Emerging investigator series: geochemistry of trace elements associated with Fe and Mn nodules in the sediment of limed boreal lakes

Abstract

Thousands of boreal lakes were limed for decades in Scandinavia to counteract the effect of anthropogenic acidification. We measured the concentrations of alkali earth metals (Ca, Mg, Ba), metals (Mn, Fe, Al, Co, Cd, Pb, Zn), metalloids (As, Mo) and phosphorus (P) in 165 surface sediment samples from 17 limed lakes, as well as the sediment column and porewater of two lakes chosen from this set. We report that formation of ferromanganese nodules is widespread in limed lakes, and that those nodules are enriched in trace elements, reaching for example 11 500, 908 and 40 μg g for Ba, Mo and As, respectively. Nodules are more abundant between the littoral and the profundal zones. Intense redox cycling of Fe and Mn at the sediment-water interface has redistributed trace elements in the sediment column. Ba, Co, Mo, Pb and Zn partitioned with Mn (oxy)hydroxides and As and P with Fe (oxy)hydroxides. Fe, Mo, Co and As remobilized to the porewater also diffused downward and were likely sequestrated with sulfides. We conclude that the diagenetic redistribution and partitioning of trace elements onto Fe-Mn nodules, rather than direct inputs from liming, is the cause of the elevated trace element burden in surface sediments.

Trace metal distribution in the bed, bank and suspended sediment of the Ravensbourne River and its implication for sediment monitoring in an urban river

“…The association of trace metals with kaolinite and other clay minerals is likely due to the presence of Fe/Mn amorphous oxides and fine organic matter in fine aggregated sediment fractions (Gilbert et al 2009;Schaider et al 2014). It is widely documented that iron/manganese oxide and organic material aggregates account for a significant proportion of metal sequestration in fluvial systems in comparison to clay minerals (Li et al 2009;Wang and Li 2011;Schaider et al 2014;Matys Grygar and Popelka 2016;Couture et al 2018).…”

Critical Processes of Trace Metals Mobility in Transitional Waters: Implications from the Remote, Antinioti Lagoon, Corfu Island, Greece

“…This distribution pattern has been described in previous studies [19,58], and is consistent with Cd dissolution after the oxic degradation near the surface of fresh organic carbon with which Cd was originally bound, and downward diffusion and fixation, in the thick zone of sub-oxic to anoxic grey-black colored, underlying sediments, which are depleted in Mn. This pattern is typical in sub-oxic sediments where authigenic accumulations, as CdS precipitates, take place [19,58,61,62]. Cadmium sulfide minerals are fully recovered by HCl [63], and this explains the high amounts of Cd extracted by the procedure (median value: 85%) in relation to the total metal.…”