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981.
Tinseau E Bartier D Hassouta L Devol-Brown I Stammose D 《Waste management (New York, N.Y.)》2006,26(7):789-800
This study aims to investigate, through mineralogical characterization (SEM, XRD) and mass-balance calculations, the effects of contact time, concrete types and presence of free water on the Tournemire argillite under in situ conditions. Three sampling zones from Excavation Disturbed Zone (EDZ) areas have been chosen: (1) dry contacts, collected at the tunnel masonry/argillite interface (contact time - 125 years), (2) wet contacts, taken close to drained areas below the tunnel roadbed in contact with the canal draining the Cernon fault water (contact time - 15 and 7 years) and at the tunnel masonry/argillite interface over 70 m from the Cernon fault (contact time - 125 years). This study shows that: in the absence of water, no significant modification of argillite is observed after 125 years, except for pyrite dissolution and gypsum precipitation; in the presence of water, precipitation of gypsum, recrystallization of mixed-layer clays, neoformation of zeolites and K-feldspars overgrowths are observed. At the concrete/argillite interface near the Cernon fault, important dolomite neoformation and leaching of chlorite and kaolinite occur. These processes are enhanced with contact time, low flow rate and the nature of the concrete (compound cement Portland CEM II 32.5). Evidence for oxidation processes linked to the EDZ (pyrite oxidation, Fe-oxy-hydroxide and gypsum precipitation) is observed. 相似文献
982.
The concept of storing radioactive waste in geological formations calls for large quantities of concrete that will be in contact with the clay material of the engineered barriers as well as with the geological formation. France, Switzerland and Belgium are studying the option of clayey geological formations. The clay and cement media have very contrasted chemistries that will interact and lead to a degradation of both types of material. The purpose of this review is to establish an exhaustive list of laboratory experiments so as to identify the reaction sequences in the evolution of both the clay minerals and accessory minerals during their alteration in an alkaline environment. We review the data on clay dissolution kinetics in this environment, and include an invaluable study of natural analogues that allow one to correlate the phenomena in time. The available data and experiments make it possible to construct predictive numerical models. However, as the quality of the data is inhomogeneous, we recommend a continuation of the thermodynamic and kinetic data acquisition. It is obvious that the numerical modeling of the alkaline disturbance will be more relevant if it can combine the advantages of the different detailed models: mineralogical completeness, combined modeling of the clay and cement media, evolution of the porosity, consideration of the pCO2 and all the surface reactions. 相似文献
983.
水环境退化较难以市场价格方式体现,是绿色GDP核算的一大难点.分析了影响水环境退化的社会经济因素、自然因素,在此基础上,构建了水环境退化的计量模型,并将社会经济发展的阶段性特征、水资源供需矛盾、降水补给变异特征和水质状况纳入模型中,采用不同参数进行描述,以保证模型的逻辑完备性和计算的简洁性.在湖州市绿色GDP核算过程中,采用该模型分别计算各县区2001-2004年水环境退化的经济损失.这些损失与当地水资源供需矛盾、水污染状况、社会经济发展等因素变化状况相符,准确反映了湖州市水环境退化的实际状况.结果表明,水环境退化的经济损失,除水污染程度外,还受到社会经济因素和降水补给等自然因素的影响. 相似文献
984.
