Effect of heavy metals and organic matter on root exudates (low molecular weight organic acids) of herbaceous species: An assessment in sand and soil conditions under different levels of contamination

9 páginas.-- 7 figuras.-- 1 tablas.-- 37 referencias.-- Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.envpol.2016.05.080.Bioavailability of heavy metals can be modified by different root exudates. Among them, low molecular weight organic acids (LMWOAs) play an important role in this process. Three plant species (Poa annua, Medicago polymorpha and Malva sylvestris), potentially used for phytoremediation, have been assessed for both metal uptake and LMWOAs excretion in contaminated environments with different concentrations of Cd, Cu and Zn. The experiments have been carried out in washed sand and in three contaminated soils where two organic amendments were added (biosolid compost and alperujo compost). The most abundant LMWOAs excreted by all studied plants were oxalic and malic acids, although citric and fumaric acids were also detected. The general tendency was that plants responded to an increase of heavy metal stress releasing higher amounts of LMWOAs. This is an efficient exclusion mechanism reducing the metal uptake and allowing the plant growth at high levels of contamination. In the experiment using wash sand as substrate, the organic acids composition and quantity depended mainly on plant species and metal contamination. M. polymorpha was the species that released the highest concentrations of LMWOAs, both in sand and in soils with no amendment addition, whereas a decrease of these acids was observed with the addition of amendments. Our results established a clear effect of organic matter on the composition and total amount of LMWOAs released. The increase of organic matter and nutrients, through amendments, improved the soil quality reducing phytotoxicity. As a result, organic acids exudates decreased and were solely composed of oxalic acid (except for M. polymorpha). The release of LMWOAs has proved to be an important mechanism against heavy metal stress, unique to each species and modifiable by means of organic amendment addition.This study was made possible by AGL2011-23617 project supported by the CICYT of the Ministerio de Ciencia e Innovación of Spain and FEDER (EU). MMar Montiel- Rozas acknowledges support from the MINECO, (FPI grant, BES-2012-05339). P. Madejon and E. Madejon are members of the “Unidad Asociada al CSIC de Uso sostenible del suelo y el agua en la agricultura (US-IRNAS)”.Peer reviewe

Amendments to enhance phytoremediation: Single or repetitive applications in time?

We tested the effectiveness of single and repetitive additions of three amendments on trace element stabilisation and volunteer vegetation development in a contaminated soil. The results showed the need of repeated addition depending on the amendment. In the case of inorganic amendments (sugar lime) a single addition was enough to accelerate natural attenuation in soil. However, when organic materials were used solubility of these compounds increased trace element availability with time and new addition were necessary for trace element stabilizationPeer reviewe

Trace elements, pH and organic matter evolution in contaminated soils under assisted natural remediation: a four year field study

A 4-year study was undertaken on the effect of three amendments (biosolid compost (BC), sugar beet lime (SL), and combination of leonardite plus sugar beet lime (LESL)) on reclamation of a moderately trace element-contaminated soil under field conditions. Results showed that organic C increased in BC and LESL treatments. BC and SL treatments increased soil pH and reduced CaCl2-extractablemetal concentrations more efficiently. At the end of the experiment, CaCl2-extractable metal concentrations decreased and were similar in all treatments pointing out the importance of the natural remediation processes in contaminated soils. Addition of amendments showed no clear reduction in EDTA-extractable trace element concentrations, even, BC and LESL subplots showed some little increase of these elements with time. Amendments did not cause any change in total trace element concentration in soil. Addition of amendments could be a successful and reliable long term technique for stabilization of trace elements in contaminated soils at a field scale with minimum maintenance.Peer reviewe

Biosolids, mycorrhizal fungi and Eucalypts for phytostabilization purposes of sulphidic mine tailings

