SSS7.4

In the coming years, food demand will increase sharply in line with population growth. So, production will have to increase mostly by area expansion, which could lead to biodiversity loss and an increase in greenhouse gas emissions. Furthermore, both land and water resources are limited and already under severe pressure, making it imperative to ensure a more productive but also sustainable agricultural system. A possible solution to this could be the reclamation of marginal lands, such as saline and drought-prone lands, or even abandoned mining areas. In this sense, phytostabilisation is considered a suitable method for their rehabilitation and reconversion to agricultural and livestock activities while protecting the food chain. Some pasture plants can tolerate adverse growth conditions, such as mine waste or soil conditions (e.g. high concentrations of potentially hazardous elements (PHE) and EC, low pH, organic C and nutrients, and poor structure and water holding capacity). However, low and slow plant growth can limit environmental rehabilitation success. The combined use of Technosols and pastures may be an effective green technology towards reclaiming these marginal areas for food production. To verify this hypothesis, we studied the development of a biodiverse pasture in two biogeochemically distinct Technosols. The pasture is composed of leguminous plants of the genus Trifolium sp. (T. michelianum var. paradana Savi, T. vesiculosum var. cefala Savi, T. resupinatum var. nitrofolus L., and T. squarrosum L.) and Medicago sp., and gramineous plants such as Lolium multiflorum Lam. Two Technosols have been built using a saline Fluvisol collected in the Tagus Estuary and a gossan waste from the São Domingos mine together with a mixture of organic and inorganic amendments. The microcosm assay consisted of four treatments set up in pots of 1.5 dm³ volume (four replicates): (i) Fluvisol (VF), control of salinity affection (EC: 7.9 dS/m; exchangeable sodium 25%); (ii) Technosol-Fluvisol (TVF); (iii) gossan waste (G), control of PHE contamination (g/kg As: 9.1; Pb: 29.6) ; and (iv) Technosol-Gossan (TG). One month after sowing (5 g seeds per pot), the pasture biomass generated so far was mowed to simulate livestock grazing. Pasture in FV showed no seed germination, thus no plant growth. In contrast, in G (10 cm stem length and 1.41 g DW), was observed seed germination followed by plant growth, with gramineous dominating over leguminous plants. In the Technosols, pasture growth improved extraordinarily, with plants reaching more than 15 cm stem length and higher biomass with 2.59 g DW on TVF and 3.8 g DW on TG. Moreover, the pasture was more biodiverse, with the presence of as many leguminous as gramineous. Upon the first cut, the pasture was left for another month for the plants to regrow, and then mowed for the last time. During this time, L. multiflorum has kept growing to similar sizes to the first mowing, while the leguminous have not regrown as effectively. Thus, an integrated biotechnological approach involving Technosols and pastures could be a useful green technology to convert marginal lands into food production areas (grazing or foraging).

How to cite: Aguilar-Garrido, A., Vidigal, P., Caperta, A. D., and Abreu, M. M.: Development capacity of a biodiverse pasture on Technosols for the rehabilitation of marginal lands (saline soils and mining waste), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-121, https://doi.org/10.5194/egusphere-egu22-121, 2022.

This study aimed to assess how the root system of Sesbania cannabina behaves under various concentrations of Cr (VI) and whether it could be a suitable species for the phyto-management of Cr (VI) contaminated soils. The experiment was conducted in rhizoboxes under greenhouse conditions using a sandy loam soil dosed with potassium dichromate giving eight different Cr (VI) concentrations (0 ppm, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 80 ppm, 160 ppm, and 360 ppm). Plant roots were photographed with a Canon 60D (18-megapixel) camera with a 50 mm prime lens and analysed with Image J image processing software.

At 360 ppm concentration, seeds of S. cannabina germinated but were unable to grow further. However, under concentrations of 0-80ppm there was no significant change observed in the root growth (Length) . At 160 ppm root growth was reduced by about 55±0.65% at 25 days and 35±0.25 % at 60 days compared to plants grown at 0 ppm. After 60 days no chromium (VI) was detected in the soil for (0 to 160 ppm) in comparison with the control (with no plants) where no changes in Cr (VI) were observed.

The absence of Cr (VI) in soil after 60 days suggests that S. cannabina can be considered as a candidate for phyto-management of soils containing up to 160 ppm Cr (VI).

How to cite: Ibne Kamal, A. K., Batty, L., and Bartlett, R.: Evaluation of the root system and phyto-management potential of Sesbania cannabina grown in hexavalent chromium contaminated soils utilizing modified rhizobox systems., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4921, https://doi.org/10.5194/egusphere-egu22-4921, 2022.

