Specimens of the oceanic decapod Systellaspis debilis were collected from six sites in the East Atlantic Ocean between 1970 and 1984, and were analysed for Mn, Fe, Cu, Zn and Cd. The data confirm that there are small but significant differences in mean metal concentrations from some sites which showed no obvious pattern in relation to geographic location of the samples. As a result, ranges of site means are quoted as baseline levels for each metal (g g-1 dry wt): 2.3 to 2.9 g Mn g-1, 31.2 to 77.8 g Fe g-1, 25.9 to 83.4 g Cu g-1, 41.9 to 92.9 gZn g-1, 11.1 to 31.8 g Cd g-1. The concentration of cadmium in S. debilis from all sites was raised relative to cadmium concentrations reported for coastal decapods, perhaps as a result of dietary enrichment. Metal accumulation may provide useful information for understanding the complex feeding behaviour of many oceanic animals. 相似文献
A performance-based method for evaluating methane (CH4) oxidation as the best available control technology (BACT) for passive management of landfill gas (LFG) was applied at a municipal solid waste (MSW) landfill in central Washington, USA, to predict when conditions for functional stability with respect to LFG management would be expected. The permitted final cover design at the subject landfill is an all-soil evapotranspirative (ET) cover system. Using a model, a correlation between CH4 loading flux and oxidation was developed for the specific ET cover design. Under Washington’s regulations, a MSW landfill is functionally stable when it does not present a threat to human health or the environment (HHE) at the relevant point of exposure (POE), which was conservatively established as the cover surface. Approaches for modeling LFG migration and CH4 oxidation are discussed, along with comparisons between CH4 oxidation and biodegradation of non-CH4 organic compounds (NMOCs). The modeled oxidation capacity of the ET cover design is 15 g/m2/day under average climatic conditions at the site, with 100% oxidation expected on an annual average basis for fluxes up to 8 g/m2/day. This translates to a sitewide CH4 generation rate of about 260 m3/hr, which represents the functional stability target for allowing transition to cover oxidation as the BACT (subject to completion of a confirmation monitoring program). It is recognized that less than 100% oxidation might occur periodically if climate and/or cover conditions do not precisely match the model, but that residual emissions during such events would be de minimis in comparison with published limit values. Accordingly, it is also noted that nonzero net emissions may not represent a threat to HHE at a POE (i.e., a target flux between 8 and 15 g/m2/day might be appropriate for functional stability) depending on the site reuse plan and distance to potential receptors.
Implications: This study provides a scientifically defensible method for estimating when methane oxidation in landfill cover soils may represent the best available control technology for residual landfill gas (LFG) emissions. This should help operators and regulators agree on the process of safely eliminating active LFG controls in favor of passive control measures once LFG generation exhibits asymptotic trend behavior below the oxidation capacity of the soil. It also helps illustrate the potential benefits of evolving landfill designs to include all-soil vegetated evapotranspirative (ET) covers that meet sustainability objectives as well as regulatory performance objectives for infiltration control. 相似文献
The historical background on adaptation of algae to various light intensities is analysed. It is argued that there is little evidence to suggest that previous growth at low light intensities enhances the ability of an alga to utilize these low light levels. Rather, the published evidence suggests that the most general response to growth at sub-optimal light intensities is a reduced ability to utilize saturating levels. The present experiments with Phaeodactylum tricornutum Bohlin have tested this concept of light intensity adaptation. Changing photosynthetic abilities during batch growth depended on the light intensity used for growth and these changes affected interpretations of the data. When measurements were made intensities appeared to photosynthesize (at all intensities) better than did those grown at higher light levels. When the changes during batch growth were taken into account, or when the alga was grown in turbidostat cultures, a different picture was obtained. Growth at reduced light intensities was accompanied by (a) increased chlorophyll content, (b) decreased rate of light-saturated photosynthesis expressed on a chlorophyll, cell number or cell protein basis, and (c) decreased activity of RuDP carboxylase. One result suggested that growth at a suboptimal light intensity did enhance the ability to utilize lower light levels. The light-saturation curve of cells grown in batch culture at 0.7 klux showed higher slopes at the low light intensities than did those grown at 12 klux. This was most marked when photosynthesis was expressed per cell, but was also apparent when it was put on a per chlorophyll basis. 相似文献
Within recent years, increasing attention has been directed to the determination of contaminant levels in urban and industrial areas involving particulate matter (dustfall, suspended matter and smoke), sulfur dioxide, hydrogen sulfide, fluorides, ozone or oxidant, oxides of nitrogen and polycyclic aromatic hydrocarbons. However, with regard to criteria and evaluation of effects, none of these pollutants has been studied as thoroughly as sulfur dioxide. Presently, three provinces in Canada have adopted acts or regulations dealing with the control of air pollution. The Ontario Act, passed in 1958 and amended in 1963 and 1964, is the most comprehensive in scope. The Damage by Fumes Arbitration Act of Ontario provides for the awarding of compensation where crops, trees or other vegetation is damaged by sulfur fumes arising from the smelting or roasting of nickel-copper ore or iron ore or from the treatment of sulfides for the production of sulfur of sulfuric acid for commercial purposes. Regulations have also been enacted in Manitoba and Alberta. A provincial act is under consideration in Saskatchewan. 相似文献
Municipal solid waste landfills represent the dominant option for waste disposal in many parts of the world. While some countries have greatly reduced their reliance on landfills, there remain thousands of landfills that require aftercare. The development of cost-effective strategies for landfill aftercare is in society’s interest to protect human health and the environment and to prevent the emergence of landfills with exhausted aftercare funding. The Evaluation of Post-Closure Care (EPCC) methodology is a performance-based approach in which landfill performance is assessed in four modules including leachate, gas, groundwater, and final cover. In the methodology, the objective is to evaluate landfill performance to determine when aftercare monitoring and maintenance can be reduced or possibly eliminated. This study presents an improved gas module for the methodology. While the original version of the module focused narrowly on regulatory requirements for control of methane migration, the improved gas module also considers best available control technology for landfill gas in terms of greenhouse gas emissions, air quality, and emissions of odoriferous compounds. The improved module emphasizes the reduction or elimination of fugitive methane by considering the methane oxidation capacity of the cover system. The module also allows for the installation of biologically active covers or other features designed to enhance methane oxidation. A methane emissions model, CALMIM, was used to assist with an assessment of the methane oxidation capacity of landfill covers. 相似文献
The original goals of this project1 were to establish the shape of a smoke curve for fine suspended particulates in New York City comparable to the International Smoke Curve used in British and other European practice, and to relate two commonly used reporting units of surface concentration, μg/m3 (European practice) and Coh/1000 lineal feet (United States practice), to each other. While not directly a goal of the project, it was essential in the course of work to study the relationship between particulate density readings taken for one hour and two hour sampling periods. Progress toward achievement of these goals is presented in the following pages. 相似文献