Articles | Volume 20, issue 14
Research article
20 Jul 2023
Research article |  | 20 Jul 2023

Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulfate soils

Joonas J. Virtasalo, Peter Österholm, and Eero Asmala

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Cited articles

Agrawal, Y. C. and Pottsmith, H. C.: Instruments for particle size and settling velocity observations in sediment transport, Mar. Geol., 168, 89–144,, 2000. 
Andriesse, W. and van Mensvoort, M. E. F.: Acid sulfate soils: distribution and extent, in: Encyclopedia of Soil Science, edited by: Lal, R., CRC Press, Boca Raton, USA, 14–19,, 2006. 
Asmala, E., Bowers, D. G., Autio, R., Kaartokallio, H., and Thomas, D. N.: Qualitative changes of riverine dissolved organic matter at low salinities due to flocculation, J. Geophys. Res.-Biogeo., 119, 1919–1933,, 2014. 
Asmala, E., Carstensen, J., Conley, D. J., Slomp, C. P., Stadmark, J., and Voss, M.: Efficiency of the coastal filter: nitrogen and phosphorus removal in the Baltic Sea, Limnol. Oceanogr., 62, S222–S238,, 2017. 
Asmala, E., Virtasalo, J. J., Scheinin, M., Newton, S., and Jilbert, T.: Role of particle dynamics in processing of terrestrial nitrogen and phosphorus in the estuarine mixing zone, Limnol. Oceanogr., 67, 1–12,, 2022. 
Short summary
We mixed acidic metal-rich river water from acid sulfate soils and seawater in the laboratory to study the flocculation of dissolved metals and organic matter in estuaries. Al and Fe flocculated already at a salinity of 0–2 to large organic flocs (>80 µm size). Precipitation of Al and Fe hydroxide flocculi (median size 11 µm) began when pH exceeded ca. 5.5. Mn transferred weakly to Mn hydroxides and Co to the flocs. Up to 50 % of Cu was associated with the flocs, irrespective of seawater mixing.
Final-revised paper