Displays

A landfill body is typically highly heterogeneous. The scale of these heterogeneities - which are relevant for the purpose of assessment of preferential flow paths, the degradation processes, and the spatio-temporally varying aging and settlements - is quite often small considering the limiting resolution and confidence of the prevalent near-surface geophysical methods. High-density areas act as obstruction to fluid flow and are important for understanding the degradation processes. These areas manifest as scatterers in the recorded seismic wavefield. Strong presence of scattered energy is typical of seismic datasets acquired on landfills. Our research has been concentrated on resolving and monitoring density and porosity variations, as well as distribution of water saturation, phreatic surface, matric suction and stress. Dedicated schemes of early-arrival waveform tomography, full-waveform inversion and interferometric seismic wavefield retrieval complemented by electrical resistivity tomography show promise in high-resolution delineation and monitoring of these properties in a heterogeneous landfill. We will discuss the results of a novel inversion scheme which allows quantitative estimation of spatio-temporally heterogeneous matric suction, stress and porosity.

How to cite: Ghose, R.: Characterization of heterogeneous landfill: seismic waveform inversion and wavefield retrieval to integrated quantitative inversion of high-resolution seismic-electrical datasets, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18235, https://doi.org/10.5194/egusphere-egu2020-18235, 2020.

What happens to quarries when they are at the end of their productive lifespan? Under Ireland’s waste authorisation regime, worked-out quarries can apply for a licence or permit to accept soil and stone as Soil Recovery Facilities (SRFs). This practice achieves a number of environmental and circular economy objectives, and is allowed for under Ireland’s Waste Management Act 1996 as amended and Waste Management (Facility Permit and Registration) Regulations 2007. Restoring the ground surface of quarries allows the site to be reused for amenity, ecological, agricultural or infrastructural development.  The beneficial recovery of excess excavated soil and stone from other sites represents a saving on the disposal of such material to landfill and in many cases significant reductions in transportation costs and carbon emissions.

Unlike landfills, SRFs are not required to have an engineered basal liner, nor are they required to install an engineered cap following completion of restoration or land-raising. The placement of externally-sourced inappropriate material at SRFs poses a potential source of chemical contamination. Geological Survey Ireland in partnership with the Irish Environmental Protection Agency (EPA) and Geosyntec Ltd have developed an innovative method to assist with the recovery of soil and stone to SRFs while minimising potential chemical impacts. In terms of the source-pathway-receptor conceptual framework, the approach aims to prevent a contaminant source being introduced to the SRF and to prevent the chemical load on the receptor (down–gradient aquifer) from newly placed material exceeding the load from the original or existing soil and stone.

Using existing topsoil geochemical baseline datasets (National Soil Database, Tellus and GEMAS) and site-specific geochemical information from two representative SRFs, a suite of Geochemically Appropriate Levels (GALs) was developed for eight Potentially Harmful metals/metalloids in soil (arsenic, cadmium, chromium, copper, mercury, lead, nickel and zinc). The GALs vary considerably across seven different geological domains in Ireland, reflecting the wide variation in the composition of Ireland’s bedrock and extensive quaternary sediment (subsoil) parent materials. This work addressed the relationship between topsoil and subsoil geochemistry, with data supporting the use of topsoil data as a proxy for subsoil data, in the absence of baseline subsoil geochemical data.

The study is designed to support the EPA and Local Authorities in establishing an approach to setting appropriate trigger levels for acceptance of uncontaminated soil and stone at SRFs and it may be reviewed periodically with improved availability of baseline soil geochemistry data in Ireland, specifically, when Geological Survey Ireland's Tellus topsoil geochemical mapping is completed nationally (projected 2028).

How to cite: Glennon, M., Gallagher, V., Meehan, R., Scanlon, R., Huskisson, S., and Webb, G.: Sustainably restoring quarry voids: Geochemically Appropriate Levels for soil recovery activities in Ireland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20395, https://doi.org/10.5194/egusphere-egu2020-20395, 2020.

Sedimentological and physical properties of the submarine mine tailings deposit of Portmán Bay, SE Spain

Andrea Baza-Varas, Jaime Frigola, Marc Cerdà-Domènech, Anna Sànchez Vidal and Miquel Canals

CRG Marine Geosciences, Dept. of Earth and Ocean Dynamics, Faculty of Earth Sciences, University of Barcelona, Spain

a.baza@ub.edu, jfrigola@ub.edu, cerda.domenech@ub.edu, anna.sanchez@ub.edu,  miquelcanals@ub.edu

About 57 Mt of mine tailings were dumped directly into the sea from 1957 to 1990 as a result of the open pit exploitation of Pb and Zn ores in Sierra de Cartagena - La Unión district, SE Spain. This led to the infilling of Portmán Bay and a seaward shoreline advance of ~ 600 m associated to the development of a submarine extension of the resulting deposit. Whereas several investigations have been carried out in the emerged portion of the tailings deposit, little information exists on the dimensions and properties of its submerged portion. Nowadays, a restoration project intends to move back the shoreline by ~250 m by dredging part of the subaerial deposit.

This contribution focuses on the sedimentological and physical properties of the materials forming the submerged deposit from where accumulation patterns could be derived. With this purpose a number of up to 4 m long gravity cores where obtained from R/V Ángeles Alvariño during the 2018 NUREIEVA-MAR1 research cruise. Subsequently, Multi Sensor Core Logger (MSCL) measurements were performed on whole and split sections in order to obtain the physical properties of the materials, namely gamma-density, magnetic susceptibility, p-wave velocity and non-contact resistivity. Furthermore, split core sections were visually described and imaged.

This led to the identification of 4 main units in the sampled materials. From bottom to top, Unit 1 consists of light-colored, bioclast-rich fine-medium sands indicative of pre-dumping inner shelf sedimentation. Unit 2 appears only in some distal cores (~ 1.3 km from shore) collected at water depths of about 40 m and is composed of brown-dark grey silty clays with abundant black patches. All measured physical properties display low and homogeneous values. This unit could be interpreted as of transitional character in between pre-dumping conditions and the first arrival of mine waste. Unit 3 is made of highly laminated clayey silts punctuated by dark sand layers and its physical properties show generally high and oscillating values. Unit 3 corresponds to the mine tailings in stricto sensu. Finally, the upper Unit 4 is composed of bioturbated homogeneous sandy silts with generally diminishing values for most of the measured physical properties. This unit results from the reworking of materials from the top of the tailings deposits mixed with post-dumping sedimentary particles.

The physical properties and elements measured have a diagnostic character in differentiating the mine tailings from former deposits and from materials resulting from reworking after the cessation of dumping. Our results also provide clues on the seaward extension of the mine tailings deposit as shown by its seaward thinning recorded in the investigated sediment cores, which is a consequence of increasing distance from the discharge point on the shore and of waste dispersal and accumulation patterns in the shallow marine environment.

How to cite: Baza Varas, A., Frigola, J., Cerdà-Domènech, M., Sànchez-Vidal, A., and Canals, M.: Sedimentological and physical properties of the submarine mine tailings deposit of Portmán Bay, SE Spain, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10529, https://doi.org/10.5194/egusphere-egu2020-10529, 2020.

