خيارات البحث
النتائج 1321 - 1330 من 1,506
Phytoremediation of an arsenic-contaminated site using Pteris vittata L. and Pityrogramma calomelanos var. austroamericana: a long-term study
2012
Niazi, Nabeel Khan | Singh, Balwant | Zwieten, Lukas van | Kachenko, Anthony George
This field study investigated the phytoremediation potential of two arsenic (As) hyperaccumulating fern species, Pityrogramma calomelanos var. austroamericana and Pteris vittata over 27-month duration at a disused As-contaminated cattle-dip site located at Wollongbar, NSW, Australia. Ferns planted in January 2009 were harvested following 10, 22 and 27 months of growth. A detailed soil sampling was undertaken in June 2009 (initial, n = 42 per plot) and limited sampling in April 2011 (after 27 months, n = 15 per plot) to measure total and phosphate-extractable As concentrations in soil at 0 − 20-, 20 − 40- and 40 − 60-cm depths. The choice of the limited number of samples was considered sufficient to estimate the changes in soil As concentration following phytoremediation based on a geostatistical model. The average frond dry biomass, As concentration and As uptake were significantly (P < 0.001 − 0.05) greater in P. calomelanos var. austroamericana than P. vittata, at all three harvests (1.6 − 4.3, 1.3 − 1.5 and 2.2 − 5.7 times, respectively). After 27-months of growth, P. calomelanos var. austroamericana removed 8,053 mg As (i.e. cumulative over three harvests) in plot B (25.4 kg As ha−1) that was 2.65 times higher than that depleted by P. vittata (3,042 mg As in plot A (9.7 kg As ha−1)). The cumulative frond As uptake data of the two fern species revealed that P. calomelanos var. austroamericana extracted 1.7 − 3.9 % and P. vittata removed 0.53 − 1.5 % of total As from soil at three depths. However, for the surface (0 − 20 cm) and subsurface (40 − 60 cm) layers, the (post-experiment) soil As data indicated that total As concentration in soil was reduced by 49 and 63 % (P < 0.05), respectively, using P. calomelanos var. austroamericana; and 17 and 15 % (P > 0.05), respectively, by P. vittata. Our results show that phytoremediation time based on observed changes in soil As based on limited sampling is not reliable; hence, it is recommended that the frond As uptake should be considered in order to evaluate the phytoremediation efficiency of the two fern species at the experimental site. Using As uptake of the two fern species, we estimate that with P. calomelanos var. austroamericana it would take 55 − 125 years to decrease mean total As content below the ecological investigation level (20 mg kg−1) in the surface and subsurface soils, whereas with P. vittata 143 − 412 years would be required to achieve this target.
اظهر المزيد [+] اقل [-]Groundwater flow and contaminant transport modeling applications in urban area: scopes and limitations
2012
Seyf-Laye, Alfa-Sika Mande | Mingzhu, Liu | Djanéyé-Bouindjou, Gbandi | Liu, Fei | Lyutsiya, Kamaletdinova | Moctar, Bawa L. | Honghan, Chen
BACKGROUND: A three-dimensional groundwater flow model was used to evaluate the groundwater potential and assess the effects of groundwater withdrawal on the regional water level and flow direction in the central Beijing area. A program of groundwater modeling aimed at estimating current contaminant fluxes to the central area and site streams via groundwater was developed. RESULTS AND DISCUSSION: The conceptual model developed for the site attempted to incorporate a complex stratigraphic profile in which groundwater flow and contaminant transport is strongly controlled by a shallow aquifer. Here, a conceptual model for groundwater flow and contaminant transport in central Beijing is presented. CONCLUSION: Model simulations indicated that a sharp drop in the hydraulic head occurs at the center of the model area, which generates a cone of depression and a continuous decline of head with respect to time as a result of heavy groundwater abstraction.
