Juan Pablo Corella

Atmospheric methane (CH ₄ ) plays a central role in Earth’s climate, yet the drivers of its decline during the high-dust conditions of glacial periods, such as the Last Glacial Maximum (LGM), remain uncertain. Previous explanations imply source-driven changes, assuming an atmospheric lifetime comparable to that of present day. Recent work shows that interactions between mineral dust and sea salt aerosols produce CH ₄ -removing chlorine radicals. In this work, we show that during the LGM, CH ₄ lifetime shortened to 7.8 years, 20% lower than that of present day. Chlorine contributed ~15% of global CH ₄ loss, fourfold that of present day. Our results reproduce ice core CH ₄ isotopic evidence, demonstrating that stronger-than-assumed atmospheric sinks can explain CH ₄ variability without invoking substantial source changes, highlighting the overlooked role of chlorine chemistry in the glacial CH ₄ budget.

Purpose: The Ebro Basin is one of the most industrialised regions of the Iberian Peninsula, yet its long-term legacy of metal contamination remains poorly constrained due to the scarcity of continuous sedimentary archives in semi-arid environments. This study reconstructs the history of mercury (Hg) and lead (Pb) pollution in the Ebro Basin using Lake Chiprana, the only permanent hypersaline lake providing a continuous, high-resolution sedimentary record in this region. Methods: A dated sediment core covering the last ~ 250 years was analysed for Hg and Pb concentrations, enrichment factors, accumulation fluxes and Pb isotopic composition. To link historical contamination with present-day processes, sedimentary data were directly compared with contemporary atmospheric deposition measured by bulk collectors located 5 km from the lake. Geochemical, isotopic and source-apportionment approaches were integrated. Results: The sedimentary record shows an increase in Hg and Pb accumulation during the mid-twentieth century, contemporaneous with the operation of a nearby coal-fired power plant. Hg and Pb enrichment factors and accumulation fluxes increased between 1950 and 1980, providing evidence of local coal combustion supported by Pb isotopic signatures. In contrast, recent decades are characterised by lower fluxes and by a clearer expression of mixed sources, including regional dust inputs, Saharan dust, biomass burning, traffic-related emissions and regional dust resuspension. Conclusion: The close agreement between recent sedimentary accumulation rates and modern atmospheric fluxes demonstrates the reliability of lake sediments as integrative monitors of pollution legacy in industrialised semi-arid regions. Lake Chiprana emerges as a key reference archive for assessing long-term Hg and Pb contamination and for disentangling historical and contemporary sources affecting soils and sediments in Southern Europe.

Antarctica, although one of the planet’s most pristine regions, is not exempt from global pollution such as mercury (Hg), an element with a complex biogeochemical cycle. Hg emissions originate from natural and anthropogenic sources, and its long atmospheric residence time allows transport to remote regions. Polar regions act as sinks for Hg, particularly in ice-free areas where periglacial processes are dominant. Fildes Peninsula (King George Island) is one of the most densely populated areas in Antarctica with permanent scientific bases, an airport, and seasonal tourism, which increases environmental impacts. There are few in-depth studies on Hg in Antarctic soils, making it crucial to improve understanding of Hg behaviour and distribution within soil profiles from site-specific areas. This work examines Hg distribution in eleven soil profiles on Fildes Peninsula, identifies relationships between Hg and physicochemical soil parameters and evaluates potential drivers controlling Hg distribution. The results show three groups of soil profiles based on Hg depth patterns and soil properties: (1) neutral profiles in which Hg decrease with depth, where Hg is mainly associated with external inputs such as erosion processes, volcanic eruptions, periglacial processes, ocean aerosols, rainwater and/or snowmelt; (2) neutral profiles in which Hg increases with depth, where Hg is mainly linked to the parent material; and (3) ornithogenic profiles, where Hg is primarily related to organic residues derived from ornithogenic inputs. Furthermore, some profiles show evidence of anthropogenic influence from combustion emissions. Overall, organic matter, iron oxides and zeolites act as important Hg drivers across all analyzed profiles. Graphical Abstract The graphical abstract summarizes the main results of the study by illustrating observed mercury (Hg) depth patterns in Antarctic soil profiles and the soil properties controlling their distribution. Maps of Antarctica indicate the locations of the sampled sites, providing the geographical context of the investigation. The central part of the graphic presents representative soil profiles showing three distinct Hg depth trends identified in the study: neutral soils with decreasing Hg concentrations with depth, neutral soils with increasing Hg concentrations toward the parent material, and ornithogenic soils characterized by Hg enrichment associated with organic residues from bird activity. Upward- and downward-pointing triangles indicate Hg concentration changes with depth and are illustrated using field photographs of the sampled profiles. Potential Hg sources (atmospheric deposition, volcanic inputs, erosion processes, anthropogenic combustion, and organic residues) are shown as external inputs. The key drivers identified by the study—organic matter, Fe₂O₃, and zeolites—are highlighted as the main controls governing Hg retention and vertical redistribution within the soil profiles. Arrow thickness indicates the relative influence of these drivers on the different soil types.

