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Internal loading potential of phosphorus in reservoirs along a semiarid watershed.

Moura, Diana Souza; Almeida, Antonia Samylla Oliveira De; Pestana, Carlos João; Girão, Laura Gomes; Capelo-Neto, José

Authors

Antonia Samylla Oliveira De Almeida

Laura Gomes Girão

José Capelo-Neto



Abstract

All rights reserved. Sediments are important to nutrient dynamics, especially due to phosphorus internal loading. Several studies have observed that internal loading could prevent water quality from improving in lakes, even when external phosphorus loading is significantly decreased. Therefore, there is an urgent need to assess the potential release of phosphorus contained in the sediment, and thus, its potential to impact water quality. In this study, the vertical and horizontal distributions of distinct phosphorus forms in the bottom sediments of artificial reservoirs, located at Forquilha watershed (Ceará, Brazil), were investigated through sequential chemical fractionation. The reservoirs Lagoa Cercada (R#1), Riacho do Algodão (R#2), Riacho Verde (R#3), Cachoeira (R#4), Chagas Manu (R#5), Quandu (R#6) and Balanças (R#7) were investigated. Reservoirs R#1 (most downstream reservoir of the watershed) and R#7 (most upstream reservoir of the watershed) had higher concentrations of total phosphorus (PT) and lower pH values, potentially exerting greater influence in phosphorus concentration in the water column. Reservoirs R#3 and R#4 presented a predominance of residual phosphorus (PRe), the least available fractions of phosphorus and thus, presented a lower potential for internal loading. Reservoirs R#5, R#1 and R#2 showed a tendency of decreasing total phosphorus (PT) as the sediment depth increased, probably indicating an increase of allochthonous phosphorus loading along time. Reservoir R#6 showed the predominance of PFeAl and PCa fractions on points A and B, respectively, showing that the characteristics of the sediments may vary in the same reservoir. Mobile (PM) and iron and aluminum-bound phosphorus (PFeAl) were the least and the most abundant fractions in most of the samples analyzed, respectively.

Citation

MOURA, D.S., ALMEIDA, A.S.O.D., PESTANA, C.J., GIRÃO, L.G., and CAPELO-NETO, J. 2020. Internal loading potential of phosphorus in reservoirs along a semiarid watershed. Revista Brasileira de recursos hídricos [online], 25, article ID e13. Available from: https://doi.org/10.1590/2318-0331.252020180023

Journal Article Type Article
Acceptance Date Oct 14, 2019
Online Publication Date Apr 17, 2020
Publication Date Dec 31, 2020
Deposit Date May 22, 2020
Publicly Available Date May 22, 2020
Journal Revista Brasileira de recursos hidricos
Print ISSN 1414-381X
Electronic ISSN 2318-0331
Peer Reviewed Peer Reviewed
Volume 25
Article Number e13
DOI https://doi.org/10.1590/2318-0331.252020180023
Keywords Water quality; Bottom sediment; Phosphorus availability; Eutrophication potential
Public URL https://rgu-repository.worktribe.com/output/915612

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