Traditionally manufactured light-weight aggregates (LWA) suffer from a fractured surface. Consequently, concrete mixes containing LWA cannot be pumped, due to the water being forced into the porous LWA pellets by the pumping pressure. This is a limitation and a cost factor in construction practise. As part of the project "Nye produkter fra gruveavfall i nord" (Novel products from mine tailings in Northern Norway), will examine mine tailings aiming to develop new products. A pilot study has aimed to develop high quality LWA suitable for pumping from Nussir mining company tailings. In 2019, Nussir ASA was granted operational licence for exploitation of the Repparfjord copper deposit in northern Norway. The tailings, 30 Mtons in total and 1-2 Mtons per year, is deposited in sea.

LWA is traditionally made from pelletized clays, where (Na, K, Mg, Ca, Fe)-aluminosilicates are heated to a viscous glassy phase and subsequently bloated by carbothermal reduction of Fe(III)-oxide, developing carbon monoxide gas inside the pellets. The pellets are then quenched in air, and this is the stage where the surface is fractured. In the pilot study, mine tailings lower in sodium and potassium have been identified, aiming to increase the thermal shock resistance enabling a non-fractured pellets surface. Experimental work was carried out by placing the pellets in a preheated furnace, subsequently quenching pellets at different predetermined times. the results from the study showed that it was possible to produce an unfractured surface, but work is still needed to optimise the bloating. The pellets had an optimal bloating temperature of 1225 °C which is almost 100 °C higher than for typical clay LWAs. Exposure time was ca 5 minutes, a bit shorter than traditional LWAs. The main project will continue the work with a series of new tailings, varying in both composition and particle size.

How to cite: Oye, B., Hoyli, R., and Danielsen, S. W.: Surface sealed light weight aggregate from mine tailings, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22598, https://doi.org/10.5194/egusphere-egu2020-22598, 2020.

Environmental aspects and the growing interest in the economical exploitation of landfills urges the need for cost-efficient workflows providing information with high spatial resolution. Especially for landfill mining, a detailed characterization of the landfill geometry and the waste composition is critical to assess the economic potential. Geophysical methods have proven to fulfill these requirements since they permit to collect data in a quasi-continuous manner. However, the subjective perception of the geophysical imaging results might bias the interpretation, e.g. the characterization of the landfill boundaries and the estimation of waste volumes. To overcome such shortcomings, we present here an unsupervised method for the post-processing of geophysical imaging to identify subsurface interfaces associated to e.g. landfill geometries, waste variation etc. Our methodology is applicable for results obtained with a single method, or the combination of different geophysical methods, e.g. refraction seismic tomography (RST), electrical resistivity tomography (ERT) or induced polarization (IP). Assuming strong contrasts in the retrieved physical properties associated to interfaces, our method computes the magnitude of the gradient vector for each point in the resolved model. In the next step, a random walker algorithm converts the gradient magnitude image into a binary image permitting to obtain the contours of subsurface regions characterized by high gradients. Originating from the centroid for such a region further base points are determined and used in the final step to compute shape and location of the corresponding interface. To demonstrate the applicability of our method we present here results obtained for a landfill located in Upper Austria, where RST, ERT and IP data were collected along several transects. Our results demonstrate that the method proposed here has the potential to enhance geophysical investigations of landfills by permitting an improved interpretation of the imaging results, as required, for instance to estimate waste volume.

How to cite: Steiner, M., Chwatal, W., Freudenthaler, A., and Flores Orozco, A.: Unsupervised delineation of landfill geometries based on geophysical imaging results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8578, https://doi.org/10.5194/egusphere-egu2020-8578, 2020.

For a large number of landfills, basic knowledge about extent, waste composition or environmental impact is incomplete. Considering the large number of non-sanitary landfills located in semi-urban areas subject to increased land use pressure plus the high cost for remediation, it is crucial to develop efficient characterization tools suitable in landfill contexts. Such tools are required on a broader level to enable the identification of landfills with high priority for remediation or high potential in terms of waste valorisation (landfill mining) and, on a more detailed level, to enable planning of remediation or landfill mining projects.

Due to the high heterogeneity and complexity of landfills, the application of different geophysical methods in combination with targeted sampling has proven to be a highly favourable approach. In contrast to conventional ground truth methods, geophysical techniques provide the possibility to characterize large portions of the landfill volume in a non-invasive and relatively efficient way. Furthermore, the application of complementary geophysical techniques reduces the risk of misinterpretation, and by verifying/calibrating the results with targeted sampling a relatively detailed landfill model can be built. However, building a landfill model from data measured at different resolution, coverage and with different uncertainties is a challenge.

We present a case study from Emersons Green (UK) where we completed multiple geophysical surveys on a former landfill site prior to its full excavation. The excavation works provided nearly continuous information on the waste and cover layer thickness as well as information on material composition from several locations. This enabled us to validate the geophysical measurements and to test different approaches for model building, as well as testing virtual sampling strategies in order to assess how the number and location of ground truth samples affects the model quality.

The case study has highlighted the advantage of a multi-geophysical approach where Electromagnetics (EM) and Magnetics (Mag) were able to provide a rapid overview of the landfill structure and its lateral extent. In contrast, Induced Polarization Tomography (IPT) and Multichannel Analysis of Surface Waves (MASW) were most suitable to delineate the bottom interface of the waste layer. IPT was in addition able to delineate the cover layer thickness and Electrical Resistivity Tomography (ERT) seemed more sensitive to changes in moisture content. For the model building, a probabilistic approach has proven to be efficient. In terms of sampling strategy a minimum number of samples are required co-located with the geophysical measurements to train the probability model. Furthermore, additional sampling points at locations where geophysical methods are only sparsely available increase the model certainty.

How to cite: Inauen, C. M., Brooks, A., Caterina, D., Chambers, J. E., Dashwood, B., Dimech, A., Gunn, D. A., Isunza Manrique, I., Neal, O., Piquet, X., Scott, D., Watlet, A., Whiteley, J. S., and Wilkinson, P. B.: Combining an integrated geophysical survey into a landfill model: A case study from Emersons Green, UK, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21855, https://doi.org/10.5194/egusphere-egu2020-21855, 2020.

Landfills are one of the major anthropogenic sources of methane (CH₄) emissions to the atmosphere, even years after being inactive. Model-based estimates of CH₄ emission from landfills are inaccurate due to uncertainties in the underlying assumptions regarding gas generation rates, oxidation and recovery parameters. In-situ measurement techniques are more reliable in quantifying CH₄ emissions, with the tracer gas dispersion method (TDM) being one of the best-validated methods. The TDM does however not allow for continuous estimation unless a higher sampling frequency for longer measurement campaigns is being used. Field studies report short-term CH₄ emission variation of several orders of magnitude, which are being driven by changes in meteorological conditions, with changes in barometric pressure being the most important. This variation makes discontinuous measurements more uncertain. In this presentation, we focus on CH₄ emission dynamics under the influence of barometric pressure changes and develop a model that can explain the dynamics.

