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Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones. 相似文献
244.
Christian Fuchs 《Environment, Development and Sustainability》2008,10(3):291-309
This paper discusses the relationship of new information and communication technologies (ICTs) and sustainable development.
It deconstructs popular myths about a sustainable information society. One myth is that telework has reduced the need to travel
and hence environmental pollution. The reality is that teleworkers make up only a small share of the total workforce, telework
can generate new social relationships and hence the need for more travelling, work-related travel produces only a small amount
of the total carbon dioxide emissions, and that the total distance travelled per employee is constantly rising. Another myth
is that information economy is weightless and dematerialized which reduces environmental impacts. The energy and resource
intensities of the ICT sector are indeed lower than the one of the total economy. The ICT sector also emits less CO2 than the total economy. But the ICT sector constitutes only a small portion of the total value added and fossil fuel combustion
is still the dominant activity of modern industrial economies. Some stakeholders argue that virtual products allow resource,
energy, and transport savings. But burning digital music on compact discs and DVDs, printing digital articles and books, etc.
results in rebound effects that cause new material and energy impacts, computers have a low life span of 2–3 years, reusable
and upgradeable computers and computer equipment are hardly used and might not be as profitable as non-reusable ones, computers
are consuming much energy. Alternatives such as energy consumption labels on ICTs and green ICTs that consume less energy
contradict dominant economic interests. A sustainable information society is a society that makes use of ICTs and knowledge
for fostering a good life for all human beings of current and future generations by strengthening biological diversity, technological
usability, economic wealth for all, political participation of all, and cultural wisdom. Achieving a sustainable information
society costs, it demands a conscious reduction of profits by not investing in the future of capital, but the future of humans,
society, and nature. 相似文献
245.
246.
T. Stoichev L. Makedonski T. Trifonova M. Stancheva F. Ribarova 《Chemistry and Ecology》2007,23(3):191-200
In spite of a worldwide reduction in the utilization of organochlorine pesticides (OCPs), they are still a problem for the aquatic environment and human health. The Black Sea is still being polluted with persistent chemicals, including OCPs. Aquatic organisms (sprat, scad, bluefish, shad, belted bonito, goby, and black mussel) with different feeding behaviours were sampled on a seasonal basis from the Bulgarian region of the Black Sea, and the concentrations of 13 OCP residues were determined. Although many of the OCPs were not detected in the samples, in all samples 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) was present mainly in the form of its metabolites 1,1-dichloro-2,2-bis(4-chlorophenyl) ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene (DDE). Only about 12% of the total DDT was present as the parent compound pp-DDT, which suggests that it was not being used recently in the region. The total DDT concentrations were generally below 150 μg kg-1 fresh weight, but higher levels—up to 354 μg kg-1 fresh weight—were also measured for fish species with a high fat content. Between-species differences were observed, even when the concentrations were presented on a fat-level basis. DDT concentrations did not show any significant changes over the 2-yr sampling period. Fish sampled in the northern areas of the Bulgarian Black Sea coast seemed to contain higher DDT levels than those from the southern areas, suggesting a major (historical) influence of the Danube River. For permanent monitoring purposes, the utility of Black Sea gobies and scad should be considered. 相似文献
247.
248.
Estimates of animal methane emissions 总被引:2,自引:0,他引:2
The enteric methane emissions into the atmospheric annually from domestic animals total about 77 Tg. Another 10 to 14 Tg are likely released from animal manure disposal systems. About 95% of global animal enteric methane is from ruminants, a consequence of their large populations, body size and appetites combined with the extensive degree of anaerobic microbial fermentation occurring in their gut. Accurate methane estimates are particularly sensitive to cattle and buffalo census numbers and estimated diet consumption. Since consumption is largely unknown and must be predicted, accuracy is limited often by the information required, i.e., distribution of animals by class, weight and productivity. Fraction of the diet lost as enteric methane mostly falls into the range of 5.5–6.5% of gross energy intake for the world's cattle, sheep and goats. Manure methane emissions are heavily influenced by fraction of disposal by anaerobic lagoon. Non-ruminants, i.e., swine, become major contributors to these emissions. 相似文献
249.
250.
Effect of periphyton grazing by Hydrobia ulvae on the growth of Zostera noltii on a tidal flat in the Dutch Wadden Sea 总被引:3,自引:0,他引:3
C. J. M. Philippart 《Marine Biology》1995,122(3):431-437
The decrease of the intertidal seagrass Zostera noltii in the Dutch Wadden Sea may have been the result of enhanced periphyton load due to eutrophication. Decrease of this seagrass species coincided with an increase in the mudsnail Hydrobia ulvae. Feeding of this mudsnail on periphyton may have partly counteracted an increase of periphyton biomass. Exclosure experiments on seagrass stands in the Dutch Wadden Sea in 1987 showed that density of periphyton on leaves of Z. noltii decreased significantly with increasing density of grazers. An increased density of mudsnails significantly enhanced the density and biomass of seagrass, in particular of the below ground parts. Since this seagrass species survives winter in temperate climate zones mainly by means of rhizomes, grazing may also influence the seagrass dynamics in the long term. Results of the experiment were in agreement with field observations on coinciding low densities of mudsnails and high densities of fouling of seagrass stands on the tidal flats of western Wadden Sea in the late 1970s. 相似文献