خيارات البحث
النتائج 1271 - 1280 من 1,310
Evaluation of the optimal strategy for ex situ bioremediation of diesel oil-contaminated soil النص الكامل
2011
Lin, Ta-Chen | Pan, Po-Tsen | Young, Chiu-Chung | Chang, Jo-Shu | Chang, Tsung-Chung | Cheng, Sheng-Shung
PURPOSE: Bioaugmentation and biostimulation have been widely applied in the remediation of oil contamination. However, ambiguous results have been reported. It is important to reveal the controlling factors on the field for optimal selection of remediation strategy. In this study, an integrated field landfarming technique was carried out to assess the relative effectiveness of five biological approaches on diesel degradation. The limiting factors during the degradation process were discussed. METHOD: A total of five treatments were tested, including conventional landfarming, nutrient enhancement (NE), biosurfactant addition (BS), bioaugmentation (BA), and combination of bioaugmentation and biosurfactant addition (BAS). The consortium consisted of four diesel-degrading bacteria strains. Rhamnolipid was used as the biosurfactant. The diesel concentration, bacterial population, evolution of CO2, and bacterial community in the soil were periodically measured. RESULTS: The best overall degradation efficiency was achieved by BAS treatment (90 ± 2%), followed by BA (86 ± 2%), NE (84 ± 3%), BS (78 ± 3%), and conventional landfarming (68 ± 3%). In the early stage, the total petroleum hydrocarbon was degraded 10 times faster than the degradation rates measured during the period from day 30 to 100. At the later stage, the degradation rates were similar among treatments. In the conventional landfarming, contaminated soil contained bacteria ready for diesel degradation. CONCLUSION: The availability of hydrocarbon was likely the limiting factor in the beginning of the degradation process. At the later stage, the degradation was likely limited by desorption and mass transfer of hydrocarbon in the soil matrix.
اظهر المزيد [+] اقل [-]An approach to determining potential surrogates for analyzing ecological patterns of planktonic ciliate communities in marine ecosystems النص الكامل
2011
Xu, Henglong | Jiang, Yong | Zhang, Wei | Zhu, Mingzhuang | Al-Rasheid, Khaled A. S.
INTRODUCTION: In order to identify a potential surrogate of planktonic ciliate communities for marine bioassessments and evaluating biological conservations, the different taxonomic/numerical resolutions and taxa as surrogates were studied in Jiaozhou Bay, northern China during a 1-year cycle (June 2007–May 2008). MATERIALS AND METHODS: Samples were collected biweekly from a depth of 1 m at each of five sites. A range of physicochemical parameters were also measured in order to determine water quality. RESULTS: The genus- and family-level resolutions maintained sufficient information to evaluate the ecological patterns of the ciliate communities in response to environmental status. The non-loricate oligotrichous ciliate assemblages in both abundance and occurrence may be used as a surrogate of planktonic ciliate communities. Heavy data transformations were an optimal strategy for the species level of planktonic ciliates, while mild data transformations were for the higher. The ordination patterns based on species biomass, occurrence, and biomass/abundance ratio matrices were significantly consistent with that of species abundance data. CONCLUSION: The results suggest that the use of simplifications at both taxonomic and numerical resolutions are time-efficient and would allow improving sampling strategies of large spatial/temporal scale monitoring programs and biological conservation researches in the marine ecosystem with a relative paucity of scientists.
اظهر المزيد [+] اقل [-]Uranium biosorption by Padina sp. algae biomass: kinetics and thermodynamics النص الكامل
2011
Khani, Mohammad Hassan
INTRODUCTION: Kinetic, thermodynamic, and equilibrium isotherms of the biosorption of uranium ions onto Padina sp., a brown algae biomass, in a batch system have been studied. DISCUSSION: The kinetic data were found to follow the pseudo-second-order model. Intraparticle diffusion is not the sole rate-controlling factor. The equilibrium experimental results were analyzed in terms of Langmuir isotherm depending with temperature. Equilibrium data fitted very well to the Langmuir model. The maximum uptakes estimated by using the Langmuir model were 434.8, 416.7, 400.0, and 370.4 mg/g at 10°C, 20°C, 30°C, and 40°C, respectively. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. Padina sp. algae were shown to be a favorable biosorbent for uranium removal from aqueous solutions.
