Anja Grawunder

Microbially assisted phytoremediation approaches for two multi-element contaminated sites

Phytoremediation is an environmental friendly, cost-effective technology for a soft restoration of abandoned mine sites. The grasses Agrostis capillaris, Deschampsia flexuosa and Festuca rubra, and the annual herb Helianthus annuus were combined with microbial consortia in pot experiments on multi-metal polluted substrates collected at a former uranium mine near Ronneburg, Germany, and a historic copper mine in Kopparberg, Sweden, to test for phytoextraction versus phytostabilization abilities. Metal uptake into plant biomass was evaluated to identify optimal plant–microbe combinations for each substrate. Metal bioavailability was found to be plant species and element specific, and influenced by the applied bacterial consortia of 10 strains, each isolated from the same soil to which it was applied. H. annuus showed high extraction capacity for several metals on the German soil independent of inoculation. Our study could also show a significant enhancement of extraction for F. rubra and A. capillaris when combined with the bacterial consortium, although usually grasses are considered metal excluder species. On the Swedish mixed substrate, due to its toxicity, with 30xa0% bark compost, A. capillaris inoculated with the respective consortium was able to extract multi-metal contaminants.

Origin of middle rare earth element enrichment in acid mine drainage-impacted areas

The commonly observed enrichment of middle rare earth elements (MREE) in water sampled in acid mine drainage (AMD)-impacted areas was found to be the result of preferential release from the widespread mineral pyrite (FeS2). Three different mining-impacted sites in Europe were sampled for water, and various pyrite samples were used in batch experiments with diluted sulphuricxa0acidxa0simulating AMD-impacted water with high sulphate concentration and high acidity. All water samples independent on their origin from groundwater, creek water or lake water as well as on the surrounding rock types showed MREE enrichment. Also the pyrite samples showed MREE enrichment in the respective acidic leachate but not always in their total contents indicating a process-controlled release. It is discussed that most probably complexation to sulphite (SO32−) or another intermediate S-species during pyrite oxidation is the reason for the MREE enrichment in the normalized REE patterns.

Rare Earth Elements in Acidic Systems – Biotic and Abiotic Impacts

Rare earth elements (REE) are heavy metals with increasing technical application and importance in science. They are found in minerals like monazite and bastnaesite, which contain especially La and Ce. In waters, REE abundance strongly depends on pH, with acid mine drainage influence resulting in higher REE concentrations. The range of REE in solids as well as in precipitation, river water, seawater, and groundwater without AMD influence, and in acidic waters is reviewed. When plotting REE abundances against the atomic numbers, the natural REE abundance shows a characteristic zig-zag pattern due to the higher stability of even masses. To recognize slight variations in the behavior of REE in different samples, concentrations are normalized to a reference standard resulting in a characteristic graph called REE pattern. These patterns can be used to identify processes leading to different distributions, e.g., related to the influence of microorganisms. In AMD-influenced areas, consortia of microorganisms adapted to these conditions colonize the soils. These organisms can tolerate high metal concentrations, low pH conditions, and low nutrient supply. In bioremediation, such microorganisms are applied to improve the metal uptake from soil into plants since they support the element solubilization and transfer. However, bacteria and fungi are also able to stabilize metals in the soil by intracellular or extracellular complexation, thus minimizing the translocation to plants, depending on species and environmental conditions. To differentiate processes, REE may be applied which is discussed in this chapter.

Neutralisation of an acidic pit lake by alkaline waste products

A former open pit where black shale (alum shale) was excavated during 1942–1965 has been water filled since 1966. The water chemistry was dominated by calcium and sulphate and had a pH of 3.2–3.4 until 1997–1998, when pH was gradually increasing. This was due to the intrusion of leachates from alkaline cement waste deposited close to the lake. A stable pH of around 7.5 was obtained after 6–7xa0years. The chemistry of the pit lake has changed due to the neutralisation. Concentrations of some dissolved metals, notably zinc and nickel, have gone down, as a result of adsorption/co-precipitation on solid phases (most likely iron and aluminium hydroxides), while other metals, notably uranium and molybdenum, are present at elevated levels. Uranium concentration is reaching a minimum of around pH 6.5 and is increasing at higher pH, which may indicate a formation of neutral and anionic uranyl carbonate species at high pH (and total carbonate levels around 1xa0mM). Weathering of the water-exposed shale is still in progress.

