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Caratterizzazione geochimica di vapor d’acqua nella Laguna di Venezia
No full textGli isotopi stabili di idrogeno e ossigeno sono ottimi traccianti dei processi atmosferici del ciclo idrologico. Recentemente si è osservato un forte interesse della comunità scientifica verso la composizione isotopica del vapore acqueo nella bassa troposfera grazie ai recenti sviluppi nel campo della spettroscopia. In questa tesi la composizione isotopica del vapore acqueo viene indagata assieme alle principali fasi con cui esso può interagire all’interno del PBL veneziano, cioè le acque superficiali della Laguna di Venezia e le precipitazioni. L’obiettivo dello studio è quindi determinare quali siano i principali processi che governano la composizione isotopica del vapore in una laguna costiera, spaziando da quelli vicino all’interfaccia acqua-aria a quelli di trasporto a lunga distanza. Il vapore acqueo è stato campionato sia in maniera discreta (intrappolamento criogenico) che analizzato in continuo mediante Cavity Ring-Down Spectroscopy. In aggiunta alle analisi isotopiche sono state effettuate anche alcune analisi chimiche esplorative sui campioni ottenuti con intrappolamento criogenico. Ne risulta che il contributo dell’evaporazione delle acque superficiali all’umidità nella bassa troposfera è il processo principale che governa la composizione isotopica nell’area di studio. Eventuali contributi dall’atmosfera libera sono risultati importanti in condizioni di alta pressione. L’analisi chimica dei campioni di vapore ha invece evidenziato alcune potenziali sorgenti di inquinamento nell’area di studio
Regional geographic traceability of Treviso Red Chicory
Full text linkFood traceability is the ability to track any food through food supply chain, from production to distribution, from where the food came (one step back) and to where the food will go (one step forward). Food geographical origin is essential to protect regional designation, ensure fair competition, prevent diffusing of food pathogen and, last but not least, improve consumer confidence. The technique of stable isotopes is an effective tool for food origin assessment and to recover consumers’ confidence; it’s generally adopted to various food such as wine, honey, coffee, dairy, vegetables, meat and so on. The aim of this work is to check the geographical origin of Treviso Red Chicory (tardivo and precoce varieties) applying the stable isotopes technique. Several environmental matrices (i.e. oil, water and vegetable) will be examined to ensure the uniqueness and quality of the final product. Two areas were investigated in Veneto (NE of Italy): the former, located in Treviso province, is regulated by the Consortium of variegated Red Chicory of Treviso and Castelfranco; the latter is located in Padova province and is not regulated by the Consortium. Approximately, 89 Chichory samples (63 for tardivo and 26 for precoce varieties) and 68 soil samples (taken at different depth: 0-20 cm and 20-40 cm) were collected. A monthly precipitation sampling (started from October 2015) were conducted in the study areas and 4 irrigation water samples were also collected. The next step of this work, focused on the stable isotope analysis of the above mentioned matrices, will hopefully give the isotopic signature of the examined product
A versatile water vapor generation module for vapor isotope calibration and liquid isotope measurements
Full text linkA versatile vapor generation module has been developed for both field-based water vapor isotope calibrations and laboratory-based liquid water isotope measurements. The vapor generation module can generate a stream of constant vapor at a wide variety of humidity levels spanning 300 to 30 000 ppmv and is fully scalable, allowing in principle an unlimited number of standards or samples to be connected to a water vapor isotope analyzer. This versatility opens up the possibility for calibrating with multiple standards during field deployment, including examining instrument humidity-isotope dependence. Utilizing the ability to generate an uninterrupted constant stream of vapor, we document an Allan deviation for 17O-excess (Delta 17O) of less than 2 per meg for an approximate 3 h averaging time. For similar averaging time, the Allan deviations for delta 17O, delta 18O, delta D, and d-excess are 0.004 parts per thousand, 0.005 parts per thousand, 0.01 parts per thousand, and 0.04 parts per thousand, respectively. Measuring unknown samples shows that it is possible to obtain an average standard deviation of 3 per meg for Delta 17O and an average standard error (95 % confidence limit) of 5 per meg.Using the vapor generation module, we document that an increase in the Allan deviation above the white noise level for integration times between 10 min and 1 h is caused by cyclic variations in the cavity temperature, which if improved upon could result in an improvement in liquid sample measurement precision of up to a factor of 2. We further argue that increases in Allan deviation for longer averaging times could be a result of memory effects and not only driven by instrumental drifts as it is often interpreted.The vapor generation module as a calibration system has been documented to generate a constant water vapor stream for more than 90 h, showing the feasibility of being used to integrate measurements over much longer periods than achievable with syringe-based injections as well as allowing the analysis of instrument performance and noise. Using clean in-house standards, we have operated the vapor generation module daily for 1-3 h for more than 6 months without the need for maintenance, illustrating its potential as a field-deployed autonomous vapor isotope calibration unit. When operating the vapor generation module for laboratory-based liquid water isotope measurements, we document a more than 2 times lower memory effect compared to a standard autosampler system
