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Результаты 181-190 из 449
Assessment of the Impact Produced by the Traffic Source on VOC Level in the Urban Area of Canosa di Puglia (Italy)
2008
Bruno, Paolo | Caselli, Maurizio | de Gennaro, Gianluigi | Scolletta, Lucia | Trizio, Livia | Tutino, Maria
Volatile organic compounds (VOC) have been monitored in 12 sites of Canosa di Puglia, a city located in the Southern of Italy, in order to identify the main VOC source--vehicular traffic or industrial--and to evaluate the critical situations in the city. Monitoring, carried out by using Radiello® diffusive samplers, has been planned taking into account the traffic density and the architecture of the city. From the study of the data it has been emerged that, among all considered VOC, benzene, toluene, ethylbenzene and xylenes (BTEX) are the pollutants at higher concentration. However no critical situation has appared from the present monitoring. Maps of daily benzene and toluene concentrations have shown that the most significant pollution phenomena happens in the center of the urban area which is in a valley with narrow roads and high buildings that do not allow an efficient dispersion of pollutants. The study of the diagnostic ratios between the toluene and benzene concentrations in the several areas (average T/B = 3.4) and the high Pearson's coefficient among the pollutants, and in particular between benzene and toluene concentrations (r = 0.9505), have suggested that in urban area these pollutants are emitted from the same source: the vehicular traffic.
Показать больше [+] Меньше [-]Chemical and Ecotoxicological Assessment of Selected Biologically Activated Sorbents for Treating Wastewater Polluted with Petroleum Products with Special Emphasis on Polycyclic Aromatic Hydrocarbons
2008
Augulyte, L. | Kliaugaite, D. | Racys, V. | Jankunaite, D. | Zaliauskiene, A. | Andersson, P. L. | Bergqvist, P.-A.
A chemical and ecotoxicological assessment of treatment of wastewater that had been polluted with petroleum products using only Activated Sludge (AS) and four biologically activated sorbents (BASs), consisting of activated sludge plus: coal-based activated carbon (-C1), coconut shell-based activated carbon (-C2), zeolite (-Z), and anthracite (-A) were conducted. The efficiency and robustness of the four wastewater treatment systems were evaluated by calculating the reduced total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) contents and the acute ecotoxicity of the effluents. The chemical analysis showed that the combined treatment systems were very effective for reducing the total petroleum hydrocarbon and readily bioavailable PAH contents. The most efficient systems were the BAS-C1 and -C2, which removed 60-88% and 99.5-99.6% of TPH and PAH, respectively. The activated sludge-only treatment was the least effective for purifying the wastewater. Chemical oxygen demand was reduced by >90% by all carbon-based BASs (BAS-C1, BAS-C2 and BAS-A). Shifts in the relative composition of the individual PAHs were identified in samples taken before and after treatment. Algal and bacterial bioassays showed that the toxicities of effluents following treatment by all four systems (except AS for algae) were reduced by more than 80% and 90%, respectively. However, crustacean tests indicated that the carbon-based BASs reduced the toxicity [V tox₍₅₀₎] only by 19-67%. Our results indicated that the combination of sorption and biodegradation processes have great potential in the treatment of petroleum products polluted wastewater and is less sensitive for inhibitors of the biological process than treatments in which activated sludge alone is used. The assessment of chemical and ecotoxicological endpoints provided valuable information, but contrasting results for one of the assays indicates that further analysis on the capacity of the different treatment systems is warranted.
Показать больше [+] Меньше [-]Benzene Biodegradation under Anaerobic Conditions Coupled with Metal Oxides Reduction
2008
Villatoro-Monzón, Wilverth R. | Morales-Ibarria, Marcia G. | Velázquez, Elia K. | Ramírez-Saad, Hugo | Razo-Flores, Elías
Anaerobic benzene biodegradation was performed in batch experiments using Rhine River sediment as inoculum and amorphous Mn(IV) or Fe(III) as independent final electron acceptors. Benzene (4.5 μmol) was degraded in 80 and 710 days in batch experiments under Mn(IV) and Fe(III) reducing conditions, respectively. Highest benzene degradation rate, 0.07 μmol/day, was obtained under Mn (IV) reducing conditions, with soluble Mn(II) and CO₂ recoveries of 71.5% and 93% regarding to the stoichiometric values, respectively. Likewise, benzene biodegradation was performed in a continuous column coupled to the reduction of Mn(IV). Efficiency of benzene biodegradation was up to 97% under steady state operation in a sediment column operated continuously for more than 160 days. The carbon dioxide and Mn(II) recoveries were 88% and 77%, respectively, of the theoretical ratio according to the stoichiometry for benzene biodegradation.