Adaptation of a Rare Earth Element Pre-concentration Method for Water Enriched in Al, Ca, Fe, and Mg

The use of rare earth elements (REE) as process indicators in water-rock interactions can be hampered by the fact that samples with high concentrations of total dissolved solids require dilution before ICP-MS analysis, which can lower REE concentrations close to or below detection limits. A pre-concentration method originally developed for chloride-dominated water with very low REE concentrations was tested for and adapted to sulfate-rich water from a mining-affected area with a pH of 6 and high concentrations of Ca, Fe, Mg, and sometimes Al. The adapted approach proved easy to implement in the field and produced very good recoveries and reliable REE patterns. Two factors, sample volume and ionic strength, were tested. Pre-concentration with high sample volumes (1000xa0mL) resulted in poor recoveries (1.8u2009±u20090.3u2009% for La up to 17.8u2009±u20090.6u2009% for Yb). When the sample volume was reduced to 25xa0mL, much better recoveries were achieved. Reducing the ionic strength by diluting the sample 1:100 or 1:1000 resulted in comparable recoveries than the approach with reduced sample volume, indicating that sample volume was more important than ionic strength. Among the tested competing elements, high concentrations of Ca, Fe, and Mg resulted in loss of light REE (La-Nd), while Al was found to reduce the recovery of all REE. Also for water with high concentrations of Ca and Fe and very low REE concentrations (ppt-range), especially La results should be considered with care after pre-concentration, and be neglected in REE patterns if necessary.ZusammenfassungDie Anwendung von Seltenen Erden Elementen (SEE) als Prozessindikatoren bei Wasser-Gesteins-Wechselwirkungen kann dadurch behindert werden, dass bei Proben mit einer hohen Konzentration an gelösten Feststoffen vor der Analyse mittels ICP-MS eine Verdünnung notwendig ist. Dadurch können die SEE-Konzentrationen bis nahe oder unter die Nachweisgrenze verringert werden. Ein Anreicherungsverfahren, ursprünglich für chloriddominierte Wässer mit geringen SEE-Konzentrationen entwickelt, wurde an sulfatreichen Wässern mit einem pH-Wert von 6 und hohen Konzentrationen von Ca, Fe, Mg und gelegentlich Al aus einem bergbaubeeinflussten Gebiet getestet und darauf angepasst. Die angepasste Vorgehensweise war im Feld leicht einsetzbar und lieferte eine sehr gute Wiederfindungsrate und zuverlässige SEE-Muster. Der Einfluss zweier Faktorenxa0wurde überprüft: Probenvolumen und Ionenstärke. Die Anreicherung aus hohen Probenvolumen (1000 mL) führte zu schlechten Wiederfindungsraten (1,8u2009±u20090,3u2009% für La bis 17,8u2009±u20090,6u2009% für Yb). Die Verringerung des Probenvolumens auf 25 mL verbesserte die Wiederfindungsraten deutlich. Die Verringerung der Ionenstärke durch Verdünnung der Probe im Verhältnis 1:100 oder 1:1000 lieferte Ergebnisse vergleichbar zum Ansatz mit reduziertem Volumen. Folglich spielt das Probenvolumen eine größere Rolle als die Ionenstärke. Hohe Konzentrationen von Ca, Fe und Mg führten zu einem Verlust der leichten SEE (La-Nd), während Al die Wiederfindungsrate aller SEE verringert. Auch für Wässer mit hohen Konzentrationen von Ca und Fe und sehr niedrigen SEE-Konzentrationen (ppt-Bereich) sollten nach der Anreicherung vor allem die Ergebnisse für La mit Bedacht genutzt und gegebenenfalls in den SEE-Mustern vernachlässigt werden.ResumenEl uso de elementos tierras raras (REE) como indicadores de interacciones agua-roca puede ser obstaculizado por el hecho de que las muestras con altas concentraciones de sólidos disueltos requieren dilución antes del análisis ICP-MS, para evitar que puedan bajar las concentraciones de REE cercanas o por debajo de los límites de detección. Se testeó un método de pre-concentración originalmente desarrollado para agua dominada por cloruros con bajas concentraciones de REE y adaptado a agua rica en sulfato proveniente de un área afectado por la actividad minera con un pH de 6 y altas concentraciones de Ca, Fe, Mg y, a veces, Al. La adaptación es fácil de implementar en campo y produce buenas recuperaciones y patrones confiables de REE. Dos factores son importantes. Primero, la pre-concentración con altos volúmenes de muestra (1000 mL) provocó pobres recuperaciones (1,8u2009±u20090,3u2009% para La hasta 17,8u2009±u20090,6u2009% para Yb). Cuando el volumen de muestra se redujo a 25 mL, se obtuvieron mucho mejores recuperaciones. Segundo, reduciendo la fuerza iónica a través de la dilución 1:100 o 1:1000 de la muestra de 25 mL, se incrementó la recuperación indicando que el volumen de la muestra fue más importante que la fuerza iónica. Entre los elementos testeados, se comprobó que altas concentraciones de Ca, Fe y Mg resultaron en pérdida de los REE livianos (La-Nd), mientras que Al reduce la recuperación de todos los REE. Para agua con altas concentraciones de Ca y Fe y muy bajas concentraciones de REE (en el rango de ppt), debería tenerse cuidado con al menos La y no confiar demasiado en las interpretaciones basadas en los patrones de REE.富铝、钙和镁水样的稀土元素浓度预处理方法

