Evaluación de la presencia de nanopartículas de TIO2 (NPs TiO2) en la cuenca del río Biobío y sus efectos sobre indicadores biológicos modelos.
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Date
2026
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Universidad de Concepción
Abstract
El aumento en la producción y uso de nanomateriales ha generado creciente preocupación respecto a su liberación y comportamiento en ecosistemas acuáticos. Entre ellos, las nanopartículas de dióxido de titanio (NPs TiO₂) destacan por su amplia aplicación en productos industriales y de consumo, como bloqueadores solares, cosméticos y pinturas, lo que incrementa su probabilidad de ingreso a cuerpos de agua a través de descargas urbanas e industriales. Sin embargo, aún existen importantes incertidumbres sobre su presencia ambiental, su comportamiento en matrices naturales y sus efectos ecotoxicológicos en organismos acuáticos.
En este contexto, el objetivo de esta investigación fue evaluar la presencia, caracterización y efectos ecotoxicológicos de NPs TiO2 en el río Biobío (Chile), integrando monitoreo ambiental, análisis fisicoquímico y evaluación biológica en organismos modelo de distintos niveles tróficos.
El estudio incluyó un monitoreo ambiental realizado durante 2022 en cuatro puntos representativos del río Biobío (Alto Biobío, Santa Bárbara, Hualqui y Hualpén), considerando diferentes estaciones del año. Se recolectaron muestras de agua superficial que fueron analizadas mediante espectrometría de masas con plasma acoplado inductivamente (ICP-MS) para determinar concentraciones elementales asociadas a TiO₂. La detección y caracterización morfológica de nanopartículas se realizó mediante microscopía electrónica de transmisión (TEM) y microscopía electrónica de barrido en modo de presión variable (VP-SEM) acoplada a espectroscopía de dispersión de energía (EDS). En paralelo, se desarrollaron bioensayos ecotoxicológicos con la microalga Chlorella vulgaris, siguiendo la guía OECD TG 201, y con el microcrustáceo Daphnia magna, mediante ensayos agudos y crónicos de acuerdo con la norma ISO 10706. Además, se evaluaron respuestas moleculares mediante RT-qPCR en genes asociados al metabolismo fotosintético (atpB, psaA, psaB, psaD, psbA y rbcL), utilizando 18S como gen de referencia.
Las nanopartículas de TiO₂ fueron detectadas en todas las estaciones de muestreo, con concentraciones entre 17,6 y 22,9 μg/L, principalmente aguas abajo de plantas de tratamiento de aguas servidas. La microscopía electrónica confirmó tamaños entre 10 y 206 nm y la presencia de fases cristalinas de anatasa y rutilo, indicando un origen mixto natural y antropogénico.
En Chlorella vulgaris, la exposición a concentraciones ambientalmente relevantes (1,1–17,6 μg/L) mostró una respuesta de crecimiento hormética, con estimulación a concentraciones intermedias y ausencia de inhibición en la dosis más alta. A nivel molecular, rbcL fue significativamente reprimido a 1,1–4,4 μg/L, mientras que psaA y psaD se sobreexpresaron a 8,8–17,6 μg/L, lo que indica un refuerzo compensatorio del fotosistema I. Estas trayectorias transcripcionales divergentes demuestran que los puntos finales moleculares revelan efectos subletales que no son evidentes únicamente a partir del recuento celular. En conjunto, estos resultados destacan el potencial de los genes relacionados con la fotosíntesis como biomarcadores tempranos para detectar estrés inducido por nanopartículas en productores primarios acuáticos.
En Daphnia magna, no se observó toxicidad aguda, pero sí efectos crónicos significativos por vía trófica, con una NOAEC de 8,8 μg/L, LOAEC de 17,6 μg/L y EC₅₀ de 17,8 μg/L (R² = 0,916). Estos valores coinciden con las concentraciones ambientales detectadas en el río, indicando un riesgo ecológico real bajo condiciones naturales de exposición.
La revisión bibliográfica incluida en esta tesis integró más de cien estudios recientes, identificando estrés oxidativo, genotoxicidad y alteraciones reproductivas como mecanismos comunes de toxicidad, y destacando la necesidad de incorporar enfoques moleculares y tróficos integrados en la evaluación de riesgo ambiental.
