Effects on metal availability of the application of tree biochar and municipal waste biosolid in a metalliferous mine tailings substrate

The phytostabilization of mine tailings requires a previous assessment of the effects of soil amendments on metal mobility. The goal of this work was to evaluate the response of metal availability (both labile and potentially available pools) to the addition of two organic amendments (a municipal waste biosolid and a tree biochar), separately and in combination, in a mine tailings substrate. For this purpose, a comprehensive comparison among several single extraction procedures and a sequential extraction procedure was performed. The effects on metals phytotoxicity were assessed through a germination test using seeds of Zygophyllum fabago. When evaluating the effect of the amendments in the labile metal pool, the biochar resulted effective in decreasing metal-extractable concentrations, especially for Cd, Mn and Zn. The treatment with biochar also showed better germination parameters (percentage of germinated seeds and sooner germination) than the rest of the unamended and amended treatments. The use of the municipal organic biosolid increased labile metal concentrations and potentially available metal pools assessed with EDTA and did not contribute to achieve better results of seed germination. Compared to the single biosolid treatment, the combination of biochar/ biosolid modulated some labile metal concentrations and showed similar germination parameters to those obtained for the treatment amended only with biochar. This positive effect of biochar in modulating the soluble metal concentrations associated with certain urban/agricultural organic materials supported the suitability of using these combinations in field applications, although a higher rate of biochar application would be recommended to obtain a more beneficial effect.Financial support for this research was provided by FEDER and the Ministerio de Ciencia e Innovación of Spain (Project CTM2014-54029-R

Effects of a soil organic amendment on metal allocation of trees for the phytomanagement of mining-impacted soils

The suitable application of phytomanagement by phytostabilisation using plant tree species in metal-polluted soils requires an assessment of the fate of metals in biological tree compartments. The goal of this work was to evaluate the effect of an urban compost amendment on metal allocation in two evergreen tree species (Pinus halepensis and Tetraclinis articulata) growing in a metal-enriched polluted substrate. A comprehensive characterisation of edaphic parameters and metal speciation was carried out. Plant analyses included metal concentrations in different tree compartments: roots, stems, branches and leaves. The amendment caused a significant increase in plant biomass for both trees, although T.articulata produced 2.5 times more biomass than P.halepensis. The amendment alleviated P deficiency in P. halepensis. This did not occur for the N deficiency detected in T. articulata. The latter showed no effect of the amendment in the allocation of metals, being most of them restricted at the root compartment (>50%). For P. halepensis, similar behaviour occurred for Cu, Pb and Zn. However, for Cd, the amendment caused its redistribution into pine shoots, probably due to its transport associated with the increased transpiration. Results indicated that T. articulata may be a promising tree species to be used in phytomanagement programs under semiarid climates due to its low metal translocation into shoots and remarkable biomass production under amendment conditions.Financial support for this research was provided by FEDER and the Ministerio de Ciencia, Innovación y Universidades of Spain (Project CTM2014-54029-R). We acknowledge Obdulia Martínez for her assistance in laboratory procedures

A critical assessment on the short-term response of microbial relative composition in a mine tailings soil amended with biochar and manure compost

Phytomanagement of tailings requires the use of soil conditioners to favour plant establishment, but their benefits on soil microbial composition need to be assessed. The goal of this work was to evaluate the effect of two organic amendments, manure compost and biochar, on soil bacterial and fungal composition at metallic mine tailings. The addition of compost caused stronger effects in most of soil parameters and microbial composition than biochar, especially at the initial stage of the experiment. However, the higher dependence on labile organic carbon for some bacterial groups at the treatments containing compost determined their decay along time (Flavobacteriales, Sphingobacteriales) and the appearance of other taxa more dependent on recalcitrant organic matter (Xanthomonadales, Myxococcales). Biochar favoured bacterial decomposers (Actinomycetales) specialised in high lignin and other recalcitrant carbon compounds. Unlike bacteria, only a few fungal orders increased their relative abundances in the treatments containing compost (Sordariales and Microascales) while the rest showed a decrease or remained unaltered. The mix biochar-compost may result the best option to support a more diverse microbial population in terms of soil functionality that is able to decompose both labile and recalcitrant carbon compounds. This may favour the resilience of the system against environmental stressors.Financial support for this research was provided by FEDER/Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación-Project CGL2017-82264-R. The experiment was performed at the facilities of the Instituto of Biotecnología Vegetal (IBV) of the Universidad Politécnica de Cartagena. We thank Borja Rojas from IBV for its help in bioinformatics processing and Dr. Francisco J. Jiménez from BIOCYMA, Consultora en Calidad y Medio Ambiente (Murcia) for his help in field sampling

