This document is the product of an internship at centro RIVE (Risorse Idriche Venete), a research center on water resources made up by Viacqua and Etra. The present vision of the team is the study of the hydrological structures in the venetian plain (mainly in the Vicenza province) and its relationship with the external factors on the area, the monitoring of water quality and the support for the development of water safety plans. The aim of this thesis is to recognize some underground water pollution episodes in the venetian plane between Astico and Agno river using some geostatistical tools; this area has been exploited for drinkable water by a large number of wells. As observed in many other plains characterized by a widespread presence of industries, the water quality of aquifers is often a target for various chemicals and compounds that may pose danger for human health. For this reason, a clear understanding of the past contamination events, as well as their impact on aquifer water quality, is very important for a management scenario; it is also a tool for evaluating the possible fate of future pollution cases. In this context, geostatistical analysis of existing data may give useful information. Unfortunately, various limitations can alter the quality of the results obtained; this uncertainty, coming from insufficient data, uneven distribution of the observed points and overall measurement variance is always present when analyzing “real world” data and the goal is only to reduce it. A great number of parameters regarding water quality is present; obviously this study cannot comprehend the analysis on the 20+ compounds present in typical laboratory test results. For this reason, thanks to past publications and the historical memory of people involved in water quality analysis, some compounds like solvents, nitrates and various pesticides are known to be concerning and therefore are selected to be studied. Furthermore, nitrates and solvents are known to be the main historical contaminations in the area characterized by industries and intensive agriculture; pesticides are different because their pattern of contamination is linked also to their metabolites. This aspect is also linked to the framework of the emerging contaminants (or contaminants of emerging concern); some compounds, if not all of them, are naturally evolving and sometimes the by-products can be as dangerous as the original compound. The methodology used for evaluation of the contamination episodes follows a logical pattern which is briefly described: the first step of the process to reach the goal is to gather and organize data. This thesis comprehends water quality analysis from 1981 to 2021 coming from various entities: Viacqua, AcegasAPS, ATO (Ambito Territoriale Ottimale) Bacchiglione, CIN (Centro Idrico di Novoledo), SPV (Strada Pedemontana Veneta), ULSS (Unità Locale Socio-Sanitaria). Then, some descriptive statistics and plots of time series are presented to recognize the overall behavior of the analyzed contaminant and the time evolution of it. After that, geostatistical tools like variograms and kriging are implemented: the overall understanding of the pollution episode can be achieved only by observing all the steps. Following this methodology, solvents contamination is observed to propagate from the upper plain towards S-E, presenting a gradual depletion in the last decade. Nitrate contamination is present in the most productive agricultural areas of the domain, and the concentrations after a initial increase in the 90's tend to stabilize. Finally, triazinic pesticides are observed throughout the decades in the domain; the geostatistical analysis is reserved only to DACT (a triazinic metabolite). Future improvements can be obtained by considering other geostatistical tools, by quantifying the spatial distribution of the various loads of contaminant and by improving the knowledge of the stratigrapghy of wells.
Questo documento è frutto di uno stage presso il centro RIVE (Risorse Idriche Venete), un centro di ricerca sulle risorse idriche formato da Viacqua ed Etra. La visione attuale del team è lo studio delle strutture idrologiche nella pianura veneta (principalmente in provincia di Vicenza) e il suo rapporto con i fattori esterni sul territorio, il monitoraggio della qualità dell'acqua e il supporto allo sviluppo di piani di sicurezza delle acque (PSA) . Lo scopo di questa tesi è di riconoscere alcuni episodi di inquinamento delle acque sotterranee nella pianura veneta tra il fiume Astico e il fiume Agno utilizzando alcuni strumenti geostatistici; quest'area è stata sfruttata per scopi potabili da un gran numero di pozzi. Come osservato in molte altre pianure caratterizzate da una diffusa presenza di industrie, la qualità dell'acqua delle falde acquifere è spesso un bersaglio per vari prodotti chimici e composti che possono rappresentare un pericolo per la salute umana. Per questo motivo, una chiara comprensione degli eventi di contaminazione passati, nonché del loro impatto sulla qualità delle acque di falda, è molto importante per uno scenario gestionale; è anche uno strumento per valutare il possibile destino di futuri casi di inquinamento. In questo contesto, l'analisi geostatistica dei dati esistenti può fornire informazioni utili. Purtroppo, varie limitazioni possono alterare la qualità dei risultati ottenuti; questa incertezza, derivante da dati insufficienti, distribuzione non uniforme dei punti osservati e varianza complessiva delle misurazioni è sempre presente quando si analizzano dati ambientali misurati. È presente un gran numero di parametri riguardanti la qualità dell'acqua; ovviamente questo studio non può comprendere l'analisi sui 20+ composti presenti nei