Sources and distribution of tracer elements in road dust: The Venice mainland case of study
No full textRoad dust is an important non-exhaust traffic source of atmospheric particulate matter, from re-suspension of finer particles carried out by wind and traffic flow. Particles of road dust have both natural and anthropogenic origin; the latter is characterized by higher concentrations of several pollutants and are significantly emitted by other non-exhaust traffic source such as the brake and road wear process. Therefore the discrimination between atmospheric particles directly emitted from abrasion process and those related to re-suspension is currently an open issue.
Unlike the exhaust sources related to the fuel combustion, the non-exhaust emissions are not regulated by Communitarian Directives, although their percentage contribution is becoming more relevant due to the recent technological upgrades in the automotive field, focused on the reduction of exhaust emissions.
In this work we studied the morphology and the chemical composition of road dust particles collected on urban, sub-urban and rural roads of Venice mainland (Northern Italy) in August 2013. Results of SEM-EDS and ICP-OES were processed with statistical tools (i.e., enrichment factors and principal components analysis) in order to identify the main pollutant sources affecting the monitored areas. Peculiar associations among Cr, Mn, Zn, Cu, Fe suggested brake pads and tires wear as the dominant source of these elements, whereas the presence of Pb, Co, Ba, Ti was attributed to the tear of the painted horizontal signals. Moreover, the presence of particles originated from the latter source was also confirmed by the presence of glass beads with diameters ranging from 20 μm to 250 μm
Human and environmental factors affecting the activity of 131I and 137Cs in urban wastewater: A case study
No full textThe analysis of radionuclides content in the waste product of urban wastewater treatment (i.e. sewage sludges) is of great concern for both the safety of workers and in a re-use perspective of the final product. The study of the behavior and the partitioning of radionuclides into sewage sludge samples can be useful not only to determine engineering issues in removal efficiency of radioactive pollutants, but also to determine the factors affecting the content and trends of radionuclides (natural and artificial) in urban wastewater systems. In this study we determine people-related and environmental factors that affect the activity of 131I (nuclear medicine) and 137Cs (fallout) in urban wastewater in a large area of northern Italy. 624 sewage sludge samples coming from 17 wastewater treatment plants were collected between 2012 and 2017 and analyzed with high resolution gamma-spectrometry. In addition to 131I and 137Cs, also the following radionuclides were analyzed for the periodic monitoring: 7Be, 40K, 60Co, 67Ga, 111In, 125I, 134Cs, 192Ir, 201Tl. 131I is the most frequently detected artificial radionuclide in sewage sludge samples (56%), showing a large variability (mean activity ± standard deviation 93 ± 184 Bq kg−1). The detection frequency of this radionuclide is significantly correlated to population density (R = 0.75, p-value<0.01) and its activity concentration is significantly correlated to wastewater treatment plant size, expressed in population equivalents (R = −0.56, p-value<0.05). The detection frequency of 131I in sewage sludge samples is modeled as a function of population density, sewer length, inflow rates and population equivalents, accounting for 83% of the variability of observations. Despite the frequency of detection, the activity of 131I was relevant for workers safety only in less than 0.5% of the cases. On the other hand, 137Cs is detected in 36% of samples and its activity shows high correlation with mean annual precipitation (R = 0.67, p-value<0.01) and the activity of natural radionuclides (R = 0.58 and 0.63, for 7Be and 40K, respectively, p-values <0.05). With a hybrid geostatistical model, we demonstrate that the spatial pattern of 137Cs activity in wastewater estimated from sewage sludge samples is consistent with soil contamination from Chernobyl fallout. Moreover, we hypothesize a possible horizontal transport of 137Cs in the study area highlighted by different trends of 137Cs activity concentration in sludges. The results of this study depict the sensitivity of sewage sludges to the persistent contamination of 137Cs, after 30 years from Chernobyl accident, and can be used as a database for future monitoring activities after any accident that includes the spreading of radioactive materials into the environment
Isotopic composition of water vapor near the air-water interface
Full text linkEvaporation is a key process in water cycle that links liquid water to the atmosphere. In the last fifty years stable
isotopes of hydrogen and oxygen have been intensively used to describe climate processes related to evaporation
and precipitation, ranging in different spatial and temporal scales. Evaporation introduces large isotopic effects
in the phases involved. The well known Craig-Gordon model (Craig & Gordon, 1965) describes those isotopic
effects involving several steps and different processes, moving from the air-water interface to the free atmosphere.
