1,720,962 research outputs found
S.TR.E.A.M., system for trace element assessment with mosses. An equation to estimate mercury concentration in freshwaters
No full textHundred experiments of Hg bioaccumulation with the aquatic moss Rhynchostegium riparioides (Hedw.) C.E.O. Jensen transplanted under laboratory conditions were carried out with the aim of (1) measuring the metal uptake at increasing water concentrations (0.25–128 μg Hg2+ L−1) and increasing exposure time (24–189 h), (2) studying the influence of pH (6.3–8.5) and water concentration of Na (3–114 mg L−1), Ca (62–125 mg L−1) and Mg (13–54 mg L−1) on the metal uptake, (3) achieving a database for mathematical and statistical elaborations, and, (4) producing an equation modelling the uptake. A linear uptake was observed for water concentrations 0.05) in the Hg uptake ratio (0.496 × 105 <= Bio Accumulation Factor <= 1.73 × 105). From a database of 28 Hg concentrations in mosses exposed to 0.25–4 μg Hg2+ L−1 for 24–114 h, a mathematical equation was produced, to assess Hg micro-contamination in water. The difference between predicted and real concentration was generally included in the range ± 50%
Assessment of intermittent trace element pollution by moss bags
No full textMoss bags of the aquatic bryophyte Rhynchostegium riparioides (Hedw.) C. Jens. were transplanted into an irrigation ditch in the Province of Vicenza (NE Italy), affected by intermittent trace element contamination due to galvanics. The study aimed at: (a) testing the ability of mosses to detect different patterns of pollution, (b) providing information about intensity and temporal extension of pollution events, and (c) localising the main sources. Moss bags were collected after 20, 34, 48 and 62 days of exposure. The concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn in the desiccated apical shoots of mosses were determined by atomic absorption spectrophotometry. The mean concentrations measured in non-contaminated stations of a previous work were adopted as background values, to calculate the contamination factor (CF). Transplants were able to: (a) detect spatial patterns of bioaccumulation, (b) reveal chronic contamination by Pb and Cu, intermittent contamination by Cr, Zn..
Development of a standard protocol for monitoring trace elements in continental waters with moss bags: inter- and intraspecific differences
No full textThis paper is a contribution for validating a standard method for trace element monitoring based on transplants and analysis of aquatic bryophytes, in the framework of the EC Directive 2000/60. It presents the results of an experiment carried out to assess significant differences in the amount and variability of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in three moss species (Cinclidotus aquaticus, Fontinalis antipyretica, Platyhypnidium riparioides) and two different parts of the moss (whole plant vs apical tips). Mosses were caged in bags made of a plastic net and transplanted for 2 weeks to an irrigation canal impacted by a waste water treatment plant. Trace element concentrations were measured by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) before and after exposure to the experimental and control sites in five samples. Enrichment factors >>2 were found for Cu, Ni, Mn, Pb and Zn in all moss species, lower in C. aquaticus, intermediate in F. antipyretica and higher in P. riparioides (the species we recommend to use). The analysis of apical tips after exposure instead of the whole plant led to (I) lower concentrations of As, Co, Cr, Fe and Zn in C. aquaticus (−7 to −30 %) and of Fe and Pb (−13, −18 %) in P. riparioides, (II) higher concentrations of Cu, Ni and Zn (+14 to +18 %) in P. riparioides, while (III) no significant difference (p > 0.05) in F. antipyretica. Data variability after exposure was generally lower in apical tips, especially in C. aquaticus and in F. antipyretica, less in P. riparioides. In the aim of standardizing the moss-bag technique, the analysis of apical tips is recommended
A factor influence study of trace element bioaccumulation in moss bags
No full textMoss bags of Rhynchostegium riparioides were exposed to different water concentrations of 11 trace elements under laboratory conditions, according to a saturated fractional factorial design (67 treated combinations), with the aim of measuring (1) element uptake and (2) the main effects and first-order interactions of influent factors. Bioaccumulation was direct proportional to water concentration, but the uptake ratio also depended on the concentration of other metals. The highest uptake ratios were observed for Al, Cu, Cr, Hg, and Pb. The multiple regression model showed that the interactions among elements exist and induce both antagonism (Fe is the most frequent competitor) and synergism (Cr exerts a great influence on Pb and Zn uptake). Interactions might be relatively strong (as for As, Cr, and Pb) or weak (Cd and Hg). This evidence should be taken into consideration in biomonitoring surveys of industrial sites, where effluents release more than one contaminant
Trapianti di briofite acquatiche per il biomonitoraggio dei metalli in traccia: risultati e prospettive della tecnica dei moss bags dopo 10 anni di studi fra Veneto e Friuli-Venezia Giulia