11 pages, 4 figures, 5 tables, 33 references.In mine tailings facilities, phytostabilisation is an attractive technology for long-term remediation. We tested the effect of the addition of biosolids combined with a native arbuscular mycorrhizal inoculum (AMF) on growth of a eucalypt (E. cladocalyx), and on trace element stabilization of sulphidic gold mine tailings. A glasshouse trial was established using four substrates: tailings (T); tailings with a layer of 5 cm topsoil (TS); tailings amended with 100 dry t ha-1 biosolids (LB), and tailings amended with 500 dry t ha-1 biosolids (HB). Half pots were inoculated with a mixture of Glomus sp. (WUM51 - 9227), Scutelaspora aurigloba (WUM51 - 53) and Acaulospora levis (WUM46) culture mix, and others were uninoculated controls. Two seeds per pot were sown in the pots and after 30 days all pots were uniformly thinned to 1 plant/pot. Plants were destructively harvested at 150 days after the sowing. Leaf and stem weights, leaf area and plant height were measured for each plant. Nutrients and trace element concentrations in leaves and stems were also determined. Addition of biosolids significantly increased mycorrhizal colonization (both ectomycorrhizal (ECM) and arbuscular mycorrhizal) in roots compared with the other treatments. Biosolids clearly improved the establishment and growth of the eucalypts. At low biosolid doses, mycorrhizal inoculum increased plant biomass production and the effectiveness of nutrient uptake. Trace element concentrations in trees of the biosolid-amended pots were in general high. It is therefore important to reduce the uptake of toxic elements by plants, which can be done successfully by adjusting amendment addition and the use of mycorrhizal inoculation, and then monitoring trace element contents of different taxa growing in the affected area.Dr. E. Madejón received financial support for her work at The University of Melbourne (Australia) from Program Salvador de Madariaga of the Spanish MEC. P Madejón thanks her Ramon y Cajal Contract financed by the Spanish Ministry of Innovation and Science.Peer reviewe

El Corredor Verde del Guadiamar como estudio de caso en el proyecto europeo RECARE

2 páginas.- 1 figuraReseña de la reunión inicial del proyecto europeo RECARE – Preventing and remediating degradation of soils in Europe through Land Care (http://www.recare-project.eu/) que tuvo lugar en Valencia, enero 2014. Entre sus objetivos se incluye el diseño, la selección y la implementación de medidas para la prevención, recuperación y restauración de zonas degradadas. Uno de los estudios de caso es el Corredor Verde del Guadiamar (Sevilla) como ejemplo de zona degradada por contaminación por elementos traza, ocasionada por un vertido minero, y donde se han aplicado diferentes técnicas de recuperación y restauración de suelos.Peer reviewe

La restauración de los suelos de la cuenca del Guadiamar

Presentación de 25 diapositivas en el Simposio LIFE 2016: Nuevas tendencias y retos en la recuperación de suelos contaminados celebrado en la Escuela Técnica Superior de Ingeniería de Montes, Forestales y del Medio Natural de la Universidad Politécnica de Madrid los días 15 y 16 de junio de 2016N

Assessment of the phytoremediation effectiveness in the restoration of uranium mine tailings

Uranium (U) contamination due to mining and metallurgical operations is a serious problem and poses a high potential threat to humans and other organisms. The application of amendments and/or plants, known as assisted phytoremediation, can accelerate the adsorption, complexation and precipitation processes in soil, and therefore can facilitate the restoration of U mining areas. This study located in the central-west of peninsular Spain was focussed on two different U mine waste dumps (MWD), where the assisted phytoremediation process was implemented. At each MWD, an area of 10 ha (approx.) was selected for sugar lime (SL) application, at a rate of 75 T ha −1. In addition, after SL addition, common grasses Cynodon dactylon, Secale cereale, and the leguminosae Vicia sativa were seeded. Evolution of soil physico-chemical properties and plant development was monitored for 69 months in Top, Medium and Low areas of both MWDs. The main results indicated a positive effect of the amendment, improving the development of the spontaneous and induced vegetation and the accumulation of soil organic matter. Values of pH were maintained in the range of the neutrality during all the experimentation period. In general, total concentrations of trace elements (including U) presented a high variability. Values were similar in the different studied areas of each MWD (Top, Medium and Low) and did not change in time. Trace elements contents were, in general, higher than those found in non-contaminated soils. However, U and Mn availability decreased with time, as well as the accumulation of trace elements (especially U and Mn) in the studied plants. Moreover, these contents were lower than the permitted limit for animal consumption. In conclusion, application of phytoremediation contributed to the stabilization of U within the soil-plant system, mainly by its positive effects on vegetation cover and the consequent increase in soil organic matter

