خيارات البحث
النتائج 361 - 370 من 775
Using Factor Analysis to Characterise Historical Trends of Trace Metal Contamination in a Sediment Core from the Tagus Prodelta, Portugal
2009
Mil-Homens, Mário | Branco, Vasco | Lopes, Cristina | Vale, Carlos | Abrantes, Fatima | Boer, Wim | Vicente, Maria
A box-core 3576 (PO287-26-1B) collected from the Tagus Prodelta in 2002 was analysed for organic carbon, ²¹⁰Pb, ²²⁶Ra, major (Al, Fe, Ca, Ti, Mg and Mn) and trace elements (Ba, Hg, Cr, Cu, Li, Ni, Pb, Sb, Sn, Sr, and Zn). Maximum concentrations of contaminants in ²¹⁰Pb-dated samples were reached in the decades between 1960 and 1980, followed by a slightly decrease in up-core metal trends. Trace metal concentrations increased in the bottom of the core (²¹⁰Pb dated as 1925) to maximum values during the 1970s. Factor analysis of geochemical data was used to reduce the 18 variables into four factors that reveal distinct origins or accumulation mechanisms controlling the chemical composition in the study area. Changes in the dominance of these factors through the time indicate not only changes in industrial activity, but also the increase of biological productivity towards the present.
اظهر المزيد [+] اقل [-]Metal Tolerance, Accumulation and Translocation in Poplar and Willow Clones Treated with Cadmium in Hydroponics
2009
Zacchini, Massimo | Pietrini, Fabrizio | Scarascia Mugnozza, Giuseppe | Iori, Valentina | Pietrosanti, Lucia | Massacci, Angelo
To evaluate the phytoremediation capability of some poplar and willow clones a hydroponic screening for cadmium tolerance, accumulation and translocation was performed. Rooted cuttings were exposed for 3 weeks to 50 μM cadmium sulphate in a growth chamber and morpho-physiological parameters and cadmium content distribution in various parts of the plant were evaluated. Total leaf area and root characteristics in clones and species were affected by cadmium treatment in different ways. Poplar clones showed a remarkable variability whereas willow clones were observed to be more homogeneous in cadmium accumulation and distribution. This behaviour was further confirmed by the calculation of the bio-concentration factor (BCF) and the translocation factor (Tf). Mean values of all the clones of the two Salicaceae species showed that willows had a far greater ability to tolerate cadmium than poplars, as indicated by the tolerance index (Ti), calculated on the dry weight of roots and shoots of plants. As far as the mean values of Tf was concerned, the capacity of willows to translocate was double that of poplars. On the contrary, the mean values of total BCF in poplar clones was far higher with respect to those in willows. The implications of these results in the selection of Salicaceae clones for phytoremediation purposes were discussed.
اظهر المزيد [+] اقل [-]A New Methodology Approach for Measuring Corporate Social Responsibility Performance
2009
Panayiotou, Nikolaos A | Aravossis, Konstantin G | Moschou, Peggy
The exact contribution of corporate social responsibility (CSR) to a company as well as to its stakeholders should be measurable in order to be evaluated correctly. The difficult task of measuring the results of CSR has been a matter of significant research both by academics and by practitioners. Some of the literature on corporate social responsibility combines CSR with stakeholder theory introducing corporate social performance. The literature has attempted to describe emerging models of the issues that lead to a coherent model of what would represent corporate social performance. However, it is the case that social aspects are “soft” in nature, therefore being difficult to quantify. Innovated methods of performance measurement such as that of Balanced Scorecard has lately been introduced in some companies in their attempt to include non-financial indicators to give a more balanced and forecasting power to the traditional financial performance assessment system, but the view of corporate social responsibility is rarely taken into account. Furthermore, management frameworks that try to cover social and environmental aspects, such as Global Reporting Initiative, by providing a number of related performance measures, are not able to connect them with corporate strategy and are poor evaluators of cause-effect relationships. In the present paper, a CSR performance measurement framework based on the adoption of the Balanced Scorecard approach is presented. For the development of the proposed framework, the existing assessment of CSR and Corporate Sustainability actions of the Greek companies of different sectors was analysed in order to identify common practices in CSR performance evaluation as well as existing limitations. Taking into account the social indicators suggested by the traditional balanced scorecard views, an extension of its structure is proposed in order to better embody the environmental and social aspects of company performance.
