Refinar búsqueda
Resultados 4531-4540 de 4,937
Influences of carbon and nitrogen sources and metal ions on the heterotrophic culture of Scenedesmus sp. LX1 Texto completo
2019
He, Yitian | Hong, Yu | Liu, Xiaoya | Zhang, Qing | Liu, Peirui | Wang, Shaoyun
In this study, the influences of organic carbon sources (OCS, including xylose, glucose, maltose, sucrose, and starch) and inorganic and organic nitrogen sources (INS, including ammonia chloride and sodium nitrate; ONS, including arginine, alanine, proline, and valine) and metal ions (including Na⁺, K⁺, Mn²⁺, Zn²⁺ and Cu²⁺) on the growth, lipid accumulation, and nitrogen and phosphorus (N&P) removal capabilities of oleaginous Scenedesmus sp. LX1 under heterotrophic conditions were investigated. The results showed that glucose was the only OCS for Scenedesmus sp. LX1 to grow well with specific growth rate of 0.935 days⁻¹, maximum biomass of 1.72 g L⁻¹, and largest removal rates of N&P and organic carbon reaching 72.228%, 93.034%, and 19.208%, respectively. After 11 days of cultivation, the maximal biomass reached in the group with starch or glucose while maximal lipid and triacylglycerol (TAG) yields reached in the groups with maltose and sucrose, respectively. Sodium nitrate was best nitrogen source as the largest algal density, maximal yields of lipids and TAGs, and highest N&P removal rates reached up to 1.105 × 10⁷ cells·mL⁻¹, 196.70 mg L⁻¹, 5.19 mg L⁻¹, 89.61% and 100%, respectively. Scenedesmus sp. LX1 was found to have great tolerance to Na⁺, K⁺, Mn²⁺, and Zn²⁺ while 0.5 mg L⁻¹ Cu²⁺ had a strong inhibition on growth and N&P removal rate of Scenedesmus sp. LX1. Concentration increasing of five metal ions all caused the yield increases of microalgal lipid and TAGs. Graphical abstract
Mostrar más [+] Menos [-]Sources and distribution of 241Am in the vicinity of a deep geologic repository Texto completo
2019
Thakur, Punam | Ward, Anderson L.
The detection, distribution, and long-term behavior of ²⁴¹Am in the terrestrial environment at the Waste Isolation Pilot Plant (WIPP) site were assessed using historical data from an independent monitoring program conducted by the Carlsbad Environmental Monitoring & Research Center (CEMRC), and its predecessor organization the Environmental Evaluation Group (EEG). An analysis of historical data indicates frequent detections of trace levels of ²⁴¹Am in the WIPP environment. Positive detections and peaks in ²⁴¹Am concentrations in ambient air samples generally occur during the March to June timeframe, which is when strong and gusty winds in the area frequently give rise to blowing dust. A study of long-term measurements of ²⁴¹Am in the WIPP environment suggest that the resuspension of previously contaminated soils is likely the primary source of americium in the ambient air samples from WIPP and its vicinity. Furthermore, the ²⁴¹Am/²³⁹ ⁺ ²⁴⁰Pu ratio in aerosols and soils was reasonably consistent from year to year and was in agreement with the global fallout ratios. Higher than normal activity concentrations of ²⁴¹Am and ²⁴¹Am/²³⁹ ⁺ ²⁴⁰Pu ratios were measured in aerosol samples during 2014 as a result of February 14, 2014 radiation release event from the WIPP underground. However, after a brief spike, the activity concentrations of ²⁴¹Am have returned to the normal background levels. The long-term monitoring data suggest there is no persistent contamination and no lasting increase in radiological contaminants in the region that can be considered significant by any health-based standard.
Mostrar más [+] Menos [-]Convergence in CO 2 emissions, carbon footprint and ecological footprint: evidence from OECD countries Texto completo
2019
Solarin, Sakiru Adebola
The aim of this paper is to augment the existing literature on convergence of CO₂ emissions, by adding carbon footprint per capita and ecological footprint per capita to the convergence debate. We use the residual augmented least squares regression to examine the stochastic convergence of the environmental indices in 27 OECD countries. Furthermore, in contrast to the previous studies which mainly used the conventional beta-convergence approach to examine conditional convergence, we use a beta-convergence method that is capable of identifying the actual number of countries that contribute to conditional convergence. The sigma-convergence of the environmental indices is also examined. The results suggest that conditional convergence exists in 12 countries for CO₂ emissions per capita, 15 countries for carbon footprint per capita and also 13 countries for ecological footprint per capita. There is evidence for sigma-convergence for all the three indicators. The policy implications of the results are discussed in the body of the paper.