اظهر المزيد [+] اقل [-]Lead concentration increase in the hepatic and gill soluble fractions of European chub (Squalius cephalus)—an indicator of increased Pb exposure from the river water
2012
Dragun, Zrinka | Krasnići, Nesrete | Strižak, Željka | Raspor, Biserka
PURPOSE: To examine if chronic exposure of feral fish to elevated Pb concentrations in the river water (up to 1 μg L−1), which are still lower than European recommendations for dissolved Pb in surface waters (7.2 μg L−1; EPCEU (Official J L 348:84, 2008)), would result in Pb accumulation in selected fish tissues. METHODS: Lead concentrations were determined by use of HR ICP-MS in the gill and hepatic soluble fractions of European chub (Squalius cephalus) caught in the Sutla River (Croatia–Slovenia). RESULTS: At the site with increased dissolved Pb in the river water, soluble gill Pb levels (17.3 μg L−1) were approximately 20 times higher compared to uncontaminated sites (0.85 μg L−1), whereas the ratio between contaminated (18.1 μg L−1) and uncontaminated sites (1.17 μg L−1) was lower for liver (15.5). Physiological variability of basal Pb concentrations in soluble gill and hepatic fractions associated to fish size, condition, sex, or age was not observed, excluding the possibility that Pb increase in chub tissues at contaminated site could be the consequence of studied biotic parameters. However, in both tissues of Pb-exposed specimens, females accumulated somewhat more Pb than males, making female chubs potentially more susceptible to possible toxic effects. CONCLUSIONS: The fact that Pb increase in gill and hepatic soluble fractions of the European chub was not caused by biotic factors and was spatially restricted to one site with increased dissolved Pb concentration in the river water points to the applicability of this parameter as early indicator of Pb exposure in monitoring of natural waters.
اظهر المزيد [+] اقل [-]Effects of phosphorus amendments and plant growth on the mobility of Pb, Cu, and Zn in a multi-metal-contaminated soil
2012
Fang, Yueying | Cao, Xinde | Zhao, Ling
PURPOSE: Phosphorus amendments have been widely and successfully used in immobilization of one single metal (e.g., Pb) in contaminated soils. However, application of P amendments in the immobilization of multiple metals and particularly investigations about the effects of planting on the stability of the initially P-induced immobilized metals in the contaminated soils are far limited. METHODS: This study was conducted to determine the effects of phosphate rock tailing (PR), triple superphosphate fertilizer (TSP), and their combination (P+T) on mobility of Pb, Cu, and Zn in a multimetal-contaminated soil. Chinese cabbage (Brassica rapa subsp. chinensis) (metal-sensitive) and Chinese kale (Brassica alboglabra Bailey) (metal-resistant) were introduced to examine the effects of planting on leaching of Pb, Cu, and Zn in the P-amended soils. RESULTS: All three P treatments greatly reduced CaCl2-extractable Pb and Zn by 55.2–73.1% and 14.3–33.6%, respectively. The PR treatment decreased CaCl2-extractable Cu by 27.8%, while the TSP and P+T treatments increased it by 47.2% and 44.4%, respectively. All three P treatments were effective in reducing simulated rainwater leachable Pb, with dissolved and total leachable Pb decrease by 15.6–81.9% and 16.3–64.5%, respectively. The PR treatment reduced the total leachable Zn by 16.8%, while TSP and P+T treatments increased Zn leaching by 92.7% and 78.9%, respectively. However, total Cu leaching were elevated by 17.8–178% in all P treatments. Planting promoted the leaching of Pb and Cu by 98.7–127% and 23.5–170%, respectively, especially in the colloid fraction, whereas the leachable Zn was reduced by 95.3–96.5% due to planting. The P treatments reduced the uptake of Pb, Cu, and Zn in the aboveground parts of Chinese cabbage by up to 65.1%, 34.3%, and 9.59%, respectively. Though P treatments were effective in reducing Zn concentrations in the aboveground parts of the metal-resistant Chinese kale by 22.4–28.9%, they had little effect on Pb and Cu uptake. CONCLUSIONS: The results indicated that all P treatments were effective in immobilizing Pb. The effect on the immobilization of Cu and Zn varied with the different P treatments and evaluation methods. Metal-sensitive plants are more responsive to the P treatments than metal-resistant plants. Planting affects leaching of metals in the P-amended soils, specially leaching of colloid fraction. The conventional assessment on leaching risks of heavy metals by determining dissolved metals (filtered through 0.45-μm pore size membrane) in leachates could be underestimated since colloid fraction may also contribute to the leaching.
اظهر المزيد [+] اقل [-]A recreational water quality index using chemical, physical and microbiological parameters
2012
Kekar, | González, Soledad Oliva | Mallea, Miguel | González, Patricia
PURPOSE: The aim of this paper was to develop a new recreational water quality index (RWQI) as a tool to ensure the health of swimmers and to take practical decisions. METHODS: RWQI was elaborated with epidemiological data, and we carried out an exhaustive study of the different guidelines for recreational waters proposed by different organisations around the world. Different parameters were chosen, considering, as a priority, the swimmer’s contact and the possibility of ingestion of water during the recreational activity. Furthermore, rating curves were established for pH, chemical oxygen demand, nitrate, phosphate, detergents, enterococci, total coliforms, faecal coliforms and Escherichia coli. RESULTS AND CONCLUSIONS: The index was applied to the data set on water quality of the Potrero de los Funes River (San Luis, Argentina), generated during 2 years (2009–2010). Following the RWQI values classification, most of the Potrero de los Funes water samples fell in the good quality range during the study period.
