خيارات البحث
النتائج 2651 - 2660 من 4,043
Quality of urban runoff in wet and dry seasons: a case study in a semi-arid zone النص الكامل
2016
Ortiz-Hernández, Joyce | Lucho-Constantino, Carlos | Lizárraga-Mendiola, Liliana | Beltrán-Hernández, Rosa Icela | Coronel-Olivares, Claudia | Vázquez Rodríguez, Gabriela
Urban runoff (UR) is a promising new resource that may alleviate growing tensions in numerous arid and semi-arid regions of the world. However, it is precisely in these zones that the available UR quality characteristics are scarcer. This work aims to evaluate a wide set of parameters to establish a detailed approach to both the quality of UR in a midsized city in Central Mexico and the feasibility of using UR to recharge aquifers. UR from an institutional land use site was sampled during wet and dry seasons and assessed for suspended solids, organic matter, nutrients, microorganisms, metals, and persistent organic chemicals (i.e., polycyclic aromatic hydrocarbons, PAH). The results were analyzed using multivariate statistical methods to identify relationships among the variables, the sampling sites and the seasons. The soil erosion and the leaching of materials due to the water flow through vegetated areas were identified as the most influencing factor on the quality of the site runoff in both dry and wet seasons. Additionally, data were more heterogeneous during the dry season, and higher pollutant concentrations were found both during the dry season and in more pervious zones. We consider UR a promising water source for recharging aquifers in arid and semi-arid zones if a program is implemented that can integrate an adequate runoff treatment system, soil protection, and other non-structural measures.
اظهر المزيد [+] اقل [-]Seasonal and storm-driven changes in chemical composition of dissolved organic matter: a case study of a reservoir and its forested tributaries النص الكامل
2016
Li, Penghui | Lee, Sang Hee | Lee, Soo Hyung | Lee, Jun-Bae | Lee, Yun Kyung | Shin, Hyun-Sang | Hur, Jin
Many drinking water supplies are located in forested watersheds, which operate as an important source of dissolved organic matter (DOM). In this study, monthly sampling campaigns were conducted from a reservoir (Daecheong Reservoir, South Korea) and its forested tributaries for five consecutive months (June to October) to examine the variations of DOM composition. Excitation-emission matrix fluorescence spectroscopy combined with parallel factor analysis (EEM-PARAFAC) was applied to track the variations of different fluorescent components within bulk DOM. Selected samples were further separated into hydrophobic (Ho) and hydrophilic (Hi) fractions. Water quality and DOM composition varied greatly with the sampling locations including the upstream and the downstream tributary sites, and the reservoir. Non-metric multidimensional scaling (NMDS) provided the information on the DOM sources and the potential processes leading to the observed DOM changes. Four of the five fluorescent components, identified by EEM-PARAFAC, were well correlated with the flow rates of the tributaries, suggesting hydrological control on DOM composition. The greatest effects were found on two terrestrial humic-like components (C1 and C2). The Ho fraction of DOM was more abundant for the post-storm samples versus the non-storm samples, supporting the important roles of hydrology on the changes in chemical composition of DOM. The amounts of the DOM resin fractions, either Ho or Hi, showed strong relationships with C1 and C2, suggesting that DOM fluorescence could be successfully applied to estimate different DOM chemical constituents in forested watersheds.
اظهر المزيد [+] اقل [-]Relationships of physiologically equivalent temperature and hospital admissions due to I30–I51 other forms of heart disease in Germany in 2009–2011 النص الكامل
2016
Shiue, Ivy | Perkins, David R. | Bearman, Nick
We aimed to understand relationships of the weather as biometeorological and hospital admissions due to other forms of heart disease by subtypes, which have been paid less attention, in a national setting in recent years. This is an ecological study. Ten percent of daily hospital admissions of the included hospitals (n = 1618) across Germany that were available between 1 January 2009 and 31 December 2011 (n = 5,235,600) were extracted from Statistisches Bundesamt, Germany. We identified I30–I51 other forms of heart disease by the International Classification of Diseases version 10 as the study outcomes. Daily weather data from 64 weather stations that have covered 13 German states, including air temperature, humidity, wind speed, cloud cover, radiation flux and vapour pressure, were obtained and generated into physiologically equivalent temperature (PET). Admissions due to other diseases of pericardium, nonrheumatic mitral valve disorders, nonrheumatic aortic valve disorders, cardiomyopathy, atrioventricular and left bundle-branch block, other conduction disorders, atrial fibrillation and flutter, and other cardiac arrhythmias peaked when PET was between 0 and 10 °C. Complications and ill-defined descriptions of heart disease admissions peaked at PET 0 °C. Cardiac arrest and heart failure admissions peaked when PET was between 0 and −10 °C while the rest did not vary significantly. A common drop of admissions was found when PET was above 10 °C. More medical resources could have been needed for heart health on days when PETs were <10 °C than on other days. Adaptation to such weather change for medical professionals and the general public would seem to be imperative.
