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Résultats 1971-1980 de 3,208
Legionella detection and subgrouping in water air-conditioning cooling tower systems in Kuwait Texte intégral
2015
Al-Matawah, Qadreyah | Al-Zenki, Sameer | Al-Azmi, Ahmad | Al-Waalan, Tahani | Al-Salameen, Fadila | Hejji, Ahmad Ben
The main aim of the study was to test for the presence of Legionnaires’ disease-causing microorganisms in air-conditioned buildings in Kuwait using molecular technologies. For this purpose, 547 samples were collected from 38 cooling towers for the analysis of Legionella pneumophila. These samples included those from water (n = 178), air (n = 231), and swabs (n = 138). Out of the 547 samples, 226 (41 %) samples were presumptive positive for L. pneumophila, with L. pneumophila viable counts in the positive water samples ranging from 1 to 88 CFU/ml. Of the Legionella culture-positive samples, 204 isolates were examined by latex agglutination. These isolates were predominately identified as L. pneumophila serogroup (sg) 2–14. Using the Dresden panel of monoclonal antibodies, 74 representatives isolates were further serogrouped. Results showed that 51 % of the isolates belonged to serogroup 7 followed by 1 (18 %) and 3 (18 %). Serogroups 4 (4 %) and 10 (7 %) were isolated at a lower frequency, and two isolates could not be assigned to a serogroup. These results indicate the wide prevalence of L. pneumophila serogroup 7 as the predominant serogroup at the selected sampling sites. Furthermore, the 74 L. pneumophila (sg1 = 13; sg3 = 13; sg4 = 3; sg7 = 38; sg10 = 5; sgX = 2) isolates were genotyped using the seven gene protocol sequence-based typing (SBT) scheme developed by the European Working Group for Legionella Infections (EWGLI). The results show that Legionella isolates were discriminated into nine distinct sequence typing (ST) profiles, five of which were new to the SBT database of EWGLI. Additionally, all of the ST1 serogroup 1 isolates were of the OLDA/Oxford subgroup. These baseline data will form the basis for the development of a Legionella environmental surveillance program and used for future epidemiological investigations.
Afficher plus [+] Moins [-]Selected current-use pesticides (CUPs) in coastal and offshore sediments of Bohai and Yellow seas Texte intégral
2015
Zhong, Guangcai | Tang, Jianhui | Xie, Zhiyong | Mi, Wenying | Chen, Yingjun | Möller, Axel | Sturm, Renate | Zhang, Gan | Ebinghaus, Ralf
China is one of the largest producers, consumers, and traders for pesticides in the world. Currently, there are more than 600 pesticide-active substances registered in China, whereas few studies were conducted to improve our understanding of the occurrence and environmental impact of current-use pesticides (CUPs) in China’s environment. In this work, 72 surface sediment samples were taken from the coastal and offshore of Bohai and Yellow seas and were analyzed for six CUPs (trifluralin, dacthal, quintozene, endosulfan, chlorpyrifos, and dicofol) and two metabolites (pentachloroanisole and endosulfan sulfate). Sediment samples were categorized as estuarine or near-shore sediments (Laizhou Bay, Taozi Bay, Sishili Bay, and Jiaozhou Bay) and offshore sediments. Trifluralin, α-endosulfan, endosulfan sulfate, chlorpyrifos, dicofol, and pentachloroanisole were detected in more than 60 % of the samples. Dicofol was the predominant compound with concentrations mostly higher than 100 pg/g dry weight (dw) with the highest concentration of 18,000 pg/g dw. Concentrations of other compounds were mainly below 100 pg/g dw. CUP levels were much lower than the sediment screening benchmark calculated. The highest levels of α-endosulfan, endosulfan sulfate, trifluralin, and chlorpyrifos existed at Laizhou Bay, whereas pentachloroanisole and dicofol had highest mean concentrations at Jiaozhou Bay. Generally, no correlation between pesticide concentrations and total organic carbon was observed either for offshore samples or for near-shore samples.
Afficher plus [+] Moins [-]Bacterial communities of Beijing surface waters as revealed by 454 pyrosequencing of the 16S rRNA gene Texte intégral
2015
Wei, Yu-Mei | Wang, Jing-Qi | Liu, Ting-Ting | Kong, Wei-Wen | Chen, Nan | He, Xiao-Qing | Jin, Yi
As a better understanding of Beijing surface water ecosystems can provide clues for environmental management and public health, here, we report a study of the bacterial communities of five Beijing surface waters conducted using 454 pyrosequencing of 16S ribosomal RNA (rRNA) genes. We expected to observe a core bacterial community among the surface waters and differences in bacterial community abundance over the different locations of sampling. In this study, we obtained a total of 60,810 trimmed reads from the five samples after the removal of unqualified reads. Bacterial sequences from the five samples were classified into taxonomic classes using the default settings of the mothur platform. Our results provided insight into the bacterial community composition of surface waters and revealed that there was a core microbial community in the microbial populations of surface samples at different geographic locations, with 13 phyla and 40 genera in common. Our findings also revealed the differences in bacterial communities among five surface water samples obtained at different locations.