اظهر المزيد [+] اقل [-]Soil Contamination From Tannery Wastes with Emphasis on the Fate and Distribution of Tri- and Hexavalent Chromium
2009
Shams, Khaled Mahmud | Tichy, Gottfried | Sager, Manfred | Peer, Thomas | Bashar, Ashtar | Jozic, Marija
Industrial wastes generated from tanneries located in the southwestern part of Dhaka, pose serious threat to the environment. Surface accumulation of trivalent chromium reaching as high as 28,000 mg/kg have been encountered at 1 km distance from the waste lagoon. In contrast, maximum concentration of hexavalent chromium is about 1 mg/kg, and is very irregularly distributed all over the area. Although soil pH is alkaline in general, a sharp drop of pH down to 3.4 has been observed at some locations. Furthermore, high chloride (Cl) and lead (Pb) concentrations pose risk for city's groundwater quality, of which Pb is vulnerable for any chelate-assisted phytoremediation as it can enhance its mobility. Scanning electron microscope study showed chromium within the structure of clay minerals, mainly illite-smectite, and also as chlorite-chromian. Presence of lepidocrocite indicates a rather reactive phase which can undergo reductive dissolution and release Cr in the environment.
اظهر المزيد [+] اقل [-]Factors Associated with Well-to-Well Variation in Nitrate Concentration of Groundwater in a Nitrate-Polluted District in Miyakonojo Basin, Southern Kyushu, Japan
2009
Sugimoto, Yasuhiro | Toyomitsu, Yukio | Muto, Isao | Hirata, Masahiko
This study monitored nitrate levels in well water and analyzed their association with well attributes (physicochemical parameters of water, location, livestock farming conditions) in a nitrate-polluted, animal industry district in central Miyakonojo Basin, southern Kyushu, Japan, to characterize the nitrate status of groundwater in the district. Water quality varied considerably among the wells, with nitrate-N concentration and natural nitrogen-15 abundance in nitrate-N (δ¹⁵N-NO₃) ranging from 1.1-44.6 mg L⁻¹ and 4.2-17.8[per thousand], respectively. There was a significant positive correlation between nitrate-N concentration and δ¹⁵N-NO₃. Nitrate-N concentration was higher in wells located at higher elevations, having larger areas of livestock barns within a 100-m radius and with higher animal populations. Wells in pig farms showed a higher nitrate tendency than those in the other situations (cattle farm, poultry farm, non-livestock farm and non-farmer). The results show that the nitrate status of groundwater in the district has not been drastically changed since 1996, and the nitrate in the wells is of multiple origins (e.g. chemical fertilizer, animal wastes) with a tendency for higher contribution of animal wastes in more heavily polluted wells. The results also highlight a need for further regular monitoring of groundwater quality in the district particularly for wells; (1) located at higher elevations, (2) with a large area of livestock barns nearby, (3) in farms with a high animal population and/or (4) in pig farms.
اظهر المزيد [+] اقل [-]A Peat Profile Record of Recent Environmental Events in the South Pennines (UK)
2009
Hutchinson, Simon M. | Armitage, Richard P.
This study investigates the impact of accidental fires and the record of recent environmental change held within a long peat core taken on Burbage Moor in the south Pennines (UK). The core has been subjected to mineral magnetic, heavy metal (via inductively coupled plasma-optical emission spectroscopy) and radiometric analyses. It may be subdivided into three zones reflecting the infilling of a basin-like depression and reveals pre-industrial conditions and the impact of recent atmospheric particulate pollution. Peak concentrations of heavy metals are relatively high (e.g., peak Pb concentration is 1,124 mg kg⁻¹). However, the mineral magnetic and heavy metal depth profiles may have been affected by post-depositional changes. The core has been influenced by drainage and a number of moor fires. The area was extensively burnt in 1976, though assessing the impact of this event is problematic, due to the perturbed nature of the profile and the inability to provide a reliable chronology.
اظهر المزيد [+] اقل [-]Electrocoagulation Studies on Treatment of Biodigester Effluent using Aluminum Electrodes
2009
Ponselvan, F Infant Anto | Kumar, Mayank | Malviya, Jodha Ram | Srivastava, Vimal Chandra | Mall, Indra Deo
In the present paper, electrocoagulation (EC) has been employed for the reduction of chemical oxygen demand (COD) reduction of a distillery wastewater (biodigester effluent) in a batch EC reactor using aluminum electrode. The individual and interactive effects of the four main independent parameters have been studied on the COD removal efficiency using a central composite experimental design. The parameters studied are current density (j): 44.65-223.25 A/m²; initial pH (pH ₀): 2-8; inter-electrode distance (g): 1-3 cm; and electrolysis time (t): 30-150 min. Pareto analysis of variance of the results showed a high coefficient of determination value (R ² = 0.9693) and satisfactory prediction for second-order regression model. Maximum COD removal efficiency of 52.23% was obtained with j = 120 A/m², pH ₀ = 6.0, g = 1 cm, and t = 150 min.
