Displays

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of compounds with multiple rings that form part of the petroleum crude oil and are considered harmful to human health. The United State Environmental Protection Agency (US EPA) have classified 16 PAHs as priority pollutants that can potentially cause cancer in human beings. These compounds normally enter the environment through oil spills that can negatively affect human health and the environment. The traditional methods used for soil remediation such as the engineering, thermal and chemical methods that involves excavation, heating and application of toxic chemicals often end up causing more harm to the environment. Thus, scientists are exploring the use of plants for the removal of pollutants from the soil known as phytoremediation in order to develop a cost effective, environmentally friendly and sustainable technique for soil remediation. This helps to overcome the issues identified in the traditional methods mentioned above as the treatment of pollutants occurs in situ without excavation and destruction of soil nor thermal heating or application of strong oxidising and reducing chemicals. This paper explains the results obtained from a study conducted on the phytoremediation of crude oil contaminated soil using Chrysopogon zizanioides under the influence of fertilizer and biosurfactants. In this research 70kg of soil was artificially spiked with 1kg of crude oil and allowed to weather for 100 days. Following this, the weathered soil was transferred into different terracotta pots for the purpose of greenhouse experiment. Thereafter, the seedlings of C. zizanioides were transplanted into the terracotta pots where some of the vegetated samples were treated with fertilizer and biosurfactants to promote the growth of the plant and solubilize the organic contaminants for easy absorption by the plants respectively. The result showed high reduction of 70% of the concentration of PAHs in samples treated with doses of both fertilizer and biosurfactants after a period of 8 months. The application of fertilizer and biosurfactants also promoted the growth of plants which resulted in high bioaccumulation of PAHs from the soil as compared to the control samples. However, the greatest yield in plant growth occurred in samples treated with fertilizer only which also resulted in the bioaccumulation of PAHs from the soil.  In conclusion the use of fertilizer and biosurfactants is highly recommended to improve the process of phytoremediation by promoting the growth of plants and enhancing the bioaccumulation and potential dissipation of organic pollutants from the soil. The benefits of this research include the creation of a cost saving, environmentally friendly and sustainable technology for soil remediation. In addition, the bye-products of the harvested plants used for the phytoremediation of crude oil contaminated soils can potentially be used as raw materials for the production of Biogas.

How to cite: Suleiman, S., Batty, L., and Lynch, I.: Biosurfactant enhanced phytoremediation of crude oil contaminated soil using vetiver grass (chrypsopogon zizanioides), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1326, https://doi.org/10.5194/egusphere-egu2020-1326, 2020.

The development of effective remediation strategies for soils contaminated by aged non-aqueous phase liquids like tars requires detailed investigation of composition, microstructure and microbial communities. We studied an aged tar spill with an overgrowing grass vegetation at a former manufactured gas plant site in Germany. The soil contained 10-120 g kg^-1 petroleum hydrocarbons, up to 26 g kg^-1 potentially toxic metals, and up to 100 mg kg^-1 polycyclic aromatic hydrocarbons. Although these substances are considered toxic and recalcitrant, the microbial biomass was up to twice as much in contaminated layers than in uncontaminated layers of the control soil. We assume the high content of vital elements, such as C (up to 500 g kg^-1), S (5 g kg^-1), P (4.8 g kg^-1), Fe (65 g kg^-1), and N in plant residues, compensates possible toxicity.

Investigation of the 2D soil microstructure on thin sections with digital light and scanning electron microscopy showed increased total porosity (2-3 times more than in control) and the share of coarse wide pores (> 50 µm, root channels and large cracks) in contaminated layers. Within the root channels aerobic conditions persist, with free inflow of soil solution and supply of root exudates.

Tar dominated particles between the coarse pores had small isolated pores, and the average distance to the next pore within the particles (assessed by Euclidian distance) was about 3 times higher than for the control soil. This highlights anaerobic conditions within the pores, where tar borne compounds are the source of nutrition and energy.

FTIR microspectroscopy showed oxidized tar on root coatings and near some isolated pores. Natural attenuation of the contaminant proceeds both under aerobic and anaerobic conditions.

Positive matrix factorization analysis of EDX spectra allowed us to map the spatial distribution of different components (quartz, feldspars, secondary minerals, metal-rich particles, tar and the embedding resin). We found presumably authigenic Fe minerals within small isolated pores and along root channels. Based on XANES spectroscopy and the difference between total Fe and Fe in Fe oxides (Fe_DCB), they contained Fe²⁺ and Fe³⁺ in different proportions, which suggests Fe reduction to be an accompanying process during tar attenuation.

The 16S rRNA analysis showed similar microbial communities on the rooted rim of the spill and the control soil. The community in the centre of the spill was less diverse and remarkably different. The contaminated profiles contained specific functional groups of bacteria (e.g. Fe-reducing Geobacteraceae or N-fixing Rhizobiales). Microfluidic droplet cultivation facilitated abundant microbial growth from tar layers under both aerobic and anaerobic conditions.

We conclude that aged tar is used as a substrate by the microbial communities, especially in the presence of grass vegetation. Natural attenuation of tar occurs in hotspots under either oxic (root channels and large connected voids) and anoxic (small isolated pores) conditions and is coupled with reduction of Fe.

