排序方式: 共有99条查询结果,搜索用时 31 毫秒
41.
Vosyliene MZ Kazlauskiene N Svecevicius G 《Environmental science and pollution research international》2003,10(2):103-107
The effects of a model mixture (HMMM) of seven heavy metals (Cu, Zn, Ni, Cr, Pb, Cd, Mn) on the rainbow trout Oncorhynchus mykiss at all stages of development (embryos, larvae, adults) were investigated based on the annual average concentrations of these metals in cooling waste waters discharging from Ignalina Nuclear Power Plant (Lithuania) into the Drūk?iai lake. According to mortality parameters, the most sensitive to HMMM were larvae, although no significant differences between the sensitivity of embryos and adult fish to HMMM were found. Maximal toxic effect of HMMM was observed during the hatching period. Long-term exposure to sublethal concentrations of HMMM affected embryo development, growth of larvae, their cardio-respiratory and behavioural responses, induced significant changes in morphological, morpho-physiological, physiological and haematological parameters of adult fish. Respiratory responses and growth parameters of fish were found to be the most sensitive to low concentrations of HMMM. Adult fish were capable of detecting and avoiding low, sublethal concentrations of HMMM. Heavy metals in a mixture at low concentrations were more toxic than single ones. According to the background of the damages induced by HMMM, after-effects in a fish organism, as well as in a whole population, can be predicted. 相似文献
42.
Catalkaya EC Bali U Sengül F 《Environmental science and pollution research international》2003,10(2):113-120
INTENTION, GOAL, SCOPE, BACKGROUND: Since the intermediate products of some compounds can be more toxic and/or refractory than the original compund itself, the development of innovative oxidation technologies which are capable of transforming such compounds into harmless end products, is gaining more importance every day. Advanced oxidation processes are one of these technologies. However, it is necessary to optimize the reaction conditions for these technologies in order to be cost-effective. OBJECTIVE: The main objectives of this study were to see if complete mineralization of 4-chlorophenol with AOPs was possible using low pressure mercury vapour lamps, to make a comparison of different AOPs, to observe the effect of the existence of other ions on degradation efficiency and to optimize reaction conditions. METHODS: In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV, UV/H2O2 and UV/H2O2/Fe2+ (photo-Fenton process) were investigated in labscale experiments for the degradation and mineralization of 4-chlorophenol. Evaluations were based on the reduction of 4-chlorophenol and total organic carbon. The major parameters investigated were the initial 4-chlorophenol concentration, pH, hydrogen peroxide and iron doses and the effect of the presence of radical scavengers. RESULTS AND DISCUSSION: It was observed that the 4-chlorophenol degradation efficiency decreased with increasing concentration and was independent of the initial solution pH in the UV process. 4-chlorophenol oxidation efficiency for an initial concentration of 100 mgl(-1) was around 89% after 300 min of irradiation in the UV process and no mineralization was achieved. The efficiency increased to > 99% with the UV/H2O2 process in 60 min of irradiation, although mineralization efficiency was still around 75% after 300 min of reaction time. Although the H2O2/4-CP molar ratio was kept constant, increasing initial 4-chlorophenol concentration decreased the treatment efficiency. It was observed that basic pHs were favourable in the UV/H2O2 process. The results showed that the photo-Fenton process was the most effective treatment process under acidic conditions. Complete disappearance of 100 mgl(-1) of 4-chlorophenol was achieved in 2.5 min and almost complete mineralization (96%) was also possible after only 45 min of irradiation. The efficiency was negatively affected from H2O2 in the UV/H2O2 process and Fe2+ in the photo-Fenton process over a certain concentration. The highest negative effect was observed with solutions containing PO4 triple ions. Required reaction times for complete disappearance of 100 mgl(-1) 4-chlorophenol increased from 2.5 min for an ion-free solution to 30 min for solutions containing 100 mgl(-1) PO4 triple ion and from 45 min to more than 240 min for complete mineralization. The photodegradation of 4-chlorophenol was found to follow the first-order law. CONCLUSION: The results of this study showed that UV irradiation alone can degrade 4-CP, although at very slow rates, but cannot mineralize the compound. The addition of hydrogen peroxide to the system, the so-called UV/H2O2 process, significantly enhances the 4-CP degradation rate, but still requires relatively long reaction periods for complete mineralization. The photo-Fenton process, the combination of homogeneous systems of UV/H2O2/Fe2+ compounds, produces the highest photochemical elimination rate of 4-CP and complete mineralization is possible to achieve in quite shorter reaction periods when compared with the UV/H2O2 process. RECOMMENDATIONS AND OUTLOOK: It is more cost effective to use these processes for only purposes such as toxicity reduction, enhancement of biodegradability, decolorization and micropollutant removal. However the most important point is the optimization of the reaction conditions for the process of concern. In such a case, AOPs can be used in combination with a biological treatment systems as a pre- or post treatment unit providing the cheapest treatment option. The AOP applied, for instance, can be used for toxicity reduction and the biological unit for chemical oxygen demand (COD) removal. 相似文献
43.