Mostrar más [+] Menos [-]The effect of financial development on ecological footprint in BRI countries: evidence from panel data estimation Texto completo
2019
Baloch, Muhammad Awais | Zhang, Jianjun | Iqbal, Kashif | Iqbal, Zeeshan
This work aims to contribute to the existing literature by investigating at the impact of financial development on ecological footprint. To achieve this goal, we have employed Driscoll-Kraay panel regression model for a panel of 59 Belt and Road countries in the period from 1990 to 2016. The findings suggest that financial development increases ecological footprint. Moreover, economic growth, energy consumption, foreign direct investment (FDI), and urbanization pollute the environment by increasing ecological footprint. In addition, several diagnostic tests have been applied to confirm the reliability and validity of the results. From the outcome of the study, various policy implications have been proposed for Belt and Road countries to minimize the ecological footprint.
Mostrar más [+] Menos [-]Environmental etiology of gastric cancer in Iran: a systematic review focusing on drinking water, soil, food, radiation, and geographical conditions Texto completo
2019
Ghaffari, Hamid Reza | Yunesian, Masud | Nabizadeh, Ramin | Nasseri, Simin | Sadjadi, Alireza | Pourfarzi, Farhad | Poustchi, Hossein | Eshraghian, Ahad
The aim of this systematic review study was to investigate the causal relationship between environmental factors and gastric cancer (GC) in Iran. In a narrow definition, the environment includes water, soil, air, and food. This definition was the main criterion for the inclusion of articles in this study. In addition, exposure to radiation and geographical conditions were considered as less investigated environmental factors in the literatures. International (PubMed, Web of Science, ScienceDirect, Scopus, and Cochran) and national (Scientific Information Database) databases were searched for articles on GC and environmental risk factors in Iran. Twenty-six articles were found to meet the inclusion criteria after title, abstract, and full text review. Risk factors identified for GC include consumption of red meat; high fat, fried, and salted meat; smoked, salted, and fried foods; some dairy products; roasted and fried seeds; strong and hot tea; and un-piped and unchlorinated drinking water, as well as exposure to radiation, loess sediment, soft and grassy soil, soil containing low concentration of molybdenum, and proximity to volcanos. Fresh fruits and vegetable, fresh fish, and honey consumption were recognized as protective agents. Given the risk factors identified, strategies to prevent GC would be educating people to choose a healthy diet and to cook and store food properly, providing access to safe drinking water, taking into account topographical and geographical conditions in choosing a right location to build residential areas, and regulating the use of radiation-emitting devices.
Mostrar más [+] Menos [-]Amalgamation of N-graphene quantum dots with nanocubic like TiO2: an insight study of sunlight sensitive photocatalysis Texto completo
2019
Lim, Ping Feng | Leong, Kah Hon | Sim, Lan Ching | Abd Aziz, Azrina | Saravanan, Pichiah
In this work, a sunlight-sensitive photocatalyst of nanocubic-like titanium dioxide (TiO₂) and N-doped graphene quantum dots (N-GQDs) is developed through a simple hydrothermal and physical mixing method. The successful amalgamation composite photocatalyst characteristics were comprehensively scrutinized through various physical and chemical analyses. A complete removal of bisphenol A (BPA) is attained by a synthesized composite after 30 min of sunlight irradiation as compared to pure TiO₂. This clearly proved the unique contribution of N-GQDs that enhanced the ability of light harvesting especially under visible light and near-infrared region. This superior characteristic enables it to maximize the absorbance in the entire solar spectrum. However, the increase of N-GQDs weight percentage has created massive oxygen vacancies that suppress the generation of active radicals. This resulted in a longer duration for a complete removal of BPA as compared to lower weight percentage of N-GQDs. Hence, this finding can offer a new insight in developing effective sunlight-sensitive photocatalysts for various complex organic pollutants degradation.
Mostrar más [+] Menos [-]Heavy metals in organs of stray dogs and cats from the city of Naples and its surroundings (Southern Italy) Texto completo
2019
Esposito, Mauro | De Roma, Antonella | Maglio, Pasquale | Sansone, Donato | Picazio, Giuseppe | Bianco, Raffaele | De Martinis, Claudio | Rosato, Guido | Baldi, Loredana | Gallo, Pasquale
The aim of the present study was to assess the concentrations of lead (Pb) and cadmium (Cd) in the liver and kidney from stray dogs (Canis lupus familiaris) and cats (Felis catus) found dead between 2014 and 2017 in the city of Naples and its surrounding areas. These organs from 290 dogs and 88 cats were collected after ordinary necropsy of stray animals. Heavy metal concentrations were determined by using atomic absorption spectrophotometry (AAS). Concentrations of Pb (up to 5.93 mg/kg) and Cd (ranging from 0.005 to 6.13 mg/kg) were detected in both livers and kidneys analyzed. Differences in concentration were found based on age class, gender, and kind of tissue for both elements, with a trend similar to those already reported in the literature for comparable studies from different countries. Cadmium levels in the kidney were significantly higher (p < 0.05) in females than those in males for both species. As regards to Pb, the highest concentrations were detected in the liver (3.45 mg/kg in dog and 5.93 in cat, respectively) followed by the renal tissue, with no significant difference depending on the animal gender. This study can be considered the first one in Italy regarding stray dogs and cats as bio-indicators of environmental contamination due to lead and cadmium, suggesting that pets could be sentinel animals to evaluate human exposure to these heavy metals.
