Model-Based Analysis of Arsenic Retention by Stimulated Iron Mineral Transformation under Coastal Aquifer Conditions.

A multitude of geochemical processes control the aqueous concentration and transport properties of trace metal contaminants such as arsenic (As) in groundwater environments. Effective As remediation, especially under reducing conditions, has remained a significant challenge. Fe(II) nitrate treatments are a promising option for As immobilization but require optimization to be most effective. Here, we develop a process-based numerical modeling framework to provide an in-depth understanding of the geochemical mechanisms controlling the response of As-contaminated sediments to Fe(II) nitrate treatment. The analyzed data sets included time series from two batch experiments (control vs treatment) and effluent concentrations from a flow-through column experiment. The reaction network incorporates a mixture of homogeneous and heterogeneous reactions affecting Fe redox chemistry. Modeling revealed that the precipitation of the Fe treatment caused a rapid pH decline, which then triggered multiple heterogeneous buffering processes. The model quantifies key processes for effective remediation, including the transfer of aqueous As to adsorbed As and the transformation of Fe minerals, which act as sorption hosts, from amorphous to more stable phases. The developed model provides the basis for predictions of the remedial benefits of Fe(II) nitrate treatments under varying geochemical and hydrogeological conditions, particularly in high-As coastal environments.

Characterization of the Pathogenic Potential of the Beach Sand Microbiome and Assessment of Quicklime as a Remediation Tool.

Beach sand may act as a reservoir for potential human pathogens, posing a public health risk. Despite this, the microbiological monitoring of sand microbiome is rarely performed to determine beach quality. In this study, the sand microbial population of a Northern Adriatic Sea beach sand was profiled by microbiological (CFU counts) and molecular methods (WGS, microarray), showing significant presence of potential human pathogens including drug-resistant strains. Consistent with these results, the potential of quicklime as a restoring method was tested in vitro and on-field. Collected data showed that adding 1-3% quicklime (w/w) to sand provided an up to -99% of bacteria, fungi, and viruses, in a dose- and time-dependent manner, till 45 days post-treatment. In conclusion, data suggest that accurate monitoring of sand microbiome may be essential, besides water, to assess beach quality and safety. Moreover, first evidences of quicklime potential for sand decontamination are provided, suggesting its usage as a possible way to restore the microbiological quality of sand in highly contaminated areas.

Regulation of deep carbon degassing by gas-rock-water interactions in a seismic region of Southern Italy.

This study is focused on fluids characterization and circulations through the crust of the Irpinia region, an active seismic zone in Southern Italy, that has experienced several high-magnitude earthquakes, including a catastrophic one in 1980 (M = 6.9 Ms). Using isotopic geochemistry and the carbon­helium system in free and dissolved volatiles in water, this study aims to explore the processes at depth that can alter pristine chemistry of these natural fluids. Gas-rock-water interactions and their impact on CO2 emissions and isotopic composition are evaluated using a multidisciplinary model that integrates geochemistry and regional geological data. By analyzing the He isotopic signature in the natural fluids, the release of mantle-derived He on a regional scale in Southern Italy is verified, along with significant emissions of deep-sourced CO2. The proposed model, supported by geological and geophysical constraints, is based on the interactions between gas, rock, and water within the crust and the degassing of deep-sourced CO2. Furthermore, this study reveals that the Total Dissolved Inorganic Carbon (TDIC) in cold waters results from mixing between a shallow and a deeper carbon endmember that is equilibrated with carbonate lithology. In addition, the geochemical signature of TDIC in thermal carbon-rich water is explained by supplementary secondary processes, including equilibrium fractionation between solid, gas, and aqueous phases, as well as sinks such as mineral precipitation and CO2 degassing. These findings have important implications for developing effective monitoring strategies for crustal fluids in different geological contexts and highlight the critical need to understand gas-water-rock interaction processes that control fluid chemistry at depths that can affect the assessment of the CO2 flux in atmosphere. Finally, this study highlights that the emissions of natural CO2 from the seismically active Irpinia area are up to 4.08·10+9 mol·y-1, which amounts is in the range of worldwide volcanic systems.

Topical Collection: International Year of Groundwater-managing future societal and environmental challenges.

Groundwater's role in maintaining the well-being of the planet is increasingly acknowledged. Only recently has society recognised groundwater as a key component of the water cycle. To improve public understanding and the proper use of groundwater, the hydrogeological community must expand its efforts in groundwater assessment, management, and communication. The International Association of Hydrogeologists (IAH) intends to help achieve the United Nation's water-related Sustainable Development Goals (SDGs) by the adoption of innovative hydrogeological strategies. This essay introduces a topical collection that encapsulates IAH's 2022 'Year for Groundwater'.

