1,720,974 research outputs found
A combined methodology to assess the intrinsic vulnerability of aquifers to pollution from agrochemicals
No full textThe groundwater vulnerability indices are valuable tools for the development of agrochemicals management strategies based on environmental/agricultural policies. The groundwater vulnerability methods of LOS, SINTACS, DRASTIC, Pesticide DRASTIC, GOD and AVI were applied for the agricultural fields of Sarigkiol basin (Northern Greece). The results of the aforementioned methods were examined and discussed in order to show how the dissimilarities in the vulnerability assessment approaches may become an advantage. The results of the methods were used to propose a combined conceptual approach which adds another two dimensions (depth and time) in the current two-dimensional vulnerability mapping (longitude, latitude) procedures. The LOS method provided information about the intrinsic vulnerability of the topsoil (30 cm) to water (+conservative pollutants) and nitrogen losses, and the AVI method described the vulnerability of the unsaturated zone to allow pollutants to reach the aquifer while the aquifer vulnerability was analysed using SINTACS, DRASTIC, Pesticide DRASTIC and GOD. In this study, the results of the SINTACS method were found more accurate to describe the local aquifer conditions. The final conceptual approach provided a stratified vulnerability (dimension of depth) of the overall hydrogeologic system using LOS for the topsoil, AVI for unsaturated zone and SINTACS for the aquifer. The dimension of time was introduced by the LOS and AVI methods, which provide quantitative results in time. The use of LOS method also highlighted the basic limitation of the other methods to describe the potential contribution to pollution of areas (especially upland areas) which are out of the aquifer boundaries
A Review and Synthesis of Bivariate Non-Linear Models to Describe the Relative Variation of Ecological, Biological and Environmental Parameters
No full textThere is a plethora of non-linear models to describe bivariate relationships related to ecological, biological and environmental problems, and this makes difficult to have a general aspect about the suitable models for a new-born dataset. Additionally, there is a special interest for bivariate non-linear models which can describe the relative variation of the dependent variable (NLR models) (i.e. these models provide a restricted range of values between 0 and 1) because they can easily be adjusted to fit different datasets which describe the same relationship. The aim of this study is to provide a review and synthesis of NLR models which can be used to describe bivariate relationships which follow bell-shaped, simple-double sigmoid, bilinear and periodical patterns. This attempt aims to save time and effort for the selection of a NLR model based on five steps (a) preparation of data, (b) visual identification of the suitable model based on pre-constructed graphs, (c) a starting point using the simpler form (base function) of the selected models which are given in complex general forms, (d) directions to increase the number of coefficients
in order to improve fitting and (e) techniques to modify the given NLR models in order to derive new ones with inverted patterns
Effects of Graphene on Soil Water-Retention Curve, van Genuchten Parameters, and Soil Pore Size Distribution—A Comparison with Traditional Soil Conditioners
Get PDFGraphene waste has had enormous growth due to many industrial applications. Agriculture exploits waste through the circular economy, and graphene waste is thereby investigated in this study as a soil conditioner for improving the physical–hydraulic properties of soil. Experiments were performed on three differently textured soils amended with traditional soil conditioners (compost, biochar, and zeolites) and graphene. The conditioners were applied at two different doses of 10% and 5% dry weight (d.w.) for compost, biochar, and zeolites, and 1.0% and 0.5% d.w. for graphene. We compared (i) the major porosity classes related to water-retention characteristics (drainage, storage, and residual porosity), (ii) bulk density, and (iii) van Genuchten water-retention curve (WRC) characteristics. Graphene application caused the largest decrease in dry bulk density (ρb), lowering the soil bulk density by about 25%. In fact, graphene had ρb of 0.01 g/cm3. The effects of graphene were more intense in the finer soil. Compost and biochar showed similar effects, but of lower magnitude compared to those of graphene, with ρb of 0.7 and 0.28 g/cm3, respectively. Although zeolites had ρb of 0.62 g/cm3, they showed quite different behavior in increasing the mixtures’ ρb. Graphene and biochar showed the most pronounced effects in the clayey soil, where storage porosity showed a reduction of >30% compared to the control. For storage porosity, the graphene treatments did not show statistically significant differences compared to the control. The results show that, when the conditioner increased drainage porosity, there was a high probability of a concomitant reduction in storage porosity. This finding indicates that graphene use for improving soil aeration and drainage conditions is viable, especially in fine soils
Land use change effects on ecosystem services of river deltas and coastal wetlands : case study in Volano–Mesola–Goro in Po river delta (Italy)
No full textThe landscape of river deltas and coastal wetlands is under a continuous alteration due the combined effects of human and natural factors. The aim of the study is to analyze the Land Use/Land Cover (LULC) changes and associated Ecosystem Services (ESs) of a protected wetland area in the Po river delta (Northern Italy). A combination of methodologies which take into account both the assessment of socio-economic benefits (approach of ESs) and the monitoring of ecosystems attributes (LULC change analysis using transition matrices TMs) were used by comparing the changes observed during two periods (1954-1976 and 1976-2008) described by different environmental protection governance. The period 1954-1976 is described by extensive land reclamations while the period 1976-2008 by significant efforts for applying environmental protection measures. The results highlighted an extensive loss of vegetated wetlands due to direct human interventions (croplands and urban areas expansion) during the first period. The direct human intervention was significantly reduced during the second period. However, vegetated wetlands losses did not follow an analogous reduction probably due to indirect human interventions and natural factors. TMs identified the exact LULC conversions while the ESs approach highlighted the significant economic impact of vegetated wetlands' losses. Waste treatment was the most important ES of the specific system providing approximately 70 % of the estimated natural capital value. The proposed combination of the selected methods (TMs and ESs) provides a detailed description of landscape changes and their economic impact, which can be used as decision support tool for landscape conservation policies
