Committee:
     PRESIDENT: MOURA BERODIA, JOSE LUIS
     SECRETARI: MARTÍNEZ DÍAZ, MARGARITA
     VOCAL NO PRESENCIAL: DE OÑA, ROCÍO
Thesis abstract: Bike’s recognition as a vital form of urban transportation underscores its capacity to enhance mobility, improve quality of life, and address several urban challenges such as air pollution, traffic congestion, and greenhouse gas emissions. This thesis explores bike’s potential, emphasizing the importance of developing infrastructure, involving the community in mobility planning, and promoting policies to maximize its benefits.The study employs a dual-pronged approach to investigate the complexities of integrating cycling into urban transportation systems. It applies a sociological perspective to identify and assess barriers to bike use and their relationship with urban characteristics. Using ordered probit models, factors such as road insecurity, linked to the lack of adequate bike infrastructure, and topography, are highlighted. Concurrently, an engineering perspective guides the design of cycling networks to cater to varied demand, user types (differentiated by bike ownership and vehicle type), and topographies, reflecting real-world conditions. The optimal bike network results from minimizing the general system costs, including both agency and user costs. For flat terrains, continuous approximation techniques optimize network efficiency and accessibility, considering the heterogeneous demand and various user types, based on bike ownership and travel chains. In contrast, for cities with varied topographies, discrete approaches incorporate topographical elements into the model. Network performance and structure are evaluated based on two route selection criteria based on vehicle type: minimizing energy for traditional bike users and minimizing time for e-bike users. This engineering perspective aims to develop cycling networks that are practical and responsive to the diverse needs of urban dwellers.The methods are empirically validated through case studies in Quito and Guayaquil, Ecuador, showcasing their efficacy in developing adaptive bike networks tailored to diverse urban contexts, thereby significantly enhancing bike mobility across varied settings.The study's findings indicate that the network's layout, including lane spacing and station locations, is primarily influenced by the concentration of trip origins and destinations rather than topography. However, topography does affect route selection, which in turn influences flow distribution and infrastructure utilization. Moreover, the variation in trip distribution across different user types has a minimal impact on the network's lane configuration but significantly affects the number of bike-sharing stations and fleet size. The necessity for a safety stock at each station leads to an oversized fleet, increasing agency costs. Despite being an individual mode of transport, the study highlights that bike-sharing systems benefit from economies of scale. As demand increases and becomes more concentrated, the cost per user decreases, resulting in denser lane networks and improved network efficiency. E-bikes emerge as a viable solution for overcoming topographical barriers, offering a significant advantage in areas with steep slopes. For instance, where users of traditional bikes might need to walk, thereby increasing overall journey times, e-bike users experience reduced travel times and physical exertion, making e-bikes efficient in urban contexts with varied topographies.Future research directions and policy recommendations are proposed, highlighting the importance of a holistic and adaptive approach to bike mobility planning. This includes integrating diverse weather-related variables, exploring other personal mobility vehicles (PMVs), and employing robust datasets to inform sustainable urban transport strategies.

Committee:
     PRESIDENT: ROCA ROSELL, ANTONI-MARIA CLARET
     SECRETARI: LAVIÑA GÓMEZ, FRANCISCO JAVIER
     VOCAL: TORO CALDERÓN, JOSÉ JAVIER
Thesis abstract: This thesis developed an understanding of what makes a community sustainable, its particular characteristics, the values it shares, its way of life and its interaction with natural systems. It categorized the concept of sustainable communities as a complex and adaptive socio-ecological system, with characteristics of socio-ecological resilience. The study focused on the structural and functional factors or elements that directly and indirectly condition and influence the life of people and the social systems that constitute them. Thesis addressed a real case study represented in the rural dairy community of Monquentiva in the Páramo de Guatavita, Colombia, as an empirical element on which the research was built. The main objective was to establish the characteristics of a theoretical model for analyzing the sustainability of a community that will shape the behavior of the social-ecological system and the factors that can affect its sustainability.By applying systems theory, the rural community was studied as a complex and adaptive socio-ecological system, emphasizing the interactions between human and non-human actors (ecological entities) and not between variables or systems (sociological phenomena). Two methodological proposals were adapted to develop the doctoral research, the first being the prospective analysis and the second the action situation framework. The action situations framework and its underlying conceptualization of SES were structured based on understanding SES resilience thinking as complex and tightly intertwined adaptive systems. The information obtained with the active participation of community stakeholders at different levels of the system was graphically represented in a theoretical model to account for the characteristics that condition the sustainability or unsustainability of the system, its social-ecological resilience, the coordination among the system of stakeholders, and the responses assumed to face emerging phenomena that can lead the community to either adapt or transform. It was concluded that the model is appropriate to describe and analyze the organization and functioning of the system of actors of the SSE dairy cattle community of Monquentiva and its resilience characteristics such as modularity, diversity, feedback mechanisms, efficiency and resources that favor social-ecological resilience. The model provides information about the current context of the community and their main productive economic activities, helps to know where to target interventions and build resilience. It should be seen as a contribution to the observation of resilient socio-ecological systems, has the potential to contribute to broader sustainability models for rural SSE, and can inform strategic adaptation planning in the face of different shocks and socio-ecological dynamics specific to rural spaces.