However, very few works in literature have tested the vertical behavior of the Craig-Gordon model in natural
conditions on both fresh and marine waters. In this work we present the results from four field experiments aimed
to describe the vertical variability of δ18O and δD in the first few meters over a large water body (the coastal
lagoon of Venice, northern Italy) and to test the Craig-Gordon model in such conditions. Each experiment involved
cryotrapping of water vapor at different height over the water surface (0.1m, 2m and 4m) and the sampling of the
liquid water at two depth (surface and 0.5m). During the experiments, water vapor was also sampled in the nearest
mainland (~2.5 km from gradient measurements) to determine the isotopic composition of background water vapor.
Liquid samples were then analyzed with a Picarro L1102-i and Thermo-Fisher Delta Plus Advantage for water
vapor and lagoon water, respectively. The last two experiments have also involved simultaneous measurements
of relative humidity using commercially-available humidity probes at each height. This approach was used to
determine a reference scale in order to compare observations to modeled estimates. Despite the coarse time
resolution due to cryotrapping method (measurements are averaged over 1.5 hours), preliminary results show
measurable differences in the isotopic composition of water vapor along the vertical gradient and good agreement
between observations and predicted values from the model. Even if this work is an exploratory phase it shows an
interesting potential to grow our understanding of the processes involved as well as a useful implementation for
future studies focused on fractionation of water isotopes due to evaporation in natural conditions
Characterization of a customized calibration unit for continuous measurements of the isotopic composition of water vapor
Full text linkThe objective of this work is the development, standardization and creation of a method to carry out continuous
measurement of oxygen and hydrogen isotopic composition of the atmospheric water vapor using a wavelengthscanned cavity ring down spectroscopy (WS-CRDS) instrument produced by Picarro, L1102-i model.
Some technical improvements of the standard instrument configuration have been made to create three different
inlet gas lines: a “standard” line, a calibration line and a line connected with the external sampler.
The calibration line is composed of a syringe-pump that continuously injects standard water into a steel tee
heated at the temperature of 170◦C and flushed with dry nitrogen gas. In this way, instantaneous and complete
vaporization of the standard water takes place. The resulting steam is characterized by a well-defined composition
in δD e δ18O values.
To allow comparison with other international data, we have characterized the individual instrumental response to
variation of the isotopic composition of the water vapor. Several humidity-isotope response functions (6000-26000
ppmv) have been estimated with three different internal standards (0.35h -8.75h -29.11h and -40.28h for
δ18O; 2.31h -58.91h -222.19h and -317.78h for δD).
Moreover, we have measured the instrumental drift at regular time intervals to apply the opportune corrections to
instrument data.
The setup has been tested using a 3.5 day continuous measurements carried out with the Picarro sampling the
water vapor outside our campus in Venice and parallel sampling using the classical cryogenic trapping procedure,
obtaining excellent results. Furthermore, our analysis technique has given good results for the standards with
values which are similar to those obtained with the isotope ratio mass spectrometry (IRMS) technique
Characterization of Rare Earth Elements in Scheelite (CaWO4) with Ion Beam Induced Luminescence
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