Although the indications contained in the European New Green Deal aim to inhibit the opening of new waste disposal sites through a circular economy of waste materials, the management of an extremely large number of municipal solid waste landfills (MSWLF) at different stages of their life cycle is a highly topical issue. Recent national regulations in Italy require the operators to monitor subsoil conditions for 30 years, but do not define clear and unambiguous guidelines.

According to analyses carried out at various landfill sites in northern Italy, monitoring activities were often found to be set up with wells equipped with piezometers. This approach is not optimal because when any contaminants are intercepted by the wells, the conditions of the subsoil may already be compromised. Therefore, the goal of our work is to develop methodologies to test and define an effective monitoring protocol that allows to mitigate the environmental and ecological risks associated with the subsurface propagation of pollutants at MSWLF sites.

The analysis of the subsoil conditions involves the design of monitoring methodologies and the interpretation of the obtained results, exploiting geological, hydrogeological and geophysical knowledge and skills. Accordingly, we rely on a research methodology based on the mutual and continuous exchange between the involved disciplines, starting from the initial geological assumptions that will be used to define a physical model of the subsurface. We mainly resort to indirect non-invasive techniques, in particular to the direct current (DC) electrical resistivity tomography (ERT) that on the one hand is indicated for identifying conductive anomalies associated with the propagation of pollutants, but on the other hand constitutes a complex ill-posed numerical problem. The major issues are related to the spatial resolution and the penetration depth of the technique that in turn control the capability to detect presence and the conditions of the extremely thin high-density polyethylene (HDPE) membrane used to isolate the landfill waste from the surroundings.

To tackle the abovementioned issues, we decided to perform properly downscaled laboratory experiments in order to test the effectiveness of DC methodology in controlled and well-known settings. Processing and interpretation of the collected geoelectrical data are supported by a new modelling code in Python programming language that is being developed.

We deem that the integration of lab and modelling tests is necessary to propose a sound standard approach to address complex and multidisciplinary problems related to landfill risk management.

How to cite: Panzeri, L., Papini, M., Formaggia, L., Scotti, A., Fumagalli, A., Arosio, D., and Longoni, L.: Lab and modelling tests to develop a geoelectric monitoring system for municipal solid waste landfills, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7788, https://doi.org/10.5194/egusphere-egu22-7788, 2022.

A detailed study of ⁹⁰Sr distribution in the overground vegetation cover within an elementary landscape geochemical system (top-slope-closing depression, ELGS) was performed in several forested and meadow test sites located in the Eastern Urals Radioactive Trace highly contaminated with this technogenic radionuclide during its release in the Kyshtym accident in 1957 (INES level 6). After selecting the suitable test sites, they were crossed by several lateral profiles along which relative altitude with a step of 1 m and precision of 1 cm was measured using theodolite Boif-DJD10. Averaged plant samples were taken at each point within a standard steel ring (14 cm diameter) later separated into the groups of cereals, legumes and other different herbs. Particular species were also collected if present at no less than seven consequent points. Strontium-90 activity was measured by the portable complex ”Colibri” (SKS-08P) developed in the Kurchatov Institute (Potapov et al., 2021). It allowed the measurement of radionuclide activity in field conditions. The determination error did not exceed 15%. Analysis of data obtained revealed the ordered variation of ⁹⁰Sr in all groups of plants. This order was presented by the cyclic (periodic) change of ⁹⁰Sr activity downslope without definite radionuclide accumulation at the foot of the slope and in depression as usually expected. A similar cyclic pattern was found for ¹³⁷Cs variation in moss cover studied in the Chernobyl zone (Dolgushin & Korobova, 2021). We consider it reflects peculiarities of water migration in the soil-plant system at the ELGS scale. Specific ⁹⁰Sr activity in forest grasses correlated with biomass volume while plant groups and species with the different activity of radionuclides significantly differed in ⁹⁰Sr variation amplitude and its maximum values. The revealed features of variation likely reflect the peculiarities of 90Sr water migration in soils, the structure of root system, and the plants' ecological demands, such as their hydrophilicity.

References

Potapov, V.N., Ivanov, O.P., Luk’yanov, V.V. et al. Portable β-Spectrometer for 90Sr Activity Field-Measurements in Radioecology and Rehabilitation of Nuclear Energy Facilities. At Energy 129, 155–162 (2021). https://doi.org/10.1007/s10512-021-00728-5

Dolgushin, D. and Korobova, E.: New data on the character of 137Cs lateral and vertical migration in soil-litter-moss cover within undisturbed elementary landscape geochemical systems on the test site in the Chernobyl abandoned zone, Russia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7691, https://doi.org/10.5194/egusphere-egu21-7691, 2021.

