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

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.

The failure of the Fundão dam in Brazil spilled contaminated sediments to the Doce river basin with high levels of pH,ether-amine and sodium. In the present study, it was established a riparian forest over contaminated sediment using two main remediation strategies: phytoremediation with native species to the Atlantic Forest, previously selected for tolerance to the sediment toxicity, and physico-chemical remediation by management of the sediment with incorporation of OM. In the experimental site (ES), 12 native species were cultivated under two treatments: T1-management of the sediments with incorporation of OM and T2-nonmanaged sediment + superficial deposition of OM. The results were compared with a degraded site (DS) affected by the contaminated sediments and a preserved site (PS) composed of a fragment of preserved Atlantic Forest. After 6 month of transplanting, plants from T1 showed a better height growth performance (up to 3m) and survival index in relation to T2, as well as a significant decline of ether-amine and sodium contents. Besides the improvement of soil fertility, the amendment with OM promoted a pH reduction, favoring ether-amine destabilization, sodium sequestration and improvement of soil microbial populations. Soil nitrification was improved as revealed by the significant increase of nitrate which seems to have favoured the rampant growth of tolerant plant species after 6 months of planting. Therefore, it is recommended the incorporation of OM to the sediment and phytoremediation with selected tolerant species to remediate sodium and ether-amine toxicity.

The largest remaining area of preserved Atlantic Forest in the Belo Horizonte City (Minas Gerais, Brazil) protects many headwaters and watercourses. Among them, the Macacos stream is considered the most preserved with high water quality. However, since 2013 this region has suffered an intense and disorderly of informal settlement process by low-income communities, which resulted in a progressive loss of the original vegetation. Due to the lack of vegetation, this area became prone to erosional process as demonstrated by the topographic analysis. The Normalized Difference Vegetation Index (NDVI) demonstrated the great impact of the settlement process over the vegetation, ranging from 1 to 0. Besides, this eroded area has faced the loss of biodiversity as estimated by the richness and Shenon's index as well as the invasion by exotic species as Brachiaria sp and Typha domingensis. Also, the erosional process in this hilly site resulted in the accumulation of high level of sediments in the Macacos stream. Therefore, the restoration of headwaters and riparian sites aiming at soil stabilization and vegetation restoration is highly recommended.

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