How to cite: Ivanov, P., Eusterhues, K., Ritschel, T., Rennert, T., Mahler, L., Martin, K., Boto, S., Rosenbaum, M., and Totsche, K. U.: Specific composition, microstructure, and grass vegetation support natural attenuation in aged tar contaminated soil, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16398, https://doi.org/10.5194/egusphere-egu2020-16398, 2020.

Polycyclic aromatic hydrocarbons (PAHs) are worldwide contaminants and, due to their long-range transport, they can accumulate far from the emission sources, in carbon-rich forest soils; thus new exploration in the indigenous microbial response to PAH exposure is important to deeper understanding of PAH natural degradation process. Since most of the studies are limited to aged PAH contaminated soils, we aimed to fill the gap in our knowledge on recent contamination. 
In order to investigate indigenous microbial community involvement in soil PAH degradation, a mesocosm trial was established. Soils from two forest systems (holm oak and black pine) were spiked with 3 PAHs (phenanthrene, pyrene and benzo[a]pyrene) and incubated under controlled conditions (T: 22 °C, R.H.: 88%). Along 360 days, structural and functional changes in soil microbial community were monitored analyzing bacterial and fungal biomass (by phospholipid fatty acid and ergosterol content) and enzyme activities (hydrolase, laccase and peroxidase).
Both soil types indicated a capability of indigenous native microbial community to degrade almost completely PAHs yet after one year, with phenanthrene and pyrene faster degrading than benzo[a]pyrene, according to their molecular weight. In pine soil, the PAH degradation proceeds with a minor extent likely in relation to the sequestration of PAHs in soil richer in organic matter. In both forest soils fungi are mainly involved in the degradation of PAHs, as highlighted by the increase of both content of the fungal marker and enzyme activity mainly carried out by fungi, e.g. laccase in holm oak soil. 
Regarding the community structure, PAH contamination influences the relative abundance of several soil microbial groups yet after 4 days from contamination, when the microbial community composition shifts towards Gram+ bacteria in holm oak soil, whereas in pine soil pyrene and phenanthrene stimulate fungi and actinomycetes. In the long-term, after one year from contamination, a variation in microbial community was more evident in the holm oak soil, with an increase of fungi in the treatment with benzo[a]pyrene, and an increase of Gram+ in the treatment with phenanthrene. All the enzymes activities, after some fluctuations in the early stages of incubation, decreased after one year. During the quick and strong PAH degradation, hydrolytic activity showed high and constant values, exhibiting a stability in the long-term after the contamination. 
The obtained findings show the role of several microbial groups in PAH natural attenuation in different forest soils. Different PAH degradation rates between systems can be attributable to soil microbiome dominated by different populations in the two investigated forest soils. The use of indigenous microorganisms in bioremediation processes can reduce the risks associated with PAH contaminated soils, and a better understanding of the effects of PAH contaminants on soil microbial community is very critical for understanding microbial activity during bioremediation. The findings highlight the importance of fungi in the potential recovery of a soil polluted by organic contaminants.

How to cite: Picariello, E., Bååth, E., Baldantoni, D., and De Nicola, F.: PAH natural attenuation in Mediterranean forest soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18435, https://doi.org/10.5194/egusphere-egu2020-18435, 2020.

With recent policy developments under the German Renewable Energies Law (Erneuerbare‐Energien‐Gesetz, EEG) and the German Waste and Recycling Law (Kreislaufwirtschaftsgesetz, KrWG) increase in organic waste utilization is expected, which can be utilized for the waste sites restoration. We present a novel application of organic amendments to reduce the mobility of iron‐cyanide (Fe‐CN) complexes and simultaneously promote vegetation. Two batches of digestates from anaerobic treatment of separately collected municipal organic waste in a two-stage semi scale biogas plant have been conditioned by a) drying, b) composting and c) pelletisation. To evaluate the influence of post-treatment of digestates on nutrient and carbon release and contaminants sorption, two batch experiments were conducted, using I) deionized water and II) potassium hexacyanoferrate (II) solution. Batch experiment I resulted in a considerably higher nutrient and carbon elution from dried digestates. Batch experiment II revealed the highest significant tot. CN conc. reduction using not composted, air dried (100%) and oven dried (82%) biowaste digestates. The FTIR analysis of dried and mortared digestate materials indicated Fe-CN complexation on inorganic (K2Mn[FeII(CN)6], NH4Fe[FeII(CN)6]) and organic constituents, and possibly formation of nitriles. In terms of rapid soil fertility enhancement and feasibility to decrease Fe-CN complexes mobility, air and oven dried fresh biowaste digestates revealed the highest efficiency.

How to cite: Sut-Lohmann, M., Knoop, C., and Raab, T.: Effect of drying, composing and pelletizing of biowaste-based digestates on providing water soluble nutrients and stabilizing iron-cyanide (Fe-CN) complexes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8013, https://doi.org/10.5194/egusphere-egu2020-8013, 2020.

