Global variability and controls on the accumulation of fallout radionuclides in cryoconite.

The accumulation of fallout radionuclides (FRNs) from nuclear weapons testing and nuclear accidents has been evaluated for over half a century in natural environments; however, until recently their distribution and abundance within glaciers have been poorly understood. Following a series of individual studies of FRNs, specifically 137Cs, 241Am and 210Pb, deposited on the surface of glaciers, we now understand that cryoconite, a material commonly found in the supraglacial environment, is a highly efficient accumulator of FRNs, both artificial and natural. However, the variability of FRN activity concentrations in cryoconite across the global cryosphere has never been assessed. This study thus aims to both synthesize current knowledge on FRNs in cryoconite and assess the controls on variability of activity concentrations. We present a global database of new and previously published data based on gamma spectrometry of cryoconite and proglacial sediments, and assess the extent to which a suite of environmental and physical factors can explain spatial variability in FRN activity concentrations in cryoconite. We show that FRNs are not only found in cryoconite on glaciers within close proximity to specific sources of radioactivity, but across the global cryosphere, and at activity concentrations up to three orders of magnitude higher than those found in soils and sediments in the surrounding environment. We also show that the organic content of cryoconite exerts a strong control on accumulation of FRNs, and that activity concentrations in cryoconite are some of the highest ever described in environmental matrices outside of nuclear exclusion zones, occasionally in excess of 10,000 Bq kg-1. These findings highlight a need for significant improvements in the understanding of the fate of legacy contaminants within glaciated catchments. Future interdisciplinary research is required on the mechanisms governing their accumulation, storage, and mobility, and their potential to create time-dependent impacts on downstream water quality and ecosystem sustainability.

Multi-sectoral impact assessment of an extreme African dust episode in the Eastern Mediterranean in March 2018.

In late March 2018, a large part of the Eastern Mediterranean experienced an extraordinary episode of African dust, one of the most intense in recent years, here referred to as the "Minoan Red" event. The episode mainly affected the Greek island of Crete, where the highest aerosol concentrations over the past 15 yeas were recorded, although impacts were also felt well beyond this core area. Our study fills a gap in dust research by assessing the multi-sectoral impacts of sand and dust storms and their socioeconomic implications. Specifically, we provide a multi-sectoral impact assessment of Crete during the occurrence of this exceptional African dust event. During the day of the occurrence of the maximum dust concentration in Crete, i.e. March 22nd, 2018, we identified impacts on meteorological conditions, agriculture, transport, energy, society (including closing of schools and cancellation of social events), and emergency response systems. As a result, the event led to a 3-fold increase in daily emergency responses compare to previous days associated with urban emergencies and wildfires, a 3.5-fold increase in hospital visits and admissions for Chronic Obstructive Pulmonary Disease (COPD) exacerbations and dyspnoea, a reduction of visibility causing aircraft traffic disruptions (eleven cancellations and seven delays), and a reduction of solar energy production. We estimate the cost of direct and indirect effects of the dust episode, considering the most affected socio-economic sectors (e.g. civil protection, aviation, health and solar energy production), to be between 3.4 and 3.8 million EUR for Crete. Since such desert dust transport episodes are natural, meteorology-driven and thus to a large extent unavoidable, we argue that the efficiency of actions to mitigate dust impacts depends on the accuracy of operational dust forecasting and the implementation of relevant early warning systems for social awareness.

Cryoconite - From minerals and organic matter to bioengineered sediments on glacier's surfaces.