Environmental assessment of mercury dispersion, transformation and bioavailability in the Lake Victoria Goldfields, Tanzania 总被引:2,自引:0,他引:2
Environmental dispersion and transformation of mercury discharged from gold mining operations has been investigated in field and laboratory studies in order to provide better understanding of the degree of mercury (Hg) pollution and bioavailability in the Lake Victoria goldfields (LVGF) ecosystems. This paper reviews results already published elsewhere and presents additional data on Hg dynamics in the LVGF. Studies conducted at the Mugusu and Rwamagaza artisanal mines indicated different degrees of Hg contamination and dispersion in environmental matrices. Mercury concentration in contaminated river sediments near the Mugusu mine varied from 6.0 to 0.5 mg/kg on a dry weight basis. The highest Hg contamination levels (165-232 mg/kg) were associated with mine tailings at the Rwamagaza mine. Mercury concentrations in fish representing different dietary habits on the southwestern shore of Lake Victoria at the Nungwe Bay were very low (2-35 microg/kg) and thought to represent background levels. These and other results suggested that the use of Hg in gold extraction in the LVGF has not caused high Hg levels in lake fish. The study of Hg in lichens showed Parmelia lichen to be an effective bioindicator for atmospheric Hg contamination due to Hg emissions from gold-amalgam firing and purification operations. The Hg levels in the lichens around the Mugusu mine ranged from 3.1 to 0.1 microg/g; the highest levels were recorded in the lichens sampled close to gold-amalgam processing sites. The regional background level in the Parmelia lichen was 0.05-0.10 microg/g, with a mean level of 0.07 microg/g. Studies of Hg transformation in the mine tailings revealed unexpectedly high methylmercury (MeHg) levels in the tailings (629-710 ng/g), which indicated that oxidation and methylation of metallic Hg in the tailings occurred at significant levels under tropical conditions. Re-equilibration of the tailings with freshwater (FW) indicated the MeHg was firmly bound in the tailings and therefore very little MeHg was released to the water column (0.2-1.5 ng/L). The methylation of Hg in tropical loamy clay soil contaminated with HgCl(2) (5 mg Hg/kg) yielded MeHg concentrations of 11 and 14 ng/g when inundated with seawater and FW, respectively, for 4 weeks. Little MeHg was transferred from the soil to the equilibrated water (< or = 0.4 ng/L). Atmospheric exposure of the soil pre-inundated with FW resulted in net degradation of MeHg during the 1st week of exposure, followed by net production and accumulation of MeHg in the soil (up to 15.5 ng/g) during atmospheric desiccation. Mercury uptake by fish from the Hg(0)-contaminated aquatic sediment-tailings system in the aquarium experiment was found to be low, suggesting the low availability of MeHg for bioaccumulation in the system. These and other results provide useful insights into Hg transformation, mobility and bioavailability in tropical aquatic systems affected by Hg pollution from gold mining operations. 相似文献
985.
Fish mercury increase in Lago Manso, a new hydroelectric reservoir in tropical Brazil 总被引:3,自引:0,他引:3
Hylander LD Gröhn J Tropp M Vikström A Wolpher H de Castro E Silva E Meili M Oliveira LJ 《Journal of environmental management》2006,81(2):155-166
It has been frequently demonstrated that mercury (Hg) concentrations in fish rise in newly constructed hydroelectric reservoirs in the Northern Hemisphere. In the present work, we studied whether similar effects take place also in a tropical upland reservoir during impoundment and discuss possible causes and implications. Total Hg concentrations in fish and several soil and water parameters were determined before and after flooding at Rio Manso hydroelectric power plant in western Brazil. The Hg concentrations in soil and sediment were within the background levels in the region (22-35 ng g(-1) dry weight). There was a strong positive correlation between Hg and carbon and sulphur in sediment. Predatory fish had total Hg concentrations ranging between 70 and 210 ng g(-1) f.w. 7 years before flooding and between 72 and 755 ng g(-1) f.w. during flooding, but increased to between 216 and 938 ng g(-1) f.w. in the piscivorous and carnivorous species Pseudoplatystoma fasciatum, cachara, and Salminus brasiliensis, dourado, 3 years after flooding. At the same time, concentrations of organic carbon in the water increased and oxygen concentrations decreased, indicating increased decomposition and anoxia as contributing to the increased Hg concentrations in fish. The present fish Hg concentrations in commonly consumed piscivorous species are a threat to the health of the population dependent on fishing in the dam and downstream river for sustenance. Mercury exposure can be reduced by following fish consumption recommendations until fish Hg concentrations decrease to a safe level. 相似文献
986.
Yasamis FD 《Environmental management》2006,38(5):823-836
Improving the performance of the state environmental agencies (SEAs) necessitates an effective institutionalization of governmental
environmental management functions. There are examples of successful and unsuccessful SEAs in several parts of the world.
Analysis and assessment of these cases can deliver useful insights for institution builders. The objective of this article
is the assessment of the institutional effectiveness of the SEAs in Turkey through the perceptions of the experts using the
Delphi Technique. In this regard, a checklist is developed including 16 criteria and 123 subcriteria to measure the institutional
effectiveness of the SEAs. Twenty-eight national and international experts have formed a Delphi panel and evaluated the national
and local conditions. Results, based on the perceptions of the experts, indicate that the overall effectiveness of the SEAs
is far less than satisfactory. Negative consensus has been reached over the effectiveness of 13 of the16 criteria and 95 of
the123 subcriteria; however, no consensus has been achieved over the remainder of the parameters. The survey has also proven
that the Delphi Technique can be effectively used for that purpose. Utilization of the checklist method is also useful in
diagnosing the problematic components of the SEAs. It is recommended that this approach be used in similar cases elsewhere. 相似文献
987.