Potato is currently the third most significant crop culture in the world, with the production of over 388 million tons in 2016. This crop is present on the tables of Serbian consumers throughout the year because of the tradition and its affordable price. Serbia has relatively good climatic conditions for potato production, which are defined by the temperature regime and the amount and frequency of precipitation. The nutritive value of the potato is mainly attributed to the chemical composition of the tuber. The element composition of tubers depends on many factors, such as: genotype, developmental phase of the plant, agroecological conditions, chemical properties of soil, fertilization and irrigation. On the other hand, geochemical origin of trace elements in the soil, the intensive agriculture production, use of contaminated soil and irrigation water may increase their toxic levels in tubers.

 Potato tubers of five varieties were produced on commercial farms at two locations in Western Serbia (Guča and Sjenica), with favorable agroecological conditions for potato production. Tuber samples of studied varieties from each location were collected at the end of growing seasons at the stage of physiological maturity. Soil samples were collected from several sites at each production location at the depth of 0–30 cm. Basic agrochemical properties of the soil samples were determined. Content of toxic (As, Cd, Pb) and potentially toxic (Al, Ba, Ni, V) elements in fresh tubers (peel and core) and soil samples was established by inductively coupled plasma–optical emission spectrometry (ICP–OES). Bioaccumulation factor (BAF) of each studied element, as the ratio between its content in the peel and in the core of the tuber and the soil, was calculated.

 According to pH values, 4.77 and 6.80, soils were clasified as very acidic (Guča location) and slightly acidic (Sjenica location), respectively. Content of studied trace elements in soils, with the exception of Ni, was within the allowable limits. Tuber peel of all studied varieties grown on both soil types was characterized with the higher content of Cd, Al, Ba and Ni, compared to the relevant core. Consenquently, the higher values of BAF were observed in the peel of tubers. Average values of BAF for the studied elements in the peel for both soil pH values 4.77 and 6.80 (Guča and Sjenica, respectively) were in the following order: Cd>Ba>Pb>As>Ni>Al=V. On the other hand, average BAF values for the core of the tuber samples were in a slightly different order, depending on the soil pH; Cd>Pb>As>Ba>Ni>Al=V (pH 4.77) and Cd>Pb>As>Ba=Ni>V (pH 6.80). The highest/lowest BAFs were calculated for Cd (0.339) in the peel and Al (0.0002) in the core, respectively. Content of As and Cd did not exeed the maximum allowed concentrations set by the national and European Union regulations, but it should be pointed out that Cd content was close to the upper limit. Also, it was noticed that the content of Pb exceeded the safe limit set for these elements according to both regulations.

Keywords: potato tuber, soil, toxic elements, ICP

Acknowledgement: This work was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Research grant No. 46009).

How to cite: Popović-Djordjević, J., Broćić, Z., Kresović, M., and Mutić, J.: Accumulation and distribution of toxic and potentially toxic elements in potato on different types of soil, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2740, https://doi.org/10.5194/egusphere-egu2020-2740, 2020.

Floodplains have received significant attention recently because they are densely populated areas, covered by fertile agricultural lands and act as diverse riverine habitats. At the same time, these important areas are sensitive receptors of PTE (Potentially Toxic Elements) contamination originating from upstream mining and industrial areas endangering food safety and the ecosystems. The large Drava River catchment has been impacted by industrial activities since historic times. Previous studies have shown that the alluvial sediments record the contamination from upstream mines and smelters (e.g. Bleiberg-Kreuth in Austria, Cave del Predil in Italy and Mežica in Slovenia).

Floodplain topsoil (depth: 0-10cm) and subsoil (depth: 50-60cm) samples in the actively flooded alluvial plains and river terraces were collected along 10 cross-sections all along the Hungarian-Croatian border river Drava. In order to study the impact of contamination on soil microbiota, the samples were analysed with ICP-MS for chemical composition, FDA (Fluorescein Diacetate) tests were made for the bulk microbial activity assessment, β-glucosidase content was measured for the rate of catabolic activities, furthermore Docosahexaenoic acid (DHA) content for describing the anabolic processes, and phosphatase enzyme for assessing the mobility of phosphorus. Total cell number was counted on Tryptone Glucose Yeast Extract and the number of fungi on Rose Bengal Agar with Chloramphenicol.

Data was modelled with data analysis methods including descriptive statistics, regression models and homogeneity tests, complemented by spatial visualisation with GIS based softwares. Results show that there is a significant difference between alluvial plain and river terrace sediment contamination, while soil depth (topsoil vs subsoil) seems to be an important factor for soil microbiological parameters.

This research contributes to a Slovenian-Hungarian OTKA project (SNN OTKA 118101). The project was co-funded by European Union Fund, ERDF, IPA, ENI (DTP2-093-2.1 SIMONA).

How to cite: Szabó, P., Jordan, G., Kocsis, T., Šajn, R., and Alijagić, J.: Assessing the impact of fluvial dynamics on floodplain soil contamination and microbiota in the transboundary Drava River Floodplain, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18996, https://doi.org/10.5194/egusphere-egu2020-18996, 2020.