En conjunto, los resultados demuestran que las nanopartículas de TiO₂ están presentes en el río Biobío y pueden alterar procesos biológicos esenciales, desde la regulación fotosintética en productores primarios hasta la reproducción de consumidores clave. Este trabajo aporta evidencia científica relevante para el monitoreo ambiental, la evaluación de riesgo ecológico y el desarrollo de marcos regulatorios orientados a la gestión de nanomateriales en ecosistemas de agua dulce en Chile.
The increasing production and widespread use of engineered nanomaterials have raised growing concerns regarding their release, environmental behavior, and potential ecological impacts in aquatic ecosystems. Among them, titanium dioxide nanoparticles (TiO₂ NPs) are one of the most extensively produced nanomaterials worldwide due to their broad applications in cosmetics, paints, food additives, and industrial products. As a consequence, these nanoparticles are frequently introduced into freshwater systems through wastewater effluents and urban discharges. Despite their extensive use, significant uncertainties remain regarding their occurrence in natural environments, their physicochemical behavior in aquatic matrices, and their ecotoxicological effects on aquatic organisms. The objective of this study was to evaluate the presence, characterization, and ecotoxicological effects of TiO₂ nanoparticles in the Biobío River (Chile), integrating environmental monitoring, physicochemical analysis, and biological assessment across different trophic levels. Environmental monitoring was conducted during 2022 at four representative sites along the Biobío River basin (Alto Biobío, Santa Bárbara, Hualqui, and Hualpén), covering seasonal variations. Surface water samples were collected and analyzed for elemental concentrations using inductively coupled plasma mass spectrometry (ICP-MS). Nanoparticle detection and morphological characterization were performed using transmission electron microscopy (TEM) and variable pressure scanning electron microscopy (VP-SEM) coupled with energy dispersive spectroscopy (EDS). Ecotoxicological effects were assessed using bioassays with organisms representing different trophic levels. Growth inhibition assays were performed with the freshwater microalga Chlorella vulgaris following OECD guideline TG 201. Additionally, acute and chronic toxicity bioassays were conducted using the freshwater microcrustacean Daphnia magna according to ISO 10706 protocols. Molecular responses were further evaluated through RT-qPCR analysis of key photosynthesis-related genes (atpB, psaA, psaB, psaD, psbA, and rbcL), using the 18S rRNA gene as a reference for normalization. TiO₂ nanoparticles were detected across all sampling locations, with concentrations ranging between 17.6 and 22.9 μg L⁻¹, particularly downstream of wastewater treatment plants. Electron microscopy confirmed nanoparticle sizes ranging from 10 to 206 nm and the presence of anatase and rutile crystalline phases, suggesting a mixed natural and anthropogenic origin. Exposure experiments with Chlorella vulgaris at environmentally relevant concentrations (1.1–17.6 μg L⁻¹) revealed a hormetic growth response, characterized by stimulation at intermediate concentrations and no inhibition at the highest tested concentration. At the molecular level, the photosynthetic gene rbcL was significantly repressed at lower concentrations (1.1–4.4 μg L⁻¹), whereas psaA and psaD were upregulated at higher concentrations (8.8–17.6 μg L⁻¹), suggesting a compensatory reinforcement of photosystem I activity. These divergent transcriptional patterns demonstrate that molecular endpoints can reveal sub-lethal stress responses that are not detectable through traditional cell density measurements. In Daphnia magna, no acute toxicity was observed; however, significant chronic effects were detected through trophic exposure pathways. Chronic toxicity parameters showed a NOAEC of 8.8 μg L⁻¹, a LOAEC of 17.6 μg L⁻¹, and an EC₅₀ of 17.8 μg L⁻¹ (R² = 0.916). Notably, these effect thresholds overlap with the environmental concentrations detected in the Biobío River, indicating a potential ecological risk under natural exposure conditions. The literature review included in this thesis synthesized more than one hundred recent studies and identified oxidative stress, genotoxicity, and reproductive impairment as the most commonly reported mechanisms associated with nanoparticle exposure. The analysis also highlighted the importance of integrating molecular biomarkers and trophic interactions into environmental risk assessment frameworks. Overall, the results demonstrate that TiO₂ nanoparticles are present in the Biobío River and can affect key biological processes ranging from photosynthetic regulation in primary producers to reproductive performance in aquatic consumers. This research contributes valuable scientific evidence for environmental monitoring, ecological risk assessment, and the development of regulatory frameworks addressing the environmental management of nanomaterials in freshwater ecosystems.
