Longevity and efficacy of lanthanum-based P remediation under changing dissolved oxygen availability in a small eutrophic lake.
Environ Sci Process Impacts
; 26(8): 1336-1347, 2024 Aug 14.
Article
em En
| MEDLINE
| ID: mdl-38766807
ABSTRACT
We set out to study the seasonal variations in porewater phosphorus and lanthanum concentrations in the dated sediment cores from a small eutrophic lake that has been treated with Phoslock, a lanthanum-modified bentonite (LMB) amendment. Three sites were sampled when the hypolimnion was either oxygenated or anoxic (i) the lake's deepest point, (ii) a littoral site receiving inflows from the catchment, and (iii) a littoral site influenced by nearby septic tanks. Phosphate (PO43--P), lanthanum (La), iron (Fe), dissolved organic carbon (DOC) and sulfate (SO42-) were measured in porewater samples. An inverse diagenetic model was used to quantify fluxes of dissolved elements across the sediment-water interface as well as the net rate of their reactions along the porewater concentration gradients. Results show that porewater P and Fe underwent strong seasonal dynamics, while La did not. P fluxes, 20-fold higher at the deepest site than elsewhere in the basin, were influenced by anoxic conditions in the hypolimnion during summer and winter, suggesting that P mobility remained sensitive to redox fluctuations despite the addition of La. At the deepest site, fluxes of P across the sediment-water interface increased from 1 to 9 × 10-9 µmol cm-2 s-1 between spring and summer, while the rate of P production to the porewater also increased a hundredfold. These increases were concurrent with Fe mobilization. Finally, sediment dating shows that the fraction of P sequestered by La is buried under freshly deposited sediment at a rate of 2-3 mm per year. These results indicate that external P fluxes and erosion control remain crucial to maintain the longevity of the LMB treatment.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
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Fósforo
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Poluentes Químicos da Água
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Lagos
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Eutrofização
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Recuperação e Remediação Ambiental
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Lantânio
Idioma:
En
Revista:
Environ Sci Process Impacts
/
Environ. sci., Process. impacts (Online)
/
Environmental science. Processes & impacts (Online)
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Canadá