اظهر المزيد [+] اقل [-]Stress tolerance and biocontrol performance of the yeast antagonist, Candida diversa, change with morphology transition النص الكامل
2016
Li, Guangkun | Chi, Mengshan | Chen, Huizhen | Sui, Yuan | Li, Yan | Liu, Yongsheng | Zhang, Xiaojing | Sun, Zhiqiang | Liu, Guoqing | Wang, Qi | Liu, Jia
As an eco-friendly management method, biological control of postharvest diseases, utilizing antagonistic yeasts, is a research topic receiving considerable attention. Detailed knowledge on the biology of yeast antagonists is crucial when considering their potential application and development as biocontrol products. Changes in the growth form, such as single-cell to pseudohyphae, have been associated with the mode of action in postharvest biocontrol yeasts. In this study, the antagonistic yeast, Candida diversa, reversibly shifted from a single-cell morphology on yeast peptone dextrose (YPD) medium with 2 % agar to a pseudohyphal morphology on YPD with 0.3 % agar. The tolerance of the pseudohyphal form to heat and oxidative stresses, as well as the biocontrol efficacy against Botrytis cinerea on apple and kiwifruit stored at 25 and 4 °C, was significantly higher as compared to the single-cell form. This study provides new information on the ability of C. diversa to change its morphology and the impact of the morphology shift on stress tolerance and biocontrol performance.
اظهر المزيد [+] اقل [-]Isobolographic analysis of the interaction between cadmium (II) and sodium sulphate: toxicological consequences النص الكامل
2016
Mera, Roi | Torres, Enrique | Abalde Alonso, Julio
Isobolographic analysis of the interaction between cadmium (II) and sodium sulphate: toxicological consequences النص الكامل
2016
Mera, Roi | Torres, Enrique | Abalde Alonso, Julio
Sulphate is an essential nutrient for autotrophic organisms and has been shown to have important implications in certain processes of tolerance to cadmium toxicity. Sodium sulphate is the main salt of sulphate in the natural environments. The concentration of this salt is increasing in the aquatic environments due to environmental pollution. The aim of this study was to investigate, using an analysis of isobolograms, the type and the degree of the interaction between Cd(II) and sodium sulphate in the freshwater microalga Chlamydomonas moewusii. Two blocks of experiments were performed, one at sub-optimal sodium sulphate concentrations (<14.2 mg/L) and the other at supra-optimal concentrations (>14.2 mg/L). Three fixed ratios (2:1, 1:1, and 1:2) of the individual EC₅₀ for cadmium and sodium sulphate were used within each block. The isobolographic analysis of interaction at sub-optimal concentrations showed a stronger antagonistic effect with values of interaction index (γ) between 1.46 and 3.4. However, the isobologram with sodium sulphate at supra-optimal concentrations revealed a slight but significant synergistic effect between both chemicals with an interaction index between 0.54 and 0.64. This synergic effect resulted in the potentiation of the toxic effects of cadmium, synergy that was related to the increase of the ionic strength and of two species of cadmium, CdSO₄ (aq), and Cd(SO₄) ₂ ² ⁻ , in the medium. Results of the current study suggest that sodium sulphate is able to perform a dual antagonist/synergist effect on cadmium toxicity. This role was concentration dependent.
