What is the project about?
Abandoned mine tailings (flotation sludge from ore washes) pose an environmental problem, mainly due to the extremely high concentrations of metals and methaloids they contain.
Due to the large number of abandoned mine tailings that exist, it is not feasible to assume the expenses and technical difficulties of restoring all of them by methods such as their removal and transport to landfill site or their encapsulation. These actions should be prioritized when the deposits entail an unacceptable risk due to collapse and/or due to their proximity to towns.
Phytomanagement can complement other more expensive options, helping to reduce the risk of deposits being a source of dispersion of potentially dangerous elements, by improving their soils, facilitating the growth of plants directly on them and improving the ecosystem.
How do we carry it out?
1. Native plants are used
With capacity of living in soils with poor physical, chemical and biological properties and extremely high metal contents. The selected species immobilize soil metals in their roots and rhizospheres.
2. Seedings and plantations with trees, shrubs and herbs are combined
This makes it possible to increase the vegetation cover in the short term, reduce erosion and promote the diversity and functional development of the ecosystem.
3. The soil is ploughed to improve its conditions
Adding amendments from organic waste (biochar and compost from urban waste) contributes to the circular economy.
4. Biochar increases the pH
It contributes to immobilizing metals, improves soil structure and provides persistent organic matter, favoring carbon sequestration.
5. Compost increases soil nutrient contents
Its main composition includes urban solid refuse (USR). It mainly provides fresh organic matter and mineral nutrients necessary for plants and soil organisms.
6. Fascines are built
They are facilitating structures that help improve the soil, the plant development and the presence of fauna.
7. Perches for birds are built
To promote the visit of frugivorous birds and thus favor the dispersion of seeds.
What actions have we carried out?
742
seedlings
- Pinus halepensis
- Tetraclinis articulata
- Atripex halimus
- Maytenus senegalensis
- Tamarix canariensis
- Stipa tenacissima
5
five species sown
- Lygeum spartum
- Dorycnium pentaphyllum
- Rhamnus lycioides
- Piptatherum miliaceum
- Lycium intricatum
44
Fascines built with pruning remains of pine branches in the area.
- They favor shaded areas
- They act as refuges for fauna
- They provide organic matter
- They trap sediment and reduce erosion
- They favor plant spread
6
Perches to encourage the visit of frugivorous birds, and thus favor the dispersion of seeds.
All the wood used to make the fascines, terraces and the bird perches were built from pruning works carried out in the surroundings of the pilot plot. Ingeniería del Entorno Natural has collaborated in the preparation of the soil and the addition of amendments. Fundación Sierra Minera has collaborated in the planting, placement of protectors, fascines and terraces built, and irrigation.
How do we monitor the results?
The growth of the 742 planted specimens is monitored and soil properties are analyzed over time in the entire experimental pilot plot.
Height and cover of each plant are measured. In addition, trunk width is measured in the trees (Tetraclinis articulata and Pinus halepensis).
How do we evaluate the effect of the fascines, the addition of the amendments and of both factors together on the plants and the soil?
For this, twelve plots of 3 m x 10 m have been established. In all there are fascines, but in six of them no amendment was added. In each plot, plants have been placed next to the sunny side and next to the shady side of the fascines. Data on temperature and soil CO2 emissions are regularly measured on each side of the fascines. Bait lamina sticks are inserted in the soil to assess the activity of edaphic invertebrates. Soil samples are collected seasnally to analyze chemical, physical and biological properties.
Plant growth is regularly measured by hand. The total cover in the plot is evaluated by means of images taken by a drone at the beginning and at the end of the project.
A CIRAS-2 device is used to regularly measure soil CO2 emissions to assess “in situ” microbiological activity.
Bait lamina sticks are inserted into the soil to assess the feeding activity of edaphic invertebrates. Soil temperature is measured periodically.
The effect of the amendments on the ecotoxicity of the soil is assessed by carrying out bioassays with edaphic invertebrates.
The effectiveness of the sowing is regularly evaluated by monitoring the germination of the sown seeds
Photo-trapping systems have been installed to monitor small mammals and reptiles and pitfall traps for insects. In addition, tours are carried out for bird watching and other fauna. These tasks are carried out in collaboration with Biocyma evironmental consulting.