Committee:
     PRESIDENT: ÁLVAREZ DÁVILA, ESTEBAN
     SECRETARI: ALVAREZ DEL CASTILLO, JAVIER
     VOCAL NO PRESENCIAL: RAMIREZ HERNÁNDEZ, WILSON ARIEL
Thesis abstract: This paper explores the interdependent relationship of cities, as an expression of the process of urbanization and human agglomeration, as well as of all their spatial, political, social, economic and environmental dynamics, with the regions that provide them with different ecosystem services, without which they would not be able to subsist.By clearly identifying how to analyze this dependence, proposals can be made to incorporate the valuation (not only an economic valuation) of these ecosystem services in the policies traditionally known as urban or city policies, as well as in the different planning instruments such as, in the case of Colombia, development plans and land use plans, which, for the purposes of this paper, are analyzed in greater depth on a metropolitan and regional scale.The proposal presented advances from the conceptual and methodological point of view through three practical exercises that allow the incorporation of ecosystem services as priorities in the sustainability policies of these territories, which should not be analyzed and managed in isolation but, on the contrary, should be analyzed as urban•regional environments, since there is a permanent exchange or flow of services that nature provides and that in most policies and visions of territorial development are seldom identified, valued and incorporated.As a case study we analyze the city of Medellín, its metropolitan area also known as the Aburrá Valley, made up of nine other physically and functionally conurbed municipalities, and its interdependent relationship with its urban•regional environment, that is, the central region of the department of Antioquia (also known as the metropolitan region), which includes at least 50 municipalities.Keywords: Ecosystem Services, Plural Valuation, Sustainability, Planning, Policies, Urban•Regional Environments, ISE Approach, Breadth of Inclusion, Delphi Method.

Committee:
     PRESIDENT: DILLMAN, KEVIN
     SECRETARI: DE PABLO RIBAS, JOAN
     VOCAL: MAYOR PILLADO, ÁLVARO
Thesis abstract: Humanity faces in the XXI Century the challenge of transformation towards a sustainable society. The ecological crisis, in which climate change plays an important role, threatens to alter the natural cycles of the planet up to a point of no return, seriously compromising both natural ecosystems and human life on the planet. Such natural degradation finds its origins in the industrial revolution, and has been fed by human activities ever since then. Over the last decades, efforts to mitigate the crisis have taken a part on the public ruling of human society at a global scale, but these have so far failed to offer real perspectives of improvement.This doctoral thesis acknowledges this situation and navigates some of the different paths through which sustainability science can contribute to mitigate the crisis. The final goal of the thesis is contributing in the development of quantified parameters of sustainability that enhance effective decision making at a public level. Due to the heterogeneity, interdisciplinarity and broadness of the field of sustainability science, the final goal of the thesis requires a previous process of defining the contextual and conceptual frameworks through literature review on various topics as well as a focus on what, where and how to quantify prior to developing the quantification method. The former involves conceptual clarification on sustainability and a sustainable society, as well as a literature review and analysis on the state of art of current public plans for sustainability at an intergovernmental level, given the global impact of the crisis. Additionally, it involves an approach to economic discussions on growth and to the field of philosophical reflections concerning the historical role of human society. The latter is defined as follows: the what is set on the climate impact of production activities, the where is set on the agricultural sector and the how is set on enhancing holisticness and comprehension of results. The consecutive process to this one is the definition and application of the new sustainability quantification method.Results of the thesis include a conceptual model of a sustainable society, an analysis on the environmental sustainability of the transformational plans within the European Green Deal, the development of a new method for quantifying the climate impact of production systems and assessing their path towards climate neutrality, as well as the application of such method on the GHG emissions from production, transport and agricultural use of N-fertilizers in Spain during the period 1960-2100. Due to the findings on the literature review, as well as throughout the different studies of this doctorate, such results are discussed with the focus set on the influence of the global economic model and precisely of economic growth on the consecution of a sustainable society.Main conclusions of this work highlight that the ecological crisis has deeper roots on human society than currently addressed by its transformational plans. In order to achieve a sustainable society, including climate neutrality, it is necessary to transform the economic model and abandon the industrial-societal axioms including a review of endless economic growth, irrational techno-optimism and dissatisfying materialism. Post-growth economics are encouraged to be further explored as they might offer the key towards human wellbeing in balance with a finite planet.