اظهر المزيد [+] اقل [-]Study of the uncertainty in NO₂ chemiluminescence measurements due to the NO-O₃ reaction in sampling lines النص الكامل
2011
Miñarro, Marta Doval | Ferradás, Enrique González | Rico, Jonathan Barberá | Alonso, Fernando Díaz | Martínez, Francisco J Marzal | Trigueros, Cristina Romero
Introduction The change in light intensity that takes place when an ambient air sample is drawn into the detection chamber of a chemiluminescence monitor generates changes in the concentrations of several species, such as NO₂, NO and O₃. Although this phenomenon has been known for several decades, there is still no commonly accepted approach on when or how to correct for it in NO₂ and O₃ readings. Discussion In this work, we have assessed the expanded uncertainty of two chemiluminescence NO x analysers commercially available according to EN 14211:2005, with the aim of establishing the maximum allowable standard uncertainty due to the reaction between NO and O₃ in the sampling system. Conclusion Although this maximum allowable uncertainty cannot be a universal value--as it will depend on the performance of each analyser--our results have led us to propose the conservative value of 2%. We have also proposed a methodology for improving data quality which could be easily implemented by those responsible for air quality data validation.
اظهر المزيد [+] اقل [-]Cultural heritage: a potential pollution source in museum النص الكامل
2011
Lee, CheolMin | Kim, YoonShin | Nagajyothi, P. C. | Thammalangsy, Soulighothai | Goung, Sun Ju Nam
Introduction The purposes of this study, as part of research projects for establishing the preservation environment of domestic cultural properties, are to identify the hazardous environmental factors which have a possibility to cause damages on long-term preservation of cultural heritage within the museum exhibition halls and the storages area, and to provide the basic data for the future establishment of preservation environment. Materials and methods The temperature (23.5 and 20.6°C,) relative humidity (52.1% and 55.4%), PM10 (31.5 and 18.9 μg/m3), CO2 (472.7 and 526.8 ppm), HCHO (20.8 and 34.0 μg/m3), CO (0.3 and 0.3 ppm), NO2 (0.012 and 0.004 ppm), TVOCs (493.6 and 788.9 μg/m3), O3 (0.003 and 0.002 ppm), Rn (0.7 and 1.5 pCi/L), and SO2 (0.003 and 0.002 ppm) as chemical factors, and airborne bacteria and fungi as biological factors, were selected for this research subjects of hazardous environmental factors, which were the subjects of the study conducted by the National Research Institute of Cultural Heritage from 2006 to 2008, and the subjects of related domestic researches performed in fragments. Results and discussion The concentration distributions of selected hazardous environmental factors in a museum environment were calculated by using the inverse variance weighted average in meta-analysis, and the concentration distributions possibly emerging in a museum exhibition halls and storages were computed through Monte Carlo simulation in order to minimize the uncertainty that can be caused from meagerness of related domestic researches.
اظهر المزيد [+] اقل [-]Heavy metal contamination and risk assessment in water, paddy soil, and rice around an electroplating plant النص الكامل
2011
Liu, Jie | Zhang, Xue-Hong | Tran, Henry | Wang, Dun-Qiu | Zhu, Yi-Nian
PURPOSE: The objective of this paper is to assess the impact of long-term electroplating industrial activities on heavy metal contamination in agricultural soils and potential health risks for local residents. METHODS: Water, soil, and rice samples were collected from sites upstream (control) and downstream of the electroplating wastewater outlet. The concentrations of heavy metals were determined by an atomic absorption spectrophotometer. Fractionation and risk assessment code (RAC) were used to evaluate the environmental risks of heavy metals in soils. The health risk index (HRI) and hazard index (HI) were calculated to assess potential health risks to local populations through rice consumption. RESULTS: Hazardous levels of Cu, Cr, and Ni were observed in water and paddy soils at sites near the plant. According to the RAC analysis, the soils showed a high risk for Ni and a medium risk for Cu and Cr at certain sites. The rice samples were primarily contaminated with Ni, followed by Cr and Cu. HRI values >1 were not found for any heavy metal. However, HI values for adults and children were 2.075 and 1.808, respectively. CONCLUSION: Water, paddy soil, and rice from the studied area have been contaminated by Cu, Cr, and Ni. The contamination of these elements is related to the electroplating wastewater. Although no single metal poses health risks for local residents through rice consumption, the combination of several metals may threaten the health of local residents. Cu and Ni are the key components contributing to the potential health risks.