How to cite: Korobova, E., Baranchukov, V., Dolgushin, D., Tarasov, O., and Mikhailovskaya, L.: About the character of variation of 90Sr concentration in plants within elementary landscape geochemical system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8381, https://doi.org/10.5194/egusphere-egu22-8381, 2022.

Abstract

The Remance gold mine, in Veraguas (central Panama), had its last mining operation in 1999, using the cyanidation process for Au separation. As a result of this activity, three waste tailings were exposed to the weather, in addition to mine dumps and the open pit mining areas. Currently the area is inhabited by peasants who develop subsistence agriculture and livestock. Therefore, the objective of this study has been to evaluate the environmental and human health risks that this area represents. The total concentrations of potentially toxic elements (PTEs) such as As, Cu, Zn, Ba, Sb and Hg were determined in mining process areas, surrounding soils and edible and inedible plants in the area; in addition to the cyanide species and the enzymatic activity by dehydrogenase (DHA) in soils. The accumulated contamination index (PLI) and potential ecological risk (RI) were calculated, the carcinogenic (CR) and non-carcinogenic (HQ) risk to human health represented by soils and edible plants was estimated.

Regarding the degree of contamination, it is observed that the contamination is considerable in the tailings and the sediments of the pithead, and it spreads to the surroundings mainly in the sediments of the streams and their terraces, and, to a lesser degree, to the soils around it, showing that the main route of dissemination is through runoff; the same trend is followed by the potential ecological risk, being extreme in the sediments of the pithead, serious in the tailings and terrace sediments, high in the stream sediments and medium in the surrounding soils. The enzymatic activity by DHA tells us that the health of the surrounding soils is better than that of the stream sediments and terrace sediments, but less than in other sites affected by mining activity in Spain. Cyanide species are linked to DHA and this in turn is favoured by organic matter (OM). On the other hand, it was observed that cyanide elutes from the tailing’s piles in a complex cyanide way, favouring the transport of PTEs associated with it to the stream sediments.

Regarding the risks to human health in soils, As and Cu concentrations exceed the limits for non-carcinogenic and carcinogenic risk in both children and adults, with the residential scenario being the worst scenario, and for adults also the agricultural scenario. In edible plants such as rice, corn, cassava and tea leaves, Sb exceeds the limit for non-carcinogenic risk, and Cu and As for carcinogenic risk. Due to the potential ecological and human health risks that the area represents, actions must be taken to reduce them.

Keywords: potentially toxic elements (PTEs), gold mine, risk assessment, edible plants, human health.

How to cite: González-Valoys, A. C., Esbrí, J. M., Jiménez Salgado, J. U., Rodríguez, R., García-Noguero, E. M., Monteza-Destro, T., Vargas-Lombardo, M., Garcia-Ordiales, E., Arrocha, J., Martínez, E., Campos, J. A., Gutierréz, E., García-Giménez, R., Jiménez-Ballesta, R., García-Navarro, F. J., and Higueras, P.: Environmental and human health risks due to mining activity in the soils and plants of the Remance mine, Panama, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9882, https://doi.org/10.5194/egusphere-egu22-9882, 2022.

In Portugal, there are numerous abandoned mines, many of them derived from an intense activity in massive sulfides. These areas have several environmental problems associated to extreme physicochemical characteristics of their wastes and leachates.

In São Domingos mine, there is an additional environmental problem derived from the percolation of acid mine drainage over the slopes. This measure, used in environmental management of waters, contributed to the total degradation of the edaphic system and enrichment of bedrock in potentially toxic elements (PTE). A sustainable strategy for environmental recovery using Technosols, designed specifically for each contaminated or degraded material, has been evaluated in this scenario. A pilot area, with ​​1.5 ha, was rehabilitated by applying a 40 cm layer of Technosol with alkaline and eutrophic properties. A biodiverse plant system with herbaceous and shrubs was applied. The efficiency of the Technosol was evaluated at short-medium term by: a)several indicators associated to plant development (visual signs of phytotoxicity or nutritional deficiency, percentage of plant cover and height) after 15 days, 1, 3 and 6 months, and b)the maintenance of soil properties after 6 months. An area without Technosol application was used as control.

In Control area, plant cover was low, with maximum values ​​of 8.8% in the third month and height <10 cm. However this vegetation cover was not with the sown plants but only native species, like Spergularia purpurea (dominant species identified) that already existed in the area.