Until recently it has been generally assumed that Ge taken up by plants is stored in phytoliths together with Si. This assumption is mostly based on the geochemical similarities between Ge and Si, while a scientific proof was lacking. The aim of the present study is to i) compare the uptake of Si and Ge in three grass species, ii) localize Ge and Si stored in above-ground plant parts and iii) evaluate the amounts of Ge and Si sequestrated in phytoliths and plant tissues. Mays (Zea mays), oat (Avana sativa) and reed canary grass (Phalaris arundinacea) were cultivated in the greenhouse on soil and sand to control element supply. Leaf phytoliths were extracted by dry ashing. Total elemental composition of leaves, phytoliths, stems and roots were measured by ICP-MS. For the localization of phytoliths and the determination of Ge and Si within leaf tissues and phytoliths scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and laser ablation ICP-MS (LA-ICP-MS) was used. The amounts of Si and Ge taken up by the species corresponded with biomass formation and decreased in the order Z. mays >P. arundinacea, A. sativa. Results from LA-ICP-MS revealed that Si was mostly localizedin phytoliths, while Ge was disorderly distributed within the leaf tissue. In fact, from the total amounts of Ge accumulated in leaves only 10% was present in phytoliths highlighting the role of organic Ge species in plant tissues and the necessity for using bulk Ge/Si instead of Ge/Si in phytoliths to trace biogeochemical cycling of Si. Moreover, our results represent important background data for the optimization of a phytomining of Ge.

How to cite: Kaiser, S., Moschner, C., and Wiche, O.: Accumulation of germanium (Ge) in plant tissues of grasses is not solely driven by its incorporation in phytoliths, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2469, https://doi.org/10.5194/egusphere-egu2020-2469, 2020.

Hyperaccumulating plants possess complex physiological traits, which allow them to thrive in soils contaminated with trace metal elements (TME). In this study, we address an important but severly understudied aspect of plant responses to TME contamination in industrially polluted soils: root system development. In this context, we present the most detailed spatiotemporal analysis of root systems in a pseudometallophyte species to date. We exposed two contrasting ecotypes of the TME hyperaccumulating model species A. halleri to various treatments of their native and foreign soils. To overcome methodological challenges that have so far prevented an in-depth understanding of root-soil interactions under TME excess, we combined rhizoboxes and multitemporal digital imaging in a novel phenotyping approach. This allowed us to assess root architectural changes as a valuable indicator of plant performance in non-metalliferous (NM) and metalliferous (M) environments, as well as under horizontal layer applications of M and NM soils. We show that environment rather than ecotype determines root growth in A. halleri and that soil properties can cause a cost of tolerance in M soil or induce TME-foraging in NM soil. Importantly, root propagation into M soil was promoted by a non-contaminated “capping” layer that facilitated initial plant development. Growing on this capping layer in the early stage provides plants with a robust and optimal root system that facilitates seedling establishment and subsequent development under TME excess. These findings are relevant for practical applications related to phytoremediation. This matter is urgent, considering that industrial pollution is spreading and hyperaccumulating species are threatened by habitat loss.

How to cite: Dietrich, C., Bilnicki, K., Korzeniak, U., Briese, C., Nagel, K. A., and Babst-Kostecka, A.: Does slow and steady win the race? Using the model species Arabidopsis halleri to remediate industrially polluted soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-476, https://doi.org/10.5194/egusphere-egu2020-476, 2020.

In short-term incubation experiment (90 days with additional preincubation) in conditions, simulating summer season in Kola Peninsula, Russia, we implemented different organic amendments — humic subtances, peat-gel, biochar — for remediation of highly contaminated soils of technogenic barrens, situated in 2 and 5 km from active nickel processing industry. Unamended soils used in experiment are characterised by ablation of upper fertile soil layer, high acidity, high content of Ni, Cu, Fe, Zn, depletion of nutrients and organic matter, and, as consequence, by the absence of natural vegetation. To predict potential influence of amendments on contaminated soils and their capacity to immobilise HM bioavailable forms and improve soil health we provide data of structural characteristics with and without additional preparations evaluated by Fourier-transformed infrared (FTIR) spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Our data support the idea of high importance of organic amendment structural characteristics and link these characteristics with observed soil physical, chemical and ecotoxicological properties.

This study was funded by Russian Foundation for Basic Research according to research project No. 18-04-01028, high-resolution mass spectrometry was supported by Russian Science Foundation grant No. 19-75-00092.

How to cite: Tregubova, P., Koptsik, G., Zherebker, A., and Stepanov, A.: Remediation of Kola Subarctic heavy metal contaminated soils via carbon pool regulation: link between structural characteristics of organic treatments with potential influence on soil properties and living organisms , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19837, https://doi.org/10.5194/egusphere-egu2020-19837, 2020.

Wastewater treatment always produces a large amount of sludge. The different uses of sludge disposal have negative consequences for the environment. Agricultural use may appear in some situations as an alternative to current solutions, both to optimize the degradation and recycling of organic and mineral elements. During this work, on the one hand, we investigated  the effect of sludge on the growth of turnip (Brassica rapa), a plant that tolerates metallic trace elements, especially lead (Liu et al., 2000) and which is considered a model plant in eco-toxicology (Sun et al., 2010), and on the other hand to determine if it has the potential to be included in phytoremediation systems.