Afficher plus [+] Moins [-]Synchrotron micro-scale study of trace metal transport and distribution in Spartina alterniflora root system in Yangtze River intertidal zone Texte intégral
2015
Feng, Huan | Zhang, Weiguo | Liu, Wenliang | Yu, Lizhong | Qian, Yu | Wang, Jun | Wang, Jia-Jun | Eng, Christopher | Liu, Chang-Jun | Jones, Keith W. | Tappero, Ryan
This study is focused on micro-scale measurement of metal (Ca, Cl, Fe, K, Mn, Cu, Pb, and Zn) distributions in Spartina alterniflora root system. The root samples were collected in the Yangtze River intertidal zone in July 2013. Synchrotron X-ray fluorescence (XRF), computed microtomography (CMT), and X-ray absorption near-edge structure (XANES) techniques, which provide micro-meter scale analytical resolution, were applied to this study. Although it was found that the metals of interest were distributed in both epidermis and vascular tissue with the varying concentrations, the results showed that Fe plaque was mainly distributed in the root epidermis. Other metals (e.g., Cu, Mn, Pb, and Zn) were correlated with Fe in the epidermis possibly due to scavenge by Fe plaque. Relatively high metal concentrations were observed in the root hair tip. This micro-scale investigation provides insights of understanding the metal uptake and spatial distribution as well as the function of Fe plaque governing metal transport in the root system.
Afficher plus [+] Moins [-]Photonic efficiency of the photodegradation of paracetamol in water by the photo-Fenton process Texte intégral
2015
Yamal-Turbay, E. | Ortega, E. | Conte, L. O. | Graells, M. | Mansilla, H. D. | Alfano, O. M. | Pérez-Moya, M.
An experimental study of the homogeneous Fenton and photo-Fenton degradation of 4-amidophenol (paracetamol, PCT) is presented. For all the operation conditions evaluated, PCT degradation is efficiently attained by both Fenton and photo-Fenton processes. Also, photonic efficiencies of PCT degradation and mineralization are determined under different experimental conditions, characterizing the influence of hydrogen peroxide (H₂O₂) and Fe(II) on both contaminant degradation and sample mineralization. The maximum photonic degradation efficiencies for 5 and 10 mg L⁻¹Fe(II) were 3.9 (H₂O₂ = 189 mg L⁻¹) and 5 (H₂O₂ = 378 mg L⁻¹), respectively. For higher concentrations of oxidant, H₂O₂ acts as a "scavenger" radical, competing in pollutant degradation and reducing the reaction rate. Moreover, in order to quantify the consumption of the oxidizing agent, the specific consumption of the hydrogen peroxide was also evaluated. For all operating conditions of both hydrogen peroxide and Fe(II) concentration, the consumption values obtained for Fenton process were always higher than the corresponding values observed for photo-Fenton. This implies a less efficient use of the oxidizing agent for dark conditions.
Afficher plus [+] Moins [-]Necrotic bark of common pine (Pinus sylvestris L.) as a bioindicator of environmental quality Texte intégral
2015
Chrzan, Anna
The aim of this study was to determine the pH and the concentration of lead, cadmium, nickel, copper and zinc in aqueous extracts of necrotic bark Pinus sylvestris L. and in adjacent soil, located in two types of forest habitat in different parts in the Niepołomice Forest in southern Poland. The Niepołomice Forest is located about 35 km east of an urban-industrial agglomeration Kraków. Despite the lack of significant differences in pine bark reaction studied, there was a clear difference in contamination of both bark and soil with heavy metals. There was a correlation between the distribution of pollutants in the forest, and the direction of the prevailing winds. More heavy metals were accumulated in the pine bark and soil from the west than the east. The high content of lead, zinc, cadmium and copper in the soils most likely results from the inflow of gas and dust pollutants from the urban-industrial agglomeration of Kraków.
Afficher plus [+] Moins [-]Design of optimal groundwater remediation systems under flexible environmental-standard constraints Texte intégral
2015
Fan, Xing | He, Li | Lu, Hong-Wei | Li, Jing
In developing optimal groundwater remediation strategies, limited effort has been exerted to solve the uncertainty in environmental quality standards. When such uncertainty is not considered, either over optimistic or over pessimistic optimization strategies may be developed, probably leading to the formulation of rigid remediation strategies. This study advances a mathematical programming modeling approach for optimizing groundwater remediation design. This approach not only prevents the formulation of over optimistic and over pessimistic optimization strategies but also provides a satisfaction level that indicates the degree to which the environmental quality standard is satisfied. Therefore the approach may be expected to be significantly more acknowledged by the decision maker than those who do not consider standard uncertainty. The proposed approach is applied to a petroleum-contaminated site in western Canada. Results from the case study show that (1) the peak benzene concentrations can always satisfy the environmental standard under the optimal strategy, (2) the pumping rates of all wells decrease under a relaxed standard or long-term remediation approach, (3) the pumping rates are less affected by environmental quality constraints under short-term remediation, and (4) increased flexible environmental standards have a reduced effect on the optimal remediation strategy.