Committee:
     PRESIDENT: GIL ROIG, JOSE MARIA
     SECRETARI: BRUGAROLAS MOLLA-BAUZA, MARGARITA MARÍA
     VOCAL: DE MAGISTRIS, TIZIANA
Thesis abstract: Currently, most of the world’s agriculture is still based on conventional farming due to its high-yield characteristics, providing food for a growing global consumer population. However, this agricultural system is simultaneously contributing to biodiversity loss and climate change, making it unsustainable for the planet. As consumers are increasingly concerned about the potential environmental and health impacts of food, sustainable agricultural practices are beginning to be explored and developed. Both the European Union (EU) and China are making efforts in this regard. In this context, the overall objective of this dissertation is to explore, from a consumer perspective, the preferences, willingness to pay (WTP), factors affecting WTP for sustainable food products, and sustainable food-related behavior in two distinct regions: the EU and China.Firstly, a meta-analysis of 80 global studies covering a wide range of sustainable attributes was conducted. Subgroup analysis and meta-regression results showed that globally, consumers’ average WTP premium for sustainable food products in percentage terms was 29.5%. It was worth noting that WTP estimates that were measured by hypothetical methods were typically higher than those by non-hypothetical approaches due to hypothetical bias. In addition, the organic attribute had significantly higher WTP values than other sustainable attributes. The fruit & vegetable category exhibited the highest WTP value, while the seafood category displayed the lowest one. Interestingly, the percentage of WTP for Asia exceeded that of North America and was similar to that of Europe.Secondly, consumers’ food purchasing and consumption patterns have been reshaped by the global public health crisis (the COVID-19 pandemic). Therefore, the changes of consumers’ food purchasing and consumption behavior in Spain and China during the COVID-19 lockdown, especially sustainable behavior, were explored. The study conducted in Spain analyzed three main dependent variables: total food consumption, expenditure, and sustainable food purchases. Data were collected from 1,203 respondents through an online semi-structured survey. To examine Chinese consumers’ sustainable buying and consumption behavior, a semi-structured questionnaire was designed, and data were collected from 1,006 participants. Three dependent variables were measured, i.e., food purchasing behavior on sustainable attributes, sustainable and healthy diets, and food waste. In these two studies, some interesting results were found. Consumers’ socio-demographic characteristics, emotions, trust in information sources, knowledge of COVID-19, risk attitudes, and risk perceptions played key roles in consumers’ sustainable food-related behavior during the lockdown.Thirdly, circular farming was studied here as a sustainable agricultural system. Using the Open-Ended Choice Experiment (OECE) methodology, we conducted a questionnaire survey with 5,591 consumers from six EU countries, aiming to explore their WTP and demand for food products produced by circular farming. Three products were focused on: pork, milk, and bread. The study found that there was a demand for food produced by circular agriculture on the European market and that consumers were willing to pay higher prices than for conventional products. Among these six countries, consumers in Spain were willing to pay the highest premium (>26%), while consumers in Hungary exhibited a relatively low WTP for these products. Consumers’ socio-demographic characteristics, environmental attitudes, and price influenced their purchases of circular food products.This dissertation provides insights for stakeholders. In addition, future research could explore consumers’ food-related behavior in the current environment and investigate the market potential of the circular food products in China.

