Nitrate Groundwater Pollution and Aquifer Vulnerability: the Case of the Osona Region
Total Page：16
File Type：pdf, Size：1020Kb
NITRATE GROUNDWATER POLLUTION AND AQUIFER VULNERABILITY: THE CASE OF THE OSONA REGION Mercè BOY ROURA Dipòsit legal: Gi. 1506-2013 http://hdl.handle.net/10803/124042 ADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs. ADVERTENCIA. El acceso a los contenidos de esta tesis doctoral y su utilización debe respetar los derechos de la persona autora. Puede ser utilizada para consulta o estudio personal, así como en actividades o materiales de investigación y docencia en los términos establecidos en el art. 32 del Texto Refundido de la Ley de Propiedad Intelectual (RDL 1/1996). Para otros usos se requiere la autorización previa y expresa de la persona autora. En cualquier caso, en la utilización de sus contenidos se deberá indicar de forma clara el nombre y apellidos de la persona autora y el título de la tesis doctoral. No se autoriza su reproducción u otras formas de explotación efectuadas con fines lucrativos ni su comunicación pública desde un sitio ajeno al servicio TDR. Tampoco se autoriza la presentación de su contenido en una ventana o marco ajeno a TDR (framing). Esta reserva de derechos afecta tanto al contenido de la tesis como a sus resúmenes e índices. WARNING. Access to the contents of this doctoral thesis and its use must respect the rights of the author. It can be used for reference or private study, as well as research and learning activities or materials in the terms established by the 32nd article of the Spanish Consolidated Copyright Act (RDL 1/1996). Express and previous authorization of the author is required for any other uses. In any case, when using its content, full name of the author and title of the thesis must be clearly indicated. Reproduction or other forms of for profit use or public communication from outside TDX service is not allowed. Presentation of its content in a window or frame external to TDX (framing) is not authorized either. These rights affect both the content of the thesis and its abstracts and indexes. DOCTORAL THESIS NITRATE GROUNDWATER POLLUTION AND AQUIFER VULNERABILITY: THE CASE OF THE OSONA REGION Mercè Boy Roura 2013 DOCTORAL THESIS NITRATE GROUNDWATER POLLUTION AND AQUIFER VULNERABILITY: THE CASE OF THE OSONA REGION Mercè Boy Roura 2013 PROGRAMA DE DOCTORAT EN CIÈNCIES EXPERIMENTALS I SOSTENIBILITAT Dirigida per: Dr. Josep Mas-Pla Dra. Anna Menció Domingo Departament de Ciències Ambientals Universitat de Girona Memòria presentada per optar al títol de doctora per la Universitat de Girona La memòria “Nitrate groundwater pollution and aquifer vulnerability: the case of the Osona region” ha estat realitzada per la Mercè Boy Roura per a l’obtenció de la Menció Internacional en el títol de Doctora, sota la direcció del Dr. Josep Mas-Pla i la Dra. Anna Menció, de l’Àrea de Geodinàmica Externa del Departament de Ciències Ambientals de la Universitat de Girona. Dr. Josep Mas-Pla Dra. Anna Menció Domingo Mercè Boy Roura Girona, Juliol del 2013 CONTENTS Abstract ……………………………..………………………..……………………………………..………………………. vii Resum ……………………………..………………………..……………………………………..………………………… ix Resumen ……………………………..………………………..……………………………………..…………………….. xiii List of publications ……………………………..………………………..……………………………………..………. xvii Acknowledgments ……………………………..………………………..…………………………………..…………. ix CHAPTER 1 – General introduction ………………………………..………………………..…………………… 1 1.1 – The state of the water resources 3 1.1.1 – Groundwater resources 5 1.1.2 – Groundwater quality 5 1.1.3 – Nitrate in groundwater 6 1.2 – A case study: the nitrate problem in the Osona region 19 1.2.1 – Geographical situation 19 1.2.2 – Geological setting 20 1.2.3 – Hydrogeological setting 26 1.2.4 – Climatology 28 1.2.5 – Agricultural and livestock activities 29 1.3 – Literature review 32 1.4 – Objectives 35 1.5 – Structure of the doctoral thesis 35 CHAPTER 2 – Analysis of vulnerability factors that control nitrate occurrence in natural 39 springs ……………………………..………………………..……………………………………..…………………… 2.1 – Introduction 41 2.2 – Spring classification 45 2.3 – Methodology 48 2.3.1 – Sampling, chemical analysis, and spring classification 48 2.3.2 – Hydrochemical background determination 48 2.3.3 – Statistical analysis 49 2.4 – Results and discussion 51 2.4.1 – Nitrate distribution and temporal evolution 51 2.4.2 – Background analysis 53 2.4.3 – Statistical analysis of major factors affecting nitrate in springs 54 2.5 – Conclusions 58 i CHAPTER 3 - Temporal analysis of spring water data to assess nitrate inputs to 61 groundwater in an agricultural area …………………..