1,721,011 research outputs found
Impacts of Nano-ZnO in Municipal Solid Waste Landfills
No full textNano-ZnO enter landfills mostly through disposal of cosmetics, UV protection and catalysts. In this study, the impact of ZnO on municipal solid waste landfills was investigated. Two conventional and two bioreactors were operated using real MSW samples at mesophilic temperature (35 ºC). Results showed that there were no significant differences on biogas and methane production between the reactors with or without nano-ZnO addition. Related with the operation types, there were slight differences observed due to the nano-ZnO concentrations during the first 140 days of this ongoing projec
A fuzzy logic based model to predict the effects of ZnO nanoparticles on methane generation in landfills
No full textNano-ZnO enters landfills mostly through disposal of cosmetics, sunscreens and catalysts. However, its effects on waste degradation are still unclear. In this paper, a fuzzy-based model is proposed to predict biogas and methane production from a bioreactor landfill in the presence of ZnO nano-particles. Eight deterministic inputs (pH, RedOx potential, chemical oxygen demand, volatile fatty acids, alkalinity, Zn concentration, Zn background and recirculation flow rate) were identified as antecedent variables. Two outputs, or consequents, were chosen: methane production rate and methane concentration in biogas. Antecedents and consequents were linked by 30 IF-THEN rules, which stated the effects of the input parameters in a linguistic form. The fuzzy model was tested on the data of a lab-scale study simulating a bioreactor landfill with 0.15 g of added nano-ZnO/kg of waste. The fuzzy model showed good performance in the prediction of methane generation, also compared to the commonly used Gompertz equation. The results confirm the potential use of fuzzy macro-approach for complex processes taking place in landfill environments with unusual operating conditions
The fate and behaviour of nano ZnO during waste stabilization in landfills
No full textAs a result of rapid development in nanotechnology in recent years, the number of commercially available nanotechnology products has exceeded one thousand. The extensive use of NMS in commercial consumer products and their eventual release to the environment through various pathways have recently raised concern about the potential impacts of these materials on the environment and human health. It is estimated that more than 50 % of nanometarials (NMS) used in cosmetics, health, electronic, textile and water treatment sectors, will ultimately be sent to landfills for final disposal after their useful lifes are over. It is reported in the literature that research activities have mostly focused on the ecotoxicity of NMS. However, the fate and behavior of NMs during waste stabilization in landfills, which play a crucial role in integrated waste management systems, is still unknown. In particular, little data is available on how these materials behave in an integrated waste management system under changing environmental conditions. The transport behavior of nanoparticles from the solid waste into leachate is also dependent on the properties of landfill leachate and the environmental factors. Therefore, it is important to investigate the fate of nanoparticles in landfills to understand and control the environmental impacts that may occur in advance. Especially, their potential impacts on waste stabilization, landfill gas production, geomembranes and the risk for the groundwater and surface water contamination are still unknown. Therefore, the main objective of this study is to provide greatly needed fundamental information and insight into the fate and impact of nano ZnO during waste stabilization in landfills. For this purpose, 70 liter lab-scale simulated conventional landfill and bioreactor landfill lysimeters were loaded with fresh municipal solid waste obtained from a real landfill site and the reactors were uniformly mixed with pre-known amounts of nano ZnO. Samples were regularly taken from leachate and gas phases, to assess the impact of nano ZnO on different phases of waste stabilization. Daily and cumulative biogas and methane production values of each reactor were monitored to determine the impact of nano ZnO on gas production
Effects of nano- ZnO on biogas generation from simulated landfills.