Показать больше [+] Меньше [-]Toxicity of Lead to Freshwater Invertebrates (Water fleas; Daphnia magna and Cyclop sp) in Fish Ponds in a Tropical Floodplain
2008
Offem, Benedict O. | Ayotunde, Ezekiel O.
Acute toxicity of Pb to the water flea; (Daphnia sp) and Copepod, (Cyclop sp) both important component of zooplankton diet of fish was determined by static assay. A positive relationship between percentage mortality and exposure concentration was found in all tests. Mean 24-h LC50, 48-h LC50 and 96-h LC50 values were 2.51 ± 0.0.04 mg l⁻¹, 1.88 ± 0.06 mg l⁻¹ and 1.65 ± 0.19 mg l⁻¹ for Daphnia spp and 3.11 ± 0.03 mg l⁻¹, 2.97 ± 0.05 mg l⁻¹ and 2.61 ± 0.09 mg l⁻¹ for Cyclop spp, respectively. For all tested species did the LC50 values decrease with time; the decrease was more marked for Daphnia spp. Observed symptoms include spiral movement followed by change of body colour to white and rapid disintegration of the skin. The Daphnia spp. appear to be more sensitive to Pb poison than Cyclop spp. The results showed that concentrations of Lead (Pb) in excess of 0.19 mg l⁻¹ and 0.30 mg l⁻¹ can be potentially harmful to Daphnia magna and Cyclop spp respectively.
Показать больше [+] Меньше [-]Cadmium Phytoextraction Efficiency of Arum (Colocasia antiquorum), Radish (Raphanus sativus L.) and Water Spinach (Ipomoea aquatica) Grown in Hydroponics
2008
Kashem, Md Abul | Singh, Bal Ram | Huq, S. M. Imamul | Kawai, Shigenao
Selection of a phytoextraction plant with high Cd accumulation potential based on compatibility with mechanized cultivation practice and local environmental conditions may provide more benefits than selection based mainly on high Cd tolerance plants. In this hydroponics study, the potential of Cd accumulation by three plant species; arum (Colocasia antiquorum), radish (Raphanus sativus L.) and water spinach (Ipomoea aquatica) were investigated. Arum (Colocasia antiquorum L.) plants were grown for 60 days in a nutrient solution with 0, 10 or 50 μM Cd, while radish and water spinach plants grew only 12 days in 0, 1.5, 2.5, 5 or 10 μM Cd. Growth of radish and water spinach plants decreased under all Cd treatments (1.5 to 10 μM), while arum growth decreased only at 50 μM Cd. At 10 μM Cd treatment, the growth of arum was similar to the control treatment indicating higher tolerance of arum for Cd than radish and water spinach. Cadmium concentrations in different plant parts of all plant species increased significantly with Cd application in the nutrient solution. Arum and water spinach retained greater proportions of Cd in their roots, while in radish, Cd concentration in leaves was higher than in other plant parts. Cadmium concentrations in arum increased from 158 to 1,060 in the dead leaves, 37 to 280 in the normal leaves, 108 to 715 in the stems, 42 to 290 in the bulbs and 1,195 to 3,840 mg kg⁻¹ in the roots, when the Cd level in the solution was raised from 10 μM Cd to 50 μM Cd. Arum accumulated (dry weight x concentration) 25 mg plant⁻¹ at 10 μM, while the corresponding values for radish and water spinach were 0.23 and 0.44 mg plant⁻¹, respectively. With no growth retardation at Cd concentrations as high as 166 mg kg⁻¹ measured in entire plant (including root) of arum at 10 μM Cd in the nutrient solution, arum could be a potential Cd accumulator plant species and could be used for phytoremediation.
Показать больше [+] Меньше [-]Biosorption of Methylene Blue from Aqueous Solutions by Hazelnut Shells: Equilibrium, Parameters and Isotherms
2008
Doğan, Mehmet | Abak, Harun | Alkan, Mahir
This paper presents a study on the batch adsorption of a basic dye, methylene blue (MB), from aqueous solution onto ground hazelnut shell in order to explore its potential use as a low-cost adsorbent for wastewater dye removal. A contact time of 24 h was required to reach equilibrium. Batch adsorption studies were carried out by varying initial dye concentration, initial pH value (3-9), ionic strength (0.0-0.1 mol L⁻¹), particle size (0-200 μm) and temperature (25-55°C). The extent of the MB removal increased with increasing in the solution pH, ionic strength and temperature but decreased with increase in the particle size. The equilibrium data were analysed using the Langmuir and Freundlich isotherms. The characteristic parameters for each isotherm were determined. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were represented well by Langmuir isotherm equation. The maximum adsorption capacities for MB were 2.14 x 10⁻⁴, 2.17 x 10⁻⁴, 2.20 x 10⁻⁴ and 2.31 x 10⁻⁴ mol g⁻¹ at temperature of 25, 35, 45 and 55°C, respectively. Adsorption heat revealed that the adsorption of MB is endothermic in nature. The results indicated that the MB strongly interacts with the hazelnut shell powder.