Landfill methane emissions were measured continuously with the eddy covariance method over several months in an inactive landfill (Skellingsted, Western Zealand, Denmark). The landfill is covered with an 80 cm thick soil layer and vegetated with grassland. Screenings of the site indicate a considerable horizontal heterogeneity of the emissions, which needs to be considered when interpreting continuously measured fluxes.

Measured methane fluxes ranged from 0 to 10 μmol∙m^-2∙s^-1. Periods with decreasing barometric pressure showed highest flux rates, while increasing barometric pressure suppressed the methane flux almost to 0 μmol∙m^-2∙s^-1. However, this dependency had a complex dynamic nature. In most of the cases, the responses of CH₄ fluxes to pressure changes were delayed by 0 to 4 hours. We developed a model concept that is able to explain this behavior, including the pressure gradient driven advective CH₄ transports through the porous soil layer above the source and diffusion between fronts of background air and landfill gas.

The general implications from this work are an estimation of the uncertainty and possibly correction of point CH₄ emission measurements, e.g. with the TDM. Additionally, the increased understanding of gas transport dynamics through terrestrial landfill covers will help to evaluate the efficiency of methane emission mitigation methods that aim at increasing methane oxidation by the establishment of biocovers.

How to cite: Kissas, K., Scheutz, C., Kjeldsen, P., and Ibrom, A.: Pressure effects on methane emissions from landfills, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17746, https://doi.org/10.5194/egusphere-egu2020-17746, 2020.

The self-burning of coal mining residues disposed at environmental conditions have been described in the literature as a phenomenon occurring worldwide. These coal related fires are of significant concern because of the risks to environment and human health due to the emission of harmful gases and particulate matter to atmosphere. Another concern is the degradation of soils and waters in surrounding areas owing to the mobilization and leaching of hazardous elements. The self-burning of coal mining waste deposits may be a very persistent phenomena over decades. The carbon content (combustible fraction) and chemical composition of coal waste materials (and some physical properties) are the most relevant factors that influence intensity and duration of the self-burning process. The comprehensive characterisation of coal waste deposit materials provide information on the self-burning process and above all useful insights about the propensity to ignition and burning and their environmental impacts. The characterization of coal waste materials can contribute to assess their reuse as a secondary source of critical raw materials and carbon based materials.

The recycling of these materials, from both burning and non-burning coal waste deposits, is in good agreement with recommendations from European Union (EU) pointing out the need for developing sustainable recovery of mining and industrial wastes to mitigate environmental impacts. The EU identifies 26 critical raw materials including inorganic trace elements and natural graphite as a critical raw materials with extremely high level of external dependence, and strongly recommends the development of measures to increase recycling of by-products and residues. In this framework, research has been dedicated to burning or already burned coal mining waste deposits in Portugal and Spain. Non-burning coal mining waste deposits from the same mining areas have also been investigated. These coal waste deposits, resulted from the discharging of coarse mine refuse from mining exploration. They are very heterogeneous and present variable amounts of coal that is the combustible fraction. The comprehensive characterization of mining waste materials as well as the identification of products formed during combustion reveals the potential environmental impact, principally due to the concentration of volatile organic compounds emitted to atmosphere. The combustion process also causes changes in trace elements’ mode of occurrence with some becoming more easily mobilised for surrounding soils and water systems by percolation or deposition of solid atmospheric particles. On the other hand, the mining waste burned materials reveal an enrichment of some trace elements, including critical raw material; and, the production of graphitic structures, including graphene. Therefore the coal wastes mining deposits are an environmental issue, they can be seen as an alternative secondary source of critical raw materials and carbon based materials.

How to cite: Ribeiro, J., Suárez-Ruiz, I., and Flores, D.: Self-burning coal mining residues – an environmental issue or a source of raw materials?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20018, https://doi.org/10.5194/egusphere-egu2020-20018, 2020.

The incremental amount of needed Raw Materials (RM) and Critical Raw Materials (CRM) cannot be totally supplied by recycling activities, and mining activities are growing more and more at global level, requiring more modern and efficient technologies and mining techniques to guarantee a sustainable mining. To reach a sustainable mining, an interdisciplinary approach, which consists in considering economic, environmental and social impacts together with new processes implementation, is needed. The focus of the present research is the exploitation of extractive waste (EW) to recover RM and CRM, considering, the technological and economical factors, together with the environmental impacts, associated to EW quarrying and dressing activities.

The present study, based on a case history from Northern Italy (Montorfano and Baveno granite quarrying area), was intended to validate the presented interdisciplinary approach for evaluating economic and environmental impacts associated to EW facility exploitation (from granite EW facility to products for ceramic industry and by products for building industry and infrastructures). Two different surveys were carried out: in 2009 and 2016, investigating four different EW facilities (Braghini, Ciana-Tane Pilastretto,Sengio, and Montorfano).

A shared methodology was applied to determine EW characteristics (geochemical, petrographycal and mineralogical), EW facility volume (geophysical  and topographic and morphologic 3D characterisation) and potential exploitable products, by-products (and CRM). Meanwhile, the Life Cycle Assessment (LCA) was applied to determine environmental impacts associated to extraction and processing phases.

The sampled materials from the EW facilities, sampled in 2009 and 2016, show highly homogeneous geochemical features (Al₂O₃: 13.02-14.65; Fe₂O₃: 1.40-2.41, TiO₂: 0.10-0.26, CaO: 0.54-2.01, MgO: 0.14-0.45, K₂O: 4.49-5.18, Na₂O: 3.08-3.64) for major elements. The alkalies (K₂O+Na₂O) and Fe₂O₃tot content of all samples are extremely important for the feldspar (l.s.) industry, and  the samples obtained after magnetic separation show a decrement of Fe₂O₃ passing from > 1.4% (not good for ceramic industry) to < 0.2% (good for ceramic industry). Moreover, a wider range of geochemical analysis was carried out in 2016 and an interesting fractionation in the treatment process is observed when considering the REE concentration: all samples of the magnetic fraction are much more concentrated than in the feeding material and can be up to one order of magnitude more concentrated than in the upgraded amagnetic portion. The total volume of dumps was estimated in about 2.1 Mm³.

The LCA reports that main environmental loads were due to the dressing plant, including climate change and freshwater eutrophication ones. Despite landfilling shows minor impacts, it has significant impact in terrestrial eco-toxicity. While climate change indicators show significantly higher loads than savings, savings and loads in freshwater eutrophication indicator are balanced. The avoided phosphate and phosphorous release to water results in high ratio of savings in freshwater eutrophication. As for environmental impacts, the SRM recovery activities are favourable for the environment compared to the use of primary sources.

The presented interdisciplinary approach is in line with the will of going towards a sustainable mining, which has to consider, together with economic and environmental factors, also social impacts and risks mitigation instruments.

How to cite: Dino, G. A., Cavallo, A., Garamvölgyi, E., Sándor, R., and Coulon, F.: Towards sustainable mining: exploiting raw materials from extractive waste facilities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6834, https://doi.org/10.5194/egusphere-egu2020-6834, 2020.

