Assessing the reclamation of a contaminated site affected by the Fundão dam tailings trough phytoremediation and bioremediation.

The rupture of the Fundão dam (Brazil) spread tailings contaminated with sodium and ether-amine into the Doce River Basin. Aiming at rehabilitating a contaminated riparian site, phytoremediation with native species of the Atlantic Forest was performed under four treatments: ES-1: physical remediation (sediment scraping) + chemical remediation (organic matter) + bioremediation (double inoculation with the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis and the plant growth-promoting bacteria Bacillus subtilis); ES-2: chemical remediation + bioremediation; ES-3: physical remediation + chemical remediation; ES-4: chemical remediation. Ether-amine and sodium contents, plant growth and, soil quality parameters were compared among treatments and relative to preserved and degraded sites. Two years after planting, the outstanding plant growth was attributed to the phytoremediation of ether-amine and ammonium, followed by a significant increase in soil microbial biomass (Phospholipid fatty acids-PLFAs), particularly the Gram+ bacteria and total fungi but not AMF, whose response was independent of the inoculation. While sodium and ether-amine declined, soil K, P, NO3- contents, dehydrogenase and acid phosphatase activities, cation exchange capacity (CEC) and soil aggregation increased, especially in ES-1. Thus, such remediation procedures are recommended for the restoration of riparian areas affected by the Fundão tailings, ultimately improving sediment fertility, aggregation and stabilization.

To the best of our knowledge, this is the only successful example of fragment of riparian Atlantic Forest successfully rehabilitated using native trees from the Atlantic Forest in the riparian zone affected by the contaminated Fundão dam tailings. For that, phytoremediation and bioremediation procedures were adopted to alleviate etheramine and sodium toxicity, resulting in the amelioration of soil fertility and particularly the stabilization of such highly disaggregated sediments, ultimately protecting the Doce river basin against these contaminants.

Rehabilitation of a Riparian Site Contaminated by Tailings from the Fundão Dam, Brazil, Using Different Remediation Strategies.

The tailings spilled by the Fundão Dam rupture in the Doce River basin (Brazil) had a high pH, elevated sodium (Na) and ether amine, and low soil organic matter. With the aim of decreasing the toxic compounds, we established 2 remediation strategies: treatment 1, phytoremediation with tolerant native species of the Atlantic Forest cultivated on scraped sediment plus the incorporation of organic matter; and treatment 2, phytoremediation with native species plus superficial deposition of organic matter. The experimental site was compared with a degraded site that the dam tailings had reached and with a preserved site, a fragment of preserved Atlantic Forest. After 12 mo, plants showed an outstanding growth, especially after treatment 1 (~4 m), and the remediation procedures resulted in significant decreases in pH (from 8.0 to ~ 6.0), Na (from 154 to 22-35 mg/kg), electrical conductivity, and ether amine (from 6.0 to 0.5 mg/kg) in both treatments. By contrast, ammonium, a product of ether amine degradation, showed a significant increase in the experimental site, along with a significant increase in nitrate and improvement of soil microbial populations assessed by phospholipid fatty acid analysis. The treatments also improved soil fertility in the experimental site, as estimated by soil nutrients, cation exchange capacity, and soil aggregation. Based on the parameters analyzed, a principal component analysis showed that samples from the degraded site and the preserved site clustered in an opposite position and those from the experimental site clustered in an intermediate position but closer to the samples from the preserved site. Overall, our results demonstrated that the remediation procedures adopted were effective and resulted in rehabilitation of a riparian forest contaminated with dam tailings that included Na and ether amine. Environ Toxicol Chem 2021;40:2359-2373. © 2021 SETAC.

Remediation of a Riparian Site in the Brazilian Atlantic Forest Reached by Contaminated Tailings from the Collapsed Fundão Dam with Native Woody Species.

The failure of the Fundão dam in Brazil spilled alkaline contaminated sediments (pH ~8) into the Doce River basin. The contaminated sediments had high levels of ether amine (6 mg/kg) and Na (54 mg/kg) in relation to those in preserved sites. In the present study, a riparian forest was established over contaminated sediment using 2 main remediation strategies: phytoremediation with species native to the Atlantic forest and previously selected for their tolerance to sediment toxicity, and physicochemical remediation by incorporating organic matter (OM) into the sediment. In the experimental site (ES), the tolerant native woody species were cultivated in 2 treatments: T1, scraping of the sediments and incorporation of the OM, and T2, nonmanaged sediment and superficial deposition of the OM. The results were compared with the findings from a degraded site (DS), which was reached by the contaminated sediments but lacked vegetation, and a preserved site (PS), which was composed of a fragment of preserved Atlantic forest. Six months after transplanting, the plants from T1 showed a better height growth performance and survival index in relation to those from T2. Furthermore, T1 showed a significant decline in the pH (to ~6) concomitant with a reduction in the ether amine and Na contents (to ~0.4 mg/kg and 23 mg/kg, respectively). There was an improvement in the soil fertility and total microbial biomass in both treatments, especially in T1. Therefore, the adopted phyto- and physicochemical remediation procedures are recommended to reclaim zones reached by dam tailings containing Na and ether amine. Integr Environ Assess Manag 2020;16:669-675. © 2020 SETAC.

A ruptura da Barragen de Fundão em Mariana (Brazil) lançou um sedimento alcalino (pH ~8) ao longo da Bacia do Rio Doce. O sedimento contaminado apresentou altos níveis de éter-amina (6 mg/kg) e Na (54 mg/kg) em relação aqueles encontrados na área preservada. No presente estudo, uma floresta riparia foi estabelecida sobre este sedimento contaminado usando-se 2 estratégias de remediação: Fito-remediação com espécies nativas da Mata Atlântica, previamente selecionadas pela tolerância à toxicidade do sedimento, e remediação físico química pela raspagem superficial do sedimento e aplicação de matéria orgânica (OM). Na área experimental (ES) as espécies arbóreas da mata Atlântica selecionadas foram plantadas sob 2 tratamentos: T1, Raspagem superficial do sedimento e incorporação da OM, e T2, sedimento não foi manejado e recebeu aplicação superficial de OM. Os resultados foram comparados com aqueles obtidos na área degradada (DS), atingida pelo sedimento contaminado e sem vegetação, assim como com aqueles obtidos em uma área preservada (PS), constituída de um fragmento de Mata Atlântica. Após seis meses do plantio as plantas de T1 apresentaram um maior crescimento em altura e maior taxa de sobrevivência que as plantas de T2. Além disto ES, especialmente T1 mostraram um significante declínio do pH (~6.0) e concomitante redução nos teores de éter-amina e Na (~0.4 mg/kg e 23 mg/kg, respectivamente). Os procedimentos de remediação permitiram também um significativo aumento da fertilidade química e da biomassa microbiana do sedimento em ambos os tratamentos, especialmente em T1. Assim, os procedimentos de remediação físico-quimica e fitoremediação aqui adotados, são recomendados para recuperar as zonas atingidas pelo rejeito da barragem contaminado com sódio e éter-amina. Integr Environ Assess Manag 2020;16:669-675.