Cistus salviifolius a promising species for mine wastes remediation

Abstract

Metal mining in Caveira and São Domingos (Portugal) generated large volumes of tailings with high total concentrations of trace elements, low pH and fertility. Autochthones plants growing spontaneously in mine areas are usually tolerant to unfavorable characteristics of tailings. The aim of this investigation was to analyze the behavior (trace elements uptake, accumulation and translocation from roots to shoots) of different populations of Cistus salviifolius plants growing spontaneously in contaminated and non-contaminated sites in order to evaluate the potential of this plant species for soils and mine wastes phytostabilization. Cistus salviifolius plants (roots and aerial parts) and soils were collected, in two mine areas (São Domingos and Caveira) and a reference area (Grândola), and were analyzed for arsenic, antimony, copper, lead, manganese and zinc concentrations. Cistus salviifolius showed tolerance for moderate acid soils (5.34<pH<5.72), with low fertility and multielemental contamination (arsenic, antimony, copper, lead and zinc). The same elements soil available fractions, extracted with ammonium acetate, were low (<7.2% of total concentration) because these elements are mainly associated with the residual fraction, and iron oxides. However, the association of arsenic (33–43% of total arsenic in both mining areas) and lead (58% of total lead in Caveira) with organic matter in mine soils, represents a potential environmental risk. All the plant populations presented translocation of nutrients (copper, manganese and zinc) to the aerial parts and storage of phytotoxic elements (arsenic, antimony and lead) in roots. None population was considered trace elements accumulator and the elements did not exceeded the phytotoxic concentrations (only arsenic in the aerial parts of São Domingos plants) and metal toxicity limits for domestic animals. Cistus salviifolius is considered suitable for phytostabilization of mining wastes in areas with semiarid characteristics.