Cultivation of vetiver in saline tailings contaminated with arsenic under phosphorus doses

Abstract

A B S T R A C TThe processing of gold ores exploited in Paracatu, MG, generates tailings that are challenging for revegetation, mainly because of the high content of arsenic and salinity. Aiming at the revegetation of the area of disposal of these tailings, the objective of this study was to evaluate the effects of phosphorus doses on vetiver plants (Chrysopogon zizanioides) and on the planting substrate, which consisted of tailings from the processing of ore named B1, exploited in Paracatu, with water restriction. Vetiver was grown for four months in the substrate under doses of 0, 140, 280, 560 and 1280 mg kg -1 of P 2 O 5 . Increasing doses of phosphorus improved the chemical characteristics of the substrate. However, the highest dose (1280 mg kg -1 P 2 O 5 ) resulted in higher toxicity of arsenic for the plants. Under the evaluated conditions, the dose of 560 mg kg -1 of P 2 O 5 is the most suitable for the fertilization of vetiver and, therefore, also for the revegetation of the substrate. Vetiver survives under low availability of water in the tailings.Cultivo de vetiver em um rejeito salino contaminado com arsênio sob doses de fósforo IntroductionSome ores exploited for gold production may contain toxic elements, such as arsenic (As), in their composition, causing environmental problems. In Brazil, gold and iron mining has contributed to the dispersion of As and its entry in the food chain (Campos et al., 2006).The tailings produced in the processing of gold ores exploited in Paracatu, MG, Brazil, have limiting characteristics to plant growth, especially acidity, salinity and high As concentrations, which compromise the process of revegetation of the basin where they are disposed. A practice that can facilitate the establishment of plants in these tailings is phosphate fertilization.The addition of P has been reported as inhibitor of As absorption (Lei et al., 2012). Phosphate and arsenate are chemically similar and share the same membrane transporters in root cells, and the transporters have higher affinity for the phosphate (Tu & Ma, 2003;Zhao et al., 2008).Besides phosphate fertilization, plants tolerant to As and to salinity may have promising responses for the revegetation of tailings. One species with desirable characteristics to start the process of revegetation is Chrysopogon zizanioides (vetiver). The species, besides having high biomass production, has high tolerance and capacity of accumulation of contaminants (Singh et al., 2007).In this context, this study aimed to evaluate the effects of P doses on vetiver plants and on the planting substrate, which consisted of tailings from the processing of one of the gold ores exploited in Paracatu, MG, Brazil, subjected to water restriction. Material and MethodsThe substrate consisted of tailings from the processing of B1 ore, which is a highly weathered phyllite, with sulfide contents around 3.0 g kg -1 , collected in Paracatu, MG, Brazil. Three samples of the substrate were collected for its initial characterization, through the determination of pH i...