Refinar búsqueda
Resultados 1711-1720 de 3,208
Temporal and spatial variations in phytoplankton: correlations with environmental factors in Shengjin Lake, China Texto completo
2015
Wang, Lan | Wang, Chao | Deng, Daogui | Zhao, Xiuxia | Zhou, Zhongze
Temporal and spatial variations in the phytoplankton community and environmental variables were investigated from February to July 2014, in the upper lake of Shengjin Lake, China. We identified 192 species of phytoplankton belonging to 8 phyla and 84 genera, of which 46.4 % of Chlorophyta, 29.2 % of Bacillariophyta, and 12.5 % of Cyanophyta. There were 14 predominant species. Marked temporal and spatial variations were observed in the phytoplankton community. The total abundance of phytoplankton ranged from 3.66 × 10⁵ to 867.93 × 10⁵ cells/L and total biomass ranging from 0.40 to 20.89 mg/L. The Shannon-Wiener diversity index varied from 3.50 to 8.35 with an average of 5.58, revealing high biodiversity in the phytoplankton community. There were substantial temporal changes in the dominant species, from Bacillariophyta and Cryptophyta to Cyanophyta and Chlorophyta. Phytoplankton biomass and abundance showed a similar increasing trend from February to July. Pearson correlations and Redundancy analysis revealed that the most significant environmental factors influencing phytoplankton community were water temperature (T), transparency (SD), and nutrient concentration. The positive correlation between the key water bird areas and phytoplankton biomass indicated that the droppings of wintering water birds had an important influence on the phytoplankton community in the upper lake of Shengjin Lake.
Mostrar más [+] Menos [-]Assessment of Toxoplasma gondii levels in zebra mussel (Dreissena polymorpha) by real-time PCR: an organotropism study Texto completo
2015
Palos Ladeiro, M. | Bigot-Clivot, A. | Aubert, D. | Villena, I. | Geffard, A.
Water quality is a public health concern that calls for relevant biomonitoring programs. Molecular tools such as polymerase chain reaction (PCR) are progressively becoming more sensitive and more specific than conventional techniques to detect pathogens in environmental samples such as water and organisms. The zebra mussel (Dreissena polymorpha) has already been demonstrated to accumulate and concentrate various human waterborne pathogens. In this study, first, a spiking experiment to evaluate detection levels of Toxoplasma gondii DNA in zebra mussel organs using real-time PCR was conducted. Overall, lower DNA levels in the hemolymph, digestive gland, and remaining tissues (gonad and foot) were detected compared to mantle, muscle, and gills. Second, an in vivo experiment with 1000 T. gondii oocysts per mussel and per day for 21 consecutive days, followed by 14 days of depuration time in protozoa-free water was performed. T. gondii DNA was detected in all organs, but greatest concentrations were observed in hemolymph and mantle tissues compared to the others organs at the end of the depuration period. These results suggest that (i) the zebra mussel is a potential new tool for measuring T. gondii concentrations and (ii) real-time PCR is a suitable method for pathogen detection in complex matrices such as tissues.
Mostrar más [+] Menos [-]Investigation of gasoline distributions within petrol stations: spatial and seasonal concentrations, sources, mitigation measures, and occupationally exposed symptoms Texto completo
2015
Sairat, Theerapong | Homwuttiwong, Sahalaph | Homwutthiwong, Kritsana | Ongwandee, Maneerat
We measured levels of VOCs and determined the distributions of benzene concentrations over the area of two petrol stations in all three seasons. Using the concentrations and sampling positions, we created isoconcentration contour maps. The average concentrations ranged 18–1288 μg m⁻³ for benzene and 12–81 μg m⁻³ for toluene. The contour maps indicate that high-level contours of benzene were found not only at the fuel dispenser areas but also at the storage tank refilling points, open drainage areas where gasoline-polluted wastewater was flowing, and the auto service center located within the station area. An assessment of the benzene to toluene ratio contour plots implicates that airborne benzene and toluene near the fuel dispenser area were attributed to gasoline evaporation although one of the studied stations may be influenced by other VOC sources besides gasoline evaporation. Additionally, during the routine refilling of the underground fuel storage tanks by a tank truck, the ambient levels of benzene and toluene increased tremendously. The implementation of source control by replacing old dispensers with new fuel dispensers that have an efficient cutoff feature and increased delivery speed can reduce spatial benzene concentrations by 77 %. Furthermore, a questionnaire survey among 63 service attendants in ten stations revealed that headache was the most reported health complaint with a response rate of 32 %, followed by fatigue with 20 %. These prominent symptoms could be related to an exposure to high benzene concentrations.