Marcelo?Azevedo?CostaEmail author Renato?Martins?Assun??o 《Environmental and Ecological Statistics》2005,12(3):301-319
Routine surveillance of a large geographic region for clusters of adverse health events, particularly cancers, often involves
small area health data, possibly controlling for exposure information. Many different methods have been proposed to test for
the presence of geographical clusters. Two of the most popular methods are the spatial scan method proposed by Kulldorff and
that using a fixed number of cases within scanning circles proposed by Besag and Newell. Although the second test is very
popular, it has some difficulties. While the scan test controls for the multiple testing problem, the Besag and Newell test
does not. Additionally, the latter method requires the setting of several tuning parameters whose values affect the test performance
and are subjectively chosen by the user. This creates a difficulty to make a fair comparison between the two methods and it
explains why there have been few formal studies evaluating their relative performances. In this paper, we modify the Besag
and Newell test allowing for the control of the error type I probability and compare its power with respect to that of the
spatial scan test. We used data sets from a publicly available simulated benchmark. We found that the two methods have similar
results, except for clusters located in sparsely populated regions, where the spatial scan method presented a better performance. 相似文献
44.
45.
Mark??agarEmail author Gunilla?Svensson Michael?Tjernstr?m 《Environmental Fluid Mechanics》2005,5(4):357-372
A real meteorological situation characterized by strong spatial and temporal variability of the meteorological fields in a
coastal region of eastern Denmark is examined in view of the transport of a passive tracer and dry deposition. Model simulations
using a full mesoscale NWP model (COAMPSTM) at different horizontal resolutions are performed. A realistic simulation showed that the differences in the amount of dry
deposited matter can reach one order of magnitude and larger, during the period of one afternoon, depending on the model horizontal
resolution. In addition, the results of an idealized experiment with straight coastline indicate that the horizontal model
resolution alone is responsible for most of the differences. This study confirms the importance of high spatial and temporal
resolution modelling for environmental applications. 相似文献
46.
Antimony speciation and contamination of waters in the Xikuangshan antimony mining and smelting area,China 总被引:3,自引:0,他引:3
Faye Liu X. Chris Le Anthony McKnight-Whitford Yunlong Xia Fengchang Wu Erika Elswick Claudia C. Johnson Chen Zhu 《Environmental geochemistry and health》2010,32(5):401-413
Water samples from Xikuangshan (China), the world largest antimony (Sb) mine with a Sb mining and smelting history of more
than 200 years, were analyzed. These water samples ranged from stream water in the vicinity of the mining and smelting area
that received seepage from ore residues to the underground mine-pit drainage. The concentrations of total Sb, Sb (III) and
Sb (V) of the samples were determined by HPLC-ICP-MS. In addition, water pH and concentrations of major cations and anions
were analyzed. All 18 samples demonstrated total Sb concentrations with ppm levels from 0.33 ppm to 11.4 ppm, which is two
to three orders of magnitude higher compared to the typical concentration of dissolved Sb in unpolluted rivers (less than
1 ppb). This is probably the first time that such high Sb contents have been documented with complete environmental information.