Assessment of the combined use of MSW and autochthonous tree species for the phytomanagement of mine wastes under semiarid climate

[SPA] El fitomanejo se considera una técnica adecuada para reducir los riesgos ambientales de depósitos mineros abandonados. Las enmiendas orgánicas y el empleo de árboles se han utilizado con éxito en estos suelos contaminados. El objetivo de este trabajo fue evaluar la adición de un residuos sólido urbano (RSU) en el crecimiento y fraccionamiento de metal(oid)es en dos especies arbóreas (P. halepensis y T. articulata) creciendo en residuos mineros. Para alcanzar los objetivos de este trabajo se llevó a cabo un experimento en macetas. El RSU mejoró los parámetros de fertilidad de suelo y aumentó la biomasa de ambas especies, aunque favoreció una mayor translocación de metales en P. halepensis. Se concluyó que el uso para el fitomanejo de residuos mineros de P. halepensis y T. articulata puede ser apropiado acompañado del uso de esta enmienda. [ENG] Phytomanagement is considered a suitable tool to reduce the environmental risks of abandoned mine tailings. Organic amendments and trees have been successfully used on metal contaminated land. The goal of this work was to assess the effects of Municipal Solid Waste (MSW) addition on plant growth and metal(loid) partitioning in two tree plant species (P. halepensis and T. articulata) growing on mine tailings. In order to achieve the objective of this work a pot experiment was carried out. The MSW improved soil fertility parameters and thus, plant growth in both plant species but also metal translocation in P. halepensis. It was concluded that the positive effects of MSW on plant growth may justify its employment in the phytomanagement of abandoned mine tailings.This project has been funded by MINECO-FEDER (CGL2014-54029-R, Project ECOMIN) and Seneca Foundation (19248/PI/14). Obdulia Martínez holds a FPI contract (BES-2015- 075838) from MINECO

Metal mobility assessment in semiarid mine tailings amended with biochar and urban compost: results of a bioassay employing a pioneer plant species