Mostrar más [+] Menos [-]Variability of cadmium, lead, and zinc tolerance and accumulation among and between germplasms of the fiber crop Boehmeria nivea with different root-types Texto completo
2015
Yang, B. | Zhou, M. | Zhou, L. L. | Xue, N. D. | Zhang, S. L. | Lan, C. Y.
Crop germplasms substantially vary in their tolerance for and accumulation of heavy metals, and assessment of this variability plays a significant role in selecting species to use in phytoremediation projects. Here, we examined germplasm-variations in cadmium (Cd), lead (Pb), and zinc (Zn) tolerance and accumulation in ramie (Boehmeria nivea), a fiber crop native to China, which has received little attention. In an 8-week greenhouse test, fourteen germplasms of ramie, among and within deep, middle, and shallow rooted-types, were compared for growth and metal accumulation traits. Results showed that both tolerance and accumulation traits varied across germplasms and rooted-types. The deep rooted-type germplasms produced more biomass and had higher tolerance to metals than the two others. In addition, considerable variations in metal accumulation were observed among plant organs (root, stem, and leaf), rooted-types, germplasms, and metal supply. However, the observed variations in metal tolerance and accumulation among both germplasms and rooted-types were not significant in most cases. In addition to supporting the idea of a certain degree of constitutional metal tolerance for ramie, our results also contribute to deep-rooted germplasms of ramie as a good candidate, rather than middle-/shallow- ones as a least-bad option, for the remediation of multi metal-contaminated soils.
Mostrar más [+] Menos [-]Identification of the sources of metal (lead) contamination in drinking waters in north-eastern Tasmania using lead isotopic compositions Texto completo
2015
Harvey, P. J. | Handley, H. K. | Taylor, M. P.
This study utilises a range of scientific approaches, including lead isotopic compositions, to differentiate unknown sources of ongoing lead contamination of a drinking water supply in north-eastern Tasmania, Australia. Drinking water lead concentrations are elevated above the Australian Drinking Water Guideline (10 μg/L), reaching 540 μg/L in the supply network. Water lead isotopic compositions from the town of Pioneer (²⁰⁸Pb/²⁰⁷Pb 2.406, ²⁰⁶Pb/²⁰⁷Pb 1.144 to ²⁰⁸Pb/²⁰⁷Pb 2.360, ²⁰⁶Pb/²⁰⁷Pb 1.094) and Ringarooma (²⁰⁸Pb/²⁰⁷Pb 2.398, ²⁰⁶Pb/²⁰⁷Pb 1.117) are markedly different from the local bedrock (²⁰⁸Pb/²⁰⁷Pb 2.496, ²⁰⁶Pb/²⁰⁷Pb 1.237). The data show that the lead in the local waters is sourced from a combination of dilapidated drinking water infrastructure, including lead jointed pipelines, end-of-life polyvinyl chloride pipes and household plumbing. Drinking water is being inadvertently contaminated by aging infrastructure, and it is an issue that warrants investigation to limit the burden of disease from lead exposure.
Mostrar más [+] Menos [-]Microbial aerobic and anaerobic degradation of acrylamide in sludge and water under environmental conditions—case study in a sand and gravel quarry Texto completo
2015
Guezennec, A. G. | Michel, C. | Ozturk, S. | Togola, A. | Guzzo, J. | Desroche, N.
