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

Hermano M Queiroz; Tiago O Ferreira; Diego Barcellos; Gabriel N Nóbrega; Juan Antelo; Xosé L Otero; Angelo F Bernardino

doi:10.1016/j.jenvman.2020.111575

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

J Environ Manage. 2021 Jan 15;278(Pt 2):111575. doi: 10.1016/j.jenvman.2020.111575. Epub 2020 Nov 2.

Authors

Hermano M Queiroz¹, Tiago O Ferreira², Diego Barcellos¹, Gabriel N Nóbrega³, Juan Antelo⁴, Xosé L Otero⁵, Angelo F Bernardino⁶

Affiliations

¹ Luiz de Queiroz College of Agriculture, University of São Paulo (ESALQ-USP), Av. Pádua Dias 11, CEP, 13418-900, Piracicaba, São Paulo, Brazil.
² Luiz de Queiroz College of Agriculture, University of São Paulo (ESALQ-USP), Av. Pádua Dias 11, CEP, 13418-900, Piracicaba, São Paulo, Brazil. Electronic address: toferreira@usp.br.
³ Graduate Program in Earth Sciences (Geochemistry), Department of Geochemistry, Fluminense Federal University, Niterói, Brazil.
⁴ Technological Research Institute, Universidade de Santiago de Compostela, Rúa Constantino Candeira, s/n. Campus Vida, 15782, Spain.
⁵ Departamento Edafoloxía e Química Agrícola, Facultade de Bioloxía, Universidade de Santiago de Compostela, Rúa Lope Gómez de Marzoa, s/n. Campus sur de Compostela, 15782, Spain.
⁶ Departamento de Oceanografia, Universidade Federal do Espírito Santo, Vitória, Espírito Santo, 29075-910, Brazil.

PMID: 33147526
DOI: 10.1016/j.jenvman.2020.111575

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.

Keywords: Crystallinity; Eutrophication; Fe oxides; Pollution; Redox processes; Samarco.

MeSH terms

Brazil
Ecosystem
Iron
Phosphorus*
Soil*

Substances

Soil
Phosphorus
Iron