Phytoremediator Potential of Ipomea asarifolia in Gold Mine Waste Treated with Iron Impregnated Biochar

Leônidas Carrijo Azevedo Melo,Edna Santos De Souza,Yan Nunes Dias,Antonio Rodrigues Fernandes,Hercília Samara Cardoso Costa

doi:10.3390/min12020150

Abstract

Growing environmental pollution in recent decades has been generating potentially toxic elements (PTE) which pose an ongoing threat to terrestrial and aquatic ecosystems and human health, especially in mining areas. Biochar and PTE-tolerant species have been used in soil remediation as they are environmentally friendly alternatives. This study aimed to assess the influence of açaí seed biochar (Euterpe oleracea Mart), impregnated with iron (BFe) or not (BC), on the bioavailability of PTEs, in a multi-contaminated soil from a gold (Au) mining area in the Amazon, using Ipomea asarifolia as a plant test since it was naturally growing on the tailings. BC increased the soil pH while BFe reduced. Biochars increased PTEs in the oxidizable fraction (linked to soil organic matter). The use of BC and BFe improved the immobilization of PTEs and BC increased arsenic (As) in the easily soluble fraction in the soil. Moreover, plants grown with biochars showed lower dry matter yield, higher concentrations of PTEs and lower nutrient content than the control treatment. According to the phytoextraction and translocation factors, Ipomea asarifolia can be classified as a species with potential for phytostabilization of Zn and tolerant to other PTEs, mainly As.

Highlights

Toxic elements (PTEs) are naturally present in the environment
The high pH of BC is due to the formation of Ca, Mg and oxyhydroxide carbonates during the pyrolysis process, especially at relatively high temperature (700 °C) [47]
The low pH of Bfe may be due to the ion exchange that occurs between basic cations on the biochar surface and Fe ions during the impregnation [48], which agrees with a marked reduction in the biochar pH from 10.7 to 4.8 after impregnation with Fe observed by Yin et al [19]

Summary

Introduction

Toxic elements (PTEs) are naturally present in the environment. Human activities, such as mining, have considerably increased the concentrations of these elements in ecosystems [1]. Waste piles from mining activities normally contain high levels of PTEs that contribute to environmental pollution [2,3,4]. Due to persistence in the environment, mobility, and speciation, PTEs can be transferred and accumulated in the food chain, resulting in adverse effects on physiological and biochemical processes in plants and soil microorganisms [6,7]. PTEs can be accumulated in vital organs of the human body, leading to a potential danger to the health of those who live in the vicinity of mining areas [8]. For the recovery of areas degraded by mining and with high levels of PTEs, several strategies have been developed, such as the use of biochar or modified biochar associated with phytoremediator species [5]

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