No full textExtensive use of nanomaterials in commercial consumer products and industrial applications eventually leads to their release to the waste streams and the environment. Nano-ZnO is one of the most widely-used nanomaterials (NMs) due to its unique properties. It is also known to impact biological processes adversely. In this study, the effect of nano-ZnO on biogas generation from sanitary landfills was investigated. Two conventional and two bioreactor landfills were operated using real MSW samples at mesophilic temperature (35 °C) for a period of about 1 year. 100 mg nano-ZnO/kg of dry waste was added to the simulated landfill reactors. Daily gas production, gas composition and leachate Zn concentrations were regularly monitored. A model describing the fate of the nano-ZnO was also developed. The results obtained indicated that as much as 99% of the nano-ZnO was retained within the waste matrix for both reactor operation modes. Waste stabilization was faster in simulated landfill bioreactors with and without the addition of nano-ZnO. Moreover, the presence of the nano-ZnO within the waste led to a decrease in biogas production of about 15%, suggesting that the nano-ZnO might have some inhibitory effects on waste stabilization. This reduction can have potentially significant implications on waste stabilization and the use of biogas from landfills as a renewable energy source
Innovative techniques for the characterization and interpretation of coastal aquifers: pumping test interpretation by means of the drawdown derivative to estimate aquifer heterogeneity
Full text linkAquifers are intrinsically heterogeneous, but the interpretation of pumping tests to estimate hydraulic aquifer parameters, such as transmissivity and storativity, is commonly performed under the assumption of homogeneity, by utilizing Theis equation. This yields interpreted parameters whose relation to aquifer heterogeneity is uncertain. To optimize Theis-based pumping test interpretation techniques for the application to heterogeneous systems, this study investigates the relationship between the interpreted parameters and the underlying heterogeneity of aquifers. Two time-dependent spatial weighting functions are derived which enable the estimation of upscaled transmissivities from a given heterogeneous transmissivity distribution. The comparison of the upscaled transmissivities to the interpreted Theis-based transmissivities from synthetically generated pumping tests reveals that their meaning depends on the properties of the Theis solution, used during the interpretation process. If the interpreted transmissivity is estimated from the drawdown derivative it relates to an upscaled heterogeneous transmissivity field, but to an upscaled homogeneous transmissivity if the drawdown itself is used. This procedure is applied to infinite aquifers and to aquifers delimited by a linear constant head boundary (BCH). It is shown that Theis-based interpretation methods allow for assessing aquifer heterogeneity. Moreover, a new pumping test interpretation method for BCH aquifers is developed which allows for estimating the transmissivity continuously from the transient drawdown. The theoretical investigations are supplemented by the evaluation of real pumping tests in an aquifer system strongly affected by tectonics. In this regard, this study confirms that pumping test interpretation can provide fundamental information on reservoir boundaries and hydrogeological
Direct impact of climate change on groundwater levels in the Iberian Peninsula
No full textThe Iberian Peninsula is a water-scarce region that is increasingly reliant on groundwater. Climate change is expected to exacerbate this situation due to projected irregular precipitation patterns and frequent droughts. Here, we utilised convolutional neural networks (CNNs) to assess the direct effect of climate change on groundwater levels, using monthly meteorological data and historical groundwater levels from 3829 wells. We considered temperature and antecedent cumulative precipitation over 3, 6, 12, 18, 24, and 36 months to account for the recharge time lag between precipitation and groundwater level changes. Based on CNNs performance, 92 location-specific models were retained for further analysis, representing wells spatially distributed throughout the peninsula. The CNNs were used to assess the influence of climate change on future groundwater levels, considering an ensemble of eight combinations of general and regional climate models under the RCP4.5 and RCP8.5 scenarios. Under RCP4.5, an average annual temperature increase of 1.7 °C and a 5.2 % decrease in annual precipitation will result in approximately 15 % of wells experiencing >1-m decline between the reference period [1986–2005] and the long-term period [2080–2100]. Under RCP8.5, with a 3.8 °C increase in temperature and a 20.2 % decrease in annual precipitation between the same time periods, 40 % of wells are expected to experience a water level drop of >1 m. Notably, for 72 % of the wells, temperature is the main driver, implying that evaporation has a greater impact on groundwater levels. Effective management strategies should be implemented to limit overexploitation of groundwater reserves and improve resilience to future climate changes.PH-ENA
Development of Fuzzylogic model to predict the effects of ZnO nanoparticles on methane production from simulated landfill
No full textNano-ZnO enters landfills mostly through disposal of cosmetics, sunscreens and catalysts. However, its effects on waste degradation are still unclear. In this paper, a fuzzy-based model is proposed to predict biogas and methane production from simulated bioreactor landfill with and without ZnO nanomaterials. Eight deterministic inputs (pH, RedOx potential, chemical oxygen demand, volatile fatty acids, alkalinity, Zn concentration, Zn background
and leachate recirculation flow rate) were identified as antecedent variables. Two outputs, or consequents, were chosen: biogas production rate and methane fraction. Antecedents and consequents were linked by 66 IF-THEN rules, which stated the effects of the input parameters in a linguistic form. The fuzzy model was tested on the data of a lab-scale study simulating a bioreactor landfill with 100 mg of added nano-ZnO per kg of dry waste.
Experimental results indicated that the addition of nano-ZnO resulted in a reduction of methane generation by about 30%.The fuzzy model showed good performance in the prediction of methane generation; in addition, the comparison with the commonly used Gompertz equation showed that the fuzzy model is more consistent with the data. Fuzzy modelling could easily handle the Zn concentration together with other parameters and it
highlighted the importance of including this input in the model. The modelling results confirmed the high potential of fuzzy macro-approach in the modelling of very complex processes taking place in landfill environments under different operating conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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