Natural surface hydrocarbons and soil faunal biodiversity: A bioremediation perspective

Hydrocarbon pollution threatens aquatic and terrestrial ecosystems globally, but soil fauna in oil-polluted soils has been insufficiently studied. In this research, soil hydrocarbon toxicity was investigated in two natural oil seepage soils in Val D'Agri (Italy) using two different approaches: (i) toxicological tests with Folsomia candida (Collembola) and Eisenia fetida (Oligochaeta) and (ii) analysis of abundance and composition of micro- and meso-fauna. Soil sampling was done along 20 m-transepts starting from the natural oil seepages. Toxicological testing revealed that no exemplars of F. candida survived, whereas specimens of E. fetida not only survived but also increased in weight in soils with higher PAH concentrations, although no reproduction was observed. Analysis on microfauna showed that Nematoda was the most abundant group, with distance from seepages not affecting its abundance. Arthropoda results showed that Acarina, Collembola and Diptera larvae represented the most abundant taxa. The highest divergence in community composition was found between soils situated near seepages and at 5 m and 10 m distance. Arthropoda taxa numbers, total abundance and Acarina were lower in soils with high PAH concentration, while Diptera larvae were not significantly affected. Earthworms, together with Nematoda and Diptera larvae, could therefore represent ideal candidates in PAH degradation studies

Hydrogeological behaviour and geochemical features of waters in evaporite-bearing low-permeability successions: A case study in Southern Sicily, Italy

Knowledge about the hydrogeological behaviour of heterogeneous low-permeability media is an important tool when designing anthropogenic works (e.g., landfills) that could potentially have negative impacts on the environment and on people’s health. The knowledge about the biogeochemical processes in these media could prevent “false positives” when studying groundwater quality and possible contamination caused by anthropogenic activities. In this research, we firstly refined knowledge about the groundwater flow field at a representative site where the groundwater flows within an evaporite-bearing low-permeability succession. Hydraulic measurements and tritium analyses demonstrated the coexistence of relatively brief to very prolonged groundwater pathways. The groundwater is recharged by local precipitation, as demonstrated by stable isotopes investigations. However, relatively deep groundwater is clearly linked to very high tritium content rainwater precipitated during the 1950s and 1960s. The deuterium content of some groundwater samples showed unusual values, explained by the interactions between the groundwater and certain gases (H2S and CH4), the presences of which are linked to sulfate-reducing bacteria and methanogenic archaea detected within the saturated medium through biomolecular investigations in the shallow organic reach clayey deposits. In a wider, methodological context, the present study demonstrates that interdisciplinary approaches provide better knowledge about the behaviour of heterogeneous low-permeability media and the meaning of each data type

A multi-parameter field monitoring system to investigate the dynamics of large earth slides–earth flows in the Northern Apennines, Italy

Large earth slides and rocks lides evolving into earth flows are quite widespread in the Northern Italian Apennines. Despite being simply referred to as landslides, many of them are, in fact, large complexes of landslides. They evolved through multiple and/or successive movements, undergoing partial and/or total reactivations. The reactivation of pre-existing landslide bodies is the prevalent mechanism for the known landslide events, as the historical records and the technical reports indicate. Landslide reactivation is, indeed, a relevant topic from the perspective of risk assessment and mitigation. A multi-parameter monitoring system was installed on a large complex of landslides that underwent partial or total reactivations after heavy rainfall events, causing damages to buildings and infrastructures. Two clusters of automatic piezometers—each coupled with an inclinometer—and a time-lapse resistivity deployment were the core of the monitoring system. A weather station, collecting data from subsurface thermometers, and a water content probe completed the system. After the construction of a new geological model of the slope, this study aimed at understanding the possible mechanisms leading to the reactivation of the landslide. This goal was achieved by gaining insights into the process of rainfall infiltration into the landslide deposits, by determining the groundwater flow and evaluating the landslide displacements. The monitoring system captured the processes that took place in the landslide bodies and the bedrock in response to a rainfall event in early February 2017, which followed a dry period of eight months. The recorded data provided indications on the variation of the hydraulic head in the groundwater within the landslide and the bedrock, particularly at the sliding surfaces. The electrical conductivity of the groundwater and the resistivity of the terrain varied across the failure surfaces. In particular, a sudden increase in the electrical conductivity was related to the locations of the main sliding surfaces. The joint analysis of time-lapse resistivity, hydraulic heads, and groundwater electrical conductivity helped identify the locations of weaker levels within the landslide masses, which were confirmed by data from inclinometers. This study improved the knowledge of the hydrogeological behaviour of a complex of landslides in heterogeneous low-permeability media. Moreover, the obtained results contributed to the understanding of the role played by different portions of the landslide complex in the evolution of the movement