The seeds were put in different substrates that contained three sludge doses: 20%, 40% and 60%, mixed with agricultural soil  which contained high levels  of metallic trace elements  exceeding the standard eligible concentration  by AFNOR. compared to  the soil, concentrations of potentiall toxic trace elements in sludge were lower than in soil. Morphological measurements were carried out during two months of planting, showing the positive effect of the sludge on the growth of the plant. The recorded biometric values (height, number of leaves, weight, rotation and height of the bulb) for all doses, far exceed those of control plants (100% soil), with high values recorded in the mixture of soil with  60% sludge.

The concentration of metallic trace elements in the different substrates and also in the leaves and the turnip bulb after two months of planting shows that the plant  accumulates and tolerates hight concentrations of elements  and can therefore be used as a phytoremediator for polluted soils. The highest levels of metal accumulation were observed on the substrate in the  soil mixture  with  60% sludge.

How to cite: Soudani, L., Maamar, B., Chafaa, M., Nouar, B., and Wiche, O.: The effect of sludge from the wastewater treatment plant of TIARET (ALGERIA) on the growth of turnip "Brassica rapa"; Morphological responses and potential efficacy of phytoremediation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-815, https://doi.org/10.5194/egusphere-egu2020-815, 2020.

Selenium (Se), a metalloid typically natural in origin, is also present in coal washery by-products such as fly-ash stockpiles. The removal of Se in coal washery by-products can be achieved through various bio-physico-chemical processes. In the attempt to find more environmentally friendly and cost effective methods phytoremediation has been selected as a remediation option. This study was a small scale, screening test that investigated the phytoremediation of Se from post coal process wastes using Brassica juncea species. Therefore, the aim of this study was to assess the concentration of Se, and target elements (As, Cd, Cu, Pb). The selected plant species was grown in coal process wastes enriched with a growth soil mix. The concentrations of the elements were determined by ICP-MS. 48% Se extraction was achieved. Low percentages of As, Cd, Cu, Pb were accumulated in the biomass, (in the order Cd>Cu>As>Pb). The results overall indicate that a minimal amount of Se can be accumulated within the plant biomass of Brassica juncea. Therefore, this study provides only as an initial step towards continued studies on phytoremediation of the coal washery by-products.

Keywords: phytoremediation; phytoextraction; selenium; Brassica juncea

How to cite: Monei, N., Veetil, S. K. P., Hitch, M., and Gao, J.: Selective Removal of selenium by phytoremediation from post mining coal wastes: practicality and implications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16117, https://doi.org/10.5194/egusphere-egu2020-16117, 2020.

As a consequence of normal root growth and development, a considerable range of organic and inorganic substances are exchanged between the root and soil, which causes changes in the biochemical and physical properties of the rhizosphere. Plants modify their rhizosphere in response to various environmental signals and stresses. Low-molecular-weight metabolites are commonly detected in this region and their exudation from plant roots has been associated with abiotic stress, such as inorganic form of manganese (Mn). In this study we investigated the root exudate constituents (phenolics and enzymes) of cucumber (Cucumis sativus L.) plants grown in Mn-free and Mn-contaminated nutrient solutions (0.5 and 100 μM, respectively) with (+Si) or without silicon (–Si) supplied as 1.5 mM silicic acid. High external Mn supply induced both growth inhibition of the whole plant and the appearance of Mn-toxicity symptoms in the leaves, while the simultaneous application of Si alleviated toxicity symptoms. At high Mn supply, concentration of phenolic compounds, as plant-borne substrates for peroxidase (POD) and polyphenol oxidases (PPO), depended on Si application. The increased concentrations of phenolic compounds (e.g., coniferyl alcohol, p-coumaric and isoferulic acid) in –Si plants were in agreement with enhanced POD and PPO activities. The activities of both enzymes were kept at a lower level in +Si plants grown at higher Mn concentrations. These results suggest that Si nutrition modulates the metabolism and utilization of phenolic compounds most probably as a consequence of the formation of Si-polyphenol complexes and their subsequent cross-linking with cell wall polymers. In –Si plants increased activity of the PPO and POD/H₂O₂ systems lead to the formation of highly reactive compounds, while in +Si plants, lignin biosynthesis is favored. H₂O₂ in the presence of elevated Mn concentrations produced potentially toxic •OH and Mn³⁺ in the Fenton reaction, which was efficiently suppressed by Si application. Silicon thus prevented the formation of toxic intermediates (•OH and Mn³⁺) and accumulation/oxidation of free phenolics leading to oxidative browning, the initial indicator of Mn-toxicity symptoms. In summary, we presented the knowledge about how cucumber can overcome hyperaccumulation of Mn by means of Si-complexation suggesting ways of improving future phytoremediation strategies.

How to cite: Dragisic Maksimovic, J. and Maksimovic, V.: Silicon alleviated manganese toxicity in cucumber by cell wall compartmentation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5091, https://doi.org/10.5194/egusphere-egu2020-5091, 2020.

