggs are lighter and shells thinner at low pH; (6) Chick growth is reduced at low pH; (7) Contamination by heavy metals and persistent organochlorines is low in the populations on acidic streams and cannot explain the impaired breeding performance. None of these features can exclude the possibilities that acidic streams either hold populations of poor quality birds, which show the above features, or that acidity affects the breeding ecology of all dippers that attempt to breed at low pH. The qualitative outcome of these two alternatives is identical.  相似文献   
32.
Environment, Development and Sustainability - Renewable energy (RE) plays an increasingly important role in the economy of almost every country in the world. In order to examine the state of...  相似文献   
33.
Rate-temperature responses in scyphozoan medusae and polyps   总被引:1,自引:0,他引:1  
The effects of temperature on oxygen consumption and spontaneous rhythmic activity have been investigated in various stages of the life histories of 3 species of jellyfish from the Chesapeake Bay, USA. All 3 species clearly show the ability to acclimate positively to temperature change. Thermal sensitivity of metabolism in the winter medusa Cyanea capillata fulva is fairly low at temperature intervals which are experienced in nature. Polyps of the two summer medusae, Chrysaora quinquecirrha and Aurelia aurita, show reduced metabolic sensitivity at temperatures normally accompanying high developmental activity and the onset of strobilation.  相似文献   
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Summary As stated at the beginning of this paper conclusions reached thus far cannot be discussed in this paper. However, a great deal of information is available for examination.EPA displayed its ability to coordinate widely separated laboratories, both Federal and private, into a smooth working team in a very short period of time. A very comprehensive study plan was also developed and implemented quickly. EPA was fortunate to have already had GCA under contract when the emergency arose. In no small part the success of the field effort was due to the managerial and technical abilities of the GCA team.Within a period of 6 weeks a plan was developed, a prime contractor retained, subcontractors hired, and field activities begun. Within a period of 3 months in excess of 8600 field samples were collected and over 12,000 field and QC samples were analyzed. During this same period 2 major data systems were developed, debugged, and placed into operation.In short this EPA project was probably the most comprehensive multimedia field project ever attempted by EPA and certainly the data is being subjected to the most strenuous quality control measures ever imposed by this Agency. The entire program is presently under peer review and the results are being prepared for publication by EPA Headquarters.Note. Originally intended to be published as part of the special issue on Exposure Monitoring: An International Workshop (Las Vegas, Nevada, October 19–22, 1981).  相似文献   
38.
In many situations, the effect of a toxic chemical on a biological system depends on both the intensity and the duration of exposure. The dependence on the time dimension can be the expression of a range of processes including the physical accumulation of toxic chemicals or their metabolites and the functional accumulation of damage. Measures and functions that have been used to describe this dependence are reviewed.Some of these functions are compared through a case study of the neurotoxicity of methylmercury. Use is made of data that indicates a dependency between the blood concentration at which monkeys were exposed and the length of time before damage was detected. Several exposure functions are fitted to these data and their appropriateness is compared. Using the most appropriate function, an exposure-response relationship is developed using probit analysis. An alternative data analysis procedure is also investigated. The apparent threshold after a 100 day exposure is estimated to be greater by a factor of 3–5 compared to the threshold for chronic exposure. Applying this factor to man, the blood concentration threshold for chronic exposure is estimated to be 40–170 ppb, a finding consistent with recent reports of neurological damage in humans exposed below the generally accepted threshold.  相似文献   
39.
  1. The Air Polluttion Monitoring System has got a significant development of late, which is in direct relation with a considerable extention and improvement of the observation network in cities and industrial areas, with creation of a new network for assessing regional and global background of the atmosphere pollution, as well as with the wide involvement of meteorologists to monitoring organization.
  2. While developing a new global monitoring system, it is necessary to take into account its relationship with the local monitoring within the region of air pollution sources, i.e. at the \lsimpact\rs level. The need in such an account is dictated first of all by the physics of pollutant spreading that states: changes in air pollution over large territories must be in a certain agreement with greater changes in the vicinity of emission sources. Methods applied in the global and local monitoring have also a number of common peculiarities. White organizing regional network for observations of the background pollution of the atmosphere twin stations (one of the pair of stations located outside the city boundaries in a small community, and the other, in the nearest city with the population of 200–400 thousand inhabitants) were established in the U.S.S.R. and in a number of socialist countries in Europe.
  3. Implementation of the twin-station principles in the U.S.S.R. has contributed to data interpretation and representativity assessment as well as to correction of the station location. Observation results from the Soviet background stations and those abroad have been compared by now according to a number of indices.
  4. The correlation of monitoring systems of various scales tells positively both on mutual improvement and completion of observational methods. The methods of obtaining integral characteristics of air pollution were used for the global monitoring, in particular spectral actinometric observations and chemical analysis of the precipitation composition. Now they find still wider employment. Thus methods of spectral actinometric measurements and data processing were used to estimate the degree of aerosol pollution of a number of industrial centres. The theory of solar radiation spreading and aerosol contents determination in urban atmosphere has also been developed. It is a generalization of an earlier developed theory, used to estimate global atmosphere pollution basing on actinometric data. The organization of precipitation collection and analysis on a network of stations around Leningrad and in Donbass area enables us to compare the admixture content in precipitations falling in industrial and agricultural areas.
  5. A considerable increase of possibilities to measure microconcentrations of sulphur dioxide, nitrogen oxides and of a number of other pollutants is connected with the use of solid solvents for sampling. Their use will allow to avoid establishment of special laboratories at background stations and only send samples by post for their analysis in centralized laboratories.
They will also allow to considerably increase precision and accuracy of measurements. The international comparisons of methods of air pollution measurements on the background level allow to judge about the effiency of these methods.  相似文献   
40.
Determination of biomass burning emission factors: Methods and results   总被引:3,自引:0,他引:3  
Biomass burning, in a broad sense, encompasses different burning practices, including open and confined burnings, and different types of vegetation. Emission factors of gaseous or particulate trace compounds are directly dependent both on the fuel type and the combustion process. Emission factors are generally calculated by stoichiometric considerations using the carbon mass balance method, applied either to combustion chamber experiments or to field experiments based on ground-level measurements or aircraft sampling in smoke plumes. There have been a number of experimental studies in the last 10 years to investigate wildfires in tropical, temperate, or boreal regions. This article presents an overview of measurement methods and experimental data on emission factors of reactive or radiatively active trace compounds, including trace gases and particles. It focuses on fires in tropical regions, that is, forest and savanna fires, agricultural burns, charcoal production, use of fuelwood, and charcoal combustion.  相似文献   
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