اظهر المزيد [+] اقل [-]Isobolographic analysis of the interaction between cadmium (II) and sodium sulphate: toxicological consequences النص الكامل
2016
Mera, Roi | Torres, Enrique | Abalde, Julio
Sulphate is an essential nutrient for autotrophic organisms and has been shown to have important implications in certain processes of tolerance to cadmium toxicity. Sodium sulphate is the main salt of sulphate in the natural environments. The concentration of this salt is increasing in the aquatic environments due to environmental pollution. The aim of this study was to investigate, using an analysis of isobolograms, the type and the degree of the interaction between Cd(II) and sodium sulphate in the freshwater microalga Chlamydomonas moewusii. Two blocks of experiments were performed, one at sub-optimal sodium sulphate concentrations (<14.2 mg/L) and the other at supra-optimal concentrations (>14.2 mg/L). Three fixed ratios (2:1, 1:1, and 1:2) of the individual EC50 for cadmium and sodium sulphate were used within each block. The isobolographic analysis of interaction at sub-optimal concentrations showed a stronger antagonistic effect with values of interaction index (γ) between 1.46 and 3.4. However, the isobologram with sodium sulphate at supra-optimal concentrations revealed a slight but significant synergistic effect between both chemicals with an interaction index between 0.54 and 0.64. This synergic effect resulted in the potentiation of the toxic effects of cadmium, synergy that was related to the increase of the ionic strength and of two species of cadmium, CdSO4 (aq), and Cd(SO4) 2 2 − , in the medium. Results of the current study suggest that sodium sulphate is able to perform a dual antagonist/synergist effect on cadmium toxicity. This role was concentration dependent.
اظهر المزيد [+] اقل [-]Metal-based optical chemosensors for CN− detection النص الكامل
2016
Bencini, Andrea | Lippolis, Vito
This critical review focuses on recent advances (2010–2015) in the detection of cyanide anion via metal-based optical chemosensors in which a change in colour and/or fluorescence intensity (or emission wavelength) of a molecular metal complex is determined by the direct interaction of the metal centre with this anion.
اظهر المزيد [+] اقل [-]PCBs in schools—where communities and science come together النص الكامل
2016
Osterberg, David | Scammell, Madeleine Kangsen
A novel aspect of the 8th International PCB Workshop at Woods Hole, MA, was the interaction between scientists and activists. While earlier workshops in this series had mentioned policy making, this Workshop focused on the problem of PCBs in schools. Focus on a problem brought an activist to give a plenary talk and facilitated a 1-day registration for other non-scientists to attend. The workshop was cohosted by the Superfund Research Programs at University of Iowa and Boston University and included active participation of each Program’s Research Translation and Community Engagement Cores. A mandate of each National Institute of Environmental Health Science (NIEHS)-funded Superfund Research Program is bidirectional communication between scientists and community groups. The authors describe the events leading up to community involvement in the Workshop and the substance of the community engagement aspects of the workshop, in particular the participation by a parent-teacher group, Malibu Unites. The authors also discuss the value of such communication in terms of making important research accessible to those who are most affected by the results and poised to use it and the value of making scientists aware of the important role they play in society in addressing difficult questions that originate in community settings.
اظهر المزيد [+] اقل [-]The aquatic fern Azolla as a natural plant-factory for ammonia removal from fish-breeding fresh wastewater النص الكامل
2016
Carlozzi, Pietro | Padovani, Giulia
This study has investigated the potential of an Azolla-Anabaena symbiosis, a marriage between the cyanobacterium Anabaena azollae and the aquatic fern (Azolla), to remove ammonia from freshwater fish breeding areas. Experiments were carried out under artificial light of 20, 70, and 140 μmol m⁻² s⁻¹. We investigated three different water temperatures for the growing Azolla, ranging from sub-optimal to optimal temperatures (15, 22, and 28 °C). The capability of Azolla to remove ammonia from wastewater was demonstrated, and the highest ammonia concentration tolerated by the symbiosis between Azolla-anabaena without any toxic effect on the aquatic ferns was ascertained. The shortest time taken to remove ammonia from wastes, 2.5 cm deep and at 28 °C, was 40 min. The ammonia removal rate (A RR) was both light and temperature dependent and the highest rate (6.394 h⁻¹) was attained at light intensity of 140 μmol m⁻² s⁻¹ and at a temperature of 28 °C; the lowest (0.947 h⁻¹) was achieved at 20 μmol m⁻² s⁻¹ and 15 °C. The depth of the fish-wastewater pool also affected the A RR with the relation between A RR and the depth being a hyperbolic function.