To significantly contribute to the available information on potentials of different plants species for use in phytomining of  Rare Earth Elements(REEs) , a screening experiment was conducted to directly compare at once 8 plant species belonging to two functional groups (herbs and grasses), grown on a soil with high  REEs concentrations. The plants were grown for 10 weeks on potted soils, each containing 2kg of soil.  The plants evaluated are Fagopyrum esculentum, Cannabis sativa, Brassica napus and Sinapis alba for the herbaceous species and Sorghum bicolor, Zea mays, Avena sativa and Festuca arundinacea for the grass species. Concentrations of the four REEs namely Cerium (Ce), Lanthanum (La), Neodymium (Nd) and Yttrium (Y) and amount/content of each REE contained in the species investigated were determined and the data obtained were subjected to the statistical analysis Multivariate Analysis of Variance to identify differences that exist between species, within and between functional groups. Results show that the differences observed in amount of each of the REEs phytomined by the different grass species are statistically insignificant. Contrastingly, significant differences exist between the concentrations and content of each of the REEs between the herbaceous species, with F. esculentum significantly showing higher potential for use in phytomining compared to the rest of the herbaceous species. Results from statistical comparison of all species shows that F. esculentum is the candidate that showed more potential for use in phytomining , with C. sativa also being the next  specie with high potential for phytomining aside from F.esculentum  when compared to the rest of the species investigated. Functional groups were compared, and results showed that the herbaceous specie have a significantly higher potential for use in phytomining of REEs compared to grass species. Results from this experiment contributes to existing knowledge on potentials of different plant species for use in phytomining and suggest possible candidates in comparison to others, for use in experiments that seek to improve the chances of using plants as an eco-friendly alternative to conventional mining of rare earth elements in commercial quantities.

How to cite: Okoroafor, P. and Wiche, O.: Screening of plants of different species and functional groups for phytomining of rare earth elements in soil, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1021, https://doi.org/10.5194/egusphere-egu2020-1021, 2020.

Chemical fractionation of germanium (Ge) and rare earth elements (REEs) in biogas residue by a two-step sequential extraction procedure

Nazia Zaffar (1), Erik Ferchau (2), Hermann Heilmeier (1), and Oliver Wiche (1)

(1) Technical University of Bergakademie, Freiberg, Institute for Biosciences, Biology/Ecology Group, Germany (naziazaffarqau@gmail.com), (2) Technical University of Bergakademie, Institute for Thermal Engineering and Thermodynamics

Ge and REEs are of increasing interest in phytoremediation and phytomining research. These elements are present in almost all soils and soil-grown plants contain considerable concentrations of these elements in their biomass. The process chain of phytomining involves i) the accumulation of target elements in harvestable plant biomass (phytoextraction), ii) production of bioenergy by burning or biogas production, and iii) the recovery of the elements from bioenergy residues.

Although literature on bulk concentrations of elements in fermentation residues is extensive until today there is only a little information on how the elements are bound/distributed in the solid/liquid phases of the fermentation residues, particularly for target elements in phytoremediation research such as Ge and REEs. Therefore, we conducted a laboratory experiment in which residues from anaerobic fermentation were separated into liquid/solid by microfiltration. Subsequently the solids were extracted by a two-step sequential extraction procedure. This procedure involved the extraction of solids with ammonium acetate (pH 7) and ammonium acetate (pH 5) to determine exchangeable as well as acid-soluble elements. As a result, we found that total concentrations in the residues were 0.5 µg/g for (Ge) and 8.7 µg/g for (REEs i.e sum of all lanthanides). In the liquid phase concentrations of Ge and REEs were very low ranging from 0.0001 µg/g Ge and 0.003 µg/g REEs respectively. Concentrations of elements in the liquid phase represented 0.01% Ge and 0.04% REEs of the total element concentrations of the material, indicating that most of the elements were bound to solids. Results from the sequential extraction revealed that percentage distribution of elements were 1.2% (exchangeable Ge) 0.5% (exchangeable REEs) and 0.8% (acid-soluble Ge) 3.8%  (acid-soluble REEs) from the total elements of the material. However, we found 99% Ge 98% REEs in residue fractions. We can conclude that most of the Ge and REEs in digestates are most probably bound into organic structures which were not attracted by extraction solutions. This has major implications for the development of methods for the recovery of the target elements were strong acids/or oxidation of organics prior to application of separation.

How to cite: Zaffar, N., Ferchau, E., Heilmeier, H., and Wiche, O.: Chemical fractionation of germanium (Ge) and rare earth elements (REEs) in biogas residue by a two-step sequential extraction procedure, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-727, https://doi.org/10.5194/egusphere-egu2020-727, 2020.