[SPA] El fitomanejo permite reducir el riesgo ambiental de balsas mineras abandonadas. El objetivo del trabajo fue evaluar la movilidad de metales en balsas mineras enmendadas con biochar y/o compost urbano y la efectividad de las enmiendas reduciendo la toxicidad de la solución edáfica para una planta pionera (Zygophyllum fabago). Se llevó a cabo un experimento en mesocosmos (20 meses) con residuo minero con y sin enmienda. Los mesocosmos se mantuvieron a capacidad de campo con agua de la red y se drenaron en diferentes momentos. Se monitorizó la solución edáfica regularmente (pH, conductividad eléctrica, carbono orgánico soluble –COS--, nitrógeno total soluble –NTS- y metales -Mn, Zn-), al igual que el drenaje. Se realizó un bioensayo con semillas de Z. fabago con la solución edáfica de mitad del experimento (germinación de semillas, crecimiento de plántulas). Los tratamientos con compost urbano mostraron mayor concentración inicial de COS y metales en solución. Se observó un descenso temporal de la concentración de DOC y metales en la solución edáfica debido a su lixiviación en el drenaje. A pesar del mayor contenido de metales, el compost urbano favoreció la elongación de la raíz debido al mayor contenido de COS y NTS en solución. [ENG] Phytomanagement allows to reduce the environmental risks of abandoned mine tailings. The aim of this work was to assess metal mobility in mine tailings amended with biochar and/or urban compost and the effectiveness of these amendments for reducing the toxicity of soil solution to a pioneer plant species (Zygophyllum fabago). A mesocosm experiment was performed (20 months) with mine wastes with and without amendment. Mesocosms were maintained at field capacity with tap water and drained at different times. Soil solution was regularly monitored (pH, electrical conductivity, dissolved organic carbon –DOC-, dissolved total nitrogen –TDN- and metals -Mn, Zn-), as well as drainage. A bioassay with seeds of Z. fabago was performed with midterm soil solution (seed germination, seedling performance). Treatments containing urban compost showed higher initial DOC and metal concentrations in solution. A decrease of DOC and metal concentrations in soil solution with time occurred due to their lixiviation in the drainage water. In spite of the higher metal pool, urban compost favoured root length due to its greater content of DOC and TDN in soil solution.Financial support for this research was provided by the Ministerio de Economía y Competitividad of Spain and FEDER (Project CTM2014-54029-R) and Fundación Séneca de CARM (19248/PI/14). Obdulia Martínez holds a FPI contract from the Ministerio de Economía y Competitividad of Spain (BES-2015-075838). Dr. González-Alcaraz holds a Marie Skłodowska-Curie contract (H2020-MSCA-IF-2015, Project ID 704332)

Influence of edaphic factors, vegetation and bacterial composition on the sustainability of phytomanagement at semiarid mine tailings

[SPA] Los depósitos de lodos de flotación son considerados un grave problema medio ambiental debido a la presencia de elevadas concentraciones de metales pesados. Con la intención de alcanzar su restauración, se han propuesto técnicas de fitomanejo consistentes en formar una cubierta vegetal estable sobre sus superficies. Para conseguir esto, puede ser beneficioso contar con una comunidad bacteriana adaptada a las condiciones adversas específicas de estos residuos. El objetivo de este proyecto fue evaluar qué factores (edáficos, vegetación y composición bacteriana) determinan la funcionalidad del suelo durante los procesos de fitomanejo en zonas mineras semiáridas. El estudio reveló que la vegetación presente en los depósitos mineros fue capaz de estimular, a pesar de las condiciones edáficas deficientes, el desarrollo de una comunidad bacteriana organotrófica implicada en ciclos biogeoquímicos de nutrientes, y por lo tanto, con capacidad para apoyar la sostenibilidad a largo plazo del sistema.[ENG] Mine tailings piles are considered one of the most environmental damaging anthropogenic issues worldwide due to the occurrence of high metal(loid)s concentrations. In order to achieve tailings’ restoration, phytomanagement has raised up as an interesting alternative, which consists of improving a self-sustaining vegetation cover. In this process the bacterial community, adapted to extreme conditions, may play an important role. The objective of this work was to elucidate which factors, including edaphic, vegetation and bacterial composition aspects, determine soil functionality in the phytomagement of mine tailings piles in semiarid areas. The presence of plants in vegetated patches at tailings revealed a positive effect on soil fertility and microbiological indicators, stimulating the presence of bacterial orders involved in key biogeochemical cycles. This functionality of impacted tailings sites, which even showed unfavourable edaphic conditions, may support its long-term sustainability.Proyecto financiado por FEDER/Ministerio de Ciencia e Innovación–Agencia Estatal de Investigación. Proyecto CGL2017-82264-R

Seasonal changes in antioxidative/oxidative profile of mining and non-mining populations of Syrian beancaper as determined by soil conditions