اظهر المزيد [+] اقل [-]Bisphenol A Adsorption Onto Metals Oxides and Organic Materials in the Natural Surface Coatings Samples (NSCSs) and Surficial Sediments (SSs): Inhibition for the Importance of Mn Oxides
2009
Li, Yu | Li, Na | Chen, Dan | Wang, Xiaoli | Xu, Zili | Dong, Deming
Selective extraction techniques followed by batch adsorption experiments and statistical analyses were employed to investigate the adsorption behavior of bisphenol A (BPA) onto the natural surface coatings samples (NSCSs) and surficial sediments (SSs) and estimate the relative contribution of components (i.e. Fe oxides, Mn oxides, organic materials and residues) to the total BPA adsorption. The results indicate that nonlinear Langmuir model can describe the adsorption behavior of BPA on the NSCSs and SSs before and after extraction treatments. The removal of Mn oxides from the NSCSs and SSs caused a significant increase in BPA adsorption, which implied that Mn oxides inhibited BPA adsorption onto solid matrix, and Fe oxides played a positive role in BPA adsorption onto the NSCSs and SSs. However, the removal of organic materials (OMs) led to a dramatic decrease in BPA adsorption, suggesting considerable amounts of BPA adsorbed onto OMs in the NSCSs and SSs. This study may provide important insights into the understanding of the transport and ultimate fate of BPA in the aquatic environments.
اظهر المزيد [+] اقل [-]Volatile Organic Compounds Selection for Incorporation in Photochemical Mechanisms and the Development of Secondary Pollution Reduction Strategies
2009
Karathanasis, Stavros | Ziomas, Ioannis
In the present work a method for the evaluation of the importance of the VOCs species is presented, aiming to provide criteria for the incorporation of these species into atmospheric photochemical mechanisms and for the successful application of secondary pollution reduction strategies. According to the method presented here, the species can be divided into more important and less important ones, taking into account their mixing ratios and emission values in combination with their reactivity. For this classification three quantitative and one qualitative criteria were introduced. Overall, it is concluded that alkenes with more than a few carbon atoms in their chain appear to be more important in urban and suburban areas, while in background conditions the alkanes, having the smaller chain (ethane, propane), become more important. In the case of alkenes there is no clear species classification, except for the biogenically emitted compounds, isoprene and limonene. In general, more important alkenes appear to be those with the smaller chain (ethene, propene, butene). Most abundant aromatics are benzene, toluene, and xylene. In background conditions higher aromatics are also important, especially 1,2,3-, 1,3,5-, and 1,2,4-trimethylbenzene. The most important carbonylic compounds are formaldehyde, acetaldehyde, and acetone. Finally, taking into account the results mentioned above, a new photochemical mechanism was developed. The species and species groups used in the proposed mechanism are: ethane, higher alkanes, ethene, propene, 2- butene, 1-alkenes, 2-alkenes, higher alkenes, benzene, toluene, m-, o-, p-xylene, 1,3,5-, 1,2,3-, 1,2,4-trimethylbenzene, higher aromatics, formaldehyde, acetaldehyde, higher aldehydes, isoprene, limonene, and other biogenic VOCs.
اظهر المزيد [+] اقل [-]Leaching of Alkali from Concrete in Contact with Waterways
2009
Setunge, Sujeeva | Nguyen, Natalie | Alexander, Brendan Lee | Dutton, Louise
Concrete is usually the preferred material for construction of structures in contact with water during their service life. Early age exposure to water is beneficial for curing of concrete structures. However, the pollution of water from freshly cast concrete in contact with water has not been investigated in detail. A significant increase in the alkalinity has recently been observed in a stream in contact with freshly installed concrete culverts. High alkalinity has caused distress to fresh water fish in the stream. A preliminary laboratory study was commenced to explore the effect of leaching of alkali into water from freshly placed concrete. Freshly cast concrete specimens were exposed to fresh water, covering a range of conditions observed in the field such as volume of concrete/volume of water, age of exposure and cement content. Analysis of the results indicated that early age contact with fresh concrete can lead to an increase in the pH levels of water up to 11, similar to the levels of pH observed in pore water inside freshly cast concrete. It was noted that until an age of 4 days from casting of concrete, the age of exposure does not significantly affect the changes in the peak pH levels of water. Continuous monitoring of water in contact with concrete also indicated that the pH levels diminish with time, which is attributed to the possible reaction of calcium hydroxide with atmospheric carbon. The paper will present the experimental study, the results, analysis and outcomes as well as planning of a more comprehensive study to observe possible ways of reducing the leaching of alkali from freshly placed concrete.
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