FEASIBILITY STUDY ON PHYTOREMEDIATION OF HEAVY METALS FROM COPPER MINING WASTES

High concentrations of heavy metals in the soil are an important environmental problem and contamination comes mainly from industrialization, often carried out without proper regulations. The mining sector is one of the major contributors to the release of dangerous substances into the environment. In Chile, this sector accounts for a major proportion of gross domestic product but has significant environmental problems linked to the risk to human health. The accumulation of waste materials, generally fine and rich in HM, takes place in large open-air deposits, called "tailing dams" and located in the vicinity of mines and processing sites. The recovery and treatment of such deposits is necessary given their increasing expansion and the resulting environmental impact. Phytoremediation is rapidly gaining attention as a biotechnology to clean up substrates that are also contaminated with heavy metals, but the possibility of applying this technique must be assessed on a case-by-case basis. In this study, the feasibility and potential of phytoextraction intervention in tailing dams in Rancagua Copper Mine was investigated. The possible perspectives of the search have been evidenced, identifying the criticalities and fixing the bases for a future experimental planting. First, the mining sector of copper in Chile was presented, analysing the extraction and transformation process, including the waste arising from it. The focus was on the analysis of tailing dams, deposits of fine material coming from floatation and thickening operations, subsequently reporting the environmental and structural risks related to their implementation and operation. Afterwards, the phytoremediation technique was presented, showing the various strategies used and the possible types of treatment. In the case of the extraction of HMs, the impact of some factors was assessed and the plants suitable for such remediation treatments were classified, highlighting the characteristics necessary for the growth and accumulation of contaminants. In addition, the assessment criteria were presented and a comparison was made with traditional remediation techniques. For the development of research, the site under study was also characterized, both from the meteorological point of view (studying variables such as temperature, precipitation, humidity, evaporation, solar radiation and wind) and from the chemical point of view. By linking the chemical analyses to the guidelines for the hazardness of the specific elements, a risk-analysis was carried out, identifying the highest degree of contamination for Arsenic, Lead, Cadmium, Chromium and Zinc. Based on the above-mentioned evidence, the species that have shown phytoextraction potential for certain contaminants have been reported. In this study it has been shown that no hyperaccumulative species have been investigated in the Chilean territory. However, few endogenous and exogenous species could be used to clean up the contaminated site. Pteris Vittata L., Brassica Juncea L. and Noccea Caerulescens showed adaptability and growth in hostile environments and resistance to multicontamination. Such plants could be the right candidates for future experimental planting.