Enrichment of Uranium in Particulate Matter during Litter Decomposition Affected byGammarus pulexL.

Abstract

Plant litter and organic matter of aquatic sediments provide a significant sink of soluble inorganic uranium species in contaminated ecosystems. The uranium content in detritus has been observed to increase significantly during decomposition. However, the influence of the decomposer community on uranium fixation remains unclear. In view of this, we investigated the influence of a shredder (the freshwater shrimp Gammarus pulex L) on uranium fixation and mobilization during the degradation of plant litter. Leaf litter from Alnus glutinosa (L.) Gaertn. with 1152 mg kg(-1) U of dry biomass (DM) and without uranium was used in a 14-day laboratory experiment. The uranium concentration in the particulate organic material (POM) at the end of experiment was 1427 mg kg(-1) DM. After 14 days of decay, the residues of the leaves show a uranium concentration of 644 mg kg(-1) DM. Uranium concentrations in the media initially increased reaching up to 63.9 microg L(-1) but finally decreased to an average value of 34.3 microg L(-1). Atthe same time, DOC levels increased from 2.43 mg L(-1) up to 11.4 mg L(-1) in the course of the experiment Hence, inorganic uranium fixation onto particulate organic matter was enhanced by the activity of G. pulex.

Invertebrate grazers affect metal/metalloid fixation during litter decomposition

“…However, the data contrast with findings from experiments revealing an impact of invertebrate shredders on metal fixation/remobilization with no influence of the DOC level (Schaller et al, 2010a;Schaller and Machill, 2012). This contrast may be explained by a lower fixation capacity of the smaller sizes of POM in the current study, because these smaller sizes of POM contain only feces of the snails and less fragmented leaf litter, compared to studies using invertebrate shredders which contains smaller parts of leaf litter (Schaller et al, 2008(Schaller et al, , 2010a, which in turn may result in lower amounts of heterotrophic biofilm growing on the smaller sized POM. However, the overall mobilization of metals/metalloids by invertebrate grazers has nothing to do with redox mediated processes as nonredox sensitive elements (Mg and Sr) show a comparable remobilization pattern to elements with increasing mobility under reduced (Mn, Co and As) as well as oxic conditions (U) (Borch et al, 2010).…”

The role of sediment properties and solution pH in the adsorption of uranium(VI) to freshwater sediments

“…Uranium, in comparison to most cationic metals, has a relatively complex solid-aqueous chemistry, which depends on a number of factors that influence the partitioning of U between the aqueous and solid phases (Ames et al, 1983;Catalano and Brown Jr, 2005;CCME, 2011;Langmuir, 1978;Markich, 2002;US EPA, 1999). Many ligands, such as phosphate, carbonate, and humic and fulvic substances can form complexes that are readily soluble and mobile in aquatic systems (Cheng et al, 2006;Franke et al, 2000;Schaller et al, 2008). However, transport of U can be limited by strong adsorption onto solid phases.…”

An ecological and ecotoxicological perspective on fine particulate organic matter in streams

“…Schaller et al . () reported enhanced fixation of uranium in faecal particles generated by a shredder, Gammarus pulex , feeding on uranium‐contaminated leaves. Similar patterns were observed for a broad range of other metals, including iron, zinc, lead and copper (Schaller, Mkandawire & Dudel, ), and also for some organic contaminants such as DDT‐metabolites (Drake, Eganhouse & McArthur, ; Lotufo & Landrum, ).…”