Уточнить поиск
Результаты 2641-2650 из 4,308
Effective characterization of Salmonella Enteritidis by most probable number (MPN) followed by multiplex polymerase chain reaction (PCR) methods Полный текст
2017
Nontyphoidal Salmonella (NTS) is a relevant pathogen involved in gastroenteritis outbreaks worldwide. In this study, we determined the capacity to combine the most probable number (MPN) and multiplex polymerase chain reaction (PCR) methods to characterize the most important Salmonella serotypes in raw sewage. A total of 499 isolates were recovered from 27 raw sewage samples and screened using two previously described multiplex PCR methods. From those, 123 isolates were selected based on PCR banding pattern—identical or similar to Salmonella Enteritidis and Salmonella Typhimurium—and submitted to conventional serotyping. Results showed that both PCR assays correctly serotyped Salmonella Enteritidis, however, they presented ambiguous results for Salmonella Typhimurium identification. These data highlight that MPN and multiplex PCR can be useful methods to describe microbial quality in raw sewage and suggest two new PCR patterns for Salmonella Enteritidis identification.
Показать больше [+] Меньше [-]Aerobic and anaerobic energy production in juvenile roach (Rutilus rutilus): regulation of glycolytic process by ethofumesate at two temperatures Полный текст
2017
Maes, V. | Betoulle, S. | Geffard, A. | Vettier, A. | David, E.
The aim of this study was to evaluate the coupled impact of an herbicide, ethofumesate, and temperature on the cellular energy metabolism of juvenile roach, especially on the glycolysis pathway. Juvenile roach were exposed to 0, 0.5, 5, and 50 μg/L of ethofumesate for 7 days in laboratory conditions at two temperatures (10 and 17 °C). The energy reserves (carbohydrate, lipid, and protein) were quantified, since the availability of substrates regulates the glycolysis. Then, the glycolysis was studied at the biochemical level by the measurement of the glycolytic flux and at the molecular level with the measurement of the relative expression of four genes encoding for glycolysis enzymes. This study revealed different effect of ethofumesate on the glycolysis pathway according to the temperature of exposure. Indeed, at 10 °C, it appeared that only the molecular regulation level was affected, whereas, at 17 °C, ethofumesate acted on the biochemical level. The differences observed between the two exposures imply the establishment of different strategies in order to maintain to cope with stress according to the temperature of exposure.
Показать больше [+] Меньше [-]Metagenomic insights into effects of spent engine oil perturbation on the microbial community composition and function in a tropical agricultural soil Полный текст
2017
Salam, Lateef B. | Obayori, Sunday O. | Nwaokorie, Francisca O. | Suleiman, Aisha | Mustapha, Raheemat
Analyzing the microbial community structure and functions become imperative for ecological processes. To understand the impact of spent engine oil (SEO) contamination on microbial community structure of an agricultural soil, soil microcosms designated 1S (agricultural soil) and AB1 (agricultural soil polluted with SEO) were set up. Metagenomic DNA extracted from the soil microcosms and sequenced using Miseq Illumina sequencing were analyzed for their taxonomic and functional properties. Taxonomic profiling of the two microcosms by MG-RAST revealed the dominance of Actinobacteria (23.36%) and Proteobacteria (52.46%) phyla in 1S and AB1 with preponderance of Streptomyces (12.83%) and Gemmatimonas (10.20%) in 1S and Geodermatophilus (26.24%), Burkholderia (15.40%), and Pseudomonas (12.72%) in AB1, respectively. Our results showed that soil microbial diversity significantly decreased in AB1. Further assignment of the metagenomic reads to MG-RAST, Cluster of Orthologous Groups (COG) of proteins, Kyoto Encyclopedia of Genes and Genomes (KEGG), GhostKOALA, and NCBI’s CDD hits revealed diverse metabolic potentials of the autochthonous microbial community. It also revealed the adaptation of the community to various environmental stressors such as hydrocarbon hydrophobicity, heavy metal toxicity, oxidative stress, nutrient starvation, and C/N/P imbalance. To the best of our knowledge, this is the first study that investigates the effect of SEO perturbation on soil microbial communities through Illumina sequencing. The results indicated that SEO contamination significantly affects soil microbial community structure and functions leading to massive loss of nonhydrocarbon degrading indigenous microbiota and enrichment of hydrocarbonoclastic organisms such as members of Proteobacteria and Actinobacteria.