Afficher plus [+] Moins [-]Aerosol optical properties under the condition of heavy haze over an urban site of Beijing, China Texte intégral
2015
Che, Huizheng | Xia, Xiangao | Zhu, Jun | Wang, Hong | Wang, Yaqiang | Sun, Junying | Zhang, Xiaoye | Shi, Guangyu
In January 2013, several serious haze pollution events happened in North China. Cimel sunphotometer measurements at an urban site of Beijing (Chinese Academy of Meteorological Sciences—CAMS) from 1 to 30 January 2013 were used to investigate the detailed variation of aerosol optical properties. It was found that Angstrom exponents were mostly larger than 0.80 when aerosol optical depth values are higher than 0.60 at the urban region of Beijing during January 2013. The aerosol optical depth (AOD) at the urban region of Beijing can remain steady at approximately 0.40 before haze happening and then increased sharply to more than 1.50 at 500 nm with the onset of haze, which suggests that the fine-mode AOD is a factor of 20 of the coarse-mode AOD during a serious haze pollution event. The single scattering albedo was approximately 0.90 ± 0.03 at 440, 675, 870 and 1,020 nm during the haze pollution period. The single scattering albedo at 440 nm as a function of the fine-mode fraction was relatively consistent, but it was highly variable at 675, 870 and 1,020 nm. Except on January 12 and 18, all the fine-mode particle volumes were larger than those of coarse particles, which suggests that fine particles from anthropogenic activities made up most of the haze. Aerosol type classification analysis showed that the dominant aerosol types can be classified as both “mixed” and “urban/industrial (U/I) and biomass burning (BB)” categories during the heavy haze period of Beijing in January of 2013. The mixed category occurrence was about 31 %, while the U/I and BB was about 69 %.
Afficher plus [+] Moins [-]TiO2 sol-gel for formaldehyde photodegradation using polymeric support: photocatalysis efficiency versus material stability Texte intégral
2015
Curcio, Monique S. | Oliveira, Michel P. | Waldman, Walter R. | Sánchez, Benigno | Canela, Maria Cristina
Photocatalysts supported on polymers are not frequently used in heterogeneous photocatalysis because of problems such as wettability and stability that affect photocatalysis conditions. In this work, we used polypropylene as support for TiO₂sol-gel to evaluate its stability and efficiency under UV radiation. We also tested the effect of the thermo-pressing PP/TiO₂system on the photocatalytic efficiency and stability under UV radiation. The films were characterized by scanning electron microscopy (SEM), UV-Vis spectroscopy and X-ray diffraction (XRD). The SEM micrographs showed that the films of TiO₂sol-gel onto PP has approximately 1.0-μm thick and regular surface and the generation of polypropylene nanowires on hot-pressed samples. XRD showed the formation of TiO₂anatase on the surface of the films made by dip-coating. All photocatalysts were tested in decontaminating air-containing gaseous formaldehyde (70 ppmv) presenting degradation of the target compound to the limit of detection. The photocatalysts showed no deactivation during the entire period tested (30 h), and its reuse after washing showed better photocatalytic performance than on first use. The photocatalyst showed the best results were tested for 360 h with no observed deactivation. Aging studies showed that the film of TiO₂causes different effects on the photostability of composites, with stabilizing effect when exposed to most energetic UVC radiation (λmax = 254 nm) and degradative effects when exposed to UVA radiation (λmax = 365 nm).
Afficher plus [+] Moins [-]Application of molecularly imprinted polymers in wastewater treatment: a review Texte intégral
2015
Huang, Dan-Lian | Wang, Rong-Zhong | Liu, Yun-Guo | Zeng, Guang-Ming | Lai, Cui | Xu, Piao | Lu, Bing-An | Xu, Juan-Juan | Wang, Cong | Huang, Chao
Molecularly imprinted polymers are synthetic polymers possessing specific cavities designed for target molecules. They are prepared by copolymerization of a cross-linking agent with the complex formed from a template and monomers that have functional groups specifically interacting with the template through covalent or noncovalent bonds. Subsequent removal of the imprint template leaves specific cavities whose shape, size, and functional groups are complementary to the template molecule. Because of their predetermined selectivity, molecularly imprinted polymers (MIPs) can be used as ideal materials in wastewater treatment. Especially, MIP-based composites offer a wide range of potentialities in wastewater treatment. This paper reviews the latest applications of MIPs in wastewater treatment, highlights the development of MIP-based composites in wastewater, and offers suggestions for future success in the field of MIPs.
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