Researchers of the group 'Applied Soil Science' of University of Almería, in collaboration with the University of Granada, the Polytechnic University of Murcia and the Leitat Technology Center Barcelona, They have shown that the reuse of sludge marble heavy metal contaminated areas contributes to the growth of vegetation, allowing recovery of the environment and improve its visual impact.
Specifically, experts have corroborated these findings in several plots of Aznalcóllar (Seville) affected by a toxic spill nearly two decades ago. they, They have managed to recover green areas that previously had remained barren.
On the other hand, They have also found that on the slopes of the marble quarries of Macael (Almería), vegetation reappears after covering the area with the mineral sludge, as it increases moisture and makes it possible to increase their rooting plants in soil.
In this sense, The researchers began this project by collecting sludge rafts originating with the quarries. After processing and characterize the microparticles, determine its composition, size and indicators of toxicity, They obtained that these residues are free of contaminants.
After that, experts conducted tests metal binding. Specifically, sludge samples were placed in contact with contaminating solutions in order to define how much of metals could adhere to the waste. "The result was that the sludge from the marble industry could precipitate most of the main pollutants in the area as copper, zinc, cadmium, arsenic and lead ", Discover the Foundation points out the researcher at the University of Almería and co-author of this study, Mariano Simón.
Once the results obtained at laboratory scale, they rehearsed in vivo in small greenhouses using different types of soils, different sludge and contaminants varied. "We tested if the mud pots promotes the growth of any type of flora, whether plants, shrubs or other vegetation ", Simon qualifies.
Throughout this process, collected in the study entitled ‘Using marble sludge and phytoextraction to remediate metal(sluggish) polluted soils’ and published in the journal Journal of Geochemical Exploration, They used the plant known as mustard (Brassica juncea).
Acid and alkaline soils
To ensure the implementation of these residues marble, They tested in two different soils. On the one hand, one acid where the pH is low and the content of soluble contaminant metals is high. "This system limits the erosion in case of rain and wind and consequently, the spread of contamination freezes ", details this scientific.
At the same time, Bioremediation is encouraged, since the plant acts as a filter retaining the metals and preventing them from reaching the water table, namely, groundwaters.
After analyzing this technique in acid soils, They also tested in contaminated alkaline soils. "In this type of soil, as those in the marble quarries or mining iron, mud does not increase the pH, calcium carbonate but also sets certain compounds such as arsenic and avoid its mobilization ", says researcher.
Muds Macael in Aznalcóllar
The results of this project have been discussed at two locations in Andalusia. On the one hand, in the Seville town of Aznalcóllar, affected by a spill of nearly two decades metals.
There, researchers moved Macael marble sludge to regenerate part of this area. "Today, after 19 years after the spill that polluted all that part occurred, there are still many clearings where vegetation does not grow because the mud sulfur mine keeps growing. With this work we have managed to recover green areas with a purely aesthetic purpose, since plants can be harmful to health after having been in contact with metals. So you can neither hunt nor gather plants ", specifies Simon.
At the same time, in the quarries of Macael, scientists coated quarry stones with mud as a blanket and then covered with the topsoil. "Before only the land was deposited on top of the quarry, but because of erosion, all this substrate was lost. In return, now, to fill gaps in the marble quarry sludge having high water holding capacity and add dirt on top, the plant roots reach the mud, because they are looking for moisture, and finally take root, ensuring growth ", said Simon.
This research project, funded by the Ministry of Economy and Knowledge of the Government of Andalusia, is the continuation of other studies where experts started working marble sludge identifying ago 10 years old.