Soil pollution by heavy metals/metalloids (HMMs) is a problem worldwide. To prevent dispersion of contaminated particles by erosion, the maintenance of a vegetative cover is needed. Successful plant establishment in multi-polluted soils can be hampered not only by HMM toxicities, but also by soil nutrient deficiencies and the co-occurrence of abiotic stresses. Some plant species are able to thrive under these multi-stress scenarios often linked to marked fluctuations in environmental factors. This study aimed to investigate the metabolic adjustments involved in Zygophyllum fabago acclimative responses to conditions prevailing in HMM-enriched mine-tailings piles, during Mediterranean spring and summer. To this end, fully expanded leaves, and rhizosphere soil, of three contrasting mining and non-mining populations of Z. fabago grown spontaneously in south-eastern Spain were sampled in two consecutive years. Approximately 50 biochemical, physiological and edaphic parameters were examined, including leaf redox components, primary and secondary metabolites, endogenous levels of salicylic acid, and physicochemical properties of soil (fertility parameters and total concentration of HMMs). Multivariate data analysis showed a clear distinction in antioxidative/oxidative profiles between and within the populations studied. Levels of chlorophylls, proteins and proline characterized control plants whereas antioxidant capacity and C- and S-based antioxidant compounds were biomarkers of mining plants. Seasonal variations were characterized by higher levels of alkaloids and PAL and soluble peroxidase activities in summer, and by soluble sugars and hydroxycinnamic acids in spring irrespective of the population considered. Although the antioxidant systems are subjected to seasonal variations, the way and the intensity with which every population changes its antioxidative/oxidative profile seem to be determined by soil conditions. In short, Z. fabago displays a high physiological plasticity that allow it to successfully shift its metabolism to withstand the multiple stresses that plants must cope with in mine tailings piles under Mediterranean climatic conditions.This work was supported by the Ministerio de Ciencia e Innovación [grant number CTM2011-23958]; Ministerio de Ciencia y Tecnología [grant number CGL2006-11569]; and Fundación Séneca [grant number FB/23/FS/02]. AL-O holds a grant from the Ministerio de Educación Cultura y Deporte [grant number AP2012-2559]. Part of this work was carried out at the Instituto de Biotecnología Vegetal, UPCT

The importance of native microbial communities in the sustainability of vegetation for the phytomanagement of semiarid mine tailings

[SPA] La presente propuesta de tesis doctoral busca aportar soluciones científico-técnicas para el fitomanejo de residuos mineros en la Sierra de Cartagena-La Unión, como parte de una estrategia de restauración ambiental sostenible a largo plazo. El objetivo general de la tesis doctoral es valorar en qué medida la adición de enmiendas orgánicas (combinación compost/biochar) y/o establecimiento de plantas pueden afectar a la estructura de las comunidades microbianas autóctonas y desencadenar procesos de evolución edáfica que redunden en la mejora de la funcionalidad del suelo desde el punto de vista microbiológico, incidiendo en aspectos relacionados con los cambios en la microbiología del suelo y el comportamiento de especies vegetales autóctonas (biomasa, acumulación de metales) dentro del contexto del fitomanejo de residuos mineros en zonas semiáridas. [ENG] This proposal of PhD thesis will focus on proposing suitable scientific and technical alternatives for the phytomanagment of metal(loid) enriched mine tailings in the Sierra of Cartagena-La Unión (SE Spain). Thus, a strategy for the environmental restoration at middle-long term will be implemented. The main goal of the project is to evaluate the effects of the addition of organic amendments (combination compost/biochar) and/or of plant growth on the structure of native microbial communities and the improvement of edaphic parameters for the phytomanagement of mine tailings in semiarid areas. The enhancement of soil functionality will be assessed attending to microbiological changes, including the structure of microbial populations and the behaviour of pioneer plant species (plant biomass, metal uptake).Financial support for this research was provided by FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación-Project CGL2017-82264-R. We acknowledge N. Andreu Somavilla and J. Ponomarenko from CGR by their help in data processing. We also acknowledge Julia Muñoz Fructuoso from IBV-UPCT for her help and assistance in lab analytical procedures

Evaluation of the rhizospheric microbiome of the native colonizer Piptatherum miliaceum in semiarid mine tailings