Показать больше [+] Меньше [-]Enhanced heterogeneous photo-Fenton process modified by magnetite and EDDS: BPA degradation Полный текст
2017
Huang, Wenyu | Luo, Mengqi | Wei, Chaoshuai | Wang, Yinghui | Hanna, Khalil | Mailhot, Gilles
In this research, magnetite and ethylenediamine-N,N′-disuccinic acid (EDDS) are used in a heterogeneous photo-Fenton system in order to find a new way to remove organic contaminants from water. Influence of different parameters including magnetite dosage, EDDS concentration, H₂O₂ concentration, and pH value were evaluated. The effect of different radical species including HO· and HO₂ ·/O₂ ·⁻ was investigated by addition of different scavengers into the system. The addition of EDDS improved the heterogeneous photo-Fenton degradation of bisphenol A (BPA) through the formation of photochemically efficient Fe-EDDS complex. This effect is dependent on the H₂O₂ and EDDS concentrations and pH value. The high performance observed at pH 6.2 could be explained by the ability of O₂ ·⁻ to generate Fe(II) from Fe(III) species reduction. GC-MS analysis suggested that the cleavage of the two benzene rings is the first degradation step followed by oxidation leading to the formation of the benzene derivatives. Then, the benzene ring was opened due to the attack of HO· radicals producing short-chain organic compounds of low molecular weight like glycerol and ethylene glycol. These findings regarding the capability of EDDS/magnetite system to promote heterogeneous photo-Fenton oxidation have important practical implications for water treatment technologies.
Показать больше [+] Меньше [-]Performance and microbial community dynamics of electricity-assisted sequencing batch reactor (SBR) for treatment of saline petrochemical wastewater Полный текст
2017
Liu, Jiaxin | Shi, Shengnan | Ji, Xiangyu | Jiang, Bei | Xue, Lanlan | Li, Meidi | Tan, Liang
High-salinity wastewater is often difficult to treat by common biological technologies due to salinity stress on the bacterial community. Electricity-assisted anaerobic technologies have significantly enhanced the treatment performance by alleviating the impact of salinity stress on the bacterial community, but electricity-assisted aerobic technologies have less been reported. Herein, a novel bio-electrochemistry system has been designed and operated in which a pair of stainless iron mesh-graphite plate electrodes were installed into a sequencing batch reactor (SBR, designated as S1) to strengthen the performance of saline petrochemical wastewater under aerobic conditions. The removal efficiency of phenol and chemical oxygen demand (COD) in S1 were 94.1 and 91.2%, respectively, on day 45, which was clearly higher than the removal efficiency of a single SBR (S2) and an electrochemical reactor (S3), indicating that a coupling effect existed between the electrochemical process and biodegradation. A certain amount of salinity (≤8000 mg/L) could enhance the treatment performance in S1 but weaken that in S2. Illumina sequencing revealed that microbial communities in S1 on days 45 and 91 were richer and more diverse than in S2, which suggests that electrical stimulation could enhance the diversity and richness of the microbial community, and reduce the negative effect of salinity on the microorganisms and enrich some salt-adapted microorganisms, thus improve the ability of S1 to respond to salinity stress. This novel bio-electrochemistry system was shown to be an alternative technology for the high saline petrochemical wastewater.
