From sinks to sources: The role of Fe oxyhydroxide transformations on phosphorus dynamics in estuarine soils

Author(s)

Queiroz, Hermano M. ; Ferreira, Tiago O. ; Barcellos, Diego ; Nobrega, Gabriel N. ; Antelo, Juan ; Otero, Xose L. ; Bernardino, Angelo F.

• Document type: Journal article
• Source: Journal of Environmental Management; v. 278, p. 11-pg., 2021-01-15.

Abstract

The availability of phosphorus (P) in estuarine ecosystems is ultimately controlled by the nature of interactions between dissolved P and the soil components (e.g., soil minerals), especially iron (Fe) oxyhydroxides. P retention on Fe oxyhydroxides and its subsequent availability depends on mineral crystallinity and susceptibility to dissolution. However, in estuarine soils, geochemical conditions (e.g., redox oscillation and high soil organic matter content) may alter the fate of P and decrease the environmental quality of estuarine waters. The large input of Fe-rich tailings into the Rio Doce Estuary in Brazil in 2015 after a rupture of a Fe ore tailings dam (i.e., "Mariana mine disaster") offers a unique framework to evaluate the Fe oxyhydroxides role in P availability in estuarine soils, their potential effects on the cycling of P and eutrophication. We observed a significant correlation between Fe minerals and the P content in the estuary soils, suggesting that P enrichment was promoted by the deposited Fe-rich tailings. Adsorption isotherm curves indicated that mine tailings had a strong affinity for P due to presence of crystalline Fe oxyhydroxides in the tailings. Significant losses of Fe (62%) and P (56%) from the estuarine soil was observed two years after the initial impact and in response to redox conditions oscillations. Additionally, the content of high crystallinity Fe oxyhydroxides decreased significantly, whereas that of low crystallinity Fe oxyhydroxides showed an increase over time. These changes were associated with the dissimilatory Fe reduction, which led an increase in the concentrations of readily available P (2015: 2.30 +/- 0.41 mg kg(-1); 2017: 3.83 +/- 1.82 mg kg(-1); p < 0.001) in the studied soils. Moreover, in 2017, the dissolved P content exceeded the recommended environmental safety limits by five times. Our results indicate that Fe oxyhydroxides are a continuous source of dissolved P for the ecosystem, and Fe-rich tailings deposited in the estuarine ecosystem may be linked to a potential eutrophication. (AU)

• FAPESP's process: 18/08408-2 - Comparative studies of the mineral transformation of iron oxide nanoparticles in mine-tailing affected sediments and soils and their impacts on mobilization and fixation of heavy metals under two contrasting redox environments
• Grantee: Tiago Osório Ferreira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/02855-0 - Redox fluctuations, iron and heavy metals dynamics in soils from Rio Doce estuary after the "Mariana (MG) disaster": an experimental approach
• Grantee: Diego Barcellos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/04259-2 - Iron biogeochemistry and its control on dynamics of trace metals in the soils of Doce River estuary after the "Mariana disaster"
• Grantee: Hermano Melo Queiroz
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 19/19987-6 - Soils and plants of the Rio Doce estuary controlling the biogeochemistry of iron and metals in response to the Mariana (MG) disaster
• Grantee: Tiago Osório Ferreira
• Support Opportunities: Regular Research Grants