No full textFra gli obiettivi del monitoraggio chimico delle acque previsto dalla Direttiva Quadro 2000/60/CE vi è la sorveglianza delle sostanze prioritarie, fra le quali si annoverano alcuni metalli pesanti che spesso generano forme d’inquinamento sporadiche o intermittenti. Ciò, sommato alla promiscuità dell’utilizzo del territorio, all’inadeguatezza della rete fognaria o degli impianti di trattamento ed all’impossibilità di controllare le sorgenti puntiformi, può determinare situazioni che generano rischi ambientali particolarmente insidiosi. Il monitoraggio biologico ed anche quello chimico basato sul campionamento dell’acqua non possono procurare informazioni rappresentative sulla reale presenza di metalli nell’ambiente, né sulla loro disponibilità biologica. L’utilizzo di accumulatori, soprattutto quelli biologici come le briofite, consente invece di ottenere stime sensibili ed integrate del livello di alterazione ambientale da metalli nella sola frazione biodisponibile. Le briofite acquatiche sono utilizzate con successo da oltre 40 anni nei più svariati contesti ambientali d’Europa e si configurano come i migliori strumenti oggi a disposizione per il monitoraggio dei metalli. Il Dipartimento di Scienze della Vita dell’Università di Trieste è impegnato da circa dieci anni in attività di studio, calibrazione ed applicazione dei trapianti di muschio (moss bags) sul territorio veneto e friulano. Questa metodica semplice ed efficace è già a disposizione degli Enti locali grazie alla collaborazione con le Agenzie Regionali per la Protezione Ambientale ed attende ora di essere standardizzata attraverso un progetto nazionale patrocinato dall’ISPRA
Moss bags as sentinels for human safety in mercury-polluted groundwaters
No full textAn equation to estimate Hg concentrations of <4 μg/L in groundwaters of a polluted area in NE Italy was set out by using transplants of the aquatic moss Rhynchostegium riparioides as trace element bioaccumulators. The equation is derived from a previous mathematical model which was implemented under laboratory conditions. The work aimed at (1) checking the compliance of the uptake kinetics with the model, (2) improving/adapting the model for groundwater monitoring, (3) comparing the performances of two populations of moss collected from different sites, and (4) assessing the environmental impact of Hg contamination on a small river. The main factors affecting Hg uptake in the field were—as expected—water concentration and time of exposure, even though the uptake kinetics in the field were slightly different from those which were previously observed in the lab, since the redox environmental conditions influence the solubility of cationic Fe, which is a negative competitor of Hg2+. The equation was improved by including the variable ‘dissolved oxygen concentration’. A numerical parameter depending on the moss collection site was also provided, since the differences in uptake efficiency were observed between the two populations tested. Predicted Hg concentrations well fitted the values measured in situ (approximately ±50 %), while a notable underestimation was observed when the equation was used to predict Hg concentration in a neighbouring river (−96 %), probably due to the organic pollution which hampers metal uptake by mosses
Oven-dried mosses as tools of trace element detection in polluted waters: a preliminary study under laboratory conditions
No full textThe concentration of 11 trace elements, plus Ca, Mg, Na and K was measured in moss bags of living and dead (oven-dried at 105°C) Platyhypnidium riparioides after a 1-week exposure to tap water, and to 0.21, 1.0, 2.5 and 4.0 μM solutions under laboratory conditions, with the aim of (1) observing the accumulation curves and (2) performing a statistical comparison in element concentrations. Uptake occurred both in living and in dead mosses following similar patterns in the two materials: a linear uptake was observed for Cd and Ni, a saturation curve for As, Cu, Hg and Pb, an unclear trend for Al and Mn and a trend leading to a maximum for Cr and Fe. An evident efflux of K indicated alterations in cell membrane permeability in living mosses and cellular damage in dead mosses. Living mosses accumulated higher concentrations of Cr (+4/+49%) and Mn (+124/+216%), while dead mosses accumulated higher concentrations of Cd (+13/+50%), Cu (+26/+51%), Ni (+22/+139%) and Zn (+22/+63%). Dead mosses maintained a considerable uptake efficiency for several trace elements, and sometimes even increased it as compared with living mosses, thus proving to be suitable for standard kits
Palladio, an Index of Trace Element Alteration for the River Bacchiglione Based on Rhynchostegium riparioides Moss Bags
No full textThe concentration of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, V and Zn was measured in the aquatic bryophyte Rhynchostegium riparioides after a 4-week transplantation at 83 stations in seven main watercourses and three smaller tributaries of the basin of the River Bacchiglione (NE Italy). The study, carried out in 9 months, aimed at establishing a database for statistical analyses to define a novel index of water quality, specifically calibrated for moss bags, and suitable for bio-monitoring purposes where autochthonous bryophytes are not available. The background level was estimated for each element, the ratio between sample and background concentration was adopted as measure of environmental alteration and a five-class interpretation scale was defined. The 73.8% of measured concentrations reflected a condition of naturality, 16.6% suspect of alteration, 7.6% sure alteration, 1.6% severe alteration and <0.5% extreme alteration. The condition of global environmental alteration (all contaminants) at each station was also defined. Forty-four stations presented absence or suspect of alteration, 39 sure alteration for one or more elements. Bivariate and multivariate analyses revealed (1) highly significant correlations (p < 0.001) between the concentrations of Co–Mn, Sb–Zn, and Fe–V, depending on both natural and human factors, (2) chemical patterns leading to galvanic industries, metallurgy or urban sewages, in some case with a geographical distribution and (3) a gradient of environmental alteration from the Pre-Alps to the lowland. Coloured maps indicate both point sources and widespread environmental alteration, highlighting not only industrial–urban areas but also some apparently undisturbed sites
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
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