Показать больше [+] Меньше [-]Evaluation of the Ecotoxicological Impact of the Pesticide Lasso® on Non-target Freshwater Species, Through Leaching from Nearby Agricultural Fields, Using Terrestrial Model Ecosystems
2008
Abrantes, N. | Pereira, R. | Soares, A. M. V. M. | Gonçalves, F.
Terrestrial Model Ecosystems (TMEs) are frequently used to assess the potentially harmful effects of contaminants on terrestrial organisms. Therefore we have used this tool to simulate the leaching phenomena from agricultural soils, within the drainage basin of Lake Vela (Figueira da Foz, Central Portugal), and to perform a subsequent evaluation of the toxicity of the leachates obtained, after the treatment of soil-cores with the herbicide Lasso® on non-target freshwater species. Hence, standard (algae: Pseudokirchneriella subcapitata; cladoceran: Daphnia magna) and autochthonous (algae: Aphanizomenon flos-aquae; cladoceran: Daphnia longispina) species were exposed to several dilutions of leachates obtained from the application of different treatments to soil-cores collected in an agricultural field in the Lake Vela surrounds: RW-soil-core irrigated with artificial rain water; RW+L-soil-core irrigated with artificial rain water after the application of Lasso®; GW+L-soil-core irrigated with groundwater collected in local wells, after the application of Lasso®. Chemical analysis confirmed the presence of alachlor (active ingredient of Lasso®) in the leachates RW+L and GW+L at concentrations of 88 and 16.9 μg L⁻¹ respectively. As expected, the results demonstrated that the leachate RW was not toxic for the tested species. However, leachates where the herbicide was applied, particularly the RW+L, was highly toxic to P. subcapitata (96 h-IC₅₀ = 9.7%), contrasting with the absence of toxic effects in A. flos-aquae. Notwithstanding the effects on algae, the reproduction and growth of both daphnids were not affected by the potential toxicity of leachates. Nevertheless, our results were consistent with the chemical analysis and alachlor ecotoxicity data reported in the literature. Our study confirmed that the current use of pesticides in the lands near Lake Vela, especially Lasso®, combined with the specific properties of local soils, can contribute to the contamination of surface and groundwater resources, through leaching, and could compromise the weak balance of the freshwater ecosystem by affecting one of the main trophic levels: the primary producers.
Показать больше [+] Меньше [-]Tidal Hydrodynamics and their Implications for the Dispersion of Effluents in Mazatlán Harbor: An Urbanized Shallow Coastal Lagoon
2008
Montaño-Ley, Y. | Peraza-Vizcarra, R. | Páez-Osuna, F.
In order to investigate the Urias Coastal Lagoon (UCL) hydrodynamics, a vertically integrated semi-implicit, non-linear, finite difference model, has been applied. The flow dynamics in this model has been described by the depth integrated shallow water equations and has been forced by prescribed free surface elevations at the open boundary in the inlet of the lagoon. The predicted instantaneous tidal elevation and the vector field of tidal velocities, reflect reasonably well the flood and ebb conditions in the coastal lagoon. Maximum tidal velocities of 0.6 m/s at the navigation channel of the lagoon and tidal ranges of 1.2 m were predicted for spring tides. Residual current of 0.01–0.06 m/s have also been predicted. The advection-diffusion process of a hypothetical pollutant released at two discrete points in the UCL depended on the intensity of water circulation; sites with slow instantaneous tidal velocities and residual currents of small magnitude presented slow advection and diffusion of the pollutant and may be considered vulnerable to the contamination, specifically the head of the lagoon where the pollutant was difficult to be removed by the tidal currents. The main channel, where the tidal currents exceed 0.6 m/s and the residual currents reached 0.06 m/s, behaved as a natural conduct for the pollutant motion. The forces involved in water circulation within the channel would be the best driving mechanism to flush contaminants from the UCL into the Ocean.
Показать больше [+] Меньше [-]Enhanced Adsorption of Metal Ions Onto Polyethyleneimine-Impregnated Palm Shell Activated Carbon: Equilibrium Studies
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.
Показать больше [+] Меньше [-]Impact of Tropical Ecosystem on the Migrational Behavior of K-40, Cs-137, Th-232 U-238 in Perennial Plants
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.
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