Mercury Concentrations in Lake Sediments – Revisiting the Predictive Power of Catchment Morphometry and Organic Matter Composition

Abstract

Lake sediments are a potential source of mercury (Hg) for aquatic biota. Here, we investigated the predictive power of (a) key parameters for lake catchment morphometry and (b) organic matter composition of sediments in an effort to account for observed variations of total (THg) and methyl (MeHg) mercury concentrations in lake sediments. Using regression models we demonstrate that the morphometric parameters lake depth as well as inclination of catchment soils and lake bottoms can significantly predict variations of THg concentrations, but not MeHg, at profundal lake sediments. Although THg and MeHg concentrations in sediments could not be predicted by specific organic matter sources, as elucidated by atomic C/N ratios, our data suggest that wetland-derived total organic carbon (TOC) contained less THg concentrations than TOC derived from mostly forested watersheds. However, TOC concentrations could significantly predict MeHg concentrations and the proportion of methylated Hg at all sediment stations. Finally, from an ecotoxicological point of view, we propose that concentrations of TOC at surface lake sediments, rather than parameters of catchment morphometry, may predict dietary sources of MeHg for benthic consumers and consequently perhaps for organisms at higher trophic levels.

Terrestrial organic matter biomarkers as tracers of Hg sources in lake sediments

“…Hg then tends to accumulate in lake sediments where increases in T-Hg are well recorded Rognerud and Fjeld 2001). Previous studies measuring T-Hg concentrations [T-Hg] in recent boreal lake sediments reported values that vary between 50 and 500 ppb Kainz and Lucotte 2006). The role of TOM dynamics on the fate of Hg in these environments has often been proposed to explain [T-Hg] differences among lake sediments (Kolka et al 1999).…”

“…Several studies have observed that the levels of T-Hg transported to lakes are related to TOM concentration (Driscoll et al 1995;Kolka et al 1999;Kainz et al 2003;Sanei and Goodarzi 2006). More precisely, some studies raised the issue that TOM quality (source, composition), more than the sole quantity of TOM entering the lake, plays a key role in the fate of Hg in the environment Kainz and Lucotte 2006;Sanei and Goodarzi 2006;Caron et al 2008;Ouellet et al 2009). The regime of atmospheric Hg deposition on soil also varies according to vegetation (Schroeder and Munthe 1998;Demers et al 2007).…”

Predicting mercury concentrations and fluxes in the water column and sediment of lakes with a limited dataset

“…For example, a larger watershed with high lake dissolved organic carbon concentration (often related to wetland area, where Hg methylation is generally very rapid) and/or low pH (reduces sulfide activity-increasing bioavailable Hg fraction, Hg 2þ activity, and possibilities for Hg 2þ or CH 3 -Hg þ to enter fish) will promote methylation within the sediments [26,28]. Correlations between MeHg, THg, and/or MeHg:THg ratios in environmental media (except biota) and watershed variables were found for inflow water, water column, and sediment in lakes through experimental research [13] and literature (e.g., [18,29,30]). …”

“…mental media can readily be obtained from available literature (e.g., [18,19] [30]. Dissolved organic carbon binds Hg, assisting in its transport from neighboring wetlands to the lake and increasing bioavailability for methylation [31].…”

Contamination trends of trace metals and coupling with algal productivity in sediment cores in Pearl River Delta, South China

“…During the recent years, significant impacts of natural organic matter (NOM) on distribution of mercury in sediments have been observed (Kainz et al, 2003;Kainz and Lucotte, 2006). Algal organic matter (AOM) as a biological pump effect in Arctic and sub-Arctic lakes may significantly affect the concentrations of mercury in sediments during the past decades (Sanei and Goodarzi, 2006;Outridge et al, 2007;Carrie et al, 2009;Stern et al, 2009).…”