Committee:
     PRESIDENT NO PRESENCIAL: ARRANZ ARRANZ, BEATRIZ
     SECRETARI: ROCA BOSCH, ELISABETH
     VOCAL NO PRESENCIAL: ALAPONT RAMON, LUIS
Thesis abstract: The following doctoral thesis presents an investigation into the application and effectiveness of Urban Living Laboratories (ULLs) as transformative educational strategies within Higher Education Institutions (HEIs) to promote Education for Sustainable Development (ESD). Through the application of a diverse methodological framework that includes comprehensive literature reviews, expert validations and extensive case study analyses, with a focus on the Delta Project of the Faculty of Architecture and Urbanism of the University of Guayaquil, this research significantly advances the understanding of how ULLs can be integrated into higher education curricula.The thesis is structured in seven chapters with its core part made up of three scientific articles. The first part presents a literature review and conceptual framework. This section provides a comprehensive review of the literature on ESD within HEIs, detailing the conceptualisation and operationalisation of ULLs. It explores the fundamental theories and practices of ESD, emphasising the role of HEIs in leading sustainability initiatives. The review also covers the characteristics and typologies of ULLs, placing them within the broader context of sustainable urban development and educational innovation.In the second part, the thesis presents an innovative evaluation tool (E-ULL-HEIs), designed to measure the impact and effectiveness of ULLs in promoting sustainable practices within the academic environment. This tool evaluates ULLs through three constructs: Synergy, Strategy and Pedagogy, which describe key interactions for ESD. Synergy emphasises cross-sectoral and disciplinary cooperation; Strategy addresses clarity of purpose and lasting outcomes; and Pedagogy combines the incorporation of new knowledge with learning and research impact.These constructs are developed into seven key indicators covering the essential elements of lifelong learning, ESD and higher education institutions. By applying this assessment tool to fifty case studies, the research validates the reliability and consistency of these indicators. The results of these studies, confirmed by exploratory factor analysis and Cronbach's alpha coefficient, demonstrate the robustness of the tool in capturing the nuanced impacts of ULL on educational strategies and community engagement. This evaluation framework not only facilitates the assessment of ULL contributions to sustainability, but also ensures their alignment with educational learning outcomes and the broader Sustainable Development Goals (SDGs).In the third part, this assessment tool is applied in the Delta Project, a ULL at the University of Guayaquil, Ecuador. This tool was crucial to identify both the strengths and weaknesses of the project. The findings highlight the impact on diversity and stakeholder participation, interdisciplinarity, curricular integration, learning and research. However, it also identified challenges in terms of cross-sectoral collaboration and student engagement, providing valuable lessons on the importance of strategic planning and adaptability.The results of this doctoral research highlight the transformative potential of ULLs in HEIs, highlighting them as central to promoting sustainable urban transitions. However, the thesis also identifies challenges in cross-sectoral collaboration and student engagement that provide critical insights into the strategic planning necessary for the successful adaptation and replication of ULL models in different cultural and academic contexts.

Committee:
     PRESIDENT: TOLLIN, NICOLA
     SECRETARI: MORATO FARRERAS, JORDI
     VOCAL: LAVIÑA GÓMEZ, FRANCISCO JAVIER
Thesis abstract: Technical, ecological, territorial, and cultural transformations at various levels and spaces of society where hydroelectric projects exist often involve conflicts, new knowledge regimes, different local practices, global mitigation frameworks, and water resource management. Therefore, the fact that hydroelectricity does not rely on fossil fuels should not imply the absence of adverse environmental effects. In fact, its development and construction require dams, concrete infrastructure, road openings, water channels, transmission power towers, and other facilities that are not new, but they do possess specific characteristics, benefits, and disadvantages.Globally, hydroenergy production presents a macro view of advantages, but little is discussed about the disadvantages and issues that arise from the construction of these structures and their surrounding systems. This research aimed to analyze hydroelectric production based on implications for energy sustainability. Through an analytical-experimental methodology with a quantitative approach, several axes were investigated.In the analysis, the thesis first involved visits to various hydroelectric projects in Ecuador, mainly, and adjacent communities to verify the environment, infrastructure, operation, collect water samples, and gather information through surveys of people living in these areas. These activities provided research elements and data on the changes contrasted since the construction of hydropower plants.Additionally, the research conducted 183 surveys to gather information and perspectives from communities near Ecuador's largest project, collected 10 water samples for physicochemical water analysis in five hydropower projects, established a relationship between hydroelectric production and technical, social, and environmental variables, and developed a connection between hydroelectricity and sustainability.The research concludes that hydroelectric energy presents itself as a renewable technology that provides benefits such as water supply to communities, flood control, greenhouse gas reduction, and clean energy as a low-carbon option. However, emerging problems exist due to unregulated exploitation and large-scale infrastructure with dams that alter the environment, making this source not entirely sustainable.Furthermore, there are parameters that impact hydroelectricity; socially, changes in customs and movements of people from their places of origin were observed; environmentally, parameters include changes in water quality, wildlife death, reduction in river fish populations, erosion, and seasonal changes; technically, parameters such as water usage for generation, construction type, and water variations that reduce plant efficiency were verified.It is conclusive that there are hidden impacts for every megawatt produced through hydroelectricity, and its generation structure is not highly clean due to the significant water resource requirement per kWh. However, hydroelectricity significantly contributes to climate change mitigation compared to fossil fuel energy production, but the availability of water resources varies, altering ecosystems and requiring careful attention due to the hidden, often intangible costs such as environmental, social, and technical parameters that occur.

