خيارات البحث
النتائج 171 - 180 من 456
Enhanced Adsorption of Metal Ions Onto Polyethyleneimine-Impregnated Palm Shell Activated Carbon: Equilibrium Studies النص الكامل
2008
Yin, Chun Yang | Aroua, Mohamed Kheireddine | Daud, Wan Mohd Ashri Wan
In this study, palm shell activated carbon was impregnated with polyethyleneimine (PEI) and the effect of impregnation on batch adsorption of Ni²⁺, Cd²⁺or Pb²⁺ as well as the equilibrium behavior of adsorption of metal ions on PEI-impregnated AC were investigated. PEI impregnation evidently increased the single metal adsorption capacities of Ni²⁺ or Cd²⁺except for Pb²⁺, where its adsorption capacities were reduced by 16.67% and 19.55% for initial solution pH of 3 and 5 respectively. This suggested that PEI-impregnated AC could be used for selective separation of Pb²⁺ ions from other metal ions. The adsorption data of all the metal ions on both virgin and PEI-impregnated AC for both initial solution pH of 3 and 5 generally fitted the Langmuir and Redlich-Peterson isotherms considerably better than the Freundlich isotherm.
اظهر المزيد [+] اقل [-]Impact of Tropical Ecosystem on the Migrational Behavior of K-40, Cs-137, Th-232 U-238 in Perennial Plants النص الكامل
2008
Kumar, Ajay | Singhal, R. K. | Preetha, J. | Rupali, K. | Narayanan, U. | Suresh, Sughandhi | Mishra, Manish K. | Ranade, A. K.
A comprehensive study was conducted to determine the soil to plant transfer factor (TFS-P) of K-40, Cs-137, Th-232 and U-238 in perennial plants from accessible areas of Mumbai, using high-resolution γ spectrometry. A total of 50 soil and 150 plants samples were collected from all over the Mumbai region where lithology is dominated by basaltic rocks. The mean concentration values for K-40, Cs-137, Th-232 and U-238 in soil was 170.06 ± 65.36, 5.19 ± 1.20, 25.72 ± 6.262 and 10.21 ± 2.82 Bq kg⁻¹ respectively, whereas in case of plants the mean concentration values were determined to be 181.82 ± 18.50, 0.44 ± 0.14, 0.84 ± 0.19 and 0.79 ± 0.22 Bq kg⁻¹ respectively. The mean activity ratio of Th-232/U-238 in plants is 1.06 while in soil the ratio is 2.5. The soil to plant transfer factor (TFS-P) calculated for K-40, Cs-137, U-238 and Th-232 are 1.05, 0.076, 0.071 and 0.031 respectively. Higher value of TFS-P for K-40, which is an integral part of stable potassium clearly indicates the physiological need of stable potassium, for maintaining the different biological mechanisms of perennial plants under tropical conditions.
اظهر المزيد [+] اقل [-]Flows of Active Pharmaceutical Ingredients Originating from Health Care Practices on a Local, Regional, and Nationwide Level in Germany--Is Hospital Effluent Treatment an Effective Approach for Risk Reduction? النص الكامل
2008
Schuster, A | Hädrich, C | Kümmerer, K
Pharmaceuticals are designed to be bioactive and therefore are among the most important chemical compounds manufactured. In recent years pharmaceuticals have been detected in a range of environment compartments, with concerns raised that they may impose a risk to both humans and environmental organisms. To support informed management of any associated risks, knowledge about their substance flows is indispensable. However, little is known about sources and attributable substance flows with regard to the use of human pharmaceuticals. Often data available on a national level are used to judge local or regional situations and to calculate expected concentrations. In this paper, computations on the use of active pharmaceutical ingredients (APIs) of drugs used in human medicine at the local, regional and national levels were conducted. Different data sources were used and raw-data were scaled up- or downwards and compared. Results of this analysis indicated that hospitals are, by far, minor sources of pharmaceuticals to the aquatic environment in comparison to non-point emissions from households. Differences in flows at the local, regional and national scales are also identified.
