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Resultados 521-530 de 711
Multi-criteria Analysis of Air Pollution with SO₂ and PM₁₀ in Urban Area Around the Copper Smelter in Bor, Serbia
2010
Nikolić, Djordje | Milošević, Novica | Mihajlović, Ivan | Živković, Živan | Tasić, Viša | Kovačević, Renata | Petrović, Nevenka
This work presents the results of 4 years long monitoring of concentrations of SO₂ gas and PM₁₀ in the urban area around the copper smelter in Bor. The contents of heavy metals Pb, Cd, Cu, Ni, and As in PM₁₀ were determined and obtained values were compared to the limit values provided in EU Directives. Manifold excess concentrations of all the components in the atmosphere of the urban area of the townsite Bor were registered. Through application of a multi-criteria analysis by using PROMETHEE/GAIA method, the zones were ranked according to the level of pollution.
Mostrar más [+] Menos [-]Trace Metal Bioaccumulation and Plant Growth on Dredged River Sediments and Biosolids Mixtures
2010
Ruiz Diaz, Dorivar A. | Darmody, Robert G. | Marlin, John C. | Bollero, German A. | Simmons, F William
Dredged river sediments and biosolids used as amendments for agricultural purposes can provide a suitable plant growth medium, a topsoil substitute. Nevertheless, trace metal bioaccumulation and risk of plant toxicity remains a concern. We conducted a greenhouse experiment to evaluate the plant growth and trace metal bioaccumulation on sediments and biosolid mixtures. These included dredged sediment from the Peoria Lakes portion of the Illinois River and class A biosolids from the Metropolitan Water Reclamation District of Greater Chicago. Six different mixtures were produced in addition to a standard greenhouse mix serving as a control. Barley (Hordeum vulgare) and snap bean (Phaseolus vulgaris) were grown on the mixtures in the greenhouse. Plants grew in all treatments, except for snap beans that were stunted likely by high salt content in unleached biosolid mixtures. The highest overall biomass production for barley was obtained in the treatment composed of 50% sediment and 50% biosolids. For snap bean, the highest biomass productions were obtained in treatments composed of ≤50% biosolids in the mixture. Trace metals in plant tissue were within ranges considered normal, except for Mo in snap bean, which was at a level considered excessive. However, addition of biosolids to sediments decreased Mo plant uptake. Based on our results, sediments mixed with biosolids make a fertile topsoil and have no inherent chemical or physical properties that would preclude its use as a plant growth medium. Adding sediments to unleached fresh biosolids improved plant growth and diminished trace metal uptake. The suggested optimal ratio of sediments to biosolids would be 80:20 to 70:30 by volume in most situations.
Mostrar más [+] Menos [-]Simulation of Groundwater Flow in a Sedimentary Aquifer System Subjected to Overexploitation
2010
Kallioras, Andreas | Pliakas, Fotios | Diamantis, Ioannis
Groundwater flow models are applied to a large variety of hydrogeological conditions in different aquifer types, in order to simulate the groundwater flow of the investigated system. This paper aims to present the application of a groundwater flow model for the simulation of a sedimentary aquifer, located in Northern Greece. The simulation involves the period between April 2003 and April 2004, and the model is divided into two distinct stress periods, each containing two different time steps. The simulation of the aquifer is found to be satisfactory, conclusion which is based on both graphical as well as arithmetical verifications. The groundwater flow simulation was achieved by the application of the MODFLOW code.
Mostrar más [+] Menos [-]Influence of Major Anions on As(V) Adsorption by Synthetic 2-line Ferrihydrite. Kinetic Investigation and XPS Study of the Competitive Effect of Bicarbonate
2010
Frau, F. | Addari, D. | Atzei, D. | Biddau, R. | Cidu, R. | Rossi, A.
