Disponibilidad ambiental de metales en sedimentos marinos del Golfo de Arauco, Chile (36°45'S - 37°10'S).
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Date
2025
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Publisher
Universidad de Concepción
Abstract
La contaminación por metales en sedimentos marinos es un problema ambiental que afecta a los ecosistemas costeros debido a su potencial toxicidad, persistencia y capacidad de bioacumulación. En este contexto, el Golfo de Arauco, se caracteriza por representar una zona de alta productividad biológica con influencia de actividades industriales y fluviales, característica que lo hacen una zona relevante para evaluar la movilidad y disponibilidad ambiental de metales. En el presente estudio se analizaron testigos sedimentarios obtenidos en tres sitios que presentan distintos niveles de intervención antrópica dentro del Golfo de Arauco, en estos sedimentos se evaluó mediante la técnica de fraccionamiento geoquímico los niveles de las formas químicas de Al, Fe, Cd, Cu, Pb, Ni y Zn presentes en los sedimentos a través del método de extracción secuencial junto al análisis geoquímico realizado con datación de 210Pb.
Los resultados muestran que la fracción residual (F5) predominó en la mayoría de los metales, indicando una baja movilidad de estos en condiciones ambientales naturales que representan el contenido litogénico del área de estudio. Sin embargo, el Cd mostró una alta proporción en las fracciones intercambiable (F1), carbonatos (F2) y reducible (F3), lo que sugiere una mayor susceptibilidad a la remobilización bajo condiciones redox variables. El cálculo de EF destacó al Cd como el metal con mayor enriquecimiento, especialmente en el testigo CGA16, donde se observó un máximo de enriquecimiento (>40 veces respecto al fondo litogénico local), que se ha mantenido desde el periodo preindustrial. En contraste, metales como Pb y Al presentaron una distribución homogénea, con baja movilidad. Además, se identificó un incremento sostenido en la tasa de sedimentación desde la década de 1970, coincidente con el comienzo de la actividad industrial a gran escala en el borde costero del Golfo de Arauco.
Las investigaciones futuras deberían enfocarse en dilucidar los mecanismos que controlan el comportamiento geoquímico del Cd en sedimentos costeros, especialmente bajo la influencia de procesos como la surgencia estacional y la diagénesis temprana. Es necesario implementar monitoreos a largo plazo para determinar si los actuales patrones de movilidad del Cd representan una amenaza crónica para los ecosistemas bentónicos o podrían derivar en eventos episódicos de contaminación. Será clave profundizar en la interacción entre ciclos biogeoquímicos, dinámica sedimentaria y presiones antropogénicas para desarrollar modelos predictivos sobre el comportamiento de los metales en sistemas costeros similares. Además, la incorporación de evaluaciones biológicas bentónicas permitiría precisar mejor el riesgo ecológico asociado a la distribución observada de los metales, particularmente en escenarios con fluctuaciones redox y perturbaciones sedimentarias.
Metal contamination in marine sediments is an environmental issue affecting coastal ecosystems due to their potential toxicity, persistence, and bioaccumulation capacity. In this context, the Gulf of Arauco represents an area of high biological productivity influenced by industrial and fluvial activities, making it a relevant site for evaluating the mobility and environmental availability of metals. This study analyzed sediment cores collected from three locations with varying levels of anthropogenic impact within the Gulf of Arauco. The geochemical fractionation technique was applied through sequential extraction procedures to evaluate the chemical forms of Al, Fe, Cd, Cu, Pb, Ni, and Zn, complemented by geochemical analysis and 210Pb dating. Results showed that the residual fraction (F5) predominated for most metals, indicating low mobility under natural environmental conditions, reflecting the lithogenic background of the study area. However, Cd exhibited a high proportion in exchangeable (F1), carbonate-bound (F2), and reducible (F3) fractions, suggesting greater susceptibility to remobilization under variable redox conditions. The enrichment factor (EF) calculation highlighted Cd as the most enriched metal, particularly in core CGA16, reaching enrichment levels exceeding 40 times the local lithogenic background, a condition persisting since preindustrial times. In contrast, metals such as Pb and Al presented a homogeneous distribution with low mobility. Additionally, a sustained increase in sedimentation rates was identified since the 1970s, coinciding with the onset of large-scale industrial activities along the coastal margin of the Gulf of Arauco. Future research should focus on elucidating the mechanisms controlling the geochemical behavior of Cd in coastal sediments, particularly under the influence of seasonal upwelling and early diagenetic processes. Long-term monitoring is necessary to determine whether the current patterns of Cd mobility pose a chronic threat to benthic ecosystems or could potentially lead to episodic contamination events. A deeper understanding of the interactions among biogeochemical cycles, sediment dynamics, and anthropogenic pressures will be essential for developing predictive models of metal behavior in similar coastal systems. Additionally, incorporating benthic biological response assessments could refine ecological risk evaluations associated with observed metal distributions, especially under scenarios involving redox fluctuations and sediment disturbances.
Metal contamination in marine sediments is an environmental issue affecting coastal ecosystems due to their potential toxicity, persistence, and bioaccumulation capacity. In this context, the Gulf of Arauco represents an area of high biological productivity influenced by industrial and fluvial activities, making it a relevant site for evaluating the mobility and environmental availability of metals. This study analyzed sediment cores collected from three locations with varying levels of anthropogenic impact within the Gulf of Arauco. The geochemical fractionation technique was applied through sequential extraction procedures to evaluate the chemical forms of Al, Fe, Cd, Cu, Pb, Ni, and Zn, complemented by geochemical analysis and 210Pb dating. Results showed that the residual fraction (F5) predominated for most metals, indicating low mobility under natural environmental conditions, reflecting the lithogenic background of the study area. However, Cd exhibited a high proportion in exchangeable (F1), carbonate-bound (F2), and reducible (F3) fractions, suggesting greater susceptibility to remobilization under variable redox conditions. The enrichment factor (EF) calculation highlighted Cd as the most enriched metal, particularly in core CGA16, reaching enrichment levels exceeding 40 times the local lithogenic background, a condition persisting since preindustrial times. In contrast, metals such as Pb and Al presented a homogeneous distribution with low mobility. Additionally, a sustained increase in sedimentation rates was identified since the 1970s, coinciding with the onset of large-scale industrial activities along the coastal margin of the Gulf of Arauco. Future research should focus on elucidating the mechanisms controlling the geochemical behavior of Cd in coastal sediments, particularly under the influence of seasonal upwelling and early diagenetic processes. Long-term monitoring is necessary to determine whether the current patterns of Cd mobility pose a chronic threat to benthic ecosystems or could potentially lead to episodic contamination events. A deeper understanding of the interactions among biogeochemical cycles, sediment dynamics, and anthropogenic pressures will be essential for developing predictive models of metal behavior in similar coastal systems. Additionally, incorporating benthic biological response assessments could refine ecological risk evaluations associated with observed metal distributions, especially under scenarios involving redox fluctuations and sediment disturbances.
Description
Tesis presentada para optar al grado de Magister en Ciencias con Mención en Oceanografía
Keywords
Sedimentos marinos, Ecología marina, Toxicologia ambiental