The Monte Bracco area (western Alps, northern Italy) is well known for the “Bargiolina” quartzite, a dimension stone that has been exploited in slabs at least since the XIII century, used as internal and external facing, especially in the Baroque. The quarries are located mainly on the top of the Monte Bracco, geologically pertaining to the Dora-Maira Massif, a crystalline massif of the Penninic Domain (Palaeozoic basement and a thin Mesozoic cover). The quartzites occur in sub-parallel lenses (thickness between 2 and 10 m), hosted by ortho- and paragneiss, locally strongly altered in clayey material (kaolinization). The quartzite varieties are characterized by a fine and homeoblastic grain size, a granular – lepidoblastic texture, with regular spaced schistosity, and the main rock-forming minerals are quartz (70 – 90 wt.%), phengite (up to 15 wt.%), K-feldspar (orthoclase, 5 – 10 wt.%, frequently altered in kaolinite) and traces of albite, chlorite and accessory minerals. The quarrying activity boomed between the XIX and the end of the XX century (up to 40 quarries), but the bad exploitation planning in the XX century, which involved the best portions of the rock body, led to partly exploited quarry benches, characterized by a residual yield rate of about 4-8%. At present the quarrying activity is nearly stopped due to low yield rate (and the consequent huge production of waste) and to the competition of the widespread “golden quartzite” from Brazil. The huge amount of quarry waste, the quartz-rich composition and the abundance of kaolin in the altered host gneiss suggest interesting applications as industrial minerals. Due to the high quartz content, the quarry waste (estimated in 2,250,000 m³) could be extracted as a secondary raw material and mineral dressed to obtain products for ceramics, refractories, abrasives and glass manufacturing. The recovery of the kaolinized host gneisses should also be evaluated: the deposit shows proper geochemical, mineralogical and petrographical characteristics for kaolin exploitation, which however should be programmed and carried out together with the exploitation of the quartzite deposit (which lays on the kaolinitic gneiss bench). Preliminary mineralogical and geochemical data (XRPD and XRF) show an appreciable amount of kaolin (8 – 25 wt. %, with a very low Fe₂O₃ content) in the altered gneisses, and a substantial compositional homogeneity in the different sampled areas. In addition to kaolin, the other main minerals are quartz, K-feldspar and a mixture of phengite and illite, a quite good “raw material” for the ceramic industry. The volume of the kaolinitic gneisses should be further evaluated by targeted field and geophysical surveys, followed by core drilling. In the perspective of a sustainable mining, it is important to move towards the integrated exploitation of the Monte Bracco area, contemporary mining both the quartzite waste and the kaolinitic gneiss (first category materials, industrial minerals), as well as the quartzite benches (second category materials, dimension stone).

How to cite: Rodeghiero, F., Alessandro, C., and Dino, G. A.: Kaolin and quartz from extractive waste: the example of the Monte Bracco area (Piedmont, northern Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10414, https://doi.org/10.5194/egusphere-egu2020-10414, 2020.

The progress and prosperity have been based on finite mineral resources and fossil fuels. Sustainable development goals of the United Nations and the implementation of the Paris Agreement, resulted in the vast utilization of a wide range of minerals for green technologies such as low-carbon applications. The global demand for raw materials has increased during the last decades (Kinnunen and Kaksonen, 2019).

In addition to clear economic and societal benefits, mining has also created environmental challenges via significant amounts of mining and quarrying waste termed as extractive waste. However, these wastes can be transformed into valuable secondary metal sources combining metals recovery and environmental management.   

The current study, focuses on reuse and recovery targeted on extractive waste from abandoned mines in Campello Monti. It is a small settlement of Valstrona village in the northern sector of Piemonte, (NW Italy). Geologically, the site is present in the ultramafic layers of mafic complex of Ivrea Verbano Zone and consists of anorthosites, gabbros, gabbro-norite, lherzolites, peridotites, pyroxenites, titanolivin. The area was exploited for nickel production from Fe-Ni-Cu-Co magmatic sulphide deposits from 1865 until 1940s. Currently, the area has waste rock and operating residues dumps.

As, the extractive waste from Campello Monti has not been moved from 1940s and recovery trials have also not been performed. Our study dealt with: (1) reusing fine fraction (<2 mm) of waste rock as soil additive, and (2) recovering raw materials from coarse fraction (>2 mm) of waste rock and operating residues, by means of dressing methods like wet shaking table and magnetic fraction.

The seed germination and plant growth experiments performed using Blok et al. (2008) showed no major detrimental impact on Lepidium sativum plants. Although the plant growth decreased to 31% after adding 45% of waste rock to sand and blonde peat mixture. However, by adding fertilizers this can be mitigated to certain extent.

The coarse fraction of waste rock crushed to <0.5 mm showed recovery of Co, Cu and Ni as 53%, 42% and 66% using shaking table. Whilst, for the same size and dressing method operating residues depicted recovery of Co, Cu and Ni in the range of 55-76%. Whilst, the recovery of these elements varied from 35-41% for operating residues and waste rocks using magnetic separation. The micro-XRF mineral mapping of the concentrates obtained from both dressing methods demonstrated presence of pyroxene, pyrrhotite, olivine, magnetite, pentlandite and chalcopyrite.

The present investigation highlights the methodologies used for obtaining raw materials from extractive waste. Thus moving from the linear economy patterns of mineral extraction to circular closed loops.

References

1. Blok, C., Perssone, G., and Wever, G. (2008). A practical and low cost microbiotest to assess the phytotoxic potential of growing media and soil. ISHS Acta Horticulturae 779: International Symposium on Growing Media. 10.17660/ActaHortic.2008.779.46.
2. Kinnunen, P.H.-M., and Kaksonen, A.H. (2019). Towards circular economy in mining: Opportunities and bottlenecks for tailings valorization. J. Clean. Prod. 228, 153–160.

How to cite: Mehta, N., Dino, G. A., Passarella, I., Ajmone Marsan, F., and De Luca, D.: Reuse of extractive waste from an abandoned mine site: case study of Campello Monti, Italy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16506, https://doi.org/10.5194/egusphere-egu2020-16506, 2020.

Fine-grained residues of ore processing, known as tailings, are an inevitable product of metal production. Such tailings are typically stored in dedicated Tailings Storage Facilities (TSF). The sedimentary-style deposition of tailings within the TSF results in a structure of sub-horizontal, internally graded layers which heterogeneously concentrate the minerals comprising the residues. Primary depositional structures may be overprinted by subsequent chemical redistribution of minerals and elements during chemical reactions and metal mobilisation. Sulphidic tailings are problematic in terms of the potential for generation of Acid and Metalliferous Drainage, while providing interesting prospects for extraction of recoverable metals. However, efforts to build accurate and reproducible geospatial models of TSFs are hampered by a lack of understanding of how to sample heterogeneous tailings materials in a way that allows the effective characterisation of both the horizontal and vertical variability. This study introduces a sampling protocol for the resource characterisation of TSFs, following the Theory of Sampling. The Davidschacht TSF in Freiberg, Germany, was used as a case study. The Davidschacht TSF was deposited between 1944 and 1969; it contains around 760,000 m³ of Cu-Zn-Pb sulphidic flotation residues originating from the processing of polymetallic hydrothermal vein ores of the Freiberg mining district. A historical drilling campaign of 10 drill holes through the whole depth of the tailings provided a basis for the study. A second drilling campaign of 68 drill holes to a depth of 3 m was carried out on a 30 m grid, and nested grids of 15 m and 7.5 m in the centre of the TSF. The drill cores were logged and a bulk sample was collected for each 1 m section. Representative samples, with 10% randomly selected for duplication, will be analysed with X-Ray Fluorescence for chemical composition and sieving and laser diffraction for particle size distribution. The modal mineralogy, mineral associations and mineral liberation of selected samples will be assessed with the Scanning Electron Microscope-based Mineral Liberation Analyser. A detailed geospatial model of the surface zone of the tailings will be constructed to assess the intrinsic horizontal variability of the TSF. Comparison with the 3D model produced by the previous deep drilling campaign will determine if the sampling and modelling was sufficient to account for the variability of the tailings.

