Distinguishing between natural and anthropogenic processes in sedimentary records from estuaries with legacy pollutants is an essential task, as it provides baselines to predict future environmental trajectories of coastal areas. Here, we have addressed the recent transformation history of the mining-impacted Nalón Estuary (Asturias, N Spain). Surface and core sediment records from marshes and tidal flats were examined through a broad multidisciplinary approach, involving micropaleontological (benthic foraminifera), sedimentological (grain-size), geochemical (trace metals, major element Al and total organic carbon), physical (magnetic susceptibility, frequency-dependent magnetic susceptibility and large microplastics) and radioisotopic (²¹⁰Pb, ¹³⁷Cs and ^239+240Pu) proxies. Results suggest that the interplay between natural (high fluvial influence and extreme hydrological events) and anthropogenic (coal and mercury mining disposals) factors induced strong sedimentation-erosion processes, further shaping the recent evolution of the estuary. Short-time scale and intense sedimentation processes were revealed by overall high sediment accumulation rates, the dilution of some geological signatures and the rapid formation of a marsh in the lower estuary bay. The increasing mining fingerprints during the 20th century were shortly interrupted by the catastrophic riverine flooding of 1938. Conversely, current erosional processes by fluvial influence led to the remobilization of contaminated sedimentary materials and exposure of mining-legacy Hg levels in tidal flats from the middle sector. Fluvial activity, floodings and taphonomic biases exerted a major control on benthic foraminifera since the 19th century, although Hg ecotoxicological effects on modern assemblages at certain areas within the estuary cannot be discarded. These findings, along with the documented enhanced erosion of marshes with 'trapped' pollutants (Hg, coal microparticles and microplastics), highlight the importance of monitoring the environmental and geomorphic processes taking place in historically-contaminated estuaries.

The aim of this study is to analyze the recent sedimentation rate in the center of the Limoncocha lagoon, a Ramsar site in the Ecuadorian Amazon, using the ²¹⁰Pb dating method and identifying the potentially toxic elements along a 50 cm sediment core. A strategy based on the application of three single and four integrated indices is used to evaluate trace element contamination with depth. Single indices show mainly As and Mo, and Cu, Ba, Cd, Ni, and Pb to a lesser extent, as responsible elements of a minor enrichment between −10 and −40 cm. The multielement slight pollution shows a mixture of potential contamination sources, probably due to agricultural, oil activities, and urban wastewater discharges. However, integrated indices applied, classify the complete core as without potential risk. The ²¹⁰Pb_excess profile shows three differentiated sections. A surface section where new materials with lower concentrations have been found, probably due to the underground currents that connect the lagoon and the nearby Napo River; a central section where CF-CS model and mass accumulation rate calculations provide a sediment accumulation rate of 0.56 ± 0.03 cm y⁻¹; finally, a deeper section with a constant ²¹⁰Pb_exces profile, showing sediment reworking probably due to local flooding’s.

The Mondego Estuary (W Portugal) experienced a process of eutrophication in the late 20^th century, making it one of the most impacted systems in southern Europe. To examine its recent environmental evolution, sedimentary records were analyzed from a multiproxy approach, involving biotic, sedimentological, geochemical, physical, and radionuclide data. Results evidenced the transformation of the estuary due to anthropogenic cumulative impacts. The closure of the upstream branch triggered rapid 'continentalization' in the southern arm, altering the hydrosedimentary regime and favoring eutrophication. However, the middle and lower sectors exhibited stronger marine influences. Foraminiferal biota responded effectively to management interventions to improve hydrodynamics, while showing no discernible ecotoxicological responses to agricultural discharges. Pesticide accumulations patterns are shaped by natural and anthropogenic factors, with strong agrochemical fingerprints in the upper and lower sectors. The topmost 20-cm layer of sediments contain high pesticide concentrations and microplastics, posing challenges for future management and pollutant mitigation.

Se ha analizado el registro sedimentario reciente del estuario del Nalón a partir de dos sondeos intermareales que han sido datados mediante ²¹⁰Pb y ¹³⁷Cs. Los resultados muestran por primera vez sus asociaciones características de foraminíferos bentónicos, constituidas por un total ^de 46 especies, así como los importantes cambios experimentados por estas asociaciones, en consonancia con las variaciones en el magnetismo ambiental, como consecuencia, posiblemente, de las actividades mineras desde 1850 CE que sugieren unas condiciones ambientales deterioradas. Estas malas condiciones persistieron durante décadas, incluso más allá del cese de la minería de mercurio y carbón, hasta el siglo XXI cuando se ha comenzado a observar una leve recuperación ambiental.

The estuaries of the northern Atlantic Iberian margin are susceptible to alteration due to human activities and transformation from relative sea-level rise.The Asturian region, northern Atlantic Iberian margin, is characterized by extensive coal and polymetallic mineral deposits, including mercury ores, which have been intensively exploited since the late 19th century. In particular, the Nalón estuary has been subjected to intense physico-chemical modifications as a result of mining of such deposits in the catchment area and port activities.This research aims to decipher the environmental transformation of the Nalón estuary and the natural and/or anthropogenic forcing mechanisms during the last 200 years. We employed a multiproxy approach (i.e., benthic foraminifera, trace metals, grain size, magnetic susceptibility, microparticles and natural and artificial radionuclides) to study three 50-cm long sediment cores extracted from the middle and lower estuary. The records show degraded ecological conditions that persisted since ~1880. These were driven by the alteration of hydrological patterns, as a result of coal and mercury mining activities in the river basin and physical modifications (e.g., factory dams, dredging activities) performed in the lower estuary. Additionally, the study of eighteen surface samples, collected from different estuarine subenvironments along the main axis of the estuary, reveals the existence of a great number of living foraminifera associated with a remarkable environmental recovery since ~2010, coinciding with the end of mining and dredging activities.Future multidisciplinary studies of these regional estuarine areas will be critical to establishing appropriate coastal management practices under a climate change and sea-level rise context.