Rare Earth Elements (elements from 57 to 71; REEs) are present in almost all soils at quantities similar to some plant nutrients such as copper and zinc and, therefore, are of increasing interest in phytomining research. In soilREEs interact with nutrient-bearing soil phases (phosphates, Fe-oxyhydroxides, soil organic matter) which ultimately lowers their mobility in soil solution and availability to plants. The availability of nutrients in the rhizosphere (especially that of phosphorous) is dependent on the activity of rootsand associated microbes, particularly their ability to acidify the surrounding soil and release chelating compounds such as carboxylates. There is a general consensus that root exudates released under P/Fe deficiency (protons and chelating compounds) can mobilize REEs in soil. However, until today information on effects of below-ground functional traits in nutrient acquisition on the mobility of REEs in the rhizosphere and uptake in soil-grown plants is very scarce.Preliminary results from greenhouse and large-scale field experiments indicate that P-inefficient species show different REE-concentrations in their leaves than P-efficient species, and that the pattern of REEs is related to the composition of root exudates.These findings highlight the role of rhizosphere processes on the availability of REEs representing important background information for the optimization of phytoextraction techniques. Moreover, we hypothesize that concentrations and fractionation pattern of REEs in plant material could potentially be used as an “easily-measurable” tool to evaluate the nutrient-acquisition strategy in plants. In ongoing experiments,this hypothesis will be rigorously tested by coupling a field sampling campaign of plant material from species with contrasting nutrient-acquisition strategies along soils with changing nutrient availability (e.g. Western Australian chronosequences) as well as controlled greenhouse experiments for mechanistic elucidation of processes involved.

How to cite: Wiche, O., Heilmeier, H., and Pourret, O.: Below-ground functional traits during nutrient-acquisition affect the availability of rare earth elements to plants , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5831, https://doi.org/10.5194/egusphere-egu2020-5831, 2020.

Electronic waste is a very complex matrix containing valuables and toxic metals. Some very specific metals like Gallium are mainly used for electronic components while also considered a “critical raw element” by the European Commission. Since those metals are used in small quantities, recovery after grinding is impossible. Consequently, those metals must be recovered by separating the components before the milling process. This separation is called dismantling and is usually done pyrometallurgically.  Here we present dismantling by means of bioleaching for the very first time.

Dismantling by bioleaching was compared with solutions containing either ferric or ferrous iron for 20 days. Although bioleaching resulted in a separation of approximately 70 %, the ferric solution reached 100 %; separation by ferrous iron was negligible.

After dismantling, the concentration of critical metals increased by a factor of 3, which can be further increased by discriminating between different components e.g. Integrated circuits resistors, capacitors.

How to cite: Monneron, B. and Schlömann, M.: Dismantling of Printed Circuit Boards by Bioleaching Solution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18757, https://doi.org/10.5194/egusphere-egu2020-18757, 2020.

Because the abundances of rare earth elements are strongly intercorrelated, lacking data can be estimated from adjacent element concentrations. Because Ce can be oxidized to Ce(IV) and Eu can be reduced to Eu(II), deviations from the calculated values have been defined as positive or negative anomalies. The anomalies permit conclusions of mineral weathering, transportation and adsorption.

Anomalies detected in soils did not cause respective anomalies in apple leaves, blossom leaves nor fruits, which prevents conclusions of geographical origin. In the apple plants, Ce showed negative anomalies throughout, particularly in the blossom leaves. To the contrary, Eu showed positive anomalies throughout, particularly in the green leaves, which suggests uptake similar to Ca.

In green leaves (apples) growing in the temperate climatic zone, concentrations of rare earth elements increase with age, like for other elements of low physiological interaction also, whereas nutritional and essential trace elements remain constant or decrease.

How to cite: Sager, M.: Rare Earth Elements – Environmental occurrence and mobilities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5209, https://doi.org/10.5194/egusphere-egu2020-5209, 2020.

The occurrence and availability of microelements in agricultural soils is of great importance for the environment, the quality of food and water, as well as for human health. United States Environmental Protection Agency (USEPA) has been specified elements such as As, Cd, Cr, Cu, Hg, Ni, Pb and Zn as key contaminants. The Geographic Information System (GIS), together with the technologies of the Global Navigation Satellite System (GNSS), made possible for the agricultural fields, parcels, not to be seen in their entirety anymore, but now, greater attention can be paid to optimizing the accuracy and reliability of the location for collecting soil samples, which provides reliable data for obtaining soil and special purpose maps. The data about the content of microelements in agricultural soils in the area of Southern Serbia are scarce.

The aim of this research was to determine the total content of eleven microelements (As, B, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb and Zn) in the agricultural soils of southern Serbia and to create a database using GIS technology with spatial analysis. A total of 150 soil samples at a depth of             0-30 cm were examined. Spatial positioning of soil sampling points was done with a handheld, professional PDA/GNSS Trimble TDC 100 4G (Android 6) device. The database was created in ArcMap 10.1. Concentrations of microelements in the soil were determined by inductively coupled plasma with optical emission spectrometry (ICP-OES).

The obtained results of analyses showed that in the agricultural soils of southern Serbia (Jablanica and Pčinja District), the content of B and Pb was slightly increased at a depth of 0-30 cm, compared to the maximum allowable concentrations set by the national regulations. Among the studied elements, the lowest total content was measured for Mo and Pb (< 1mg/kg) whereas Mn had the highest total content (> 2000 mg/kg). This can be seen clearly on the special purpose maps provided using GIS technology.