Element distribution in fruiting bodies of Lactarius pubescens with focus on rare earth elements

During growth and senescence, fungal fruiting bodies accumulate essential and non-essential elements to different extent in their compartments. This study bases on a dataset of 32 basidiocarps of the ectomycorrhizal Lactarius pubescens sampled in a former U mining area. Statistical analyses were combined with rare earth element (REE, La-Lu) patterns to study the element distribution within sporocarp compartments and between three different age classes. For this purpose, fruiting bodies were separated into stipe, pileus trama, pileipelles and lamellae, dried and digested with HNO3. While macronutrient (e.g. K, Mg, P, S) contents resemble those of a non-mining affected site, several elements (e.g. Co, Mn) were site-specifically taken up relative to elevated soil contents. With statistics, two main element distribution groups for L.xa0pubescens were revealed: mainly essential (Cu, Mg, Mn, P, S, Zn, Cd, Co, Ni) and mainly non-essential elements (Al, Ca, Fe, Sr, U, REE). The highest REE contents were found in pileipelles and lamellae, corresponding to relatively small cell sizes. Stipes and pileus trama had low REE contents due to their function as transport systems. During growth, light REE (La-Nd) were strongly enriched in lamellae and pileipelles. Middle REE (Sm-Dy) enrichment was found both in soil and fungal biomass. Contents of nutrients decrease with age, while non-essential elements are enriched especially in pileipelles and lamellae. A weak positive Ce anomaly appeared in the bioavailable soil fraction and in the pileipelles of younger individuals. Substrate dependent uptake thus gets reduced with sporocarp senescence, possibly due to redistribution.

Microbial consortia in radionuclide rich groundwater

In water-rock interactions, microbes play an important role in mobilization and immobilization of metals, including radionuclides. Water of three wells from a rhyolite joint aquifer known for high Rn and Ra concentrations were investigated for their microbial communities and hydrochemistry. The saline waters of NaCl type were used to isolate strains of the native microbe population. Both Gram-negative, like Pseudomonas grimontii, and Gram-positive, e.g. Mycobacterium hodleri, were identified. These microbes can produce siderophores, necessary to supply the cells with iron. In addition to iron, such small molecules may complex other elements, including radionuclides. Thus, they can impact the mobility of radionuclides in the groundwater. The potential of microbial processes in radionuclide reactive transfer is further discussed with respect to other potential mechanisms.

REE fractionation and distribution of Fe, Ni and U in the soil-water-biomass system along the flow path of Gessenbach, Eastern Thuringia (Germany)

Fraxinus excelsior, Glyceria fluitans and Hypholoma subericaeum were investigated as contemporary indicators for the impact of acid mine drainage (AMD) in the soil-water-biomass system. The study was carried out in a (former) U mining area with special emphasis on the elements Fe, Ni and U and the fractionation of Rare Earth Elements which can be found in higher contents in growth locations close to groundwater discharge from the underground mines. F. excelsior showed higher contents of these elements in sapwood, than in heartwood.