H/V measurements as an effective tool for the reliable detection of landslide slip surfaces: Case studies of Castagnola (La Spezia, Italy) and Roccalbegna (Grosseto, Italy)

AbstractA variety of methods (detailed geomorphological surveys, geotechnical investigations, local instrumentation, satellite data, and radar interferometry) along with geophysical techniques may be used to investigate slope instabilities and to detect the inhomogeneities of materials as well as their properties, boundaries, and sliding surfaces. Of these techniques, the method based on seismic noise measurements allows abrupt changes in seismic impedance at landslide boundaries resulting from varying levels of seismic velocity and material density to be detected. Peaks of the Horizontal to Vertical Spectral Ratio have proven to serve as effective indicators of the resonance frequency of low-impedance surface layers. In this work, horizontal to vertical spectral ratio surveys of the Castagnola (La Spezia, Italy) and Roccalbegna (Grosseto, Italy) landslides were carried out. From roughly 100 single-station measurements made inside and outside the landslides at each site, we define a threshold number of single-station seismic noise measures beyond which information is redundant because the variation in reconstructed impedance contrast surfaces is not significant. This approach allows one to reliably retrieve the geometry of a landslide body, ultimately generating useful information for determining whether further measurements are needed to improve landslide body reconstruction

Soil characterization for shallow landslides modeling: a case study in the Northern Apennines (Central Italy)

In this paper, we present preliminary results of the IPL project No. 198 \u201cMulti-scale rainfall triggering models for Early Warning of Landslides (MUSE).\u201d In particular, we perform an assessment of the geotechnical and hydrological parameters affecting the occurrence of landslides. The aim of this study is to improve the reliability of a physically based model high resolution slope stability simulator (HIRESSS) for the forecasting of shallow landslides. The model and the soil characterization have been tested in Northern Tuscany (Italy), along the Apennine chain, an area that is historically affected by shallow landslides. In this area, the main geotechnical and hydrological parameters controlling the shear strength and permeability of soils have been determined by in situ measurements integrated by laboratory analyses. Soil properties have been statistically characterized to provide more refined input data for the slope stability model. Finally, we have tested the ability of the model to predict the occurrence of shallow landslides in response to an intense meteoric precipitation

Hydrogen-Rich Gas Produced by the Chemical Neutralization of Reactive By-Products from the Screening Processes of the Secondary Aluminum Industry

In the framework of the industry of secondary aluminum, the chemical neutralization of highly reactive materials that come from the pre-treatment screening processes of scraps (beverage cans and domestic appliances) was investigated through experiments in aqueous alkaline solutions. Metallic aluminum-rich by-products are classified, according to EU law, as dangerous waste, as they can potentially develop flammable gases capable of forming explosive mixtures with air. In this way they cannot be disposed of in landfills for non-hazardous wastes if chemical neutralization is not planned and performed beforehand. In this way, these experiments were mainly aimed at unraveling the oxidation rate and at quantifying the production of hydrogen-rich gases from the reactions of the metallic aluminum-rich by-products in a water-rich alkaline (liquid or vapor) environment. Reactions were carried out in a stainless-steel batch mini-reactor with metering and sampling valves, with the resulting gases analyzed by gas-chromatography (GC). The experimental setup was planned to avoid the following issues: (i) the corrosion of the reactor by the alkaline solution and (ii) the permeability of the system to hydrogen (i.e., possible leaks of H2), related to the fast kinetics and short duration of the reactions (which may hinder a pile-up-effect) between the solid by-products and the liquid. The procedure was defined by a controlled interaction process between metals and liquid, using NaOH to increase reaction rates. The experimental runs performed in the mini-reactor proved to be effective for eliminating the reactive metallic aluminum, reaching a maximum hydrogen production of 96% of the total gases produced in the experiments. The relations between gas generation (up to 55 bar of H2 in the experiments, which lasted for four days) and each specific parameter variation are discussed. All the obtained results can be transferred and applied to (i) the possible industrialization of the method for the chemical neutralization of these dangerous by-products, increasing sustainability and workplace safety, (ii) the use of the resulting hydrogen as a source of energy for the furnaces of the secondary aluminum industry itself, and (iii) new technological materials (e.g., “foamed geopolymers”), by using hydrogen as a foaming agent, coupled with aluminosilicate materials, during geopolymeric reactions

Degradation of biogas in a simulated landfill cover soil at laboratory scale: Compositional changes of main components and volatile organic compounds

A laboratory experiment lasting 28 days was run to simulate a typical landfill system and to investigate the compositional changes affecting the main components (CH4, CO2, and H2) and nonmethane volatile organic compounds from biogas generated by anaerobic digestion of food waste and passing through a soil column. Gas samples were periodically collected from both the digester headspace and the soil column at increasing distances from the biogas source. CH4 and H2 were efficiently degraded along the soil column. The isotopic values of δ13C measured in CH4 and CO2 from the soil column were relatively enriched in 13C compared to the biogas. Aromatics and alkanes were the most abundant groups in the biogas samples. Among these compounds, alkylated benzenes and long-chain C3+ alkanes were significantly degraded within the soil column, whereas benzene and short-chain alkanes were recalcitrant. Terpene and O-substituted compounds were relatively stable under oxidising conditions. Cyclic, alkene, S-substituted, and halogenated compounds, which exhibited minor amounts in the digester headspace, were virtually absent in the soil column. These results pointed out how many recalcitrant potentially toxic and polluting compounds tend to be relatively enriched along the soil column, claiming action to minimise diffuse landfill gas (LFG) emissions. The proposed experimental approach represents a reliable tool for investigating the attenuation capacities of landfill cover soils for LFG components and developing optimised covers by adopting proper soil treatments and operating conditions to improve their degradation efficiencies