In the area with Technosol application, the plants did not show visible signs of phytotoxicity or nutritional deficiency. The percentage of plant cover increases rapidly. After 15 days plant cover was 10–30% and between first and third month, when there were warmer and dry conditions, the coverage increased to 70% and 90%, respectively.  After 6 months, coinciding with a change in the vegetative cycle and very dry and hot period from summer, the vegetation only decrease ≈10%. The height varied between 40 to 60 cm, reaching these maximum values in the third month. The plant development remained during the monitoring period. This plant evolution shows the significant water-holding capacity and fertility of the Technosol.

After 6 months, Technosol samples maintained the alkaline and eutrophic properties and physico-chemical characteristics (pH 7.5–7.8, 85 g C/kg, 6 g N/kg, Capacity of cation change 54.3–73 cmol+/kg). In the Technosol was not verified an enrichment by PTE, due to its direct contact with acidic and contaminated material. In Control area, the substrate maintained acidic reaction conditions (pH 3.5–3.6), very low fertility and high concentration of several elements.

Application of the Technosol contributed to the environmental recovery of mine areas, with very acid material with multielementar contamination where it is inexistent an edaphic system. This green technology is an effective solution to the conversion non-productive areas to productive areas.

Acknowledgment: This work was executed by EDM under a concession contract for environmental remediation of legacy mines in Portugal, in collaboration with ISA-ULisboa, LEAF and Inproyen, and was financed by POSEUR EC Cohesion Funds (145/POSEUR/2020). This research is into the scope of the project UID/AGR/04129/2020.

How to cite: Aran, D., Abreu, M. M., Diamantino, C., Carvalho, E., and S. Santos, E.: Recovering abandoned mine area under semi-arid conditions with Technosols: a pilot assay in São Domingos legacy site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12578, https://doi.org/10.5194/egusphere-egu22-12578, 2022.

Sulfide mine tailings present particular challenges in terms of risks of environmental recovery due to the acid lixiviation rich in several metal(oids) and sulfates. The conventional closure systems of these tailings have very high cost of implementation and, especially, maintenance of plant cover and continuous leachates treatment. Therefore, the improvement of the chemical characteristics of the tailings and their leachates is a more cost-effective strategy, especially if sustainable technologies are used. The use of designed Technosols is an option. The current study advances past field and laboratory findings by integrating a circular-economy approach into the chemical and soil science-based treatment of such tailings.

A column assay under controlled conditions was set up in order to evaluate the efficiency of a designed Technosol, applied into two ways, on the chemical improvement of the leachates from sulfide-rich tailing. A designed Technosol with alkaline and eutrophic properties was mixed with tailing material (TEC1) or applied as a superficial and distinct layer (TEC2). Tailing without treatment was used as control. The evolution of pH, Electrical conductivity (EC), Fe and sulfates levels was evaluated during 6 weeks in percolated leachates.

The tailing material was previously assessed as having pH ≈2.5 and total concentrations of 104-110 g Fe/kg and 60.0-67.5 g S/kg. Percolated leachates had a pH values between 1.73 and 2.68  and high EC (≈10 mS/cm) that indicate the high amount of several elements and, consequently, their environmental risk.

The first week’s pH increased to ≈6.5 for the TEC1 while in TEC2 was ≈2.5. Following weeks, the pH stabilized at around 7.3 in the TEC1 and 2.6 in the TEC2..  The EC decreased in the first week 73% in the TEC1 and 81% in the TEC2, compared to control. In control, EC presented upwards spikes within the first two weeks, reaching almost 14 mS/cm, and then more stable values. . Notably, the EC for TEC 1 was low (<1.6 mS/cm) and rather stable throughout the experiment, for TEC2 it presented large, gradual drops in the first two weeks, followed by rather stable value  and slightly lower than control. Fe concentrations largely mirrored these EC patterns. Iron concentrations in control were high varying 60 and 7546 mg/L during the assay. Technosol application was effective in the diminution of Fe concentrations in the leachates (TEC1 > 1000-fold and TEC2 2-100 fold lower than control).

Overall, both application mode of the Tecnhosol contribute to improvements in the leachates quality. Nonetheless, these results showed that TEC1 approach might result in more stable and better chemical quality of the leachates. Importantly, these findings also suggest the improvement in the tailing structure of TEC1 compared to TEC2, contributing to lower risk of lixiviation into the lower layers.

Acknowledgment: This research was supported by Fundação para a Ciência e Tecnologia, within the scope of the project UID/AGR/04129/2020 (Project Non-foodCropMine).

How to cite: S. Santos, E., Pastrac Lungu, A., and Arán, D.: Effect of Technosol application way on chemical quality of percolated leachates from sulfide-rich tailing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12756, https://doi.org/10.5194/egusphere-egu22-12756, 2022.