The singularity of current environmental change in high mountain environments can only be tested by comparison with long-term time series beyond anthropogenic impact. Here, we present a 4-ka sedimentary record from Lake Montmalús (Andorra, 2,433 m a.s.l.), obtained through the integration of sedimentology, grain-size end-member modelling, bulk geochemistry, and the analysis of stable isotopes in organic matter (δ13CV-PDB, δ15NAIR) and heavy metals (Pb, Hg, As), alongside monitoring data. Pre-industrial fluctuations in detrital delivery and organic carbon burial largely reflect hydroclimatic variability, with increased transport occurring during the humid phases of the Iberian-Roman period (200 BCE-300 CE) and the Late Antiquity Little Ice Age (400-765 CE). In contrast, the last two centuries show unprecedented, synchronous changes driven by industrialisation and climate warming. Since around 1850 CE, and particularly after around 1960 CE, organic carbon burial has increased as C/N declined. Meanwhile, δ13CV-PDB and δ15NAIR have become more negative, indicating a stronger algal contribution to the carbon budget, intensified respiration processes, and longer summer stratification. The late 20th century marks a lake regime shift, with the onset of finely laminated deposition in the deep areas and persistently anoxic deep waters (Mn/Fe rise). Heavy metals (Pb and Hg) peaked in the industrial era (early 20th century) and declined after environmental regulations were enforced in the late 20th century. Arsenic shows a distinct late-modern enrichment after 1995 CE, reaching its maximum during the 2000s decade, decoupled from runoff proxies, and likely related to the activity of a garbage burning treatment plant nearby. Our results highlight the vulnerability of high-alpine lakes to the combined effects of warming, changing precipitation seasonality, and atmospheric pollution. They show that the lake regime change in the mid-20th century had no precedent in the previous 4000 years. The range of natural changes during millennia prior to industrial times also provide a baseline against which to evaluate resilience, and to design targeted monitoring of lake dynamics and contaminant deposition in these rapidly changing mountain environments.

Tropospheric iodine plays a key role in ozone depletion and new particle formation. Understanding how iodine responds to climatic shifts is crucial for predicting future atmospheric composition. Here, we present high‐resolution iodine fluxes in the EGRIP (East GReenland Ice Core Project) ice core in central Greenland spanning the last 15.7 kyr. By integrating these data with complementary proxies from other ice and marine sediment cores, we explore both the temporal and spatial patterns of iodine deposition across the Greenland ice sheet. We find lower iodine fluxes at EGRIP compared to RECAP and NEEM ice cores over the last 15.7 kyr, explained by the lower efficiency of iodine transport to the interior of the ice sheet. Our results show that during the cold periods of the Last Glacial Termination (15.7–11.7 kyr before present), iodine fluxes at EGRIP were higher than during the Holocene, likely due to enhanced long‐range transport of iodine adsorbed onto dust and sea‐salt aerosols under stronger glacial wind regimes. In contrast, during the Holocene, the sources and transport pathways of iodine shifted to marine sources. We infer that iodine was increasingly emitted from the expanded seasonal sea ice area and biologically active subpolar North Atlantic waters, though overall fluxes at EGRIP were lower than during the glacial period, reflecting the reduction in long‐range transport. After rising until 5 kyr before present, iodine fluxes declined throughout the Neoglacial, in concomitance with regional cooling, increased sea ice extent, and reduced ocean productivity.

