1,720,956 research outputs found
Predicting the contribution of a local emission source in mid-range transport of DDT and its deposition in terrestrial and aquatic ecosystems in Northern Italy
No full textA recently developed dynamic multiple box multimedia fate model (Gridded-SoilPlusVeg, or GSPV) was developed and implemented to account for the environmental variation and the effect of directional advective transport of chemicals towards different compartments and geographical locations. A chemical plant located in Pieve Vergonte in Ossola Valley produced and emitted DDTs for around 50 years. In the previous study the fate and transport of p,p’-DDT emitted from the chemical plant were evaluated in nearby areas (up to 12 km). In this paper, the GSPV model was run for p,p’-DDT from its production period and decades after the production stop in 1996 (a total of 100 years) for a much larger study area (40,000 km2) in order to evaluate the contribution of a local source on a larger scale. Additionally, the deposition fluxes into the lakes were calculated and were used as input into a dynamic fugacity-based aquatic model to calculate DDT concentration in water and sediments of three Prealpine lakes: Lake Maggiore, Lake Como and Lake Lugano. The results of the simulations were compared with the monitoring and literature data. The results obtained from GSPV allowed to estimate the atmospheric deposition fluxes and identify the role of this source for the regional scale contamination in terrestrial and aquatic ecosystems
Spatially resolved environmental fate models: A review
No full textSpatially resolved environmental models are important tools to introduce and highlight the spatial variability of the real world into modeling. Although various spatial models have been developed so far, yet the development and evaluation of these models remain a challenging task due to several difficulties related to model setup, computational cost, and obtaining high-resolution input data (e.g., monitoring and emission data). For example, atmospheric transport models can be used when high resolution predicted concentrations in atmospheric compartments are required, while spatial multimedia fate models may be preferred for regulatory risk assessment, life cycle impact assessment of chemicals, or when the partitioning of chemical substances in a multimedia environment is considered. The goal of this paper is to review and compare different spatially resolved environmental models, according to their spatial, temporal and chemical domains, with a closer insight into spatial multimedia fate models, to achieve a better understanding of their strengths and limitations. This review also points out several requirements for further improvement of existing models as well as for their integration
Estimating temporal and spatial levels of PAHs in air using rain samples and SPME analysis: Feasibility evaluation in an urban scenario
No full textThere is a growing interest in evaluating the role of concentration changes of contaminants in temporal and spatial gradients. This is often relevant for fast moving environmental phases such as air and water. In this paper, small volumes of rainwater were sampled as proxy for air concentrations of Polycyclic Aromatic Hydrocarbons (PAHs): rain was collected in three sampling sites (high traffic, restricted traffic and a low traffic zone) in Como. Solid phase micro extraction (SPME) was used for the extraction to reduce required sample volumes, allowing the acquisition of more samples in time. Rain samples highlighted a spatial and temporal variability along a traffic gradient in the Como city, especially for the most abundant PAH, e.g. phenanthrene. Air concentrations were then estimated from rain concentrations. The results show that this is a cheap and promising method, although requiring rainfall/snowfall conditions, that can be used to perform monitoring campaign of air concentrations at a higher temporal and spatial resolution than the adopted standard methods (e.g. high-volume air samplers). The results could be employed for evaluation of the exposure, emission profiles and calibration of fate models
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
Bioaccumulation of PCBs and their hydroxy and sulfonated metabolites in earthworms: Comparing lab and field results
No full textSulfonated and hydroxy-sulfonated PCBs were recently discovered by our group as new PCB soil contaminants, constituting about 1% of their parent compounds in soil. Here we investigate for the first time the bioaccumulation of these metabolites as well as hydroxy-PCBs and native PCBs in earthworms. A sequence of three experiments, at increasing complexity and ecological realism, were performed with four different earthworm species (Eisenia foetida Savigny, Lumbricus terrestris L, Allolobophora chlorotica Savigny and Aporrectodea caliginosa Savigny) exposed to contaminated soils. The first experiment confirmed that when exposing earthworms to soil contaminated with a single hexa-chlorinated congener (PCB 155), no formation of polar metabolites in earthworms could be detected. This allowed to plan the following two experiments, using a soil from a PCB contaminated site and rich in relatively high levels (10–130 μg kg−1) of hydroxy-, sulfonated-, and hydroxy-sulfonated-PCBs. Bioaccumulation factors (BAFs) and bioconcentration factors (BCFs) were then obtained in the second and third experiments, to compare the accumulation behavior of these chemicals in laboratory and natural conditions. Regressions between BAF/BCF and Log Kow/Log D, produced a variety of results, being generally significant between BCF and PCBs and not significant in the other cases. In general, the metabolites accumulated in earthworms with detectable concentrations in their tissues (8–115 μg kg−1), although sulfonated and hydroxy-sulfonated PCBs showed BAF and BCF values lower (up to two orders of magnitude) than those calculated for the parent PCBs, given their lower lipophilicity
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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