How to cite: Blannin, R., Frenzel, M., Tolosana-Delgado, R., and Gutzmer, J.: Development of a sampling protocol for the resource definition of sulphidic Cu-Zn-Pb tailings in an industrial tailings storage facility, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1585, https://doi.org/10.5194/egusphere-egu2020-1585, 2020.

Quartz sand deposit Ravno is the biggest quartz sand deposit in the Dolenjska region in Slovenia with an area of 1.25 km². Quartz sand at the site is selectively excavated using mechanical methods. Presently, at the processing plant near the deposit, the main final mineral processing technique is flotation. Prior to the flotation, quartz sand undergoes classification and attrition. Final products produced at the plant are natural sand, washed sand and floated sand.
Recently, mining companies have been turning to simpler processing systems, such as gravity concentration, due to the price increase of floatation reagents, simplicity of the process and lower environmental impact.
Overview of the deposit and current methods used in the processing plant are presented, as a prologue to further work on the process alteration possibilities – a change from flotation to gravity concentration.

How to cite: Kuzmanić, T. and Bedeković, G.: Overview of a quartz sand deposit and processing plant for the future process alteration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12763, https://doi.org/10.5194/egusphere-egu2020-12763, 2020.

The peculiar landscape of Carrara (Apuan Alps) is well renown all over the world for the many naturalistic and anthropic landforms which are strictly related to quarrying activity. The valuable white Apuan marble was exploited since the first millennium BC predating the Roman period and was chosen by many artists, as Michelangelo, for their masterpieces. The pluri-millennial quarrying activity left a high density of quarries (among the highest in the world), determining a unique landscape dominated by anthropic landforms including the huge quarry dump deposits, locally called “ravaneti”.

Waste materials from marble quarrying of Carrara basin retain typical textural characteristics closely linked to the different techniques adopted over time for marble extraction. Therefore, quarry dumps represent a key access for reconstructing the evolution of the Apuan marble exploitation. For this reason, ancient ravaneti assume an inestimable value within the historical and cultural heritage of Italy.

In this highly dynamic context, the shape of quarry dump deposits is frequently modified because of their continuous addition and re-exploitation, also due to the necessity of preventing slope processes inducing instability (i.e. debris flows). In fact, during the last decades widespread debris flows frequently affected the area representing serious hazardous events for quarrying activity, infrastructures as well as urban centres.

Here we present the “Geomorphological Map of Ravaneti of Carrara Marble Basins”, developed applying a detailed landscape analysis, updated to 2017, using remote sensing data and field surveys in key sites. All the data were managed in GIS environment and collected into a properly created geomorphological database of the Apuan Alps. The map shows the spatial distribution of quarry dumps according to their geomorphological and sedimentological characteristics.

We identified and quantified the number and the extent of areas affected by natural processes, as debris flows, landslides and running water erosional landforms. Quarry dump deposits were distinguished on the basis of the size of the debris, the weathering of the clasts surface and different vegetal cover degree. The presence and abundance of fine matrix in quarry dump deposits play a relevant role in favouring their stability and in regulating their reservoir effect during intense precipitation events. The geomorphological characterization represents a relevant tool for the monitoring and management of ravaneti suggesting both potentially removable and potentially worthy of geo-conservation quarry dumps on the bases of ì) their historical heritage, ìì) their role in slope instabilities, and ììì) their role in preventing hazardous flooding events, being this sector among the rainiest regions of Europe.

Considering that ravaneti are highly hazardous being widely affected by debris flows, the updated geomorphological data will be relevant for evaluating most susceptible areas and for developing risk assessment models.

How to cite: Alderighi, L., Baroni, C., and Salvatore, M. C.: Geomorphological mapping as a tool to characterize and manage quarry dump deposits: the case study of Carrara marble basins, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10580, https://doi.org/10.5194/egusphere-egu2020-10580, 2020.

The End-of-waste concept was introduced by the ‘Thematic Strategy on the prevention and recycling of waste’ adopted by the European Commission, in which it proposed to specify the conditions for the cessation of waste status as part of the revision of the Waste Framework Directive (Directive 2008/98/EC). The Directive states that a waste shall lose its status if it is submitted to a recovery operation (including recycling) and comply with specific eligibility criteria. The strategic goal of the End-of-waste is to promote recycling, helping to ensure a high level of environmental protection through the reduction of the consumption of critical raw materials and the quantities of waste destined for disposal.

In the mining sector, the reduction of landfill material may be obtained not only by finding a suitable recovery of the material as a by-product, but also identifying the best available cutting technique to be used on the basis of the physical, chemical and mechanical characteristics of the stones. The choice of the best cutting technique could lead to high efficiency and performance, high quality of the cut surfaces and a very low environmental impact by reducing energy consumption, decreasing the concentration of heavy metals in the sludge and producing less waste.

In this context, an analysis of the procedures for cutting different types of ornamental stones into slabs together with the evaluation of sludge production for the different cutting methods has been carried out.

Three types of analysis were conducted in parallel. The first concerns the characterization of the stones and the choice of the type of cutting machine. The analyses carried out were: petrographic analysis, compression strength, flexural strength, apparent density and water absorption. Also ultrasonic pulse velocity (UPV) and Knoop analyses were performed in order to establish the workability class of the stones, and their classification in accordance with previous research works (EASE R3).

The second analysis involves calculating the amount of sludge produced in the three different cutting technologies, taking into account the same block characteristics. The third analysis was conducted on the sludge resulting from the processing of blocks cut into slabs. A comparison was carried out on the quality of the sludge produced, or type and quantity of metals present, taking into account the three different technologies. The tests carried out were: chemical analysis, magnetic separation test and SEM analysis of the metal fraction.

The study could provide stone producers with a technological, scientific instrument to identify the best cutting techniques for the processing of their stones, in order to obtain a good efficiency process, optimize the recovery process, increase the economic advantages, and evaluate the possible reuse of the sludge through a proactive waste management strategy.

How to cite: Zichella, L., Bellopede, R., and Marini, P.: Ornamental stone cutting processing and sludge production evaluation with the goal of ending waste., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13801, https://doi.org/10.5194/egusphere-egu2020-13801, 2020.