Le rôle des eaux souterraines dans le maintien du bien-être de la planète est de plus en plus reconnu. Ce n'est que récemment que la société a reconnu les eaux souterraines comme un élément clé du cycle de l'eau. Pour améliorer la compréhension du public et l'utilisation appropriée des eaux souterraines, la communauté hydrogéologique doit étendre ses efforts en matière d'évaluation, de gestion des eaux souterraines et de communication à leur sujet. L'Association Internationale des Hydrogéologues (AIH) entend contribuer à la réalisation des objectifs du développement durable (ODDs) des Nations unies liés à l'eau par l'adoption de stratégies hydrogéologiques innovantes. Cet essai présente une collection thématique qui résume l''Année pour les eaux souterraines' 2022 de l'AIH.

El papel de las aguas subterráneas para mantener el bienestar del planeta está cada vez más reconocido. Sólo recientemente la sociedad ha reconocido que las aguas subterráneas son un componente clave del ciclo del agua. Para mejorar la comprensión pública y el uso adecuado de las aguas subterráneas, la comunidad hidrogeológica debe aumentar sus esfuerzos en materia de evaluación, gestión y comunicación de las aguas subterráneas. La Asociación Internacional de Hidrogeólogos (AIH) pretende contribuir a la concreción de los Objetivos de Desarrollo Sostenible (ODS) de las Naciones Unidas relacionados con el agua mediante la adopción de estrategias hidrogeológicas innovadoras. Este artículo presenta una colección temática que engloba el 2022 como 'Año Internacional para las Aguas Subterráneas' de la AIH.

O papel das águas subterrâneas na manutenção do bem-estar do planeta é cada vez mais reconhecido. Só recentemente a sociedade reconheceu as águas subterrâneas como um componente chave do ciclo da água. Para melhorar a compreensão pública e o uso adequado das águas subterrâneas, a comunidade hidrogeológica deve expandir seus esforços na avaliação, gestão e comunicação das águas subterrâneas. A Associação Internacional de Hidrogeólogos (AIH) pretende ajudar a alcançar os Objetivos de Desenvolvimento Sustentável (ODS) das Nações Unidas relacionados à água por meio da adoção de estratégias hidrogeológicas inovadoras. Este ensaio apresenta uma coleção tópica que encapsula o 'Ano para as Águas Subterrâneas' de 2022 da AIH.

Climate change and its effect on groundwater quality.

Knowing water quality at larger scales and related ground and surface water interactions impacted by land use and climate is essential to our future protection and restoration investments. Population growth has driven humankind into the Anthropocene where continuous water quality degradation is a global phenomenon as shown by extensive recalcitrant chemical contamination, increased eutrophication, hazardous algal blooms, and faecal contamination connected with microbial hazards antibiotic resistance. In this framework, climate change and related extreme events indeed exacerbate the negative trend in water quality. Notwithstanding the increasing concern in climate change and water security, research linking climate change and groundwater quality remain early. Additional research is required to improve our knowledge of climate and groundwater interactions and integrated groundwater management. Long-term monitoring of groundwater, surface water, vegetation, and land-use patterns must be supported and fortified to quantify baseline properties. Concerning the ways climate change affects water quality, limited literature data are available. This study investigates the link between climate change and groundwater quality aquifers by examining case studies of regional carbonate aquifers located in Central Italy. This study also highlights the need for strategic groundwater management policy and planning to decrease groundwater quality due to aquifer resource shortages and climate change factors. In this scenario, the role of the Society of Environmental Geochemistry is to work together within and across geochemical environments linked with the health of plants, animals, and humans to respond to multiple challenges and opportunities made by global warming.

Reaction of the carbonate Sibillini Mountains Basal aquifer (Central Italy) to the extensional 2016-2017 seismic sequence.

Hydrogeological perturbations in response to earthquakes are widely described worldwide. In carbonate aquifers, a post-seismic discharge increase is often attributed to an increase of bulk permeability due to co-seismic fracturing and the attention on the role of faults to explain the diversion of groundwater is increasing. We focus on the reaction of carbonate hydrogeological basins to extensional seismicity, taking as an example the effects of the Central Italy 2016-2017 seismic sequence, on the Basal aquifer of the Sibillini Mountains area. Geo-structural, seismological and ground deformation data were collected and merged with artificial tracer tests results and with a 4-years discharge and geochemical monitoring campaign. The main NNW-directed groundwater flow was diverted to the west and a discharge deficit was observed at the foot-wall of the activated fault system with a relevant discharge increase, accompanied by geochemical variations, at the fault system hanging-wall. The observed variations are consistent with the combined action of a permeability increase along the activated fault systems, which modified the predominant pre-seismic along-strike regional flow, and with hydraulic conductivity increase due to fracturing, determining a fast aquifers emptying. We show that the prevailing mechanism depends on the aquifer systems position with respect to the activated faults.