Tzialla CE Veresoglou DS Papakosta D Mamolos AP 《Journal of environmental management》2006,80(1):90-98
Soil physicochemical characteristics, total aboveground biomass, number of species and relative abundance of groups and individual species were measured along a moisture gradient in a pasture, flooded in part during winter through early summer, adjacent to Pamvotis lake in Ioannina, Greece. Soil and vegetation measurements were conducted in 39 quadrats arranged in four zones perpendicular to the moisture gradient. The zone closest to the lake, recently separated from the lake, became part of the pasture and its soil texture was quite different from that of the other zones with a substrate containing 91% sand. Except for pH, this zone had the lowest values in the other five soil physicochemical characteristics measured (organic matter, total and extracted inorganic nitrogen, Olsen extracted phosphorus and extractable potassium); in the other zones organic matter, total nitrogen, phosphorus and potassium tended to increase from the driest to the wettest zone. Total aboveground biomass, ranging from 280 to 840 gm-2, is high for herbaceous pastures in the conditions of Mediterranean climate and it was not related to distance from the lake's shoreline, although the highest values were measured at intermediate distances, or to any of the various soil characteristics measured. Also, the number of species/0.25 m2 was not related to any of the various soil characteristics, but it was highest at the intermediate distances from the lake's shoreline. Species composition varied along the moisture gradient. Forbs as well as annual grasses and legumes declined in abundance from the driest to the wettest places; the reverse was the case for sedges and perennial grasses and legumes. These results indicate that the soil moisture gradient was the principal factor affecting soil characteristics and plant species composition. Since most species were recorded in all the four zones of the pasture, indicating that these can tolerate all variations in abiotic conditions of pasture, the vegetation zonation seems to be influenced by competition. Each functional group of species tends to dominate in a particular range of the soil moisture gradient where it is better suited and tends to exclude competitively other species. Management practices (mowing and grazing) affect the kinds of processes which maintain the observed community structure either by preventing the establishment of later successional species, like reeds and woody species, or by moderating the shoot competition, especially in the wetter zones, and thus permitting the creeping species to grow successfully. 相似文献
988.
989.
Dimitrakopoulos PG Siamantziouras AS Galanidis A Mprezetou I Troumbis AY 《Environmental management》2006,37(6):826-839
We conducted a field experiment using constructed communities to test whether species richness contributed to the maintenance
of ecosystem processes under fire disturbance. We studied the effects of diversity components (i.e., species richness and
species composition) upon productivity, structural traits of vegetation, decomposition rates, and soil nutrients between burnt
and unburnt experimental Mediterranean grassland communities. Our results demonstrated that fire and species richness had
interactive effects on aboveground biomass production and canopy structure components. Fire increased biomass production of
the highest-richness communities. The effects of fire on aboveground biomass production at different levels of species richness
were derived from changes in both vertical and horizontal canopy structure of the communities. The most species-rich communities
appeared to be more resistant to fire in relation to species-poor ones, due to both compositional and richness effects. Interactive
effects of fire and species richness were not important for belowground processes. Decomposition rates increased with species
richness, related in part to increased levels of canopy structure traits. Fire increased soil nutrients and long-term decomposition
rate. Our results provide evidence that composition within richness levels had often larger effects on the stability of aboveground
ecosystem processes in the face of fire disturbance than species richness per se. 相似文献
990.
The extensive literature on environmental justice has, by now, well defined the essential ingredients of cumulative risk,
namely, incompatible land uses and vulnerability. Most problematic is the case when risk is produced by a large aggregation
of small sources of air toxics. In this article, we test these notions in an area of Southern California, Southeast Los Angeles
(SELA), which has come to be known as Asthmatown. Developing a rapid risk mapping protocol, we scan the neighborhood for small
potential sources of air toxics and find, literally, hundreds of small point sources within a 2-mile radius, interspersed
with residences. We also map the estimated cancer risks and noncancer hazard indices across the landscape. We find that, indeed,
such large aggregations of even small, nondominant sources of air toxics can produce markedly elevated levels of risk. In
this study, the risk profiles show additional cancer risks of up to 800 in a million and noncancer hazard indices of up to
200 in SELA due to the agglomeration of small point sources. This is significant (for example, estimates of the average regional
point-source-related cancer risk range from 125 to 200 in a million). Most importantly, if we were to talk about the risk
contour as if they were geological structures, we would observe not only a handful of distinct peaks, but a general “mountain
range” running all throughout the study area, which underscores the ubiquity of risk in SELA. Just as cumulative risk has
deeply embedded itself into the fabric of the place, so, too, must intervention seek to embed strategies into the institutions
and practices of SELA. This has implications for advocacy, as seen in a recently initiated participatory action research project
aimed at building health research capacities into the community in keeping with an ethic of care. 相似文献