Polyacrylamides (PAMs) are used in sand and gravel quarries as water purification flocculants for recycling process water in a recycling loop system where the flocculants remove fine particles in the form of sludge. The PAM-based flocculants, however, contain residual amounts of acrylamide (AMD) that did not react during the polymerization process. This acrylamide is released into the environment when the sludge is discharged into a settling basin. Here, we explore the microbial diversity and the potential for AMD biodegradation in water and sludge samples collected in a quarry site submitted to low AMD concentrations. The microbial diversity, analyzed by culture-dependent methods and the denaturing gradient gel electrophoresis approach, reveals the presence of Proteobacteria, Cyanobacteria, and Actinobacteria, among which some species are known to have an AMD biodegradation activity. Results also show that the two main parts of the water recycling loop—the washing process and the settling basin—display significantly different bacterial profiles. The exposure time with residual AMD could, thus, be one of the parameters that lead to a selection of specific bacterial species. AMD degradation experiments with 0.5 g L⁻¹AMD showed a high potential for biodegradation in all parts of the washing process, except the make-up water. The AMD biodegradation potential in samples collected from the washing process and settling basin was also analyzed taking into account on-site conditions: low (12 °C) and high (25 °C) temperatures reflecting the winter and summer seasons, and AMD concentrations of 50 μg L⁻¹. Batch tests showed rapid (as little as 18 h) AMD biodegradation under aerobic and anaerobic conditions at both the winter and summer temperatures, although there was a greater lag time before activity started with the AMD biodegradation at 12 °C. This study, thus, demonstrates that bacteria present in sludge and water samples exert an in situ and rapid biodegradation of AMD at low concentration, whatever the season, and in both the aerobic and anaerobic parts of the water recycling system.
Mostrar más [+] Menos [-]In situ reactive oxygen species production for tertiary wastewater treatment Texto completo
2015
Guitaya, Léa | Drogui, Patrick | Blais, Jean François
The goal of this research was to develop a new approach for tertiary water treatment, particularly disinfection and removal of refractory organic compounds, without adding any chemical. Hydrogen peroxide can indeed be produced from dissolved oxygen owing to electrochemical processes. Using various current intensities (1.0 to 4.0 A), it was possible to in situ produce relatively high concentration of H₂O₂with a specific production rate of 0.05 × 10⁻⁵ M/min/A. Likewise, by using ultraviolet-visible absorption spectroscopy method, it was shown that other reactive oxygen species (ROS) including HO*radical and O₃could be simultaneously formed during electrolysis. The ROS concentration passed from 0.45 × 10⁻⁵ M after 20 min of electrolysis to a concentration of 2.87 × 10⁻⁵ M after 100 min of electrolysis. The disinfection and the organic matter removal were relatively high during the tertiary treatment of municipal and domestic wastewaters. More than 90 % of organic compounds (chemical oxygen demand) can be removed, whereas 99 % of faecal coliform abatement can be reached. Likewise, the process was also effective in removing turbidity (more than 90 % of turbidity was removed) so that the effluent became more and more transparent.
Mostrar más [+] Menos [-]Use of alum water treatment sludge to stabilize C and immobilize P and metals in composts Texto completo
2015
Haynes, R. J. | Zhou, Y.-F.