Committee:
     PRESIDENT: SÁNCHEZ GARCÍA, M. MERCEDES
     SECRETARI: RAHMANI MEDDOUR, DJAMEL
     VOCAL: IGLESIAS MARTÍNEZ, EVA
Thesis abstract: The adaptation of the agri-food system towards more sustainable models is a pressing need to guarantee food security for current and future generations, in the face of population growth, scarce natural resources and climate change. To meet the challenges of producing more sustainably, new food production systems have been developed, they incorporate the principles of circular economy. Circular production systems reduce the consumption of new external inputs and the generation of waste, reducing adverse environmental effects and allowing the recovery of nutrients. This thesis addresses two of the main links in the shortest value chain of the agri-food system, "the producer and the consumer", and their response towards the incorporation of sustainability approaches, such as circularity. The objective is to analyze whether the circular agriculture practices identified as more sustainable are accepted by agricultural producers and the factors that influence their adoption, as well as the preference of consumers and their willingness to pay for these circular production innovations, in order to try to convert the results obtained into evidence that can serve as a basis for generating adequate and coherent public policies, to support and facilitate the adoption of circular innovations. . In relation to the above, in the first instance a semi-structured questionnaire was applied to agricultural producers from: Spain, Austria, Czech Republic and Italy, in which the hierarchical analysis method (AHP) to measure preferences and the scale of the New Ecological Paradigm NEP were included to measure environmental attitudes. Results showed an adoption readiness of 48.24% and that the acceptance of the proposed circular innovations is closely related to the environmental objectives, level of education, previous adoption experience and environmental attitudes of farmers. We also found that institutional support plays an important role in adoption decisions. With regard to consumers, in a first approach, through a survey of 5,246 consumers in Germany, the Netherlands, Italy, the Czech Republic and Spain, their willingness to pay for beef fillet produced in a circular livestock system was analyzed, using the Discrete Choice Experiments (DCE) method. This study included the analysis of the behaviors that influence their preferences, based on the Theory of Planned Behavior (TPB). The results allowed us to observe that there is a potential market for circular beef fillet. Although preferences are heterogeneous, consumers are generally willing to pay a higher premium for circular beef steak than conventional steak and lower than for organic beef. Of the components of planned behavior theory, social norms and behavioral control perception increased preferences for circular production beef steak, while environmental attitudes increased preferences for organic beef steak, and reduced preference for conventional beef steak. Subsequently, the preferences of 5,591 consumers in Spain, Poland, Italy, Hungary, Croatia and Belgium were analyzed, as well as their willingness to pay for pork, milk and bread labelled as circular and presented as more sustainable, in terms of reducing greenhouse gas emissions and optimizing nutrients. This analysis included sustainable consumption behavior, focused on purchasing, use, and recycling habits. The results showed that about 27% of participating consumers preferred foods from circular systems. As in the previous study, the results highlighted the importance of consumers' environmental attitudes in determining their preferences for environmentally sustainable products. All of the above results on consumers allow us to suggest to governments, policy makers and other sectors involved in sustainable food production, the standardization of food labels obtained through circular agriculture systems and the design of educational programs to increase knowledge about the problems generated by unsustainable consumption habits.

