Transferencia de elementos potencialmente tóxicos en plantas comestibles desarrolladas en tecnosoles mineros experimentales

Resumo

Potentially Toxic Elements (PTEs) represent a major environmental concern, due to their high persistence characteristics, as well as their bioaccumulation capacity. Soils affected by the presence of PTEs represent a large surface area on our planet. Agricultural areas located in the proximity of sites potentially contaminated by past mining activities are of particular relevance, due to the transfer of PTEs from the soil to the biotic environment, through the sequence soil-plant-trophic chain-fauna-human being which represents a public health risk, affecting to flora and fauna. These soils restorations require studies and methodological applications, which must be profitable and put in value the circular economy principle. In this PhD thesis, an experimental study was developed to respond to this challenge, by manufacturing technosols with different wastes, and verifying their effectiveness through a Quantitative Risk Analysis (QRA) which asseses whether there is a carcinogenic risk or systemic danger to human health and surrounding fauna. In this study, the uptake of PTEs of the following vegetable plants was assesed: lettuce, onion, broccoli, leek, chard and salicornia. The crops were grown on 5 types of soil: TC (contaminated soil): 50% Lo Poyo + 25% Cabezo Rajao + 25% Portman), T1 (natural soil), T2 (50% TC + 50% T1), T3 (75% TC + 25% CDW), T4 (75% TC + 25% limestone filler). By the manufacturing of these technosols, the principle of the circular economy was put into practice, evaluating construction and demolition waste (CDW) and other industrial waste with a high calcium carbonate content and converting them into high-value subproducts for the restoration of contaminated soils. The experiment was carried out in a greenhouse, and the concentration of As, Cd, Cu, Pb and Zn in soils, rhizospheres, leachates and plants were analyzed. The soil chemical characteristics were determined, as well as mobilisation studies with different reagents to simulate diverse environmental conditions which allowed predicting the behaviour of PTEs in the different technosols. A methodology was carried out based on the calculation/estimation of the risk to health and ecosystems which represents the presence of PTEs in soils affected by past mining activities and agricultural soils, especially the surrounding fauna. The efficacy of these technosols used as a restoration methodology for soils potentially contaminated by PTEs was also evaluated by characterising and assessing risks according to the possible land uses (agricultural, residential and industrial). The results obtained in plants determined similar values to those established in Regulation (UE) 2023/915, with the exception of the species that developed in TC. Very different uptake and translocation behaviours were observed depending on the plant species crop. The Quantitative Risk Assesment (QRA) showed that there is no danger to human health through ingestion of crops grown in technosols, there is only risk for leek consumption due to the presence of arsenic. The studies on wild boar found a higher risk and danger especially from the consumption of root vegetables. The QRA carried out in 7 possible land use scenarios to assess the efficacy of technosols showed excellent results, with no risk and no hazard from ingestion for all studied PTEs (except As). Assessment by inhalation and dermal routes showed no health risk. The assessment of construction and demolition wastes as well as limestone filler showed similar efficacy as soil restoration amendments, and were considered very suitable for the natural attenuation of contamination through the manufacture of technosols