The potential competitive effect of background electrolytes (Na₂HPO₄ ·2H₂O, NaHCO₃, Na₂SO₄ and NaCl solutions) on arsenate adsorption onto synthetic 2-line ferrihydrite has been studied by means of kinetic batch experiments conducted at pH values from 4.0 to 10.0 and at anionic concentrations of 0.01 and 0.1 M. The results indicate that the adsorptive capacity of ferrihydrite for arsenate decreases strongly in the presence of phosphate species at pH in the range of 4-10 and in the presence of bicarbonate at pH 8.3 as a consequence of their competitive effect. Analogously to phosphate, a surface interaction of inner-sphere type between ferrihydrite and bicarbonate is suggested. Chloride has negligible effects on arsenate adsorption processes, confirming it as an outer-sphere ion that does not compete with the inner-sphere binding peculiar to arsenate onto ferrihydrite. Sulphate exhibits an intermediate behaviour; at 0.01 M concentration, the competitive effect of sulphate is similar to that of chloride, whereas at 0.1 M concentration sulphate shows a moderate influence on arsenate adsorption. The results of the kinetic studies can be summarised by the following order of competitive capacity: phosphate > carbonate > sulphate > chloride. The process of arsenate adsorption follows pseudo-second order kinetics and the reaction half-time notably increases in the presence of strong competitor anions such as phosphate and carbonate with respect to an ineffective competitor anion such as chloride. Modelling of arsenate adsorption with PHREEQC, according to the Generalized Two-Layer Model, confirms that the pH effect is notably less important than the competitive effect of carbonate species in determining the amount of arsenate adsorbed onto ferrihydrite at pH 8.3 in 0.1 M NaHCO₃ solution, whereas the model greatly underestimates the competitive effect of carbonate species at pH 8.3 in 0.01 M NaHCO₃ solution. The results of the batch experiments in 0.1 M NaHCO₃ solution are substantiated by XPS analyses of ferrihydrite after immersion in the same solution, both with and without dissolved arsenate. XPS confirms the interaction between ferrihydrite surface and arsenate; the binding energy of As3d shifts towards higher binding energies after adsorption with respect to the pure compound Na₂HAsO₄·7H₂O taken as reference standard. In presence of carbonate species, the As3d binding energy is found at intermediate values. XPS quantitative analysis shows a depletion of arsenate on ferrihydrite surface, providing further evidence of the competition of the two species (i.e. arsenate and bicarbonate) for the ferrihydrite adsorption sites. Important environmental implications concerning arsenic mobility, as well as possible application in various fields (e.g. irrigation agriculture, soil decontamination, water treatment), might derive from these findings.
Mostrar más [+] Menos [-]Remediation of Metal Contaminated Soil by Organic Metabolites from Fungi I—Production of Organic Acids
2010
Arwidsson, Zandra | Johansson, Emma | von Kronhelm, Thomas | Allard, Bert | van Hees, Patrick
Investigations were made on living strains of fungi in a bioremediation process of three metal (lead) contaminated soils. Three saprotrophic fungi (Aspergillus niger, Penicillium bilaiae, and a Penicillium sp.) were exposed to poor and rich nutrient conditions (no carbon availability or 0.11 M d-glucose, respectively) and metal stress (25 µM lead or contaminated soils) for 5 days. Exudation of low molecular weight organic acids was investigated as a response to the metal and nutrient conditions. Main organic acids identified were oxalic acid (A. niger) and citric acid (P. bilaiae). Exudation rates of oxalate decreased in response to lead exposure, while exudation rates of citrate were less affected. Total production under poor nutrient conditions was low, except for A. niger, for which no significant difference was found between the poor and rich control. Maximum exudation rates were 20 µmol oxalic acid g⁻¹ biomass h⁻¹ (A. niger) and 20 µmol citric acid g⁻¹ biomass h⁻¹ (P. bilaiae), in the presence of the contaminated soil, but only 5 µmol organic acids g⁻¹ biomass h⁻¹, in total, for the Penicillium sp. There was a significant mobilization of metals from the soils in the carbon rich treatments and maximum release of Pb was 12% from the soils after 5 days. This was not sufficient to bring down the remaining concentration to the target level 300 mg kg⁻¹ from initial levels of 3,800, 1,600, and 370 mg kg⁻¹in the three soils. Target levels for Ni, Zn, and Cu, were 120, 500, and 200 mg kg⁻¹, respectively, and were prior to the bioremediation already below these concentrations (except for Cu Soil 1). However, maximum release of Ni, Zn, and Cu was 28%, 35%, and 90%, respectively. The release of metals was related to the production of chelating acids, but also to the pH-decrease. This illustrates the potential to use fungi exudates in bioremediation of contaminated soil. Nonetheless, the extent of the generation of organic acids is depending on several processes and mechanisms that need to be further investigated.