اظهر المزيد [+] اقل [-]Source Analysis and Hazard Screening of Xenobiotic Organic Compounds in Wastewater from Food-Processing Industries النص الكامل
2008
Maya-Altamira, L | Eriksson, E | Baun, A
In this study we present and apply a methodology for identifying environmentally hazardous compounds in food industry wastewaters (FIW). The methodology comprises a source analysis and a hazard screening of xenobiotic organic compounds based on environmental distribution, persistence, bioaccumulation, and toxicity in aqueous and solid phases. This approach was applied to four selected FIW representing fish, pork meat, and vegetable production. Included in this approach was an analytical-chemical screening of 137 xenobiotic organic compounds showing that 13 compounds and groups of compounds could be detected in the FIW composite samples. The combined source analysis revealed that 161 xenobiotic organic compounds could potentially be present in these four FIW. The main sources were raw materials and their processing, but also packaging and cleaning of the production facility contributed to the total number of compounds potentially present. Using the hazard screening procedure it was found that 29 and 102 compounds should be considered for further hazard assessment in the aqueous and solid phases, respectively. It is important to note that 12% of the 161 compounds could not be evaluated for environmental hazards due to lack of inherent data on degradability, toxicity, and bioaccumulation. Furthermore, for 91% of the compounds no information was found on anaerobic biodegradability. The presented procedure contributes with a systematic source analysis and a ranking of the xenobiotic organic compounds that could cause environmental concern. In this way the procedure can provide guidance to operators and decision makers on handling options for wastewater streams in food processing industries.
اظهر المزيد [+] اقل [-]Material Flows in Sweden 2004 النص الكامل
2008
Carlsson, Arvid | Palm, V | Sörme, L | Wadeskog, A
This paper presents and discusses the method and results of account for material flows in Sweden for the year 2004. The results show that it is possible to compile material flow data from existing sources in the Swedish statistical system. By using the European classification system of goods, the Combined Nomenclature, as the basic unit of the data collection, both data collection and aggregation into material flow categories were made possible. Although these data exist in the statistical system, they are not easily available for the scientific community. This is due to several reasons, such as the aggregation of data in the system of statistics not corresponding to the material flow account structure and the fact that data on import and export of materials are organised differently than data for domestic extraction. Almost 50% of the material flows in Sweden are flows of minerals, mainly construction minerals followed by iron ores. Most of the extracted iron ores are exported. In comparison with other European countries this generates a unique situation with Sweden as the only net exporter of iron ores. The flow of biomass in terms of wood is also considerable (26% of the Swedish material flows in 2004). The domestic material consumption (inflow) per capita in 2004 was 8 tonnes minerals, 6 tonnes biomass and almost 3 tonnes of fossil fuels. Of the material flows of fossil fuels petroleum and natural gas dominates with 90%.
اظهر المزيد [+] اقل [-]Wet Deposition of Nitrogenous Pollutants and the Effect of Storm Duration and Wind Direction: A Case Study from Inland Southern California النص الكامل
2008
Padgett, Pamela E. | Minnich, Richard A.
Meteorological factors affecting concentration of dissolved inorganic nitrogen in rain were examined. Rain samples were collected on an event basis from a location 100 km east of the Los Angeles Basin. Analysis of the data demonstrated a double decay function where small increases in rain volume resulted in large decreases in nitrogen concentration. In separate time series collections of individual storms, storm wind direction also influenced nitrogen concentrations
اظهر المزيد [+] اقل [-]Nitrogen Fractions and Release in the Sediments from the Shallow Lakes in the Middle and Lower Reaches of the Yangtze River Area, China النص الكامل
2008
Wang, Shengrui | Jin, Xiangcan | Jiao, Lixin | Wu, Fengchang
Different nitrogen (N) fractions from 14 sediments from the shallow lakes in the middle and lower reaches of Yangtze River area before and after N release experiments were investigated, and the content of different N fractions, and contribution of different N fractions to the N released from sediments were also studied. Ion-exchangeable form (IEF-N), carbonate form (CF-N), iron-manganese oxide form (IMOF-N) and organic matter-sulfide form (OSF-N) accounted for 2.72~17.67%, 0.47~4.43%, 1.18~3.49% and 31.05 to 71.61% to total N, respectively. The N released was higher than 50% from IEF-N, approximately 35% from OSF-N, 6 and 8% from CF-N and IMOF-N on the average. Approximately 27.32~70.02% of IEF-N, 10.37~32.11% of CF-N, 11.37~33.43% IMOF-N and 2.02~8.19% OSF-N were released. For the sediments that were slightly polluted, IEF-N was the main N fraction that may be released and its contribution to total N released was more than 63.07%, for the sediments that TN was higher than 3,540.27 mg·kg-¹, OSF-N would become the main N fraction that can be released and its contribution to total N released was more than 45%.