Chemical alteration and mineral growth under high pCO2 conditions: Insights from the mineral chemistry of carbonate phases in the Caprese Reservoir (Northern Apennines, central Italy)

Carbon cycle is one of the most complex geochemical cycles of the Earth as it involves atmosphere, hydrosphere, biosphere and lithosphere. Among these different geochemical spheres, mechanisms and reaction rates governing migration and fixation of carbon (i.e. fluxes), such as the stability of the different carbonates minerals under specific conditions in crustal reservoirs, are still matter of detailed studies. In this work, SEM and XRD investigations and EMP analyses were combined to study the mineralogical and chemical compositions of carbonate phases occurring in strongly altered Triassic volcanic rocks, hosting a CO2 reservoir (namely the Caprese Reservoir), located in eastern Tuscany (central Italy). The Caprese crustal fluid reservoir, lying at 3300 m depth beneath the Quaternary San Cassiano basin, hosts a supercritical CO2-(N2)-rich phase and a Na-Cl-rich saline (up to 81.5 g/L) brine. The mineralogical assemblage consists of authigenic microcrystalline quartz, Ca-Fe-Mg carbonates, Na-K-clay minerals and Fe-oxides, the primary minerals being almost completely chemically altered by secondary processes. Scanning electron microscope images and cation (Ca-Fe-Mg) contents in carbonates highlighted that zoned ankerite was re-grown on calcite crystals due to interactions processes with CO2-rich fluids. The geochemical and mineralogical data provided useful insights for understanding both the processes that formed the C-bearing minerals and their growth in deep, saline reservoirs

Occurrence and Quantification of Natural and Microplastic Items in Urban Streams: The Case of Mugnone Creek (Florence, Italy)

The terrestrial environment is an important contributor of microplastics (MPs) to the oceans. Urban streams, strictly interwoven in the city network and to the MPs’ terrestrial source, have a relevant impact on the MP budget of large rivers and, in turn, marine areas. We investigated the fluxes (items/day) of MPs and natural fibers of Mugnone Creek, a small stream crossing the highly urbanized landscape of Florence (Italy) and ending in the Arno River (and eventually to the Tyrrhenian Sea). Measurements were done in dry and wet seasons for two years (2019–2020); stream sediments were also collected in 2019. The highest loads of anthropogenic particles were observed in the 2019 wet season (109 items/day) at the creek outlet. The number of items in sediments increased from upstream (500 items/kg) to urban sites (1540 items/kg). Fibers were the dominant shape class; they were mostly cellulosic in composition. Among synthetic items, fragments of butadiene-styrene (SBR), indicative of tire wear, were observed. Domestic wastewater discharge and vehicular traffic are important sources of pollution for Mugnone Creek, especially during rain events. The study of small creeks is of pivotal importance to limit the availability of MPs in the environment

Towards a National-Scale Dataset of Geotechnical and Hydrological Soil Parameters for Shallow Landslide Modeling

One of the main constraints in assessing shallow landslide hazards through physically based models is the need to characterize the geotechnical parameters of the involved materials. Indeed, the quantity and quality of input data are closely related to the reliability of the results of every model used, therefore data acquisition is a critical and time-consuming step in every research activity. In this perspective, we reviewed all official certificates of tests performed through 30 years at the Geotechnics Laboratory of the Earth Science Department (University of Firenze, Firenze, Italy), compiling a dataset in which 380 points are accurately geolocated and provide information about one or more geotechnical parameters used in slope stability modeling. All tests performed in the past (in the framework of previous research programs, agreements of cooperation, or to support didactic activities) were gathered, homogenized, digitalized, and geotagged. The dataset is based on both on-site tests and laboratory tests, it accounts for 40 attributes, among which 13 are descriptive (e.g., lithology or location) and 27 may be of direct interest in slope stability modeling as input parameters. The dataset is made openly available and can be useful for scientists or practitioners committed to landslide modeling

Occurrence and Quantification of Natural and Microplastic Items in Urban Streams: The Case of Mugnone Creek (Florence, Italy)

The terrestrial environment is an important contributor of microplastics (MPs) to the oceans. Urban streams, strictly interwoven in the city network and to the MPs’ terrestrial source, have a relevant impact on the MP budget of large rivers and, in turn, marine areas. We investigated the fluxes (items/day) of MPs and natural fibers of Mugnone Creek, a small stream crossing the highly urbanized landscape of Florence (Italy) and ending in the Arno River (and eventually to the Tyrrhenian Sea). Measurements were done in dry and wet seasons for two years (2019–2020); stream sediments were also collected in 2019. The highest loads of anthropogenic particles were observed in the 2019 wet season (109 items/day) at the creek outlet. The number of items in sediments increased from upstream (500 items/kg) to urban sites (1540 items/kg). Fibers were the dominant shape class; they were mostly cellulosic in composition. Among synthetic items, fragments of butadiene-styrene (SBR), indicative of tire wear, were observed. Domestic wastewater discharge and vehicular traffic are important sources of pollution for Mugnone Creek, especially during rain events. The study of small creeks is of pivotal importance to limit the availability of MPs in the environment