normali test di laboratorio. Per questo motivo, grazie alle pubblicazioni passate e alla memoria storica delle persone coinvolte nell'analisi della qualità dell'acqua, alcuni composti come solventi, nitrati e pesticidi sono noti per essere contaminanti nell'area e quindi vengono selezionati per essere studiati. La metodologia utilizzata per la valutazione degli episodi di contaminazione segue uno schema logico che viene brevemente descritto: il primo step è la raccolta e l'organizzazione dei dati. Questa tesi comprende l'analisi della qualità delle acque dal 1981 al 2021 provenienti da vari enti: Viacqua, AcegasAPS, ATO (Ambito Territoriale Ottimale) Bacchiglione, CIN (Centro Idrico di Novoledo), SPV (Strada Pedemontana Veneta), ULSS (Unità Locale Socio-Sanitaria) . Successivamente vengono presentati alcuni indicatori statistici e grafici di serie temporali per riconoscere il comportamento complessivo del contaminante analizzato e l'evoluzione temporale di esso. Successivamente, vengono implementati strumenti geostatistici come variogrammi e kriging: la comprensione complessiva dell'episodio di inquinamento può essere raggiunta solo osservando tutti i passaggi. Seguendo questa metodologia, si sono studiati i casi di contaminazione da solventi, nitrati e pesticidi. Miglioramenti futuri possono comprendere l'uso di altri strumenti geostatistici, la quantificazione dei carichi di contaminanti utilizzati nell'area e la loro distribuzione spaziale. Infine una conoscenza complessiva delle stratigrafie dei pozzi analizzati potrebbe fornire indicazioni interessanti nell'area.
Spatio-temporal variability of groundwater quality in the High Venetian Plain between the Astico and Agno Rivers
MARCON, FRANCESCO
2021/2022
Abstract
This document is the product of an internship at centro RIVE (Risorse Idriche Venete), a research center on water resources made up by Viacqua and Etra. The present vision of the team is the study of the hydrological structures in the venetian plain (mainly in the Vicenza province) and its relationship with the external factors on the area, the monitoring of water quality and the support for the development of water safety plans. The aim of this thesis is to recognize some underground water pollution episodes in the venetian plane between Astico and Agno river using some geostatistical tools; this area has been exploited for drinkable water by a large number of wells. As observed in many other plains characterized by a widespread presence of industries, the water quality of aquifers is often a target for various chemicals and compounds that may pose danger for human health. For this reason, a clear understanding of the past contamination events, as well as their impact on aquifer water quality, is very important for a management scenario; it is also a tool for evaluating the possible fate of future pollution cases. In this context, geostatistical analysis of existing data may give useful information. Unfortunately, various limitations can alter the quality of the results obtained; this uncertainty, coming from insufficient data, uneven distribution of the observed points and overall measurement variance is always present when analyzing “real world” data and the goal is only to reduce it. A great number of parameters regarding water quality is present; obviously this study cannot comprehend the analysis on the 20+ compounds present in typical laboratory test results. For this reason, thanks to past publications and the historical memory of people involved in water quality analysis, some compounds like solvents, nitrates and various pesticides are known to be concerning and therefore are selected to be studied. Furthermore, nitrates and solvents are known to be the main historical contaminations in the area characterized by industries and intensive agriculture; pesticides are different because their pattern of contamination is linked also to their metabolites. This aspect is also linked to the framework of the emerging contaminants (or contaminants of emerging concern); some compounds, if not all of them, are naturally evolving and sometimes the by-products can be as dangerous as the original compound. The methodology used for evaluation of the contamination episodes follows a logical pattern which is briefly described: the first step of the process to reach the goal is to gather and organize data. This thesis comprehends water quality analysis from 1981 to 2021 coming from various entities: Viacqua, AcegasAPS, ATO (Ambito Territoriale Ottimale) Bacchiglione, CIN (Centro Idrico di Novoledo), SPV (Strada Pedemontana Veneta), ULSS (Unità Locale Socio-Sanitaria). Then, some descriptive statistics and plots of time series are presented to recognize the overall behavior of the analyzed contaminant and the time evolution of it. After that, geostatistical tools like variograms and kriging are implemented: the overall understanding of the pollution episode can be achieved only by observing all the steps. Following this methodology, solvents contamination is observed to propagate from the upper plain towards S-E, presenting a gradual depletion in the last decade. Nitrate contamination is present in the most productive agricultural areas of the domain, and the concentrations after a initial increase in the 90's tend to stabilize. Finally, triazinic pesticides are observed throughout the decades in the domain; the geostatistical analysis is reserved only to DACT (a triazinic metabolite). Future improvements can be obtained by considering other geostatistical tools, by quantifying the spatial distribution of the various loads of contaminant and by improving the knowledge of the stratigrapghy of wells.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/29552