Large extensional earthquakes push-up terrific amount of fluids.

How large earthquakes are triggered is a key question in Earth science, and the role played by fluid pressure seems to be crucial. Nevertheless, evaluation of involved fluid volumes is seldom investigated, if not unaccounted for. Moreover, fluid flow along fault zones is a driving factor for seismicity migration, episodic heat and chemical transport. Here we show that time repeated (4D) seismic tomography resolves changes of Vp and Vp/Vs during the Mw6.2 2009 L'Aquila normal faulting sequence, that indicate a post-failure fluid migration from hypocentral depths to the surface, with a volume estimated between 5 and 100 × 106 m3 rising at rates up to 100 m/day. This amount inferred by tomograms is surprisingly consistent with the about 50 × 106 m3 surplus water volume additionally measured at spring discharge, spread in time and space along the 700 km2-wide regional carbonate fractured aquifer. Fluids were pushed-up within a huge volume across the fault and expelled from the area of large coseismic slip. Such quantities of fluids liberated during earthquakes add unprecedented constraints to the discussion on the role of fluids during and possibly before earthquake, as well as to the potential impact on the pristine high-quality drinkable groundwater, possibly affecting the biodiversity of groundwater dependent ecosystems too.

In situ arsenic immobilisation for coastal aquifers using stimulated iron cycling: Lab-based viability assessment.

Arsenic (As) is one of the most harmful and widespread groundwater contaminants globally. Besides the occurrence of geogenic As pollution, there is also a large number of sites that have been polluted by anthropogenic activities, with many of those requiring active remediation to reduce their environmental impact. Cost-effective remedial strategies are however still sorely needed. At the laboratory-scale in situ formation of magnetite through the joint addition of nitrate and Fe(II) has shown to be a promising new technique. However, its applicability under a wider range of environmental conditions still needs to be assessed. Here we use sediment and groundwater from a severely polluted coastal aquifer and explore the efficiency of nitrate-Fe(II) treatments in mitigating dissolved As concentrations. In selected experiments >99% of dissolved As was removed, compared to unamended controls, and maintained upon addition of lactate, a labile organic carbon source. Pre- and post experimental characterisation of iron (Fe) mineral phases suggested a >90% loss of amorphous Fe oxides in favour of increased crystalline, recalcitrant oxide and sulfide phases. Magnetite formation did not occur via the nitrate-dependent oxidation of the amended Fe(II) as originally expected. Instead, magnetite is thought to have formed by the Fe(II)-catalysed transformation of pre-existing amorphous and crystalline Fe oxides. The extent of amorphous and crystalline Fe oxide transformation was then limited by the exhaustion of dissolved Fe(II). Elevated phosphate concentrations lowered the treatment efficacy indicating joint removal of phosphate is necessary for maximum impact. The remedial efficiency was not impacted by varying salinities, thus rendering the tested approach a viable remediation method for coastal aquifers.

Changes in groundwater trace element concentrations before seismic and volcanic activities in Iceland during 2010-2018.

We analysed temporal variations of trace element concentrations in groundwater from a 101 m-deep borehole (HA01) in northern Iceland during 2010-2018 and compared them with seismic and volcanic events that occurred in the same period to identify potential hydrogeochemical precursors. An increase of B, Al, V, Li and Mo concentrations started from eight months to one month before the 2014 Bárðarbunga eruption (~115 km from HA01), a major rifting event in central Iceland, while Ga and V concentrations began to increase one day and one month after the onset of the event, respectively. We also found that concentrations of some trace elements (Li, B, Ga, Mo, Sr, Rb and Fe) significantly increased before an Mw 5.0 earthquake that occurred ~80 km from the borehole in 2018. However, other notable hydrogeochemical changes were detected during the monitoring period without apparent correlation with the seismic and volcanic events in the region. This study shows that the systematic long-term hydrogeochemical monitoring in seismic and volcanic areas is critical to advance the science of seismic and eruptive precursors. Furthermore, the use of statistical tools, such as Principal Component Analysis (PCA) and Change Point (CP) detection can help identify the most useful chemical elements and validate the trend variability of those elements in the time series, reducing arbitrary choices of pre-seismic and pre-volcanic hydrogeochemical anomalies as potential precursors.

New observations in Central Italy of groundwater responses to the worldwide seismicity.

