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Terbuthylazine contamination of the aquifer north of Vicenza (North-East Italy)
No full textBackground and Goal. Agricultural practices can affect the quality of aquifers given that they are often located in cropped areas, so significant amounts of pesticides can be found in the water. In particular, triazine herbicides are always carefully checked by the official monitoring systems. The goal of this study was to find the mean concentration of terbuthylazine in an Italian aquifer and to set up a mass balance of this compound.
Methods. Terbuthylazine concentrations in the aquifer were measured in various check-wells during 1998-2004, and the value of censored data were estimated using a Gompertz inverse in order to evaluate the overall mean concentration. The total terbuthylazine load in the recharge area was calculated on the basis of surveys of cropped land and the main weed control techniques applied in the area. Data on aquifer water balance were obtained from previous studies.
Results and Discussion. The herbicide terbuthylazine applied in the recharge zone can be transported by surface water and enter the aquifer. Detected concentrations were always well below the EU drinking water limit and the fraction that can reach the groundwater under normal cropping practices is small, very likely less than 0.2%.
Recommendations and Outlook. The use and application rates of pesticides should be strictly regulated in recharge areas. Vegetated buffer strips can mitigate the impact of herbicides on surface water through reducing drift and early-spring runoff. Attention should also be paid to the fate of the main metabolites from soil biochemical processes
MONITORAGGIO ELETTRICO AD ALTA RISOLUZIONE PER LO STUDIO DELLE PROPRIETA' DI TRASPORTO IN UN ACQUIFERO SUPERFICIALE
No full textSIMULATION OF HERBICIDE CONTAMINATION OF THE AQUIFER NORTH OF VICENZA (NORTHEAST ITALY)
No full textThe contamination of the aquifer north of Vicenza (North-East Italy) by atrazine, simazine and alachlor has been simulated developing a simple model based on the fugacity model. The simulation has been carried out taking into account the period 1964–1990 and the results have been compared with the analytical data of the period 1987–1990.
The median concentration (C50) of atrazine measured in the aquifer was 0.028, 0.044 and 0.015 μg/l in 1987, 1988 and 1989–1990 respectively. The simulated values showed a satisfactory behaviour of the model concerning the order of magnitude of the phenomenon. Similar results have been obtained for simazine and alachlor
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
Thirty-year monitoring of s-triazine herbicide contamination in the aquifer north of Vicenza (north-east Italy)
No full textThe aquifer north of Vicenza, Italy, is one of the main and most studied drinking water reservoirs within the Veneto region. The area is an intensive cropland, and monitoring of s-triazine herbicides and metabolites has been carried out since the late eighties. This study analysed the trends of atrazine (ATR), terbuthylazine (TBZ), deethyl-atrazine (DEA), and deethyl-terbuthylazine (DET) concentrations from 1987 to 2016 and related the variations of agricultural land use, herbicide load, and pesticide regulations to the residence time of pollutants in the aquifer. In total, 785 water samples collected from 82 selected check wells were analysed with high-resolution gas chromatography combined with mass spectrometry. Non-detects were substituted by one-half the limit of detection. Over the 30 years of monitoring, concentrations of all of the pollutants decreased at all sampling sites. Since the beginning, TBZ and DET residues have been systematically lower than ATR and DEA, respectively, with more than 70% of the data below the limit of detection and never exceeding the European Maximum Acceptable Concentration (MAC) for a single pesticide (0.1 μg/L). The highest concentrations of ATR and DEA showed a spatial shift along the flow direction, suggesting an increase in groundwater residence time from the recharge zone to the accumulation zone of the aquifer. The last residues of ATR were found 27 years after its ban. Although all of the concentrations were lower than those found elsewhere in Europe, the sum of s-triazines overcame the MAC in 20% of the samples. Considering the structural and toxicological similarities of s-triazines, these findings confirm the necessity of better characterisation of the toxicological risk posed by mixtures
A tracer test in a shallow heterogeneous aquifer monitored via time-lapse surface electrical resistivity tomography
No full textWe illustrate a case study of a saline tracer test in a shallow, highly heterogeneous aquifer, monitored by means of surface time-lapse ERT. The test was aimed at identifying the system's hydraulic properties. Some of the expected limitations of the method particularly caused by the strong decrease in ERT resolution with depth and the consequent problems with mass balance and moment calculation could be partly balanced by the use of direct measurements of groundwater electrical conductivity and tracer concentration at one selected location. The vast heterogeneity of the system, ranging in litholotty from clay to gravel at a scale of meters to tens of meters, reflects itself in the tracer migration and distribution over time: The tracer is trapped in the low-permeability regions and from these it is slowly released over time. High-resolution surface ERT proves effective at picturing this system behavior over time. The extreme heterogeneity is also a challenge in the attempt to translate bulk electrical conductivity into estimates of groundwater electrical conductivity and, hence, solute concentration because surface conductivity in fine sediments has an important role. The test results could be used to identify some of the key parameters for solute transport, namely, mean groundwater velocity and aquifer dispersivity at the scale of the test by means of transport model calibration
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
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
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