اظهر المزيد [+] اقل [-]Heterogeneous photocatalytic degradation of methyl orange in schwertmannite/oxalate suspension under UV irradiation
2012
Wu, Yong | Guo, Jing | Jiang, Danjun | Zhou, Pei | Lan, Yeqing | Zhou, Lixiang
INTRODUCTION: Schwertmannite was synthesized through an oxidation of FeSO4 by Acidithiobacillus ferrooxidans LX5 cell suspension at an initial pH 2.5 and 28°C for 3 days and characterized using X-ray diffraction spectroscopy and scanning electron microscope. The schwertmannite photocatalytic degradation of methyl orange (MO) by oxalate was investigated at different initial pH values, concentrations of schwertmannite, oxalate, and MO. RESULTS: The results demonstrated that photodegradation of MO in the presence of schwertmannite or oxalate alone was very weak. However, the removal of MO was significantly enhanced when schwertmannite and oxalate coexisted in the reaction system. Low pH (4 or less) was beneficial to the degradation of MO. The optimal doses of schwertmannite and oxalate were 0.2 g L−1 and 2 mM, respectively. Hydroxyl radicals (·OH) and Fe(II), the intermediate products, were also examined during the reaction to explore their correlation with the degradation of MO. CONCLUSION: A possible mechanism for the photocatalytic decomposition of MO in the study was proposed. The formation of Fe(III)-oxalate complexes on the surface of schwertmannite was a precursor of H2O2 and Fe(II) production, further leading to the yield of ·OH responsible for the decomposition of MO.
اظهر المزيد [+] اقل [-]Transformation and biodegradation of 1,2,3-trichloropropane (TCP)
2012
Samin, Ghufrana | Janssen, Dick B.
PURPOSE: 1,2,3-Trichloropropane (TCP) is a persistent groundwater pollutant and a suspected human carcinogen. It is also is an industrial chemical waste that has been formed in large amounts during epichlorohydrin manufacture. In view of the spread of TCP via groundwater and its toxicity, there is a need for cheap and efficient technologies for the cleanup of TCP-contaminated sites. In situ or on-site bioremediation of TCP is an option if biodegradation can be achieved and stimulated. This paper presents an overview of methods for the remediation of TCP-contaminated water with an emphasis on the possibilities of biodegradation. CONCLUSIONS: Although TCP is a xenobiotic chlorinated compound of high chemical stability, a number of abiotic and biotic conversions have been demonstrated, including abiotic oxidative conversion in the presence of a strong oxidant and reductive conversion by zero-valent zinc. Biotransformations that have been observed include reductive dechlorination, monooxygenase-mediated cometabolism, and enzymatic hydrolysis. No natural organisms are known that can use TCP as a carbon source for growth under aerobic conditions, but anaerobically TCP may serve as electron acceptor. The application of biodegradation is hindered by low degradation rates and incomplete mineralization. Protein engineering and genetic modification can be used to obtain microorganisms with enhanced TCP degradation potential.
اظهر المزيد [+] اقل [-]Analytical improvements of hybrid LC-MS/MS techniques for the efficient evaluation of emerging contaminants in river waters: a case study of the Henares River (Madrid, Spain)
2012
Pérez-Parada, Andrés | Gómez-Ramos, María del Mar | Martínez Bueno, María Jesús | Uclés, Samanta | Uclés, Ana | Fernández-Alba, Amadeo R.