Mostrar más [+] Menos [-]Spatial identification of environmental health hazards potentially associated with adverse birth outcomes Texto completo
2019
Svechkina, Alina | Portnov, Boris A.
Reduced birth weight (RBW) and reduced head circumference (RHC) are adverse birth outcomes (ABOs), often linked to environmental exposures. However, spatial identification of specific health hazards, associated with these ABOs, is not always straightforward due to presence of multiple health hazards and sources of air pollution in urban areas. In this study, we test a novel empirical approach to the spatial identification of environmental health hazards potentially associated with the observed RHC and RBW patterns. The proposed approach is implemented as a systematic search, according to which alternative candidate locations are ranked based on the strength of association with the observed birth outcome patterns. For empirical validation, we apply this approach to the Haifa Bay Area (HBA) in Israel, which is characterized by multiple health hazards and numerous sources of air pollution. We identified a spot in the local industrial zone as the main risk source associated with the observed RHC and RBW patterns. Multivariate regressions, controlling for personal, neighborhood, and geographic factors, revealed that the relative risks of RHC and RBW tend to decline, other things being equal, as a function of distance from the identified industrial spot. We recommend the proposed identification approach as a preliminary risk assessment tool for environmental health studies, in which detailed information on specific sources of air pollution and air pollution dispersion patterns is unavailable due to limited reporting or insufficient monitoring.
Mostrar más [+] Menos [-]The dynamic time-varying effects of financial development, urbanization on carbon emissions in the Yangtze River Delta, China Texto completo
2019
Wang, Feng | Fan, Wenna | Chen, Chao | Liu, Juan | Chai, Wei
Based on the time series data of the Yangtze River Delta region from 1993 to 2015, this paper uses the state space model and the mediating effect model to investigate the time-varying effect and its mechanism of financial development (measured by two indicators: financial scale and financial efficiency), urbanization on carbon emissions. The results show a positive in the short term and negative in the long-run impact of financial scale on carbon emissions, while the impact of financial efficiency on carbon emissions is negative in the short term and positive in the long term, and the impact of urbanization on carbon emissions is always positive. Moreover, the results of mediating effect test demonstrate that urbanization is a positive partial mediating effect in the path of financial scale and financial efficiency influencing carbon emissions, and the mediating effect accounts for 71.64% and 61.69% of the total effect, respectively. The mediating effect of financial development includes chain effect and parallel effect; in the chain mediating effect, financial scale has a negative mediating effect with 27.40% of the total effect in the path of urbanization affecting carbon emissions, whereas financial efficiency plays a positive role with 2.07%; in the parallel mediating effect, the individual effect of financial scale and financial efficiency accounts for 24.39% and 1.05%, respectively.
Mostrar más [+] Menos [-]Studies on mercury occurrence in inorganic constituents of Polish coking coals Texto completo
2019
Dziok, Tadeusz | Strugała, Andrzej | Włodek, Adam
During the cokemaking process, a significant amount of mercury occurring in a coal blend is released to the atmosphere. One of the ways of reducing this emission is to reduce mercury content in a coal blend. This could be obtained through the coal washing process. The optimization of this process requires the knowledge of mercury occurrence in coal, especially in its inorganic constituents. A qualitative analysis of mercury occurrence in the inorganic constituents of Polish coking coals was performed using an electron probe microanalyzer (EPMA). For that purpose, selected samples of rejects and middling products derived from the washing process in dense media separators and jig concentrators were examined. The obtained results have confirmed a strong connection between mercury occurrence and the presence of sulfides (pyrite, marcasite, and chalcopyrite) in Polish coking coals. Significant amounts of mercury were also noticed for barite, siderite, and aluminosilicates. The highest value of mercury content, at the level of 0.100%, was obtained for marcasite. For the analyzed coals, the effectiveness of mercury removal in the washing process was determined by the forms of pyrite occurring in coal. The highest values of effectiveness of mercury removal were obtained in the case of coals for which the large framboidal pyrite aggregates with chalcopyrite overgrowths were noticed. It was also found that middling products were characterized by the occurrence of the Hg-rich overgrowths of pyrite on organic matter. To achieve a significant reduction in mercury content in clean coal, it is necessary to develop an effective method of removing this form of pyrite from hard coal.
Mostrar más [+] Menos [-]