Attending the 12th International Conference on Mine Closure

Last September, the 12th International Conference on Mine Closure was celebrated in Leipzig (Germany). This conference, organized by the Technical University Bergakademie Freiberg, is one of the world`s reference events among the mine closure professionals. The main conference topics that were discussed and that have been found as the main issues were:  establishing integrated life of mine planning, design sustainable land uses from the social and environmental perspective, increasing the post-mining assets value, and establishing  stable and self-regenerating ecosystems, among others.

Due to the urgent necessity of improving reclamation of mining areas, abandoned and/ or in transition to close, researchers from IRNAS-CSIC, University of Seville, University of Reading and Haute École Condorcet have collaborated to present a paper and an oral communication in this conference.

Gil-Martínez M, Domínguez MT, Navarro-Fernández CM, Crompot H, Tibbett M , Marañón T (2018). Long-term effects of trace elements contamination on soil microbial biomass and enzyme activities, in C Drebenstedt, F von Bismarck, A Fourie & M Tibbett (eds), Proceedings of the 12th International Conference on Mine Closure, Technical University Bergakademie Freiberg, Germany, pp. 633-644.

Results from the applied strategy of phytostabilisation on mining areas contaminated by heavy metals were presented. In our study area known as Guadiamar Green Corridor, where phytostabilisation have happened over 19 years, forestation has been found to improve soil fertility and microbial biomass, which is an indicator of improved soil quality. Moreover, different tree species have been found to affect soil chemistry and biology in different ways. White poplar was found to increase soil pH and to recover nutrients levels. However, stone pine was found to acidify the soil, increasing heavy metal availability and reducing microbial communities. In conclusion, previous to forestation is recommended to select the most suitable species for the specific conditions of the mining area to reclaim.

In this conference, Marta Gil-Martínez, predoctoral researcher from IRNAS-CSIC, had the opportunity to visit the Wismut Uranium Tailings Remediation Project , which started back in 1991 and currently clean-up, re-contouring and implementation of covers tasks are still in place. Last cover consists in revegetation to establish some forest and pastures areas, in order to maximize biodiversity.

 

Graduate Thesis on phytostabilization and soil organic matter

Trees planted in contaminated soils provide organic matter, contributing to a reduced mobility of contaminants and the process called “phytostabilization”.

Within the collaboration between IRNAS, CSIC and the University of Seville, Juan Fernando Montero supervised by the RESTECO researcher María T. Domínguez, has presented in July 2018, in the Faculty of Chemistry, the Graduate Thesis titled “Caracterizing fractions of organic carbon in forested soils after the Aznalcóllar mine accident (Guadiamar Green Corridor)”.

In this study, several fractions of soil organic carbon were analyzed, comparing sites under different tree species (white poplar, stone pine and wild olive). The study was repeated in two contrasted areas, with different soil acidity levels.

Using Fourier-transform infrared spectroscopy (FTIR), functional groups were caracterized in samples of soil and litter. The spectra of soil samples differed from those of litter, especially when the soil was neutral to basic, due to the higher intensity of microbial acitivity and litter decomposition in those sites.

Plant functional traits and ecosystem properties

Plant traits resulting from evolutionary and physiological processes have produced a global and extraordinary functional diversity among the myriad of species colonizing contrasted habitats within the planet Earth.

Trait-based ecology helps us to understand better the community assemblage, ecosystem function and the responses to environmental changes.

Researchers of the RESTECO project and the Córdoba University have participated in the Symposium “Trait covariation: structural and functional relationships in plant ecology”, at Exeter (UK) during 27-29 June 2017.

Two comunications were presented:

1) Functional traits of trees affect soil properties and provision of ecosystem services. A study of seven tree species planted on remediated soils in the Guadiamar Green Corridor (Seville, Spain) has shown significant differences in traits (SLA, SRL, LDMC, RMDC) and chemical composition of leaves and roots. These traits differences influence the tree capacity to immobilize contaminants (trace elements) into the soil, remediation technique called phytostabilization. Traits also influence tree capacity to store carbon into biomass and soil, therefore contributing to climate change mitigation.