Al-rich mineral resources are one of the essential components for the production of the novel sustainable mineral binders. Belite-sulfoaluminate (BCSA) cements, which are considered as low-carbon and low-energy, allows the substitution of natural raw materials with secondary ones. In East-Southeast European countries (ESEE) there are huge amounts of various industrial and mine residues that are either landfilled or currently have a low recycling rate. These residues are generated from mining activities (mine waste) and as a by product of different types of industry, such as thermal power plants, steel plants or the aluminium industry (slags, ashes, red mud, etc.). Within the framework of the RIS-ALiCE project, in cooperation with 15 project partners from Slovenia, Austria, France, Hungary, Serbia, Bosnia and Herzegovina and Macedonia, a network of relevant stakeholders has been established in the field of currently unused aluminium-containing mine and industrial residues. Inside the created network mine and industrial residues have been mapped and valorised in order to evaluate their suitability for the use in innovative and sustainable low CO₂-mineral binder production. Aluminium-containing residues are characterized with respect to their chemical, physical and radiological composition using different analytical methods such as X ray fluorescence spectroscopy, ICP optical emission spectrophotometry, gravimetry, X ray powder diffraction, gamma spectroscopy, etc. The long-term activity of network between wastes holders/producers and mineral end users will be enabled via developed Al-rich residues registry, including a study of the potential technological, economic and environmental impacts of applying the innovative methodology of the sustainable secondary raw materials management in ESEE region. Developed registry with the data valuable for both, waste providers as waste users in ESEE region, can be later-on upscaled also to other regions of Europe. It will provide the data on the available and appropriate Al-rich secondary resources, which will enablethe production of innovative low-CO₂ cements.

Keywords: secondary raw material, alternative binders, Al-rich residues, networking, mapping, valorisation, registry.

How to cite: Šter, K. and Kramar, S.: Al-rich industrial residues for mineral binders in ESEE region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21237, https://doi.org/10.5194/egusphere-egu2020-21237, 2020.

The release of landfill gas is responsible for approximately 3 % of the global greenhouse gas emissions. Especially a high content of organic matter in municipal solid waste (MSW) in wet areas may enhance the microbial activity and the production of landfill gas and leachate as metabolic products. Accordingly, the delineation of saturated zones and biogeochemically active and inactive areas is critical for designing adequate stabilization systems to limit the environmental impact of landfills on greenhouse gas production. Therefore, landfill investigations with high spatial resolution are critical for environmental protection. Geophysical methods are a cost-efficient possibility to obtain almost continuous information about subsurface properties at various spatial scales, which can help to identify biogeochemical active zones. Within this case study we investigate the applicability of three geophysical methods, namely (i) the electrical resistivity tomography (ERT), (ii) the induced polarization (IP) method and (iii) the transient electromagnetic (TEM) method to characterize the landfill geometry and to discriminate between biogeochemically active and inactive areas. The investigated landfill is located close to Vienna (Austria) and consists of a mixture of MSW, construction and demolition waste (CDW) and excavated soil. We conducted ERT and IP measurements along 17 profiles distributed over the area of the landfill to provide high resolution images of the subsurface down to 8 m depth. Additionally, we used transient electromagnetic measurements along selected profiles to provide information on deeper structures of the landfill as well as to evaluate the electrical conductivity obtained with ERT. Our results show that the electrical conductivity obtained by both ERT and TEM is mainly sensitive to the increase in the fluid conductivity associated to leachate production and migration. Additionally, a decrease in electrical conductivity is associated to CDW and dry MSW and can help to distinguish between different waste types. However, images of the polarization effect obtained with the IP method, expressed in terms of the phase of the complex conductivity, revealed an improved contrast to characterize variations in the architecture and biogeochemical activity of the landfill. Hence, our study demonstrates that the geophysical methods we applied are well-suited for landfill investigations permitting an improved characterization of landfill geometry and variation in waste composition. In particular, the IP method can delineate between biogeochemically active and inactive zones.

How to cite: Aigner, L., Gallistl, J., Steiner, M., Brandstätter, C., Fellner, J., and Flores Orozco, A.: Landfill investigation using geophysical methods for an improved characterization of the landfill geometry and for assessing microbiological activity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11681, https://doi.org/10.5194/egusphere-egu2020-11681, 2020.

The sustainable vision of the Dynamic Landfill Management (DLM) deals not only with present but also with long-term waste management. In this context, DLM enhances the environmental assessment of landfills after closure as well as the recovery of materials and energy resources, for which, a proper characterization is required. To this end, geophysical methods have demonstrated their suitability for landfill exploration, characterization and monitoring. Due to the complexity of these sites and challenges in data acquisition and/or processing, the use of multiple methods is the best approach for landfill investigations. In this work, we used multiple geophysical methods, co-located with several trial pits and boreholes, to estimate the structure of a waste disposal site located in a quarry, and to better delineate the underlying geology composed of limestone. We applied electrical resistivity tomography (ERT), time-domain induced polarization (IP), H/V spectral ratio from microtremor records and magnetometry. We made a structural joint interpretation using the different datasets and the ground truth data. First, the ERT and IP data were individually inverted, and a first structural model was derived. Afterwards, we followed a parametric analysis of the H/V data to corroborate the thickness of some layers at the position of the seismic stations. Then, this model was used to compute synthetic magnetic data and by comparing them with the observed total field magnetic anomalies, a refined model was produced. We evaluated the improvement of including magnetic modelling by using a probabilistic approach previously reported. This approach is based on the computation of conditional probabilities by comparing the inverted models with the co-located data from trial pits and boreholes. Overall, we delineated the lateral and vertical extension of the waste body, the distribution of ash and lime deposits and estimated the upper limit structure of the bedrock.

How to cite: Isunza Manrique, I., Caterina, D., Inauen, C., Watlet, A., Dashwood, B., Debouny, T., Hermans, T., and Nguyen, F.: Assessment of magnetic data for landfill characterization by means of a probabilistic approach, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15880, https://doi.org/10.5194/egusphere-egu2020-15880, 2020.

In recent years, increased pressure on land use has underscored the need for characterisation of waste composition and distribution in old landfills. In some cases, a lack of information about waste types and potential leachate migration may also pose risks to the environment. Additionally, the emerging potential for retrieving raw materials from old landfills via enhanced landfill mining has further driven the need for developing better informed landfill inventories. Characterising landfills traditionally relies on two main sources of information: historical reports and ground truth data. However, historical reports on old landfills are not always available or are often incomplete, and relying only on ground truth data (drilling or trenching) is costly and requires extrapolation of, and interpolation between, sparse point-data. Geophysical techniques provide an additional, complementary way for characterising landfills, and a means of non-invasively gathering volumetric information on large portions of the surveyed area. Although, in many cases, the complexity and heterogeneity of the internal structure of the landfill makes it difficult to rely on measurements of one single geophysical property alone.