Mostrar más [+] Menos [-]The Development of SPE Procedures and an UHPLC Method for the Simultaneous Determination of Ten Drugs in Water Samples
2010
Baranowska, Irena | Kowalski, Bartosz
Analytical procedures for the determination of pharmaceuticals from different therapeutic groups were proposed. These groups included the corticosteroids prednisolone and dexamethasone; the β-blockers sotalol, metoprolol, propranolol, and carvedilol; and the analgesic nonsteroidal anti-inflammatory drugs paracetamol, aspirin, metamizole, and ketoprofen. Reversed-phase ultrahigh performance liquid chromatography with an ultraviolet detector, different columns, different mobile phases, and gradient elution programmes were used to obtain the best separations within the shortest possible time. Solid-phase extraction was examined as a preconcentration step. The Oasis HLB column, with the highest recoveries (over 90% for most of the drugs), was chosen for the analysis of surface waters. Limits of detection ranged from 0.06 to 0.39 μg L⁻¹ for all drugs after optimisation of all analytical steps.
Mostrar más [+] Menos [-]Assessment of Radionuclides, Trace Metals and Radionuclide Transfer from Soil to Food of Jhangar Valley (Pakistan) Using Gamma-Ray Spectrometry
2010
Khan, Hasan M. | Chaudhry, Zahid S. | Ismail, Muhammad | Khan, Khalid
The gamma spectrometric analysis of soil and essential foodstuffs, e.g., wheat, millet, potato, lentils and cauliflower, which form the main component of the daily diet of the local public, was carried out using high purity germanium (HpGe) detector coupled with a computer based high-resolution multi-channel analyzer. The activity concentration in soil samples for ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 30.0 Bq kg⁻¹ to 81.2 Bq kg⁻¹, 31.4 Bq kg⁻¹ to 78.25 Bq kg⁻¹ and 308.8 Bq kg⁻¹ to 2177.6 Bq kg⁻¹, with mean values of 56.2, 58.5 and 851.9 Bq kg⁻¹, respectively. The average activity measured for ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples was found higher than the world average. The major radionuclide found in the food items studied was ⁴⁰K, while ²²⁶Ra, ²³²Th and ¹³⁷Cs were detected in very nominal amounts. The results clearly indicate that these radionuclides have no health hazard to human beings, as they are well below the annual limit of intake (ALI) for these radionuclides. The transfer factors of these radionuclides from soil to food were also studied. The mean transfer factors of ⁴⁰K, ²²⁶Ra, ²³²Th and ¹³⁷Cs from soil to food were estimated to be about 0.17, 0.07, 0.16 and 0.23, respectively. An artificial radionuclide, ¹³⁷Cs, was also present in detectable amount in all samples. The internal and external hazard indices were measured and had mean values of 0.70 and 0.55, respectively. Absorbed dose rates and effective dose have been determined in the present study. Concentration of trace metals, such as Cr, Pb, Ni and Zn, was also determined in the soil samples. The concentrations of radionuclides and trace metals found in these samples during the present study were nominal and do not pose any potential health hazard to the general public.