اظهر المزيد [+] اقل [-]Modeling Biodegradation of Nonylphenol النص الكامل
2008
Jahan, Kauser | Ordóñez, Raúl | Ramachandran, Ravi | Balzer, Shira | Stern, Michael
Nonylphenol is the primary breakdown product of nonylphenol ethoxylates, a certain class of nonionic surfactants. Nonylphenol has been found to be toxic to aquatic organisms and has been suspected of being harmful to humans due to its xenoestrogenic properties. Although there are known releases of nonylphenol to the environment, there is a lack of data describing the extent of biodegradation. This study thus focuses on much needed information on the biodegradation kinetics of nonylphenol. Oxygen uptake, cell growth and nonylphenol removal data were collected using batch reactors in an electrolytic respirometer. Nonylphenol removal, cell growth and substrate removal rates were modeled by the Monod, Haldane, Aiba, Webb, and Yano equations. The differential equations were solved by numerical integration to simulate cell growth, substrate removal, and oxygen uptake as a function of time. All models provided similar results with the Haldane model providing the best fit. The values of the kinetic parameters and the activation energy for nonylphenol were determined. These values can be used for predicting fate and transport of nonylphenol in the environment. The validity of applying each model to the biodegradation of nonylphenol was analyzed by computing the R ² values of each equation.
اظهر المزيد [+] اقل [-]Granulometric Relationships for Urban Source Area Runoff as a Function of Hydrologic Event Classification and Sedimentation النص الكامل
2008
Ying, G. | Sansalone, J.
This study investigated particulate matter (PM) granulometry delivered in source area runoff as a function of hydrologic transport and settling. At a Baton Rouge, LA paved urban watershed, event runoff volume and PM load were “fully captured” and recovered in settling tanks. Events were differentiated as mass-limited (ML) or flow-limited (FL) and PM differentiated into suspended (1 to ~25 μm), settleable (~25 to 75 μm), sediment (75 to 4,750 μm) fractions; and also particle size distributions (PSDs). Suspended sediment concentration (SSC)-turbidity relationships were unique for FL events compared to ML events; while 60 min of quiescent settling produced a single distinct relationship across all events. ML events transported higher proportions of settleable and sediment mass compared to higher suspended mass for FL events. Event-based ratios of settled and unsettled turbidity as well as SSC mass were statistically different for ML and FL events. For the same settling conditions, treatment of ML and FL events were statistically different. Results demonstrated that PM separation by a unit operation was a deterministic function of granulometry, hydrodynamics, unit operation mechanisms and loads, but significantly influenced by the indeterminate nature of local climate; and hydrology which drives PM delivery and is not known a priori. Combining the influences of scour and lack of maintenance, unit operation performance is non-stationary and cannot be described by a single value. Treatment should be tied to an effluent concentration; granulometry and load.
اظهر المزيد [+] اقل [-]Distribution of Heavy Metals in Marine Sediments of Palermo Gulf (Sicily, Italy) النص الكامل
2008
Tranchina, L. | Basile, S. | Brai, M. | Caruso, A. | Cosentino, C. | Miccichè, S.
Concentrations of Cr, Cu, Hg, Pb and Zn have been measured, by atomic absorption spectrophotometry, in the fine fraction (<63 μm) of surface sediments collected in 30 sites in the Palermo Gulf (Sicily, Italy) in order to assess the levels and the spatial distribution of these elements. Enrichment factors calculated with respect to clean areas have been considered to discriminate between levels due to background or to pollution contributions. The sampling stations, which form a grid inside these areas, are characterized by geographic proximity and by the presence of pollution sources. Ratio matching technique along with hierarchical clustering, minimum spanning tree and principal component analysis have been used for the statistical analysis of data, allowing to better describe the spatial distribution of metal levels. Our work allowed to assess the anthropogenic contribution to the pollution of the area under investigation through industrial and domestic wastes, presence of an harbour area and river inflow.
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