Показать больше [+] Меньше [-]First flush characteristics of rainfall runoff from a paddy field in the Taihu Lake watershed, China Полный текст
2017
Li, Songmin | Wang, Xiaoling | Qiao, Bin | Li, Jiansheng | Tu, Jiamin
Nonpoint storm runoff remains a major threat to surface water quality in China. As a paddy matures, numerous fertilizers are needed, especially in the rainy seasons; the concentration of nitrogen and phosphorus in rainfall runoff from farmland is much higher than at other times, and this poses a great threat to water bodies and is the main reason for water eutrophication, especially in high concentration drainages. To date, most studies regarding the characteristics of pollutants in rainfall runoff have mainly been concentrated on urban runoff and watershed runoff; therefore, it is particularly important to investigate the characteristics of nitrogen and phosphorus loss in rainfall runoff from paddy fields. To study the characteristics of nitrogen and phosphorus loss and whether the first flush effect exists, continuous monitoring of the rainfall runoff process of six rainfall events was conducted in 2013, of which four rainfall events during storm, high, middle, and low intensity rainfalls were analyzed, and runoff and quality parameters, such as suspended solids (SS), total nitrogen (TN), ammonium nitrogen (NH₄ ⁺-N), nitrate nitrogen (NO₃ ⁻-N), total phosphorus (TP), and phosphate (PO₄ ³⁻-P), were analyzed to determine the relationship between runoff and water quality. The paddy field is located north of Wuxi Lake Basin along the Hejia River upstream in Zhoutie town, Yixing city. An analysis of the load distribution during rainfall runoff was conducted. Event mean concentration (EMC) was used to evaluate the pollution situation of the paddy field’s rainfall runoff. A curve of the dimensionless normalized cumulative load (L) vs. normalized cumulative flow (F) (L-F curve), the probability of the mass first flush (MFFn), and the pollutants carried by the initial 25% of runoff (FF₂₅) were used to analyze the first flush effect of the paddy field runoff, and different contaminants show different results: the concentration of nitrogen and phosphorus fluctuate and follow a similar trend as runoff changes, NO₃ ⁻-N concentration is lower in the early part of runoff and higher in the later, and TP mainly occurs in the particle state in storm runoff and mainly in the dissolved state when the rainfall intensity is smaller. Nitrogen and phosphorus losses from paddy fields are closely related to the average rainfall intensity and the max rainfall intensity, and the runoff loss of nitrogen and phosphorus is more severe when the rainfall intensity is large. Based on an analysis of multiple methodologies, TN and NH₄ ⁺-N show a certain degree of a first flush effect, whereas the first flush effect of TP is not obvious. The first flush effect of SS is obvious in larger intensity rainfall and shows a slight secondary flush effect in smaller rainfall events.
Показать больше [+] Меньше [-]Quantification of the fate of mesotrione applied alone or in a herbicide mixture in two Brazilian arable soils Полный текст
2017
Mendes, Kassio Ferreira | Martins, Bianca Assis Barbosa | dos Reis, Marcelo Rodrigues | Pimpinato, Rodrigo Floriano | Tornisielo, Valdemar Luiz
The effects of mesotrione, S-metolachlor, and terbuthylazine, applied in mixture, on soil biodegradation remain insufficiently researched. However, herbicide mixtures have been a common practice in agricultural systems in the last years. Understanding the fate of soil-applied herbicides may help on planning weed management tactics towards more sustainable and efficient weed control. Therefore, this study evaluated the fate of mesotrione alone and in mixture with S-metolachlor and terbuthylazine when applied to two contrasting arable Brazilian soils. Mineralization and degradation experiments were conducted using ¹⁴C-mesotrione alone or in mixture. From the 49-day laboratory incubation data, increased mineralization half-life of mesotrione was observed for the mixture of herbicides, ranging from a 4-day increase for the sandy loam soil to a 1-day increase in the sandy clay texture soils. Mesotrione degradation rate had a twofold increase in the sandy loam compared to the sandy clay soil. Two metabolites can be identified from mesotrione degradation, 4-methyl-sulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4-methylsulfonyl benzoic acid (AMBA). Indices for the score of ubiquity in groundwater indicated mesotrione possesses leaching potential for both soils. Applying mesotrione alone or in mixture did not influence the amount of bound residues from mesotrione. However, mesotrione degradation rate was influenced by soil texture regardless if applied alone or in mixture. Mesotrione biotransformation was relatively quick, indicating that this herbicide has low persistence and, consequently, low residual effect on crops and weeds when present in similar soils to this present study.