Evaluation of pastures for horses grazing on soils polluted by trace elements

12 pages,3 figures, 9 tables, 46 references.-- Adjuntamos página de errata.Pasture established on polluted soil may pose a risk to grazing livestock creating a requirement for mechanical management which may affect biodiversity and expend energy. The risk associated with managing pasture by grazing horses (non-edible livestock) is being assessed in the Guadiamar Valley (SW Spain), where soils are polluted with trace elements following a major pollution incident. Soil pollution does not affect biomass production or floristic composition of pasture, although both variables influence trace element accumulation in herbage. Element concentrations in herbage are below maximum tolerable limits for horses. Faecal analysis showed regulated absorption of essential elements, while non-essential elements seemed preferentially excreted. Elemental content of horse hair did not differ in animals from polluted and control pastures. If pastures are managed by grazing, periodic monitoring is recommended in view of the long-term chronic trace element exposure in these systems. 2008 Springer Science+Business Media, LLC.We acknowledge the Regional Ministry of Environment (Junta de Andalucía) for supporting this study and the Spanish Ministry of Education for a PFU grant awarded to M.T. Domínguez. Dr. P Madejón thanks her Ramón y Cajal contract financed by the Spanish Ministry of Innovation and Science.Peer reviewe

River banks and channels as hotspots of soil pollution after large-scale remediation of a river basin

8 páginas.-- 6 figuras.-- 2 tablas.-- referenciasRiparian areas are highly dynamic systems where the control of soil pollution might be particularly challenging. Limited accessibility to river banks and bed sediments makes reclamation operations particularly difficult in these topographical positions, in comparison to floodplains. This usually leads to the large-scale spread of pollutants following pollution episodes in riparian areas. Here, we aimed to evaluate the persistence of trace-element pollution in the soils of Guadiamar River Valley (SW Spain), a large-scale remediation after a mine-spill. We monitored topsoil along the river basin, and in different topographical positions across the river section (river channel, river banks and floodplain), 16. years after a pollution episode and subsequent remediation program. River channels and banks were identified as hotspots of soil pollution, where soluble concentrations of As, Cd and Zn were significantly higher than in floodplains. Along the basin, soil pH and carbonate content was highly variable as a result of contrasted geological background, differential loads of sulfide deposition after the accident and irregular effectiveness of the applied amendments. Cadmium and Zn showed the highest levels of long-term re-distribution from the pollution source. The results suggests that the stabilization and remediation of soil pollution in river banks and channels, often overlooked when achieving remediation works, should be a priority for land managers.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement n° 603498 (RECARE). M.T.D. was supported by a Juan de la Cierva postdoctoral grant awarded by the Spanish Ministry of Economy and Competitiveness. We are grateful to Patricia Puente and Cristina García for their help at different stages of the study.Peer Reviewe

Soil contamination

Capítulo sobre "Contaminación del Suelo" que forma parte del libro colectivo "Amenazas del Suelo en Europa" editado por Jannes Stolte et al. y publicado por el Joint Research Centre de la Unión Europea. Es un trabajo de revisión que ha resultado del proyecto europeo RECARE (http://www.recare-project.eu/).This report presents the result of WP2 of the RECARE project. One of the objectives of WP2 is to provide an improved overview of existing information on soil threats and degradation at the European scale. In particular, this chapter 8 deals with soil contamination, providing comprehensive, thematic information on this soil threat in Europe with due attention given to the Driving force-Pressure-State-Impact-Response to soil threats.European Commission, Joint Research Centre. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement n° 603498 (RECARE).Peer reviewe