How do turbidite systems behave from the hydrogeological point of view? New insights and open questions coming from an interdisciplinary work in southern Italy

Turbidite successions can behave either as aquitards or aquifers depending on their lithological and hydraulic features. In particular, post-depositional processes can increase rock permeability due to fracture development in the competent layers. Thus, at a local scale, turbidite systems warrant further detailed investigations, aimed at reconstructing reliable hydrogeological models. The objective of this work was to investigate from the hydrogeological perspective a turbiditic aquifer located in southern Italy, where several perennial and seasonal springs were detected. Considering the complex hydrodynamics of these systems at the catchment scale, to reach an optimal characterization, a multidisciplinary approach was adopted. The conceptual framework employed microbial communities as groundwater tracers, together with the physicochemical features and isotopic signature of springs and streams from water samples. Meanwhile, geophysical investigations coupled with the geological survey provided the contextualization of the hydrogeological data into the detailed geological reconstruction of the study area. This modus operandi allowed us to typify several differences among the samples, allowing identification of sources and paths of surface water and groundwater, along with diffuse groundwater outflow along streams. As a final result, a hydrogeological conceptual model was reconstructed, underlining how at a very local scale the lithologic, hydraulic, and geomorphological heterogeneity of the studied relief can lead to an improved hydrogeological conceptual model compared to that of other turbidite systems. These results open new questions about the hydrogeological behavior of turbiditic aquifers, which could be pivotal in future research. In fact, these systems could support relevant ecosystems and anthropic activities, especially where climate change will force the research of new (and probably less hydrogeologically efficient) water sources

Mechanisms of earthquake induced chemical and fluid transport to carbonate groundwater springs after earthquakes

Mechanisms by which hydrochemical changes occur after earthquakes are not well documented. We use the 2016-2017 central Italy seismic sequence, which caused notable hydrochemical transient variations in groundwater springs to address this topic, with special reference to effects on fractured carbonate aquifers. Hydrochemistry measured before and after the earthquakes at four springs at varying distances from the epicenters all showed immediate post-mainshock peaks in trace element concentrations, but little change in major elements. Most parameters returned to pre-earthquake values before the last events of the seismic sequence. The source of solutes, particularly trace elements, is longer residence time pore water stored in slow moving fractures or abandoned karstic flowpaths. These fluids were expelled into the main flow paths after an increase in pore pressure, hydraulic conductivity, and shaking from co-seismic aquifer stress. The weak response to the later earthquakes is explained by progressive depletion of high solute fluids as earlier shocks flushed out the stored fluids in the fractures. Spring \u3b413CDIC values closest to a deep magma source to the west became enriched relative to pre-earthquake values following the August 24th event. This enrichment indicates input from deeply-sourced dissolved CO2 gas after dilation of specific fault conduits. Differences in carbon isotopic responses between springs are attributed to proximity to the deep CO2 source. Most of the transient chemical changes seen in the three fractured carbonate aquifers are attributed to local shaking and emptying of isolated pores and fractures, and are not from rapid upward movement of deep fluids

Groundwater is a hidden global keystone ecosystem

Groundwater is a vital ecosystem of the global water cycle, hosting unique biodiversity and providing essential services to societies. Despite being the largest unfrozen freshwater resource, in a period of depletion by extraction and pollution, groundwater environments have been repeatedly overlooked in global biodiversity conservation agendas. Disregarding the importance of groundwater as an ecosystem ignores its critical role in preserving surface biomes. To foster timely global conservation of groundwater, we propose elevating the concept of keystone species into the realm of ecosystems, claiming groundwater as a keystone ecosystem that influences the integrity of many dependent ecosystems. Our global analysis shows that over half of land surface areas (52.6%) has a medium‐to‐high interaction with groundwater, reaching up to 74.9% when deserts and high mountains are excluded. We postulate that the intrinsic transboundary features of groundwater are critical for shifting perspectives towards more holistic approaches in aquatic ecology and beyond. Furthermore, we propose eight key themes to develop a science‐policy integrated groundwater conservation agenda. Given ecosystems above and below the ground intersect at many levels, considering groundwater as an essential component of planetary health is pivotal to reduce biodiversity loss and buffer against climate change