Linking circular economy and environmental rehabilitation in the designed Technosols for highmountain pastures implementation

Although at different features and intensities, both abandoned and active mines as well as other industrial areas associated to mining activity, have several environmental problems associated to extreme physicochemical characteristics of their materials, wastes and/or leachates. The conventional closure systems do not contribute to the improvement of the chemical characteristics of some contaminated materials and its leachates. Moreover, superficial layer of soil applied in the conventional closure systems have very high cost of implementation and, especially, maintenance since this is periodically fertilized with organic amendments and re-sown.  

Nowadays, the strategies and technologies for tailings and deposits closure should be based on sustainability and the circular economy. In this context, an effective solution is the use of Technosols derived of wastes and designed specifically for each contaminated/degraded materials in order to remediate, at integrated level, the different components of the ecosystem and reconverting non-productive and degraded areas. The development and in situ application of designed Technosols to growth of highmountain pastures was carried out, firstly, under controlled conditions to evaluate the physic-chemical quality of the designed Technosols and then under field conditions. After superficial application of the Technosol on tailing deposit containing sulfide-rich wastes, plant cover was monitored for one year. The efficiency of Technosol in the improvement of chemical characteristics of mine wastes located under it was evaluated. Technosol was also evaluated in order to confirm the maintenance of its properties and characteristics.

Even in the highmountain conditions, a rapid germination, development and coverage of the surface by herbaceous species was obtained. In three months, there was less than 35% of bare soil. The percentage of bare soil decreased over time and in six months plant cover reached more than 85 % and a height of 65 cm. The productivity of the pasture was between 3 and 9 kg/m2. Plants did not show visible signs of phytotoxicity or nutritional deficiency and elements concentrations in shoots were in normal range, considering plants species in general.  Pasture does not seem to represent an environmental risk for domestic animals that exist in the areas adjacent. The chemical characteristics and andic and eutrophic properties of the Tecnosol were maintained. The Tecnosol stimulated the functionality of the microorganisms-soil-plant system, as well as the alteration of chemical characteristic and microbiological communities of the deposit.

Acknowledgment: This research was supported by Portuguese funds, through Fundação para a Ciência e Tecnologia, within the scope of the project UID/AGR/04129/2020.