Distribution of total Sb and Sb species was investigated, taking into account the respective local environment (in the mining
area or close to the smelter, etc.). Sb (V) was the predominant valence in all 18 samples. Only trace levels of Sb (III) were
detected in 4 of the 18 samples. Geochemical speciation modeling showed the dominant species was Sb(OH)6−. It is also probably the first time that such high Sb contents have been documented in the natural environment with Sb speciation
distribution information. Several potential oxidation pathways are also discussed that might have facilitated the oxidation
of Sb (III) in the natural environment. Signs of intoxication were observed among local mine workers with extensive exposure
to different forms of Sb for a long period of time. 相似文献
47.
Viviana Re Seynabou Ciss�� Faye Abdoulaye Faye Serigne Faye Cheikh Becaye Gaye Elisa Sacchi Gian Maria Zuppi 《Environmental monitoring and assessment》2011,172(1-4):605-622
In recent years, the unregulated increase of the population in coastal areas of developing countries has become source of concern for both water supply and quality control. In the region of Dakar (Senegal), approximately 80% of water resources come from groundwater reservoirs, which are increasingly affected by anthropogenic pressures. The identification of the main sources of pollution, and thus the aquifer vulnerability, is essential to provide a sound basis for the implementation of long-term geochemically based water management plans in this sub-Saharan area. With this aim, a hydrochemical and isotopic survey on 26 wells was performed in the so-called Peninsula of Cap-Vert. Results show that seawater intrusion represents the main process affecting groundwater chemical characteristics. Nitrates often exceed the World Health Organization drinking water limits: stable isotopes of dissolved nitrate ( $\updelta ^{15}$ N and $\updelta ^{18}$ O) indicate urban sewage and fertilizers as a major source of contamination. Results depict a complex situation in which groundwater is affected by direct and indirect infiltration of effluents, mixing with seawater and freshening processes from below. Besides the relevance of the investigation at a regional level, it represents a basis for decision-making processes in an integrated water resources management and in the planning of similar monitoring strategies for other urban coastal regions. 相似文献
48.
Ghisi Nde C Ramsdorf WA Ferraro MV de Almeida MI Ribeiro CA Cestari MM 《Environmental monitoring and assessment》2011,180(1-4):589-599
Diverse genetic biomarkers have been used to evaluate the effects of pollution by mutagenic agents such as metals and pesticides, as well as a large variety of chemical substances derived from human activities. This work researched the effects that an exposure of 60 days to the insecticide Fipronil (concentrations of 0.05, 0.10 and 0.23 μg/L) can cause in the fish Rhamdia quelen using Comet assay with gills, histopathological analysis of gills and the Piscine Micronucleus test and Nuclear Morphological Alterations. The results for the Comet assay and for gills histopathological injuries showed no difference between the control group and the contaminated groups. In the Piscine Micronucleus test, the smallest concentration of Fipronil (0.05 μg/L) was similar as the control group, while concentrations of 0.10 and 0.23 μg/L caused more damage to the DNA. These results suggested that only the highest concentrations of Fipronil tested cause damage in erythrocytes, but none of these concentrations was sufficient to alter the DNA in the gill cells. R. quelen may be a less sensitive bioindicator than other fish that have been tested. On the other hand, the concentrations used may not have been sufficient to detect alterations in the DNA of R. quelen with the chosen tests. Works like this take on great importance given the enormous quantity of substances that are thrown daily into the environment in an uncontrolled way, without evaluation of the consequences. The application of these tests with other concentrations, tissues and exposure times is suggested for future works. 相似文献
49.
In this paper a PSIAC-based multi-parameter fuzzy pattern recognition (MPFPR) model is proposed and applied for classifying and ranking the potential soil erosion (PSE). In this approach, standard value matrix is used to define the membership degrees of each catchment to each class and the feature values are used for alternative ranking. The characteristic of PSE for each class is expressed by linguistic variables. The proposed method is straightforward, easy to understand, very practical, and its results may easily be interpreted. To assess the performance of the model, the results of PSIAC MPFPR and original PSIAC method are interpreted and compared with the observed data. It is shown that the proposed approach reflects the fuzzy nature of the soil erosion more efficiently and is quite robust for application in real world cases. 相似文献
50.