Показать больше [+] Меньше [-]Characteristics and mechanisms of nickel adsorption on biochars produced from wheat straw pellets and rice husk Полный текст
2017
Shen, Zhengtao | Zhang, Yunhui | McMillan, Oliver | Jin, Fei | Al-Tabbaa, Abir
The adsorption characteristics and mechanisms of Ni²⁺ on four-standard biochars produced from wheat straw pellets (WSP550, WSP700) and rice husk (RH550, RH700) at 550 and 700 °C, respectively, were investigated. The kinetic results show that the adsorption of Ni²⁺ on the biochars reached an equilibrium within 5 min. The increase of the solid to liquid ratio resulted in an increase of Ni²⁺ removal percentage but a decrease of the adsorbed amount of Ni²⁺ per weight unit of biochar. The Ni²⁺ removal percentage increased with the increasing of initial solution pH values at the range of 2–4, was relatively constant at the pH range of 4–8, and significantly increased to ≥98% at pH 9 and stayed constantly at the pH range of 9–10. The calculated maximum adsorption capacities of Ni²⁺ for the biochars follow the order of WSP700 > WSP550 > RH700 > RH550. Both cation exchange capacity and pH of biochar can be a good indicator of the maximum adsorption capacity for Ni²⁺ showing a positively linear and exponential relationship, respectively. This study also suggests that a carefully controlled standardised production procedure can make it reliable to compare the adsorption capacities between different biochars and investigate the mechanisms involved.
Показать больше [+] Меньше [-]Vascular plants as ecological indicators of metals in alpine vegetation (Karkonosze, SW Poland) Полный текст
2017
Wojtuń, Bronisław | Samecka-Cymerman, Aleksandra | Żołnierz, Ludwik | Rajsz, Adam | Kempers, AlexanderJ.
Calluna vulgaris, Carex rigida, Deschampsia flexuosa, Nardus stricta and Vaccinium myrtillus are abundant in the vegetation of mountainous areas in Northern and Central Europe. Knowledge of their ability to accumulate increased amounts of metals could be useful in the evaluation of environmental pollution in the alpine tundra of high mountains. Additionally, this investigation may contribute to understanding the rate and direction of recent vegetation change in Karkonosze and similar types of environments. Our investigation revealed that Carex rigida, C. vulgaris and V. myrtillus contain excessive Mn concentrations in shoots with the highest BF for this element compared to the BFs of other elements. C. rigida, with Cu, Mn and Zn concentrations exceeding the toxicity thresholds for plants, seems to be the best metal phytoaccumulator for Nardus stricta grasslands Carici (rigidae)-Nardetum (CrN) and alpine heathlands Carici (rigidae)-Festucetum airoidis (CrFa) associations in the Karkonosze. Based on relevant BFs >1, it can be stated that the following plant available metals were transferred to shoots: Cu, Mn and Ni by C. vulgaris; Cd, Cu, Mn, Ni and Zn by C. rigida; Cd, Cu, Mn, Ni and Zn by D. flexuosa; Cu, Mn, Ni and Zn by N. stricta and Cu, Mn and Zn by V. myrtillus.
Показать больше [+] Меньше [-]Prediction of municipal solid waste generation using artificial neural network approach enhanced by structural break analysis Полный текст
2017
Adamović, Vladimir M. | Antanasijević, Davor Z. | Ristić, Mirjana Đ | Perić-Grujić, Aleksandra A. | Pocajt, Viktor V.
This paper presents the development of a general regression neural network (GRNN) model for the prediction of annual municipal solid waste (MSW) generation at the national level for 44 countries of different size, population and economic development level. Proper modelling of MSW generation is essential for the planning of MSW management system as well as for the simulation of various environmental impact scenarios. The main objective of this work was to examine the potential influence of economy crisis (global or local) on the forecast of MSW generation obtained by the GRNN model. The existence of the so-called structural breaks that occur because of the economic crisis in the studied period (2000–2012) for each country was determined and confirmed using the Chow test and Quandt–Andrews test. Two GRNN models, one which did not take into account the influence of the economic crisis (GRNN) and another one which did (SB-GRNN), were developed. The novelty of the applied method is that it uses broadly available social, economic and demographic indicators and indicators of sustainability, together with GRNN and structural break testing for the prediction of MSW generation at the national level. The obtained results demonstrate that the SB-GRNN model provide more accurate predictions than the model which neglected structural breaks, with a mean absolute percentage error (MAPE) of 4.0 % compared to 6.7 % generated by the GRNN model. The proposed model enhanced with structural breaks can be a viable alternative for a more accurate prediction of MSW generation at the national level, especially for developing countries for which a lack of MSW data is notable.
Показать больше [+] Меньше [-]