2) Within plant traits, roots are little known, despite their crucial role in the plant strategies of resource use and the ecosytem funcioning. Variation patterns of 5 root traits in 80 woody plant species from 18 samplig sites and 5 zones of South Spain have been studied. A strong correlation among traits indicates a main dimension along the root economics spectrum. However, other dimensions such as root diameter and the association with mycorrhizal fungi are also relevant.

The abstract and copy of the poster can be consulted in Digital CSIC repository:

Marañón et al. (2017) Traits influence the role of trees on ecosystem services: phytostabilization of trace elements and carbon sequestration.

Villar at al. (2017) Root traits across environmental gradients in Mediterranean woody communities: are they aligned along a single acquisition-conservation axis?

Potential of eucalypt trees for remediation of contaminated soils

The use of trees to immobilize contaminants (phytostabilization) is a low-cost and effective method of soil remediation.

Researchers of IRNAS, CSIC and New Zealand have evaluated the potential of red gum (Eucalyptus camaldulensis) to phytostabilize soils contaminated by trace elements (TE). Within the research project RESTECO, the ET concentration in soils and in eucalypt leaves and flowers has been investigated in 7 sites along the Gudiamar River valley. In general, the concentration of elements such as As, Cd, Cu, Pb and Zn in aboveground tissues was relatively low, and lower than toxic levels.

Eucalyptus camaldulensis is a fast-growing tree with a large root system; because of its tolerance to TE contamination and the low transfer of metals towards the aboveground tissues it can be considered suitable for phytoremediation of contaminated soils.

In addition, there was significant correlation between the concentration of Cd, Mn and Zn (but neither for Cu nor Pb) in their leaves and in the rhizosphere. Therefore, the eucalypt´s leaves may serve as bioindicators of the soil contamination for Cd, Mn and Zn.

The study has been published on June 30th 2017 in the open access journal PLOS ONE.

Madejón P, Marañón T, Navarro-Fernández CM, Domínguez MT, Alegre JM, Robinson B, Murillo JM (2017) Potential of Eucalyptus camaldulensis for phytostabilization and biomonitoring of trace-element contaminated soils. PLoS ONE 12(6): e0180240.

 

Evaluation of measures to remediate contaminated soils: European meeting

The RECARE project is focused on preventing and remediating degradation of soils in Europe.

A Plenary Meeting has been held at Hella (Iceland), from May 29th to June 2nd 2017. Each of the 17 study sites participating in the project presented their results.

Photo: Erik van den Elsen

The Group SOIL-PLANT, from the IRNAS, CSIC, presented their results about two measures applied for the remediation of contaminated soils at the Guadiamar Green Corridor: a) amendment addition and b) tree plantation.

Those results are part of a joint work by the projects RECARE and RESTECO.

Copies of the presentation and poster can be consulted at the repository Digital CSIC.

Presentation at 5th Ecosummit of Montpellier

ecos2016_300x250The 5th International Ecosummit, Ecological Sustainability, has been held at Montpellier, France, with more than 1,400 participants from 88 countries.

One of the scientific sessions was focused on Soil-plant interactions and soil ecosystem services delivery. In this session, researchers of IRNAS, CSIC have presented results on tree plantations in the Guadiamar Green Corridor (Seville, Spain) and their role in soil trace elements stabilization and carbon sequestration.

The importance of tree-soil interactions was remarked for the delivery of two ecosystem services: 1) improvement of soil quality by phytostabilization of contaminants, and 2) mitigation of climate change by carbon sequestration in biomass and soil.

Marañón, T., Domínguez, M. T., Navarro Fernández, C. M., Madejón, P., Burgos, P., Gil Martínez, M., & Murillo, J. M. (2016). Tree-soil interactions and the provision of ecosystem services in contaminated soils: trace elements phytostabilization and carbon sequestration. 5th International Ecosummit. Ecological sustainability. Engineering change. Montpellier, 29 August-1 September 2016.

Copy in pdf of the slides can be consulted in the CSIC repository.