………………………..………………………… 3.1 – Introduction 63 3.2 – Geological and hydrogeological setting 66 3.2.1 – Regional geology and hydrogeology 66 3.2.2 – Spring characterization 67 3.2.3 – Meteorology 68 3.3 – Methodology 69 3.3.1 – Field sampling and chemical analysis 69 3.3.2 – Exploratory statistics and geostatistical analyzes 70 3.4 – Results 71 3.4.1 – Hydrochemistry of the springs 71 3.4.2 – Discharge, electrical conductivity and nitrate time series 74 3.4.3 – Nitrate accumulated mass load 77 3.4.4 – Geostatistical analysis 79 3.5 – Discussion 84 3.6 – Conclusions 87 CHAPTER 4 - Regression model for aquifer vulnerability assessment of nitrate pollution 89 in Osona …………………..………………………..……………………………………..………..…………………. 4.1 – Introduction 91 4.2 – The study area 93 4.3 – Methodology 96 4.3.1 – Calibration data set 96 4.3.2 – Explanatory variables 97 4.3.3 – Model development and vulnerability maps 100 4.4 – Results and discussion 102 4.4.1 – Calibration data set 102 4.4.2 – Examination of the explanatory variables through calibration process 102 4.4.3 – Model building 104 4.4.4 – Validation of the model 109 4.4.5 – Vulnerability maps 109 4.5 – Conclusions 114 CHAPTER 5 – General discussion ……..………………….………………………..…………………………….. 117 CHAPTER 6 – General conclusions .………………………..…………………………………………………..… 127 References ……………………………..………………………..……………………………………..………………….. 133 ii LIST OF FIGURES Figure 1.1 – Water uses by sector 3 Figure 1.2 – Water source by sector 4 Figure 1.3 – The biogeochemical nitrogen cycle 7 Figure 1.4 – Water cycle and sources of nitrogen pollution 10 Figure 1.5 –European groundwater bodies with poor chemical quality due to nitrates 13 Figure 1.6 – Groundwater quality monitoring sites in Spain with occurrence of nitrate 15 Figure 1.7 – Nitrate concentrations in groundwater and water public supply in Catalonia 15 Figure 1.8 – Situation of the Osona region and its main geographical units 20 Figure 1.9 – Geological map with cross-sections representative of Plana de Vic 24 Figure 1.10 – Stratigraphic column and geological cross-sections of Plana de Vic 25 Figure 1.11 – Potentiometric map of the Plana de Vic hydrogeological system 27 Figure 1.12 – Climatogram for the Osona region (data from 1940 to 2000) 29 Figure 1.13 – Land uses of the Osona region 30 Figure 1.14 – Evolution of head of pigs from 1961 to 2011 in Spain 31 Figure 1.15 – Evolution of head of pigs and AFOs in Osona from 1982 to 2009 31 Figure 2.1 – Map of the geographical and geological setting of springs and study area 43 Figure 2.2 – Spring typology according to geological setting 47 Figure 2.3 – Nitrate evolution (in mg/L) represented by box plots, precipitations and 52 potential evapotranspiration (in mm), during the study period Figure 2.4 – Cumulative plot distribution of NO3--N in the study area, and determination 54 of the background threshold Figure 2.5 – Error bar diagrams for nitrate concentration vs. land use and geological 59 setting 1 (95% confidence) Figure 2.6 – Error bar diagrams for nitrate concentration vs. land use and geological 59 setting 2 (95% confidence) Figure 3.1 – Map of the geographical and geological setting of springs and the study 64 area, with the locations and characteristics of the springs Figure 3.2 – Conceptual scheme of subsurface flow feeding a spring and the aquifer in a 66 similar geological setting Figure 3.3 – Springs and their surrounding areas representative of each Hydrological 68 Response Type (HRT) Figure 3.4 – Evolution of rainfall, discharge, EC and nitrate concentration over the 75 sampling campaigns for springs belonging to Hydrological Response Type 1 (HRT 1) iii Figure 3.5 – Evolution of rainfall, discharge, EC and nitrate concentration over the 76 sampling campaigns for springs belonging to Hydrological Response Type 2 (HRT 2) Figure 3.6 – Evolution of rainfall, discharge, EC and nitrate concentration over the 76 sampling campaigns for springs belonging to Hydrological Response Type 3 (HRT 3) Figure 3.7 – Evolution of rainfall, discharge, EC and nitrate concentration over the 77 sampling campaigns for springs belonging to Hydrological Response Type 4 (HRT 4) Figure 3.8 – Normalized nitrate accumulated