Committee:
     PRESIDENT: AGUILERA BENAVENTE, FRANCISCO
     SECRETARI: ALCARAZ SENDRA, OLGA
     VOCAL: GUAITA PRADAS, INMACULADA
Thesis abstract: The scarcity of information that allows understanding the importance of natural resources from an economic approach is a limitation to establish parameters related to environmental investment in conservation plans. This research proposes a methodology that allows modeling the variability of páramo land uses and the Ecosystem Valuation (EV) of the Chambo-Ecuador sub-basin from a bioeconomic monitoring that links the economic rent of páramo land uses with remote sensing tools and geographic information systems. The main results of the methodology determined that temporal monitoring of land covers is essential to identify areas of greatest vulnerability to EV degradation. The thresholds, functions and interrelationships determined in the Cart Decision Tree (CDT), Multilayer Perception (MLP), Multivariate Adaptive Regression Splines (MARS) and Support Vector Machines (SVM) models for land cover recognition were efficient; the models performed 88%, 85%, 83% and 81% respectively. The hybridization of the models, Markov chains and cellular automata was appropriate for predicting future land cover changes in Andean areas in relation to their VE, the methods achieved acceptable accuracy for recognizing páramo land uses. The variables chosen for land cover classification were adequate to identify land cover particularities.The opportunity cost and benefit transfer methods proposed obtained a good performance in the evaluation of food production trajectories linked to environmental services (ES) of carbon supply and concentration associated with indirect and support ES, so it was determined that the information from the dynamics of environmental services is an important indicator to understand the real state of the resource and consequently allows understanding the necessary strategies to undertake sustainable actions for ecological management.The mapping generated allowed us to determine that the páramo decreased by 13% between 2000-2010 and 19% between 2010-2020. It was estimated that the loss of the ecosystem between 2000 and 2030 will increase to 28%. From the first year of the study to the last year considered in the work, the páramo will go from occupying 92% to 64% of the area studied. The changes in the EV reveal that the categories with anthropogenic activity analyzed maintain a constant growth that has a direct impact on the EV of the páramo. The most affected areas are those up to 3500 meters above sea level. The EV of the Chambo sub-basin from 2000 to 2020 will increase from 2.86×108 USD to 2.59×108 USD and it is estimated that by 2030 the EV will decrease to 2.48×108 USD, which leads us to recognize that, although the loss of the EV of the natural resource is not critical, its degradation is increasing.Through this methodology it will be possible to obtain, in a practical way, data on the conservation status of the resource over time, allowing to solve problems related to the scarcity of data and leading to the understanding of changes in the area from a socioecological approach, i.e., covering the environmental impacts of human activities on natural systems. The basis of the developed method allows replication of the methodology.The information generated by this study will be of vital importance to understand the causes of the changes in the Andean systems in monetary and environmental terms, which will allow the development of management plans and conservation policies aimed at protection and sustainable management from an economic approach.

Committee:
     PRESIDENT: DE PABLO RIBAS, JOAN
     SECRETARI: SANCHÍS SANDOVAL, JOSEP ÀNGEL
     VOCAL: DÍAZ CRUZ, SILVIA
Thesis abstract: The widespread and increasing use of silver nanoparticles (AgNPs) in various products is leading to their release into different environmental compartments, especially into aquatic environments. These particles can enter these environments through various pathways, for example, gradually via effluents from wastewater treatment plants (WWTPs) or accidentally through spills onto soil or into rivers. This thesis presents a detailed analysis of the transport (advection-dispersion) and dispersion of silver nanoparticles (AgNPs) in both surface and groundwater, considering mass balances, various mathematical models, and factors influencing their mobility and retardation. For surface waters, continuous and point discharges are considered, and an analytical model is used to represent the behavior of AgNPs in the river. For groundwater, point discharges are considered. The interaction of AgNPs with porous media in groundwater (retardation process) is also taken into account, which allows for the calculation of the maximum concentration of AgNPs in groundwater. Initially, a Fuzzy Logic model is developed to assess the environmental risk in aquatic ecosystems based on the concentration and toxicity of AgNPs. The toxicity is determined with great adaptability by including variables such as shape, size, and coating of the nanoparticles, allowing a more accurate risk assessment. This model is applied to a discharge of AgNPs into the river from WWTP effluents or an accident. The results show that in all cases, the risk of AgNPs due to direct accidental discharge into the river poses a higher risk than that from WWTPs. Subsequently, a hybrid model is developed that integrates Monte Carlo simulation (for concentration calculation) with the developed Fuzzy Logic model. This integration provides a tool for assessing the environmental risk of AgNPs due to a spill onto the soil. Two scenarios are proposed after the spill: discharge of AgNP-contaminated aquifer water into the river and use of this aquifer water for wetland recharge. The concentration distribution of AgNPs by river discharge is below the proposed legal limit, while in the wetland use scenario, legal limits are not met in any case, indicating a higher risk associated with this latter use. After conducting a sensitivity analysis, it has been proved that the developed Hybrid model, which combines Fuzzy Logic and Monte Carlo techniques, is a useful and versatile tool for managing uncertainty in risk assessment.