اظهر المزيد [+] اقل [-]Tracking fluorescent dissolved organic matter in multistage rivers using EEM-PARAFAC analysis: implications of the secondary tributary remediation for watershed management النص الكامل
2016
Nie, Zeyu | Wu, Xiaodong | Huang, Haomin | Fang, Xiaomin | Xu, Chen | Wu, Jianyu | Liang, Xinqiang | Shi, Jiyan
Profound understanding of behaviors of organic matter from sources to multistage rivers assists watershed management for improving water quality of river networks in rural areas. Ninety-one water samples were collected from the three orders of receiving rivers in a typical combined polluted subcatchment (diffuse agricultural pollutants and domestic sewage) located in China. Then, the fluorescent dissolved organic matter (FDOM) information for these samples was determined by the excitation–emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Consequently, two typical humic-like (C1 and C2) and other two protein-like (C3 and C4) components were separated. Their fluorescence peaks were located at λ ₑₓ/ₑₘ = 255(360)/455, <250(320)/395, 275/335, and <250/305 nm, which resembled the traditional peaks of A + C, A + M, T, and B, respectively. In addition, C1 and C2 accounted for the dominant contributions to FDOM (>60 %). Principal component analysis (PCA) further demonstrated that, except for the autochthonous produced C4, the allochthonous components (C1 and C2) had the same terrestrial origins, but C3 might possess the separate anthropogenic and biological sources. Moreover, the spatial heterogeneity of contamination levels was noticeable in multistage rivers, and the allochthonous FDOM was gradually homogenized along the migration directions. Interestingly, the average content of the first three PARAFAC components in secondary tributaries and source pollutants had significantly higher levels than that in subsequent receiving rivers, thus suggesting that the supervision and remediation for secondary tributaries would play a prominent role in watershed management works.
اظهر المزيد [+] اقل [-]Induced metal redistribution and bioavailability enhancement in contaminated river sediment during in situ biogeochemical remediation النص الكامل
2016
Liu, Tongzhou | Zhang, Zhen | Mao, Yanqing | Yan, Dickson Y. S.
In situ sediment remediation using Ca(NO₃)₂ or CaO₂ for odor mitigation and acid volatile sulfide (AVS) and organic pollutant (such as TPH and PAHs) removal was reported in many studies and fieldwork. Yet, the associated effects on metal mobilization and potential distortion in bioavailability were not well documented. In this study, contaminated river sediment was treated by Ca(NO₃)₂ and CaO₂ in bench studies. Through the investigation of AVS removal, organic matter removal, the changes in sediment oxidation-reduction potential (ORP), microbial activity, and other indigenous parameters, the effects on metal bioavailability, bioaccessibility, and fraction redistribution in sediment were evaluated. The major mechanisms for sediment treated by Ca(NO₃)₂ and CaO₂ are biostimulation with indigenous denitrifying bacteria and chemical oxidation, respectively. After applying Ca(NO₃)₂ and CaO₂, the decreases of metal concentrations in the treated sediment were insignificant within a 35-day incubation period. However, the [SEMₜₒₜ-AVS]/f OC increased near to the effective boundary of toxicity (100 μmol g⁻¹ organic carbon (OC)), indicating that both bioavailability and bioaccessibility of metals (Cu, Zn, and Ni) to benthic organisms are enhanced after remediation. Metals were found redistributed from relatively stable fractions (oxidizable and residual fractions) to weakly bound fractions (exchangeable and reducible fractions), and the results are in line with the enhanced metal bioavailability. Compared with Ca(NO₃)₂, CaO₂ led to higher enhancement in metal bioavailability and bioaccessibility, and more significant metal redistribution, probably due to its stronger chemical reactive capacity to AVS and sediment organic matter. The reactions in CaO₂-treated sediment would probably shift from physicochemical to biochemical heterotrophic oxidation for sediment organic matter degradation. Therefore, further investigation on the long-term metal redistribution and associated mobility as well as bioavailability is recommended.
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