Climate models predict an increase in extreme hydrological events (droughts and floods) as global temperatures respond to anthropogenic increases in greenhouse gases. This change in the pattern of extreme events due to global climate change raises uncertainties in assessing the risk of future droughts and floods. Conventionally, this problem has been addressed from a “top-down” approach based on downscaling of climate models. The development of this approach generates a high uncertainty that, in practice, does not allow determining in a reasonable and operational manner the magnitude of the change. Recently, it has been proposed to move towards a “bottom-up” approach of progressive adaptation to change based on the experience of recent events. It is assumed that future climate change will not create entirely new types of extreme weather events that have never before occurred on the planet. In this work, we review the main paleo-records (geological and botanical), which allow us to characterize and quantify hydrological extremes and their relation to climate variability at multi-decadal and secular time scales. This information is relevant to advance in the adaptation to extreme events in the context of climate change, particularly in the design of infrastructures, urbanism and territorial planning.

Atmospheric mercury (Hg) emissions represent a persistent global threat to ecosystems and human health. Stable Hg isotopes have emerged as powerful tools to trace historical pollution sources and reconstruct depositional pathways in natural archives. In this study, we present a 4000-year reconstruction of Hg isotopic composition from two Pyrenean lake sediment records (Lake Marboré and Lake Estanya) located along an altitudinal gradient and compare them with those of a nearby ombrotrophic peatland (Estibere mire). Both lakes exhibit a long-term increase in Hg accumulation rates and shifts in isotope values since the onset of the Modern Period (∼16th century), consistent with intensified anthropogenic emissions. However, the isotopic patterns differ: Lake Estanya, located in a lowland area with historical land-use changes, reflects a more localized Hg signal, whereas the high-elevation, remote Lake Marboré preserves a broader regional atmospheric imprint, dominated by wet deposition. The comparison with Estibere mirepristine and situated within the same air mass trajectory as Marboréreveals a consistent offset in Δ¹⁹⁹Hg values yet strikingly similar temporal trends, indicating a shared regional source signal modulated by ecosystem-specific processes. This multiarchive and multialtitude framework provides a rare opportunity to disentangle Hg source signatures from depositional and postdepositional transformations. Moreover, variations in even-MIF (Δ²⁰⁰Hg) in the alpine lake show the potential to reflect past climate phases, highlighting the additional value of Hg isotopes as paleoclimatic proxies. Our results underscore the importance of integrating different ecosystem archives to improve reconstructions of atmospheric Hg dynamics and to refine interpretations of legacy pollution and climate interactions.

Hypersaline lakes are sensitive and increasingly threatened ecological and depositional environments that are host to a diverse spectrum of industrial services, natural resources, and environmental processes. Furthermore, they are also important repositories of high-resolution palaeoenvironmental information and are potentially key archives in the reconstruction of environmental, climatic conditions and past human impacts in areas where other such repositories may not be available. Many saline lakes are threatened by increased farming and irrigation practices and the effects of global warming. Geochemical XRF analyses of a transect of sediment cores from Laguna Salada de Chiprana, a permanent hypersaline lake in the Iberian Peninsula, provide insights into geochemical processes and palaeoenvironmental changes occurring at the site throughout the last 300–400 years. Key changes identified within the sequence are defined both from a spatial and temporal aspect and characterise the profundal and littoral sub-environments of the lake. Initially, the onset of a phase of widespread agriculture and irrigation in the region occurred in the late 16–17th century to ~1850AD and was associated with relative increases in lake levels. This was followed by decreasing lake levels between 1850 and 1950AD, likely associated with increasing evaporative processes and decreased irrigation returns to the lake, which also allowed for increased organic productivity in the profundal setting. This may have been associated with the transition of the site to a wetland-type setting, where biological processes were able to flourish in the shallower central depocentres of the lake. In sequence, the introduction of farm machinery and changing irrigation patterns occurred around 1950, causing small increases in lake levels, colonization by charophytes as well as increased organic productivity in the littoral setting, likely due to the establishment of suitable environments for biological processes to occur in the shallower margins of the lake when water levels rose. From this period to the present day, slow drawdown of the lake has occurred coupled with increasing management of the site by the regional government, leading to several phenomena. Evaporative processes are high throughout the lake; there are falling but highly variable water levels and there is a segmentation of organic productivity, whereby falling lake levels permit increased organic productivity in the profundal setting but decrease productivity in the littoral setting due to the establishment of harsh evaporitic and erosive conditions in this area. The reconstruction reveals the high sensitivity of Lake Chiprana as an environmental archive and illustrates the need to utilise multiple sediment cores for accurate palaeoenvironmental reconstructions of saline lakes due to the strong variability in depositional and geochemical sub-environments.