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

Abstract

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

Rehabilitation Proposal for a Rural Settlement Affected By the Fundão Dam Tailings (Mariana-Brazil): A Study Case

“…The N-NH4 content was also found to be elevated in the settler properties (ES), but similar to the PS. In contrast, N-NO3 was strongly inhibited (Table 1), a finding also reported by [2] and [9] in dam tailing sediments. Higher levels of N-NH4 probably derive from ether-amine, but the low N-NO3 contents suggest a lack of soil-nitrifying bacteria as a result of a decline of microbial communities and diversity due to the dam tailings [2], [9], [13].…”

“…In contrast, N-NO3 was strongly inhibited (Table 1), a finding also reported by [2] and [9] in dam tailing sediments. Higher levels of N-NH4 probably derive from ether-amine, but the low N-NO3 contents suggest a lack of soil-nitrifying bacteria as a result of a decline of microbial communities and diversity due to the dam tailings [2], [9], [13]. Sodium toxicity may inhibit plant growth, induce senescence and cause plant mortality [14] and ammonium may be toxic to native and agronomic species [15].…”

“…Metals in the sediments were registered at the same levels as preserved sites not affected by the dam tailings [2] and the regional background, both before [6] and after [7] the disaster. Despite the great impact of these contaminants over such a vast area [2], [8], [9] were able to establish a pioneer remediation model to reduce the ether-amine and sodium in a riparian area affected by contaminated sediment by using phyto-and physical-chemical co-strategies. These strategies were able to remediate and reclaim the affected site.…”

“…2 A and B, and also in reports by ANVISA (Brazilian Health Regulatory Agency) [16] . However, such toxicity may be remediated by both woody and agro-pastoral species, as shown by [8] - [9]. Such remediation strategies allowed the recovery of soil fertility and significant improvement in plant growth [9].…”

“…However, such toxicity may be remediated by both woody and agro-pastoral species, as shown by [8] - [9]. Such remediation strategies allowed the recovery of soil fertility and significant improvement in plant growth [9]. Besides, the impact of flooding may be controlled by restoring riparian forests using a buffer zones system [11].…”