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Research article2020Peer reviewedOpen access

New Insights Into Legacy Phosphorus From Fractionation of Streambed Sediment

Lannergard, Emma E.; Agstam-Norlin, Oskar; Huser, Brian J.; Sandstrom, Sara; Rakovic, Jelena; Futter, Martyn N.

Abstract

Streambed and lake sediment was studied in Savjaan, a eutrophic mesoscale catchment (722 km(2)) in central Sweden. Triplicate sediment cores from five lakes and nine streams, ranging from headwater to fourth order, were sampled. The sediment was analyzed with a sequential extraction method, where six different phosphorus (P) fractions were measured. The results showed that streambed sediments store considerable amounts of P and in some cases have comparable P contents (g/kg DW) to lake sediment. Land use, soil type, and drainage area (location in the catchment) had a significant effect on the different P fractions found in surficial sediments. Sediment from lakes and forested headwater streams generally had high proportions of organic P and iron bound P. In larger streams located in agricultural areas on clay soils closer to the catchment outlet, with dense sediment and a relatively low proportion of organic matter, P was to a larger extent bound to calcium. Streambed sediment may be an important catchment scale P store and should be considered when modeling catchment P dynamics. The large stores of streambed legacy P should also be considered when performing ditch maintenance to avoid unnecessary mobilization of bioavailable P.

Keywords

catchment study; streambed sediment; phosphorus fractionation; internal loading; legacy phosphorus; ditch maintenance

Published in

Journal of Geophysical Research: Biogeosciences
2020, Volume: 125, number: 9, article number: e2020JG005763Publisher: AMER GEOPHYSICAL UNION