PURPOSE: Instrumental capabilities and software tools of modern hybrid mass spectrometry (MS) instruments such as high-resolution mass spectrometry (HRMS), quadrupole time-of-flight (QTOF), and quadrupole linear ion trap (QLIT) were experimentally investigated for the study of emerging contaminants in Henares River water samples. METHODS: Automated screening and confirmatory capabilities of QTOF working in full-scan MS and tandem MS (MS/MS) were explored when dealing with real samples. Investigations on the effect of sensitivity and resolution power influence on mass accuracy were studied for the correct assignment of the amoxicillin transformation product 5(R) amoxicillin-diketopiperazine-2′,5′ as an example of a nontarget compound. On the other hand, a comparison of quantitative and qualitative strategies based on direct injection analysis and off-line solid-phase extraction sample treatment were assayed using two different QLIT instruments for a selected group of emerging contaminants when operating in selected reaction monitoring (SRM) and information-dependent acquisition (IDA) modes. RESULTS AND DISCUSSION: Software-aided screening usually needs a further confirmatory step. Resolving power and MS/MS feature of QTOF showed to confirm/reject most findings in river water, although sensitivity-related limitations are usually found. Superior sensitivity of modern QLIT-MS/MS offered the possibility of direct injection analysis for proper quantitative study of a variety of contaminants, while it simultaneously reduced the matrix effect and increased the reliability of the results. Confirmation of ethylamphetamine, which lacks on a second SRM transition, was accomplished by using the IDA feature. CONCLUSION: Hybrid MS instruments equipped with high resolution and high sensitivity contributes to enlarge the scope of targeted analytes in river waters. However, in the tested instruments, there is a margin of improvement principally in required sensitivity and data treatment software tools devoted to reliable confirmation and improved automated data processing.
اظهر المزيد [+] اقل [-]Quantification of bisphenol A, 353-nonylphenol and their chlorinated derivatives in drinking water treatment plants
2012
Dupuis, Antoine | Migeot, Virginie | Cariot, Axelle | Albouy-Llaty, Marion | Legube, Bernard | Rabouan, Sylvie
Bisphenol A (BPA) and nonylphenols (NP) are of major concern to public health due to their high potential for human exposure and to their demonstrated toxicity (endocrine disruptor effect). A limited number of studies have shown that BPA and NP are present in drinking water. The chlorinated derivatives that may be formed during the chlorination step in drinking water treatment plants (DWTP) exhibit a higher level of estrogenic activity than their parent compounds. The aim of this study was to investigate BPA, 353NP, and their chlorinated derivative concentrations using an accurate and reproducible method of quantification. This method was applied to both surface and treated water samples from eight French DWTPs producing from surface water. Solid-phase extraction followed by liquid chromatography–tandem mass spectrometry was developed in order to quantify target compounds from water samples. The limits of detection ranged from 0.3 to 2.3 ng/L for BPA and chlorinated BPA and from 1.4 to 63.0 ng/L for 353NP and chlorinated 353NP. BPA and 353NP were found in most analyzed water samples, at a level ranging from 2.0 to 29.7 ng/L and from 0 to 124.9 ng/L, respectively. In most of DWTPs a decrease of BPA and 353NP was observed between surface water and treated water (36.6 to 78.9 % and 2.2 to 100.0 % for BPA and 353NP, respectively). Neither chlorinated BPA nor chlorinated 353NP was detected. Even though BPA and 353NP have been largely removed in the DWTPs studied, they have not been completely eliminated, and drinking water may consequently remain a source of human exposure.
اظهر المزيد [+] اقل [-]Alteration of in vitro and acute in vivo toxicity of textile dyeing wastewater after chemical and biological remediation
2012
Ben Mansour, Hedi | Houas, Ikram | Montassar, Fadoua | Ghedira, Kamel | Barillier, Daniel | Mosrati, Ridha | Chekir-Ghedira, Leila
INTRODUCTION: Textile industry is one of the most common and essential sectors in Tunisia. However, the treatment of textile effluents becomes a university because of their toxic impacts on waters, soils, flora, and fauna. MATERIALS AND METHODS: The aim of this work was to evaluate the ability of Pseudomonas putida mt-2 to decolorize a textile wastewater and to compare the biologic decolorization process to the chemical one currently used by the textile industry. RESULTS: P. putida exhibited a high decolorizing capacity of the studied effluent, compared to the coagulation–flocculation method with decolorization percentage of 86% and 34.5%, respectively. Genotoxicity of the studied effluent, before and after decolorization by P. putida mt-2, was evaluated in vitro, using the SOS chromotest, and in vivo, in mouse bone marrow, by assessing the percentage of cells bearing different chromosome aberrations compared to not treated mice. In addition, textile effluent statistically significant influenced acetylcholinesterase and butyrylcholinesterase activities and lipid peroxidation (p < 0.01) when compared to not-treated mice. Coagulation–flocculation treatment process used by industry was revealed to be ineffective. Indeed toxicities persisted after treatment and the effluent did not show any statistically significant decrease in toxicities compared to non-treated effluent. Our results indicate that P. putida is a promising and improved alternative to treating industrial scale effluent compared to current chemical decolorization procedures used by the Tunisian textile industry.
اظهر المزيد [+] اقل [-]