Here, we present an integrated geophysical survey conducted at a landfill site in the Greater London area. The site consists of a former sand, gravel and clay quarry, which was utilised as a solid waste landfill from the 1940s. The landfill was progressively filled with domestic and commercial waste, reaching a peak in activity in the late 1960s and 1970s. Since the landfill has ceased to operate, the site is now relatively flat, covered by grass and used for horse grazing. Our geophysical campaign comprised a combination of several geophysical techniques including rapid mapping (Electromagnetic Induction, EMI; Magnetometry) and profiling techniques (Electrical Resistivity Tomography, ERT; Induced Polarization; IP; Multichannel Analysis of Surface Waves, MASW). The results show a strong contrast in geophysical character between the eastern and the western side of the surveyed area, attributed to a significant change in waste composition. The geophysical results are compared with two intrusive sampling campaigns comprising a series of boreholes, trial pits and Cone Penetration Tests (CPT). Correlating these ground truth data with the geophysical results allows the identification of different geophysical properties related to distinct waste types, from which it is possible to outline zones of similar waste composition within the landfill site.

How to cite: Watlet, A., Inauen, C., Dashwood, B., Whiteley, J., Creusel, T., Isunza Manrique, I., Caterina, D., Scott, D., and Chambers, J.: Integrated geophysical imaging of a solid waste landfill (Greater London, UK), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19568, https://doi.org/10.5194/egusphere-egu2020-19568, 2020.

Water reservoirs with synthetic geomembranes are widely used for storing water resources and chemical solutions in the agricultures and industries, respectively. Leakages of water reservoirs are respondible for the loss of water resources and the spread of contaminants. It is usually difficult to perceive and localize the leakage of water reseroirs. As a cheap, non-invasive, and non-destructive geophysical technique, the mise-à-la-masse method is used to detect leaks of water reservoirs. In principle, the positive (A) and negative (B) current electrodes are placed inside and outside the reservroir, respectively. A number of voltage electrodes are located around the reservoir and potentials relative to a remote reference potential electrode are measured. In the data processing, a method silimar to the self-potential inversion method is proposed to inverse the voltages recorded around the reservoir. Forward modeling was first carried out to simulate the mise-à-la-masse measurement. A kernel matrix (i.e., the collection of Green’s funstions) from forward modelings was imported to the inverse modeling. In inverse modeling, a global objective function with a data misfit term and regularization term is minimized to invert the measured voltages. An initial model based on the distribution of root mean square values between the observation and the simulation data is first given to the inversion algorithm. A weighting matrix and a minimum support function is used to strengthen the detection resolution of the leak of reservoirs. The distributions of source current density from the inverse modeling are used to provide the best estimated of the positions of leaks. Two laboratory and one field experiments are used to verify the effectiveness and reliability of the mise-à-la-masse method. The results show that the proposed method and inversion algorithm can localize a single leak. For a leak with a crack shape, the inversion algorithm detects the location of the leak with a small bias. Effects of the leak size and an undetected condutive zone on the inversion results are further analyzed. For the side leakage, the inverse algorithm overestimated the depth for a small-size leak, while is slightly underestimated the depth of big leaks. For the bottom leakage, effects of the leak size on inversion results are negligable. An undetected conductive zone could significantly distort the inversion results. This study provides an efficient approach to detect the leakage of reservoirs. In addtion, for the leakage of leachate in landfills or mine tailings, the mise-à-la-masse method is also a promising method.

How to cite: Ling, C. and Revil, A.: Application of a Mise-à-la-Masse approach to detect the leak of water reservoirs, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7736, https://doi.org/10.5194/egusphere-egu2020-7736, 2020.

Burning coal, or municipal solid waste, in thermal power plants and in metallurgical industries is responsible for the production of large amounts of combustion residues, which depending on their particle size and density, are usually referred to as fly or bottom ash. Nowadays, they represent one of the main types of industrial waste generated. Although their composition is strongly dependent on the material burned, they typically contain ferro-aluminosilicate minerals with potentially toxic trace elements and inorganic compounds that can cause environmental problems when stored in non-sanitary landfills. At the same time, they also represent an economically interesting secondary resource as they can be valorised by replacing aggregates/additives in cement or ceramics production. Surprisingly, despite the environmental and economic considerations for these materials, their geophysical properties remain largely unknown. A better understanding of their geophysical identity could enable using geophysical methods to, for example, improve the estimation of the volume and quality of recoverable resources from ash deposition sites. In this contribution, we show the results of geophysical investigations carried out in three of these sites located in Belgium. The main geophysical techniques involved are electrical resistivity tomography, time-domain induced polarization and frequency-domain electromagnetic induction. The deposits studied generally exhibit high electrical conductivity presumably due to the high hygroscopy of fly ash, the high chlorides content and the presence of ferro-aluminosilicate minerals, each of which enhancing electrical conduction mechanisms, although the effect of the first two is conditioned by the level of water saturation present. The presence of magnetite, or other ferri- or ferromagnetic materials, may explain the high magnetic susceptibility observed. Yet, while representing a relatively homogeneous type of waste, strong variations in geophysical properties were observed between and within different sites. This suggests a great influence of the ash production process, but also of the site-specific conditions. These first results argue for further field and laboratory experiments to validate the exploratory geophysical survey results and to identify the decisive influencing factors explaining the observed electrical and magnetic response. Improved insight in the geophysical signature of fly ash deposits will allow for more accurate interpretations of geophysical measurements, in its turn providing a more sound basis for guiding conventional sampling design and thereby contributing to a more reliable assessment of the value of these industrial waste landfills in terms of the secondary resources they can deliver.

How to cite: Caterina, D., Isunza Manrique, I., Michel, H., Bobe, C., Lucas, H., Nguyen, F., and Van De Vijver, E.: Evaluating the resource recovery potential of fly ash deposits using electrical and electromagnetic methods, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17610, https://doi.org/10.5194/egusphere-egu2020-17610, 2020.

Whether environmental or economic interests are at stake, characterization of landfills is becoming a key operation. Characterization not only concerns old landfills, but also modern engineered landfills where the assessment and monitoring of internal processes such as leachate and biogas generation is of a primary importance. Nowadays, characterization is mostly carried out by conventional invasive methods based on drilling/trenching, sampling and laboratory analyses. Although they provide direct and analytical information, their spatial coverage, or representability, remains a major drawback. In addition, they can be expensive and increase the risk of damaging contamination barriers. Therefore, non- to minimally- invasive characterization geophysical techniques emerge as a complementary option. They allow to better capture the spatial heterogeneity across a site and are more cost-effective than punctual measurements alone. Furthermore, when compared with limited ground truth data, they may provide insights into waste composition, water content or temperature. The present study highlights the added value of a multiple geophysical approach to characterize a landfill located in Engelskirchen in Germany. Leppe landfill was used as a municipal solid waste (MSW) deposit site from 1982 until the end of 2004. Since then, only ash coming from the MSW incineration is discarded, mostly on top of the previous MSW deposit. The combination of geophysical methods used in this study included electrical resistivity tomography (ERT),  induced polarization (IP), multichannel analysis of surface waves (MASW) and horizontal to vertical noise spectral ratio (HVSNR). The 3D ERT and IP model allowed to identify dry zones within the waste (which may have a direct impact on biogas production) and to roughly discriminate the layer of ash from the MSW layer. Seismic velocity model provided by MASW permitted to significantly improve the delineation between the two layers. HVNSR results combined with the information provided by MASW were used to estimate the thickness of the top layer on a larger area using a bilayer hypothesis. These geophysical characterization results were validated with available ground truth data. Overall, in the present case seismic methods showed to be more suited than geoelectrical techniques for the distinction between the ash and MSW layers.