Keywords: soils, agriculture, microelements, GIS, southern Serbia

How to cite: Cakić, J., Aleksić, I., Popović-Djordjević, J., Bogosavljević, J., and Djordjević, A.: Spatial analysis of total content of microelements in the agricultural soils of southern Serbia - GIS study, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4619, https://doi.org/10.5194/egusphere-egu2020-4619, 2020.

Sediments of the banks of the Buriganga River, Bangladesh, are contaminated with heavy metals from industrial activity, especially Chromium (Cr). These carcinogens pose a serious risk to human and environmental health (Nargis et al., 2018). Sesbania cannabina, a leguminous fodder crop with rapid growth and high biomass production, is found to be naturally growing in these areas (Sarwar et al., 2015) and may have phytoremediation potential (Varun et al., 2017). This study aims to determine whether Sesbania cannabina can be grown from seed under chromium stressed conditions to establish this species as a possible phyto-extractor.

In this experiment toxicity testing of Chromium (K₂Cr₂O₇) on seed germination was carried out using two growth media: Murashige and Skoog basal medium (MS0); and filter paper (Whatman Grad 1), by top of media or top of paper method respectively. In all cases, seeds were germinated under controlled conditions; 12 h full spectrum light at temperature 28°C ± 1°C and relative humidity of ~ 75% for 5 days. Seeds were pre-treated with H₂O₂ (6% v/v) for 5 minutes and primed with 65°C water for 5 minutes, before the addition of Cr. Under low Cr concentrations (0 to 50 ppm) there was no significant effect observed in germination or root length. Under high Cr concentrations 98-100% of seeds germinated in both growth media, but root length decreased to almost half that of controls in ≥ 500 ppm Cr, and root elongation was negligible or stopped in ≥ 1000 ppm Cr. Confocal micrographs (stained with propidium iodide) indicate that damage to the cell wall of lateral root tips of germinated seeds increased with the concentration of Cr. There was no significant difference observed between the two growth media.

Thus it can be concluded that Sesbenia cannabina can tolerate Cr contamination, and is able to germinate and grow in up to 500 ppm Cr. Given the ability of SC to grow in semi-arid to sub-humid climates, and a range of environmental conditions including seasonally submerged soils, there is great potential for SC to be adopted as a tool for phytoremediation of Cr contaminated soils in Bangladesh and elsewhere.

How to cite: Ibne Kamal, A. K., Batty, L., Bartlett, R., Suleiman, S., and Chustecki, J.: Germination potential of Sesbania cannabina in 2 Chromium (Cr) spiked growth media, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5952, https://doi.org/10.5194/egusphere-egu2020-5952, 2020.

Phytomining is a phytoassisted technique for the extraction of economically valuable elements from soils and offers a promising chance to improve the supply of critical raw materials such as germanium (Ge) and rare earth elements (REEs). The efficiency of phytoextraction depends on numerous soil-associated and plant-associated factors (e.g. concentrations of target elements in potentially plant available soil fractions, rhizosphere processes and uptake mechanisms of plants). The aim of this study was to evaluate the effect of different soil properties (pH, compost amendment) on the mobility of selected target elements for phytoremediation (As, Pb, Cd, Zn) and phytomining (Ge, REEs) in soil and accumulation in shoots of different genotypes and populations of Phalaris arundinacea. In a field experiment we cultivated 10 different genotypes and populations of Phalaris arundinacea on four different substrates with similar element concentrations but different pH-values (pH 6.6 – 7.8) and levels of compost amendment (5l /m² compost or without compost). On each of the substrates, we cultivated Phalaris arundinacea (genotypes) with two replicates on plots 4 m² each and installed suction cups to collect soil solution. After harvest concentrations of Ge, REEs, P, Fe, Mn, Zn, Pb, As and Cd in shoots and soil solution were determined with ICP-MS. Compared to the slight alkaline soil, acidic soil conditions significantly increased shoot concentrations of Fe, Mn, As, Cd, Pb and REEs. Under acidic soil conditions addition of compost further increased the concentrations of all investigated target elements in shoots of P. arundinacea except of As. In soil solution only concentrations of Fe and Mn significantly increased due to the compost amendment, while concentrations of P, Ge, REEs, Cd and Pb decreased. Shoot concentrations of all investigated elements, particularly REEs, showed remarkable differences among the genotypes and population and this responds of the plants was in turn influenced by substrate properties suggesting phenotypic plasticity during element acquisition in the rhizosphere. In future experiments the heritability of these traits will be rigorously tested in order to establish optimized seed material. We conclude that amendment of soil with compost seems to be a sustainable approach to enhance the uptake of plant nutrients and REEs into shoots of Phalaris arundinacea. However, the role of plant genetics and consequently processes during element acquisition in the rhizosphere and uptake remain field of further research but if proven this would have major implications for the optimization of phytoextraction techniques.

How to cite: Moschner, C., Schwabe, R., and Wiche, O.: Effect of soil pH, compost amendment and plant genotype on the accumulation of target elements in phytoremediation and phytomining research in shoots of Phalaris arundinacea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4199, https://doi.org/10.5194/egusphere-egu2020-4199, 2020.