Cryoconite is a mixture of mineral and organic material covering glacial ice, playing important roles in biogeochemical cycles and lowering the albedo of a glacier surface. Understanding the differences in structure of cryoconite across the globe can be important in recognizing past and future changes in supraglacial environments and ice-organisms-minerals interactions. Despite the worldwide distribution and over a century of studies, the basic characteristics of cryoconite, including its forms and geochemistry, remain poorly studied. The major purpose of our study is the presentation and description of morphological diversity, chemical and photoautotrophs composition, and organic matter content of cryoconite sampled from 33 polar and mountain glaciers around the globe. Observations revealed that cryoconite is represented by various morphologies including loose and granular forms. Granular cryoconite includes smooth, rounded, or irregularly shaped forms; with some having their surfaces covered by cyanobacteria filaments. The occurrence of granules increased with the organic matter content in cryoconite. Moreover, a major driver of cryoconite colouring was the concentration of organic matter and its interplay with minerals. The structure of cyanobacteria and algae communities in cryoconite differs between glaciers, but representatives of cyanobacteria families Pseudanabaenaceae and Phormidiaceae, and algae families Mesotaeniaceae and Ulotrichaceae were the most common. The most of detected cyanobacterial taxa are known to produce polymeric substances (EPS) that may cement granules. Organic matter content in cryoconite varied between glaciers, ranging from 1% to 38%. The geochemistry of all the investigated samples reflected local sediment sources, except of highly concentrated Pb and Hg in cryoconite collected from European glaciers near industrialized regions, corroborating cryoconite as element-specific collector and potential environmental indicator of anthropogenic activity. Our work supports a notion that cryoconite may be more than just simple sediment and instead exhibits complex structure with relevance for biodiversity and the functioning of glacial ecosystems.

Author Correction: Cryoconite as a temporary sink for anthropogenic species stored in glaciers.

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Cryoconite as a temporary sink for anthropogenic species stored in glaciers.

Cryoconite, the typical sediment found on the surface of glaciers, is mainly known in relation to its role in glacial microbiology and in altering the glacier albedo. But if these aspects are relatively well addressed, the same cannot be said about the geochemical properties of cryoconite and the possible interactions with glacial and peri-glacial environment. Current glacier retreat is responsible for the secondary emission of species deposited in high-altitude regions in the last decades. The role played by cryoconite in relation to such novel geochemical fluxes is largely unknown. Few and scarce observations suggest that it could interact with these processes, accumulating specific substances, but why, how and to what extent remain open questions. Through a multi-disciplinary approach we tried to shed lights. Results reveal that the peculiar composition of cryoconite is responsible for an extreme accumulation capability of this sediment, in particular for some, specific, anthropogenic substances.

Classifying zones of suitability for manual drilling using textural and hydraulic parameters of shallow aquifers: a case study in northwestern Senegal.

A method is proposed that uses analysis of borehole stratigraphic logs for the characterization of shallow aquifers and for the assessment of areas suitable for manual drilling. The model is based on available borehole-log parameters: depth to hard rock, depth to water, thickness of laterite and hydraulic transmissivity of the shallow aquifer. The model is applied to a study area in northwestern Senegal. A dataset of boreholes logs has been processed using a software package (TANGAFRIC) developed during the research. After a manual procedure to assign a standard category describing the lithological characteristics, the next step is the automated extraction of different textural parameters and the estimation of hydraulic conductivity using reference values available in the literature. The hydraulic conductivity values estimated from stratigraphic data have been partially validated, by comparing them with measured values from a series of pumping tests carried out in large-diameter wells. The results show that this method is able to produce a reliable interpretation of the shallow hydrogeological context using information generally available in the region. The research contributes to improving the identification of areas where conditions are suitable for manual drilling. This is achieved by applying the described method, based on a structured and semi-quantitative approach, to classify the zones of suitability for given manual drilling techniques using data available in most African countries. Ultimately, this work will support proposed international programs aimed at promoting low-cost water supply in Africa and enhancing access to safe drinking water for the population.