How to cite: Debouny, T., Caterina, D., Isunza Manrique, I., Beese-Vasbender, P., and Nguyen, F.: Landfill characterization by multi-method geophysical investigation: the case study of Leppe (Germany), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18151, https://doi.org/10.5194/egusphere-egu2020-18151, 2020.

The future mining potential of a landfill site requires the assessment of the likely volume and distribution of recoverable materials of value, within an overall waste body. Whilst more recently constructed landfill sites may have some record of the type and volume of waste deposited, as well as information concerning the extent of an overall site, there is often scant information available for older landfills. For such sites, the potential for the recovery of waste materials will require some form of rapid characterisation (valorisation) of the waste, such that the cost-effectiveness of any mining operation may be estimated.

Geophysical survey techniques offer the potential to rapidly delineate variations in material properties and may be deployed at a range of scales to suit the dimensions of a site or expected level of heterogeneity within the waste. The majority of geophysical techniques are also non-invasive, which is particularly important where potentially hazardous waste is expected, or where the integrity of environmental protection measures such as geotextile membranes must be maintained.

This case study presents the application of number of geophysical survey techniques to characterise the waste within a filled portion of an active landfill in Normandy, France (Les Champs Jouault) and is a pilot site for the RAWFILL project. The site has been operational since April 2009 and was chosen in part due to the large volume of information concerning the construction and nature of the waste materials deposited. This permitted a reasonably well-constrained interpretation of the geophysical data collected. The site poses a number of interesting issues relating to the fact that the site generates and harvest biogas/methane from the waste materials utilising an injected/recirculated leachate system, with individual waste cells fully sealed with an impermeable geomembrane (liner), which also sits above the waste and is then covered with natural soils. The presence of the liner above the waste prohibited the use of Electrical Resistivity Tomography (ERT) for the geophysical characterisation.

The case study presented used multiple phases of geophysical survey to characterise the solid waste, as well as to target intrusive sampling undertaken at the site. A number of geophysical techniques were applied, including Ground Penetrating Radar (GPR), Electro-Magnetic (EM) and Magnetic techniques, as well as seismic techniques (Multi-channel Analysis of Surface Waves (MASW) and Horizontal to Vertical Signal Ratio (HVSR)). The initial survey provided valuable information concerning the thickness of cover above the geomembrane across the survey area, the extent of individual cells as well as variations in waste condition/composition within individual cells and the overall thickness of waste materials/depth to subgrade/bedrock.

The measured geophysical properties have been used to model both the lateral and vertical extents of the landfill as well as to map the distribution of material properties (potential resource). Preliminary findings were used to target a tranche of intrusive sampling (and further geophysical investigation) designed to ground-truth the geophysical data, with the knowledge gained from this exercise used to valorise the potentially recoverable waste materials present in the form of a Resource Distribution Model (RDM).

How to cite: Dashwood, B., Inauen, C., Watlet, A., Isunza Manrique, I., Caterina, D., Loisel, S., Vivien, G., Chambers, J., and Nguyen, F.: Multi-phase geophysical survey to characterise waste materials in a modern engineered landfill site, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18068, https://doi.org/10.5194/egusphere-egu2020-18068, 2020.

Older landfills are notorious for being vague black boxes. The amount, type and location of the dumped material was rarely or inaccurately recorded. This lack of information can be a problem during redevelopment projects, remining projects and risk assessments for the landfill. To decrease the analytical and spatial uncertainties in the conceptual model of the landfill during these investigations, we need accurate sampling and analysis methods but also sufficient amount of data. A High Resolution Site Characterisation (HRSC) approach is based on measurements and data density that are in the same order of heterogeneity of the site. This approach, that we apply on a daily base in soil contamination projects, was applied in collaboration with Witteveen+Bos on a former landfill site in Flanders. In this project an Optical Image Probe (OIP) combined with Electrical Conductivity (EC) measurements was used with a direct push rig. Using this probe, at a rate of 1 frame each 1.5cm, the subsoil layers were explored with a visual light camera integrated in the probe. The data were studied and compared to landfill trenches to identify the layers. It could be concluded that the probing’s were a good supplement to the trench data. This because of the speed of data acquisition, the less intrusive character and reduced Health and Safety concerns for workers and surrounding.

How to cite: Vercruyssen, M., Naert, M., Buffel, P., Van Herreweghe, S., and Brangers, H.: The Optical Image Probe as a tool for high resolution site characterisation (HRSC) in landfills - a testcase, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22626, https://doi.org/10.5194/egusphere-egu2020-22626, 2020.

The characterization and monitoring of landfills has become a major concern, not only for assessing the associated environmental impact (e.g., groundwater contamination) but also for evaluating the potential for recovery of secondary resources, in particular for the production of raw materials and energy. For both objectives, it is crucial to have knowledge of the waste composition and the current landfill conditions (e.g. water saturation level). Near-surface geophysical surveys have been proven effective for the non-invasive investigation of landfills, in which different methods have been used depending on the specific survey targets.  Because of its sensitivity to two subsurface physical properties, electrical conductivity (EC) and magnetic susceptibility (MS), frequency-domain electromagnetic (FDEM) induction has been successfully applied to the qualitative characterization of urban and industrial landfills, including mine tailings. Yet, due to the generally complex composition and strongly heterogeneous spatial distribution of waste deposits, reconstructing a reliable landfill model from surface geophysical measurements remains challenging. Geostatistical inversion emerges as powerful tool to improve the landfill modelling from geophysical data, allowing for a more detailed description of the spatial distribution of the properties of interest and the associated uncertainty. Additionally, it provides a flexible framework for integrating data from geophysical surveys and conventional sampling from drilling or trenching.

In this work, we present a new geostatistical inversion technique able for the simultaneous inversion of FDEM data for EC and MS, which optimize the landfill modelling procedure and is sensitive towards change on the physical properties of interest. This method is based on an iterative procedure where ensembles of subsurface models of EC and MS are generated with stochastic sequential simulation and co-simulation. These simulated models are conditioned locally by existing borehole data for these properties and by a spatial continuity pattern imposed by a variogram model. Synthetic instrument response data, including both the in-phase and quadrature-phase components of the FDEM response, are generated from each model using a forward model connecting the data domain (FDEM data) with the model domain (subsurface physical properties). The misfit between the observed and forward-modelled FDEM data, weighted according to the depth sensitivity of the FDEM response toward changes in EC and MS, is used to drive the generation of a new set of models in the next iteration. We illustrate the inversion procedure with synthetic landfill example data sets which were created based on real data collected at a mine tailing in Portugal and a municipal solid waste landfill in Belgium.

How to cite: Narciso, J., Azevedo, L., Van Meirvenne, M., and Van De Vijver, E.: Geostatistical inversion of electromagnetic induction data for landfill modelling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20650, https://doi.org/10.5194/egusphere-egu2020-20650, 2020.