The study of the rhizospheric microbiome in native plants should be a prerequisite before carrying out the phytomanagement of mine tailings. The goal of this work was to evaluate the rhizospheric microbiome of Piptatherum miliaceum in semiarid mine tailings. A comprehensive edaphic characterization was performed including the description of soil microbial composition in the rhizosphere of P. miliaceum growing at a mine tailings pile and at a control site. Plant nutritional and isotopic compositions were also determined. Neutral pH of the tailings (7.3) determined low metal extractability in 0.01 M CaCl2 (e.g. < 1 mg/kg for Zn). In spite of the contrasting edaphic fertility conditions of both sites, N (~ 15 g kg−1) and P (~ 400 mg kg−1) leaf concentrations were similar. The lower δ15N at the tailings plants (− 4.50‰) compared to the control (6.42‰) indicated greater efficiency of P. miliaceum for uptaking N under the low fertility conditions of the tailings (0.1% total soil nitrogen). The presence at the tailings of bacterial orders related to the cycling of N, such as Rhizobiales, could have contributed to enhance N acquisition. The lower leaf δ13C values at the tailings (− 30.22‰) compared to the control (− 28.47‰) indicated lower water use efficiency of the tailing plants. Some organotrophic bacterial and fungal groups in the tailings’ rhizospheres were also found in the control site (e.g. Cytophagales, Sphingobacteriales for bacteria; Hypocreales, Pleosporales for fungi). This may indicate that P. miliaceum is able to shape its own specific microbiome at the tailings independently from the initial microbial composition of the tailings.Grant CTM2017-82264-R funded by MCIN/AEI/10.13039/501100011033 and ERDF “A way of making Europe”. We also thank Mr Francisco Crispín Fuentes Narváez for facilitating the access to the sampling area. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Financial support for this research was provided by FEDER and the Ministerio de Ciencia e Innovación of Spain (Project CTM2017-82264-R)

The combined used of tree species and biochar amendments for the phytomanagement of mine tailings under semiarid climate

[SPA] La presente propuesta de tesis doctoral busca aportar soluciones científico-técnicas para la revegetación de residuos procedentes de las labores de concentración de mineral (balsas mineras) en el contexto semiárido de la Sierra de Cartagena-La Unión, como una estrategia de restauración ambiental sostenible a medio y largo plazo que incluya la reducción de los riesgos de ecotoxicidad asociados a la presencia de metales y metaloides. Para ello se estudiará el efecto del biochar (sólo y en combinación con otra enmienda orgánica) sobre el comportamiento biogeoquímico y la toxicidad de residuos mineros y si dicho efecto puede favorecer el papel de Pinus halepensis y Tetraclinis articulata como especies clave para la restauración de balsas mineras. Además, se realizarán muestreos de ecología de las comunidades vegetales asociadas a éstas dos especies que crecen espontáneamente en balsas mineras. Por último, se practicarán bioensayos de ecotoxicidad con semillas, plántulas e invertebrados edáficos. [ENG] The present PhD Thesis proposal aims to provide technical-scientific solutions for the reclamation of mine tailings in the semiarid area of the Sierra de Cartagena-La Unión, as a strategy for achieving a sustainable environmental restoration. The reduction of risks associated to metal(loid)s will be also considered. In order to achieve this aim, the effects of biochar addition (alone and in combination with other organic amendment) on the biogeochemical behavior and ecotoxicity of the mine tailings will be studied. In addition, the role of Pinus halepensis and Tetraclinis articulata as key species for the restoration of mine tailings will be discussed. Ecology surveys on the spontaneous communities associated to these two species on mine tailings will be performed. Finally, ecotoxicological bioessays employing seeds, seedlings and edaphic invertebrates will be tested.Este proyecto ha sido financiado por el Ministerio de Economía y Competitividad y FEDER (CGL2014-54029-R) y la Fundación Séneca de la Región de Murcia (19248/PI/14). Obdulia Martínez disfruta de un contrato FPI (BES-2015-075838) del Ministerio de Economía y Competitividad