Alum water treatment sludge is composed of amorphous hydroxyl-Al, which has variable charge surfaces with a large Brunauer-Emmett-Teller (BET) surface area (103 m⁻² g⁻¹) capable of specific adsorption of organic matter molecules, phosphate, and heavy metals. The effects of adding dried, ground, alum water treatment sludge (10 % w/w) to the feedstock for composting municipal green waste alone, green waste plus poultry manure, or green waste plus biosolids were determined. Addition of water treatment sludge reduced water soluble C, microbial biomass C, CO₂ evolution, extractable P, and extractable heavy metals during composting. The decrease in CO₂ evolution (i.e., C sequestration) was greatest for poultry manure and least for biosolid composts. The effects of addition of water treatment sludge to mature green waste-based poultry manure and biosolid composts were also determined in a 24-week incubation experiment. The composts were either incubated alone or after addition to a soil. Extractable P and heavy metal concentrations were decreased by additions of water treatment sludge in all treatments, and CO₂ evolution was also reduced from the poultry manure compost over the first 16–18 weeks. However, for biosolid compost, addition of water treatment sludge increased microbial biomass C and CO₂ evolution rate over the entire 24-week incubation period. This was attributed to the greatly reduced extractable heavy metal concentrations (As, Cr, Cu, Pb, and Zn) present following addition of water treatment sludge, and thus increased microbial activity. It was concluded that addition of water treatment sludge reduces concentrations of extractable P and heavy metals in composts and that its effect on organic matter stabilization is much greater during the composting process than for mature compost because levels of easily decomposable organic matter are initially much higher in the feedstock than those in matured composts.
Mostrar más [+] Menos [-]Dynamics of effluent treatment plant during commissioning of activated sludge process unit Texto completo
2015
Bafana, Amit | Kumāra, Gulaśana | Kashyap, Sanjay M. | Kanade, Gajanan S. | Shinde, Vilas M.
Industrial effluent treatment plants (ETPs) are very important in protecting the environment and different life forms from harmful industrial waste. Hence, the efficiency of ETPs must be regularly monitored, particularly after major repair or replacement work. Present study evaluated the performance of an ETP over a period of 4 months, during which aeration tank (T1) of the activated sludge unit was replaced with a new one (T2). System had to be maintained operational during this transition, which warranted close monitoring of the system performance due to the daily load of hazardous industrial wastewater. Analysis showed that the raw wastewater was highly variable in composition and contained many hazardous organic and inorganic pollutants, such as heavy metals, bisphenol A and cyanoacetylurea. It showed significant toxicity against HepG2 cells in vitro. However, the ETP was found to successfully treat and detoxify the wastewater. Denaturing gradient gel electrophoresis (DGGE) analysis showed large temporal fluctuations in the ETP microbial community, which is consistent with the variable composition of wastewater. It indicated that functional stability of the ETP was not associated with stability of the microbial community, probably due to high microbial biodiversity and consequently high functional redundancy. In conclusion, the CETP showed consistent level of detoxification and microbial community dynamics after switching to T2, indicating successful development, acclimatization and commissioning of T2.
Mostrar más [+] Menos [-]Characterisation of CIME, an experimental chamber for simulating interactions between materials of the cultural heritage and the environment Texto completo
2015
Chabas, A. | Fouqueau, A. | Attoui, M. | Alfaro, S. C. | Petitmangin, A. | Bouilloux, A. | Saheb, M. | Coman, A. | Lombardo, T. | Grand, N. | Zapf, P. | Berardo, R. | Duranton, M. | Durand-Jolibois, R. | Jerome, M. | Pangui, E. | Correia, J. J. | Guillot, I. | Nowak, Stefan
An approach consisting in combining in situ and laboratory experiments is often favoured for investigating the mechanisms involved in the weathering of the materials of the cultural heritage. However, the realistic simulation in the laboratory of the environmental conditions ruling the interactions of atmospheric compounds with materials is a very complex task. The aim of this work is to characterise CIME, a new chamber specially built to simulate the interactions between materials of the cultural heritage and the environment. The originality of this instrument is that beside the usual climatic parameters (temperature, relative humidity, solar radiation) and gaseous pollutants, it also allows the controlled injection of different types of particulate matter such as terrigenous, marine and anthropogenic. Therefore, varied realistic atmospheric environments (marine or urban) can be easily simulated within CIME. In addition to the technical description of CIME, this paper shows the first results obtained by the impact of gaseous pollutants on non-durable glass, bronze and limestone. The first experiments for the deposition of different particles (calcite, clays, soot and halite) are also presented.
Mostrar más [+] Menos [-]