Mostrar más [+] Menos [-]Evaluation of Loads and Sources of Heavy Metals in Tama River, Tokyo
2010
Sakata, Masahiro | Takagi, Tomoharu | Mitsunobu, Satoshi
The loads and sources of heavy metals (Cd, Co, Cu, Mn, Mo, Ni, Pb, V, and Zn) in the midstream of Tama River were evaluated on the basis of their chemical analyses in ordinary and stormwater runoff from July 2007 to November 2008. Tama River is one of the three major rivers flowing into Tokyo Bay. The total annual water discharges differed largely for 2007 and 2008, depending on the scales of typhoon rainfalls and other heavy rainfalls in each year. The concentrations of the metals other than Mo in the river did not change markedly at a flow rate of less than approximately 200 m³ s⁻¹, but at higher flow rates, the concentrations of all the metals increased linearly with the increase in the log of flow rate (r ² = 0.94-0.99). The annual loads of heavy metals for 2007 and 2008 were estimated using regression equations between the above parameters and the hourly flow rate data for each year. For the metals other than Mo, the contribution of the loads at higher flow rates (>200 m³ s⁻¹) was much larger than that at lower flow rates (<200 m³ s⁻¹), showing the importance of the particulate loads (primarily crustal materials) during storm runoff following typhoon rainfalls and other heavy rainfalls. In contrast, the loads of Mo at lower flow rates accounted for major portions (56-78%) of the total loads, because of a relatively small contribution of particulate load during storm runoff. The contribution of the loads of Mo, Zn, Cd, Cu, and Ni at lower flow rates to the annual loads was larger than that of other metals. It was found that the concentrations of these metals in ordinary runoff are strongly affected by the discharge of treated water from sewage treatment plants which are located along the catchment. Thus, treated water from sewage treatment plants may be the primary source contributing to the present pollution of Mo, Zn, Cd, Cu, and Ni in Tokyo Bay.
Mostrar más [+] Menos [-]Surrogate Correlations and Near-Infrared Diffuse Reflectance Sensing of Trace Metal Content in Soils
2010
Wu, Chun-Yu | Jacobson, Astrid R. | Laba, Magdeline | Kim, Bojeong | Baveye, Philippe C.
Near-infrared diffuse reflectance sensing (NIRS) of soils has been the object of considerable interest and research in the last few years. This has been motivated by the prospect that this method seems to provide a cheap, convenient alternative to conventional, time-consuming methods for the measurement of a wide range of soil parameters. In particular, various authors have advocated that NIRS could be used to measure rapidly and non-destructively the concentration of trace metals in surface soils. Correlation analyses between NIRS spectra and trace metal concentration have yielded inconclusive results to date, suggesting that trace metal concentration may belong to a class of “tertiary” soil parameters, linked to NIRS spectra through “surrogate”, or indirect, correlations, involving some other primary or secondary parameter like clay or organic matter content, to which NIRS spectra are very sensitive. To assess the validity of this surrogate correlation hypothesis in the case of trace metals, experiments were carried out with soil samples varying only in the amount of trace metals they contain. Field-aged Hudson and Arkport soil pots spiked with Cu and Zn, freshly spiked samples of the same soils, and samples of a metalliferous peat soil from Western New York naturally rich in Cd and Zn were subjected to NIRS under laboratory conditions. Detailed analysis indicates that the NIR spectrum is sensitive to sample handling, including the orientation of the samples in the NIRS instrument, but that, at the same time, there is no discernable effect of the presence of trace metals on any part of the NIR spectrum. These results provide strong experimental support to the hypothesis of “surrogate” correlation for trace metals, and indicate that trace metals, even in severely contaminated soils, should not interfere with the NIR sensing of primary or secondary parameters, like organic matter content. Further work is needed to determine if this feature of NIR spectra extends to other soil chemical parameters.
Mostrar más [+] Menos [-]Constructed Wetlands Treating Runoff Contaminated with Nutrients
2010
Scholz, M. | Hedmark, Å
The aim was to assess the role of Phragmites australis (Cav.) Trin. ex Steud. in experimental, mature, and temporarily flooded vertical flow wetland filters treating urban runoff rich in organic matter. During the experiment, ammonium chloride was added to sieved concentrated road runoff to simulate primary treated urban runoff contaminated with nitrogen. Five days at 20°C N-allylthiourea biochemical oxygen demand (BOD) and chemical oxygen demand removal efficiencies were relatively lower for planted than unplanted filters. Moreover, there was no significant difference for BOD removal for all filters under fluctuating inflow concentrations of sulfate. The nitrogen removal performances of planted filters were more efficient and stable throughout the seasons compared to those of unplanted filters. A substantial load of nitrogen (approximately 500 mg per filter) was removed by harvesting P. australis. Plant uptake was the main removal mechanism for nitrogen during high concentrations (10 mg/L) of ammonia-nitrogen in the urban runoff.
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