The increasing production and widespread use of engineered nanomaterials have raised growing concerns regarding their release, environmental behavior, and potential ecological impacts in aquatic ecosystems. Among them, titanium dioxide nanoparticles (TiO₂ NPs) are one of the most extensively produced nanomaterials worldwide due to their broad applications in cosmetics, paints, food additives, and industrial products. As a consequence, these nanoparticles are frequently introduced into freshwater systems through wastewater effluents and urban discharges. Despite their extensive use, significant uncertainties remain regarding their occurrence in natural environments, their physicochemical behavior in aquatic matrices, and their ecotoxicological effects on aquatic organisms. The objective of this study was to evaluate the presence, characterization, and ecotoxicological effects of TiO₂ nanoparticles in the Biobío River (Chile), integrating environmental monitoring, physicochemical analysis, and biological assessment across different trophic levels. Environmental monitoring was conducted during 2022 at four representative sites along the Biobío River basin (Alto Biobío, Santa Bárbara, Hualqui, and Hualpén), covering seasonal variations. Surface water samples were collected and analyzed for elemental concentrations using inductively coupled plasma mass spectrometry (ICP-MS). Nanoparticle detection and morphological characterization were performed using transmission electron microscopy (TEM) and variable pressure scanning electron microscopy (VP-SEM) coupled with energy dispersive spectroscopy (EDS). Ecotoxicological effects were assessed using bioassays with organisms representing different trophic levels. Growth inhibition assays were performed with the freshwater microalga Chlorella vulgaris following OECD guideline TG 201. Additionally, acute and chronic toxicity bioassays were conducted using the freshwater microcrustacean Daphnia magna according to ISO 10706 protocols. Molecular responses were further evaluated through RT-qPCR analysis of key photosynthesis-related genes (atpB, psaA, psaB, psaD, psbA, and rbcL), using the 18S rRNA gene as a reference for normalization. TiO₂ nanoparticles were detected across all sampling locations, with concentrations ranging between 17.6 and 22.9 μg L⁻¹, particularly downstream of wastewater treatment plants. Electron microscopy confirmed nanoparticle sizes ranging from 10 to 206 nm and the presence of anatase and rutile crystalline phases, suggesting a mixed natural and anthropogenic origin. Exposure experiments with Chlorella vulgaris at environmentally relevant concentrations (1.1–17.6 μg L⁻¹) revealed a hormetic growth response, characterized by stimulation at intermediate concentrations and no inhibition at the highest tested concentration. At the molecular level, the photosynthetic gene rbcL was significantly repressed at lower concentrations (1.1–4.4 μg L⁻¹), whereas psaA and psaD were upregulated at higher concentrations (8.8–17.6 μg L⁻¹), suggesting a compensatory reinforcement of photosystem I activity. These divergent transcriptional patterns demonstrate that molecular endpoints can reveal sub-lethal stress responses that are not detectable through traditional cell density measurements. In Daphnia magna, no acute toxicity was observed; however, significant chronic effects were detected through trophic exposure pathways. Chronic toxicity parameters showed a NOAEC of 8.8 μg L⁻¹, a LOAEC of 17.6 μg L⁻¹, and an EC₅₀ of 17.8 μg L⁻¹ (R² = 0.916). Notably, these effect thresholds overlap with the environmental concentrations detected in the Biobío River, indicating a potential ecological risk under natural exposure conditions. The literature review included in this thesis synthesized more than one hundred recent studies and identified oxidative stress, genotoxicity, and reproductive impairment as the most commonly reported mechanisms associated with nanoparticle exposure. The analysis also highlighted the importance of integrating molecular biomarkers and trophic interactions into environmental risk assessment frameworks. Overall, the results demonstrate that TiO₂ nanoparticles are present in the Biobío River and can affect key biological processes ranging from photosynthetic regulation in primary producers to reproductive performance in aquatic consumers. This research contributes valuable scientific evidence for environmental monitoring, ecological risk assessment, and the development of regulatory frameworks addressing the environmental management of nanomaterials in freshwater ecosystems.
Description
Tesis presentada para optar al grado de Doctor en Ciencias Ambientales con mención en Sistemas Acuáticos Continentales.
Keywords
Dióxido de titanio, Nanopartículas, Organismos acuáticos, Ríos, Monitoreo ambiental