Une méthode est. proposée utilisant l'analyse des logs stratigraphiques des forages pour la caractérisation des aquifères peu profonds et pour l'évaluation des zones favourable pour le forage manuel. Le modèle repose sur l'analyse des paramètres extraits des logs de forage disponibles: profondeur au socle, profondeur au niveau piézométrique, épaisseur de la latérite et transmissivité hydraulique de l'aquifère peu profond. Le modèle est. appliqué à une zone d'étude dans le nord-ouest du Sénégal. Un ensemble de données de logs de forages a été traité en utilisant l'application informatique TANGAFRIC développée au cours de la recherche. Après une procédure manuelle pour attribuer une catégorie standardisée décrivant les caractéristiques lithologiques, l'étape suivante et une extraction automatique des différents paramètres texturaux et l'estimation de la conductivité hydraulique en utilisant des valeurs de référence disponibles dans la littérature. Les valeurs de conductivité hydraulique estimées à partir des données stratigraphiques ont été partiellement validées, en les comparant aux valeurs mesurées à partir d'une série de pompages d'essais réalisés sur des forages de grand diamètre. Les résultats indiquent que cette méthode permet de produire une interprétation fiable du contexte hydrogéologique peu profond en utilisant des informations généralement disponibles dans la région. La recherche contribue à améliorer l'identification de régions pour lesquelles des conditions sont en faveur de forages manuels. Ceci est. réalisé en appliquant la méthode décrite, basée sur une approche structurée et semi-quantitative, pour classer l'aptitude de zones à des techniques données de forage manuel en utilisant les données disponibles dans la plupart des pays africains. En fin de compte, ce travail appuiera les programmes internationaux proposés visant à promouvoir l'approvisionnement en eau potable à un faible coût en Afrique et à améliorer l'accès à l'eau potable pour la population.

Se propone un método que utiliza el análisis de registros estratigráficos de pozos para la caracterización de acuíferos poco profundos y para la evaluación de áreas aptas para la perforación manual. El modelo se basa en el análisis de parámetros extraídos de registros de pozos disponibles: profundidad de la roca dura, profundidad del agua, espesor de laterita y transmisividad hidráulica del acuífero poco profundo. El modelo se aplica a un área de estudio en el noroeste de Senegal. Un conjunto de datos de registros de perforaciones se ha procesado utilizando un paquete de software (TANGAFRIC) desarrollado durante la investigación. Después de un procedimiento manual para asignar una categoría estándar que describe las características litológicas, el siguiente paso es la extracción automatizada de diferentes parámetros texturales y la estimación de la conductividad hidráulica usando los valores de referencia disponibles en la literatura. Los valores de conductividad hidráulica estimados a partir de datos estratigráficos han sido parcialmente validados, comparándolos con valores medidos de una serie de ensayos de bombeo realizados en pozos de gran diámetro. Los resultados muestran que este método es capaz de producir una interpretación confiable del contexto hidrogeológico superficial usando información generalmente disponible en la región. La investigación contribuye a mejorar la identificación de áreas donde las condiciones son aptas para la perforación manual. Esto se logra aplicando el método descrito, basado en un enfoque estructurado y semicuantitativo, para clasificar la idoneidad para determinadas técnicas de perforación manual utilizando datos disponibles en la mayoría de los países africanos. En última instancia, este trabajo apoyará los programas internacionales propuestos para promover el suministro de agua a bajo costo en África y mejorar el acceso al agua potable para la población.

Um método é proposto usando análise estratigráfica de perfis de poços para a caracterização de aquíferos rasos e avaliação de áreas favoráveis para perfuração manual. O modelo é baseado na análise dos parâmetros extraídos de perfis de poços disponíveis: profundidade da rocha dura, profundidade da água, espessura da laterita, e transmissividade hidráulica do aquífero raso. O modelo é aplicado a uma área de estudo no noroeste do Senegal. Os perfis dos poços foram processados usando o programa de computador (TANGAFRIC) desenvolvido durante a pesquisa. Após um procedimento manual para assinalar uma categoria padrão descrevendo as características litológicas, o próximo passo é a extração automática de diferentes parâmetros texturais e a estimativa da condutividade hidráulica usando os valores de referência disponíveis na literatura. Os valores de condutividade hidráulica estimados de dados de estratigrafia foram parcialmente validados comparando estes com valores medidos através de uma série de testes de bombeamento realizados em poços de grande diâmetro. Os resultados mostram que este método é capaz de produzir uma interpretação confiável do contexto hidrogeológico raso usando informações disponíveis na região. A pesquisa contribui para promover a identificação de áreas onde as condições são favoráveis para perfuração manual. Isso é obtido aplicando o método descrito, baseado no processo estruturado e semiquantitativo para classificar a favorabilidade para uma certa técnica de perfuração manual usando os dados disponíveis na maioria dos países Africanos. Por último, este trabalho suportará programas internacionais propostos com o objetivo de promover o abastecimento de água a baixo custo na África e aumentar o acesso seguro a água potável para a população.