اظهر المزيد [+] اقل [-]Pesticide removal from waste spray-tank water by organoclay adsorption after field application to vineyards النص الكامل
2011
Suciu, Nicoleta A. | Ferrari, Tommaso | Ferrari, Federico | Trevisan, Marco | Capri, Ettore
PURPOSE: The main objective of this work was to develop and test a pilot scheme for decontaminating pesticide-containing water derived from pesticide mixtures used to protect vineyards, in which the scheme comprises adsorption by an organoclay and includes a system where an enhanced or rapid microbial degradation of the adsorbed residues can occur. METHODS: In laboratory experiments, the Freundlich adsorption coefficients of formulations of two fungicides, penconazole and cyazofamid, onto the organoclay Cloisite 20 A were measured in order to predict the efficiency of this organoclay in removing these fungicides from the waste spray-tank water. Subsequently, the adsorption tests were repeated in the pilot system in order to test the practical operation of the depuration scheme. RESULTS: The adsorption tests with the pilot system show 96% removal of both fungicides over a few hours, similar to the efficiency of removal predicted from the laboratory adsorption tests. The formulation type may influence the efficiency of clay recovered after adsorption. Regarding the waste disposal, for instance, the organoclay composted after the treatment, cyazofamid showed significant dissipation after 90 days, whereas the dissipation of penconazole was negligible. CONCLUSION: The depuration scheme developed showed to be efficient for decontaminating pesticide-containing water derived from vineyards, but additional treatments for the adsorbed residues still appear to be necessary for persistent pesticides. However, future decontamination research should be attempted for water contaminated with pesticides containing antifoaming agents in their formulations, in which case the present pilot system could not be applied.
اظهر المزيد [+] اقل [-]Energy budget in Daphnia magna exposed to natural stressors النص الكامل
2011
Bergman Filho, Tullus Ullus | Soares, Amadeu M. V. M. | Loureiro, Susana
Energy budget in Daphnia magna exposed to natural stressors النص الكامل
2011
Bergman Filho, Tullus Ullus | Soares, Amadeu M. V. M. | Loureiro, Susana
Background, aim, and scope Climate changes are nowadays an important issue of concern, and it is expected that in the near future it will be intensified, leading to extreme environmental conditions. These changes are expected to originate additional sources of stress; therefore, the exposure of organisms to natural stressors is receiving an increased importance in risk assessment. Organisms tend to avoid extremely environmental conditions looking for optimum conditions. This work aimed to evaluate the effects of natural stressors on the energetic reserves of Daphnia magna using the quantification of lipids, proteins, and sugars. Materials and methods Daphnids were exposed to different temperature regimes (16, 18, 22, 24, and 26°C), food levels (2, 1.5, 1, 0.5, and 0 and 4, 4.5, 5, 5.5, and 6 × 10⁵ cells/ml Pseudokirchneriella subcapitata) and oxygen depletion (2 to 6 mg DO/L) and their energy reserves quantified. Protein, lipid, and sugar contents where compared between daphnids exposed to control conditions and ones exposed to considered stress situations. Results and discussion Significant changes in energy reserves content after a 96-h exposure were observed in temperatures 16, 22, 24, and 26°C. In the exposure to different food levels, daphnids showed significant differences on their energetic reserves when exposed to higher or lower levels of algae when compared with the control. Oxygen depletion did not affect significantly their energy budget. Conclusions The results from this work demonstrate that the environmental alterations related mainly to temperatures variations and food availability produced changes in D. magna energetic reserves. These changes can be transposed to the population levels as they are a result of changes in the metabolic rate and physiological processes that are related to growth and maturation.
اظهر المزيد [+] اقل [-]Energy budget in Daphnia magna exposed to natural stressors النص الكامل
1000 | 2011
Bergman, Tullus Ullus | Soares, Amadeu M. V. M. | Loureiro, Susana
Background, aim, and scope Climate changes are nowadays an important issue of concern, and it is expected that in the near future it will be intensified, leading to extreme environmental conditions. These changes are expected to originate additional sources of stress; therefore, the exposure of organisms to natural stressors is receiving an increased importance in risk assessment. Organisms tend to avoid extremely environmental conditions looking for optimum conditions. This work aimed to evaluate the effects of natural stressors on the energetic reserves of Daphnia magna using the quantification of lipids, proteins, and sugars. Daphnia magna Daphnids were exposed to different temperature regimes (16, 18, 22, 24, and 26A degrees C), food levels (2, 1.5, 1, 0.5, and 0 and 4, 4.5, 5, 5.5, and 6 x 10(5) cells/ml Pseudokirchneriella subcapitata) and oxygen depletion (2 to 6 mg DO/L) and their energy reserves quantified. Protein, lipid, and sugar contents where compared between daphnids exposed to control conditions and ones exposed to considered stress situations. Results and discussion Significant changes in energy reserves content after a 96-h exposure were observed in temperatures 16, 22, 24, and 26A degrees C. In the exposure to different food levels, daphnids showed significant differences on their energetic reserves when exposed to higher or lower levels of algae when compared with the control. Oxygen depletion did not affect significantly their energy budget. Conclusions The results from this work demonstrate that the environmental alterations related mainly to temperatures variations and food availability produced changes in D. magna energetic reserves. These changes can be transposed to the population levels as they are a result of changes in the metabolic rate and physiological processes that are related to growth and maturation.