A size-age model based on bootstrapping and Bayesian approaches to assess population dynamics of Anguilla anguilla L. in semi-closed lagoons
No full textA size-age modelling technique is presented for assessing the vital rates, stock and recruitment of eel populations in semi-closed lagoons with fully monitored migration of silver eels. Data for yellow and silver European eels (Anguilla anguilla L.) were obtained in 2011 from the Comacchio lagoon (Italy). The analysis was performed in three steps: (i) correction of yellow eel data, which are affected by the fyke nets selectivity during samplings, (ii) estimation of survival curve, stock, recruitment and metamorphosis rates of the population (calibration using data from 2011) and (iii) validation of the model using the observed amount of silver eel migrating population of the next year. A bootstrap procedure was used to assess the level of uncertainty for each parameter using the 95% intervals of the highest posterior density distribution HPDD (Bayesian approach). The measured abundance of silver eels was 0.56 ind·ha-1, while the yellow eel abundance and recruitment were estimated by the model for 2011 at 8.77 ind·ha-1 and 5.99 ind. ha-1 respectively. The model performance during validation was satisfactory as the observed total mass of migrating population of 2012 (3777 kg) was inside the 95% HPDD intervals (3197-3839 kg) of model's predictions. The estimated stocks and recruitment were at least ten times lower from the respective estimations of previous studies of 1989 highlighting the crucial conditions of the population. The proposed modelling approach can provide significant information about eel population conditions, facilitating the evaluation of a range of management options in the context of eel conservation plans
Two (or more) for one: Identifying classes of household energy- and water-saving measures to understand the potential for positive spillover
Get PDFA key component of behavior-based energy conservation programs is the identification of target behaviors. A common approach is to target behaviors with the greatest energy-saving potential. The concept of behavioral spillover introduces further considerations, namely that adoption of one energy-saving behavior may increase (or decrease) the likelihood of other energy-saving behaviors. This research aimed to identify and describe household energy- and water-saving measure classes within which positive spillover is likely to occur (e.g., adoption of energy-efficient appliances may correlate with adoption of water-efficient appliances), and explore demographic and psychographic predictors of each. Nearly 1,000 households in a California city were surveyed and asked to report whether they had adopted 75 different energy- and/or water-saving measures. Principal Component Analysis and Network Analysis based on correlations between adoption of these diverse measures revealed and characterized eight water-energy-saving measure classes: Water Conservation, Energy Conservation, Maintenance and Management, Efficient Appliance, Advanced Efficiency, Efficient Irrigation, Green Gardening, and Green Landscaping. Understanding these measure classes can help guide behavior-based energy program developers in selecting target behaviors and designing interventions
Moistube irrigation (MTI) discharge under variable evaporative demand.
Get PDFWe investigated the conceptual capability of Moistube irrigation (MTI) to discharge under zero applied positive pressure and under varied climatic conditions by inducing an artificial evaporative demand (Ed) or negative pressure around Moistube tubing. This study was premised on the null hypothesis that an artificially induced Ed or negative pressure does not impact MTI discharge. Moistube tubing was enclosed in a 1 m long PVC conduit. A 20 l water reservoir placed on an electronic balance provided a continuous supply of water whilst a three-speed hot air blower facilitated the radiative factor and advection process. The procedure was conducted under varied climatic conditions with three air velocity (ua) treatments namely; 1.2 m.s-1, 2.5 m.s-1, and 3.0 m.s-1 and the experiment run times were 159 h, 134 h and 10 h, respectively. The average temperature (Tave) and relative humidity (RH) data for ua = 1.2 m.s-1 were 53°C and 7.31%, whilst for ua = 2.5 m.s-1, Tave was 56°C and RH = 7.19%, and for ua = 3.0 m.s-1, Tave was 63°C and RH = 6.16%. The experimental data was input into the four variable Penman-Monteith method to compute the evaporative demand (Ed). For each Ed, the instantaneous mass flow rate ([Formula: see text]) was recorded using an electronic balance and subsequently converted to volumetric flow rates. For each of the air velocities, the respective Ed values obtained were 0.16, 0.31 and 0.36 mm.d-1. The Bowen ratios (r) were well below 1 (r < 1), which suggested a sufficient supply of moisture to evaporate. For Ed = 0.16 mm.d-1 the vapour pressure deficit (VPD) was 113.08 mbars, whilst for Ed = 0.31 mm.d-1 and for Ed = 0.36 mm.d-1 the VPD were 129.93 mbars and 150.14 mbars, respectively. The recorded discharges (q) at normalised time (t*) = 1 h for Ed = 0.16 mm.d-1 was 7.67*10-3 l.hr-1.m-1 length, whilst for Ed = 0.31 mm.d-1 q = 14.5*10-3 l.hr-1.m-1 length, and for Ed = 0.36 mm.d-1 q = 20.8*10-3 l.hr-1.m-1 length. The imposed negative pressure causes an exponential increase in Moistube™ discharge, thus disproving the null hypothesis. The higher the evaporative demand the higher the discharge. This phenomenon allows MTI to be used for deficit irrigation purposes and allows irrigators to capitalize on realistic soil matric potential irrigation scheduling approach
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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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