Chemical and physical responses of groundwater to seismicity have been documented for thousands of years. Among the waves produced by earthquakes, Rayleigh waves can spread to great distances and produce hydrogeological perturbations in response to their passage. In this work, the groundwater level, which was continuously recorded in a monitoring well in Central Italy between July 2014 and December 2019, exhibited evident responses to dynamic crustal stress. In detail, 18 sharp variations of the groundwater level due to worldwide Mw ≥ 6.5 earthquakes were observed. Apart from earthquakes that occurred in Papua New Guinea and those with a hypocentral depth > 150 km, all far away Mw ≥ 7.6 earthquakes produced impulsive oscillations of groundwater. As the earthquake magnitude decreased, only some earthquakes with 6.5 ≤ Mw < 7.6 caused groundwater level perturbations, depending on the data acquisition frequency and epicentral distance from the monitoring well. A clear correlation between earthquake distance and magnitude in hydrogeological responses was found. Our results shed light on the hydrosensitivity of the study site and on the characteristics of fractured aquifer systems. Detecting the water table variations induced by distant earthquakes is another step towards a correct identification of (preseismic) hydrogeological changes due to near-field seismicity.

Hydrogeochemical changes before and during the 2016 Amatrice-Norcia seismic sequence (central Italy).

Seismic precursors are an as yet unattained frontier in earthquake studies. With the aim of making a step towards this frontier, we present a hydrogeochemical dataset associated with the 2016 Amatrice-Norcia seismic sequence (central Apennines, Italy), developed from August 24th, with an Mw 6.0 event, and culminating on October 30th, with an Mw 6.5 mainshock. The seismic sequence occurred during a seasonal depletion of hydrostructures, and the four strongest earthquakes (Mw ≥ 5.5) generated an abrupt uplift of the water level, recorded up to 100 km away from the mainshock area. Monitoring a set of selected springs in the central Apennines, a few hydrogeochemical anomalies were observed months before the onset of the seismic swarm, including a variation of pH values and an increase of As, V, and Fe concentrations. Cr concentrations increased immediately after the onset of the seismic sequence. On November 2016, these elements recovered to their usual low concentrations. We interpret these geochemical anomalies as reliable seismic precursors for a dilational tectonic setting.

Earthquakes trigger the loss of groundwater biodiversity.

Earthquakes are among the most destructive natural events. The 6 April 2009, 6.3-Mw earthquake in L'Aquila (Italy) markedly altered the karstic Gran Sasso Aquifer (GSA) hydrogeology and geochemistry. The GSA groundwater invertebrate community is mainly comprised of small-bodied, colourless, blind microcrustaceans. We compared abiotic and biotic data from two pre-earthquake and one post-earthquake complete but non-contiguous hydrological years to investigate the effects of the 2009 earthquake on the dominant copepod component of the obligate groundwater fauna. Our results suggest that the massive earthquake-induced aquifer strain biotriggered a flushing of groundwater fauna, with a dramatic decrease in subterranean species abundance. Population turnover rates appeared to have crashed, no longer replenishing the long-standing communities from aquifer fractures, and the aquifer became almost totally deprived of animal life. Groundwater communities are notorious for their low resilience. Therefore, any major disturbance that negatively impacts survival or reproduction may lead to local extinction of species, most of them being the only survivors of phylogenetic lineages extinct at the Earth surface. Given the ecological key role played by the subterranean fauna as decomposers of organic matter and "ecosystem engineers", we urge more detailed, long-term studies on the effect of major disturbances to groundwater ecosystems.

Does groundwater protection in Europe require new EU-wide environmental quality standards?

The European Groundwater Directive could be improved by limiting the scopes of the Annexes I and II to the manmade and natural substances, respectively, and by defining a common monitoring protocol. The changes in the European landuse patterns, in particular the urban sprawl phenomena, obscure the distinction between the point and diffuse sources of contamination. In the future more importance will be given to the household contamination. Moreover, the agricultural environment could be used for developing new conceptual models related to the pharmaceuticals.

Evaluation by chemical parameters of the pollution state of the agricultural-industrial settlement of the Fucino Plain.

In the present work are reported the results of a monitoring on a vast scale, carried out through evaluation of opportune chemical parameters, of the pollution state of the agricultural-industrial settlement of the Fucino Plain. The parameters took into consideration have been the presence of wide consumption pesticides and of ionic species as Cl-, NO2-, NO3-, NH4+, the quantification of the dissolved oxygen, of the temperature, of the conductivity, of pH and eH. Collected data are used for chemometric elaboration. The water systems examined, by means of drawing campaigns carried out at regular intervals in winter, spring, summer, and autumnal seasons, are represented by superficial waters constituting a network of irrigation canals fed by stratum and meteoric waters. In this work are reported the results relative to the drawing campaigns.