اظهر المزيد [+] اقل [-]Response of denitrification genes nirS, nirK, and nosZ to irrigation water quality in a Chinese agricultural soil النص الكامل
2011
Zhou, Zhi-Feng | Zheng, Yuan-Ming | Shen, Ju-Pei | Zhang, Li-Mei | He, Ji-Zheng
PURPOSE: Denitrification is an important biochemical process in global nitrogen cycle, with a potent greenhouse gas product N2O. Wastewater irrigation can result in the changes of soil properties and microbial communities of agricultural soils. The purpose of this study was to examine how the soil denitrification genes responded to different irrigation regimes. MATERIALS AND METHODS: Soil samples were collected from three rural districts of Beijing (China) with three different irrigation regimes: clean groundwater (CW), reclaimed water (RW), and wastewater (WW). The abundance and diversity of three denitrification microbial genes (nirS, nirK, and nosZ) were examined by real-time polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) molecular approaches. RESULTS AND DISCUSSION: The abundance of nirS in the WW treatment was higher than that in the CW treatment, and no significant difference was found between the RW and CW or WW treatments. The abundance of nirK gene of the RW and WW treatments was higher than that of the CW treatment. There was no difference for nosZ gene among the three treatments. Correspondence analysis based on the DGGE profiles showed that there was no obvious difference in the nosZ gene composition, but nirS and nirK genes changed with different irrigation regimes. CONCLUSIONS: Irrigation with unclean water sources enhanced the soil NO 3 − content and changed the abundance and composition of soil denitrifiers, and different functional genes had different responses. Irrigation with unclean water sources increased the abundance of nirK gene and changed the community structures of nirS and nirK genes, while nosZ gene was relatively stable in the soil. These results could be helpful to explore the mechanisms of the variation of denitrification processes under long-term wastewater irrigation and partially explain the reason of more N2O output in the field with wastewater irrigation.
اظهر المزيد [+] اقل [-]Monuments as sampling surfaces of recent traffic pollution النص الكامل
2011
Rampazzi, Laura | Giussani, Barbara | Rizzo, Biagio | Corti, Cristina | Pozzi, Andrea | Dossi, Carlo
Background, aim and scope A new approach towards monuments, considering them as a passive sampler of pollution, is presented. Cultural Heritage objects suffer daily the damages of environmental pollution, especially in those areas interested by heavy traffic. Since monuments undergo only periodic conservation or maintenance works, surfaces are able to accumulate atmospheric deposit and to record changes in its composition. An optimised analytical protocol was developed in order to quantify platinum and rhodium at trace level on surfaces. The two elements have become tracers of automobile emissions in recent years, since the introduction of catalytic converters, and could have catalytic effects on the decay reactions of natural and artificial stone materials. As a first case study, the cement mortar surfaces of a twentieth century monument, the Camerlata Fountain, in Como (Italy) were investigated. Materials and methods The surfaces of the monument were scraped in areas both exposed to atmosphere and sheltered by the architectural elements of the building. The powders were dissolved by microwave-assisted mineralisation with a solution of HCl and HNO₃. The solution was filtered, irradiated and analysed by adsorptive cathodic stripping voltammetry. The powders were also analysed by infrared spectroscopy and X-ray diffraction in order to determine the chemical and mineralogical composition. Results and discussion An analysis protocol was set up considering the matrix effect and the expected low concentrations of the two metals. The results enlightened variable concentration values and distribution areas of platinum (0.013-45 μg/kg) and rhodium (0.55-274.4 μg/kg), suggesting the ability of artificial stone surfaces to accumulate the two elements. The sample chemical and mineralogical composition was consistent with a typical cement plaster interested by decay phenomena. Conclusions This work investigated the relation between Cultural Heritage and pollution by another point of view. The analytical protocol presented in this paper was effective in determining platinum and rhodium in traces on the investigated stone surfaces with negligible matrix effects. Recommendation and perspectives The presence of platinum and rhodium on monument surfaces should be of significant interest when planning Cultural Heritage conservation. A better knowledge of the role of the two metals in decay phenomena could impact in a positive way artwork conservation.
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