Contamination history of suspended river sediments accumulated in oxbow lakes over the last 25 years

Abstract

Background, aims, and scope Embankment of meandering river systems in many industrial areas results in the formation of artificial oxbow lakes that may act as perennial or intermittent traps for river sediments. Their deposits can be dated using a combination of historical and stratigraphic data, providing a good means to study historical records of contamination transported by rivers. Contamination history over the last few decades is of special significance for Central and Eastern Europe as it can reflect high pollutant levels in the second half of the twentieth century and the subsequent improvement after the fall of the Iron Curtain. The purpose of this study was to investigate recent sediments of an oxbow lake of the Morava River, Czech Republic, their stratigraphic records, sediment architecture, and history of contamination. Materials and methods Seven ground-penetrating radar (GPR) profiles and three sediment cores up to 4 m deep were studied. The stratigraphy of the cores was inferred from visible-light spectrophotometry, X-ray radiography, grain size analysis, and semiquantitative modal analysis of sandy fractions. The sediments were dated using the 137 Cs mass activity and combinations of stratigraphic and historical data. The cores were sampled for concentrations of heavy metals and persistent organic pollutants. Wet sampled, lyophilized, and sieved sediments were extracted and analyzed for heavy metals by inductively coupled plasma mass spectrometry (ICP-MS) of aqua regia leachate and for persistent organic pollutants by gas chromatography (GC-ECD and GC-MS). Results Three distinct sedimentary sequences (S1, S2, and S3) were identified. The basal sequence S1 represents river channel sediments deposited before the formation of the oxbow lake, most likely before the 1930s. The boundary between the S1 and S2 sequence correlates with the level of sediment dredging from 1981 evidenced from historical data. The overlying sequences S2 and S3 represent a postdredging sediment wedge, which progrades into the lake. 137 Cs dating revealed a distinct Chernobyl 1986 peak at ∼150 cm depth inferring sedimentation rates up to 7.7 cm/year. Sediment contamination abruptly increased from the pre1930s deposits to the post-1981 deposits. The concentration levels increased two to five times for Pb, As, Zn, and Cu, about 10 to 15 times for Cr, Sb, and Hg, up to 34 times for Cd, and 25 to 67 times for DDTs, PCBs, and PAHs. The concentrations of most contaminants remained approximately constant until the late 1980s when they started to decrease slowly. The decreasing trends

Effect-directed analysis (EDA) in aquatic ecotoxicology: state of the art and future challenges

“…Especially sediments represent important long-term sinks for many toxicants (Apitz 2008;Brils et al 2007;Bunge et al 2007;Chen and White 2004;Forstner and Salomons 2008;Karlsson et al 2008;Kase et al 2008;Keiter et al 2006), which can become bioavailable through flood events or benthic or bottomdwelling organisms (Babek et al 2008;Gerbersdorf et al 2007;Hilscherova et al 2007;Schulze et al 2007;Wolz et al 2009). Consequently, there has been an increasing awareness of the relevance of particle-bound contaminants in the environment, an aspect that has not been considered satisfactorily in classic EDA approaches.…”

GPR and aerial imageries to identify the recent historical course of the Obra River and spatial extent of Obrzańskie Lake, altered by hydro-technical works

“…An anthropogenic alteration of sediment structures was also presented by the GPR surveys conducted by Jol and Smith (1995) and Ekes and Hickin (2001). Babek et al (2008) used GPR measurement to retrace a fragment of a meandering channel transformed into an artificial canal (the Morava River, the Czech Republik). Other examples are the transformations of the Obra River bed pattern (western Poland; Słowik 2011a), the Quadalquivir River bed, and Doñana Wetlands (Alonso 2009).…”

Transformation of a lowland river from a meandering and multi-channel pattern into an artificial canal: retracing a path of river channel changes (the Middle Obra River, W Poland)

“…In some cases, river courses were modified by an anthropogenic intervention in such a way that it is impossible to discern humaninduced changes from the natural state. There are many examples of transformation of natural river bed patterns into artificial canals (e.g., the Trent River: Large and Petts 1996; the Morava River: Babek et al 2008). Another type of human intervention was construction of mills (e.g., Large and Petts 1996; the Obra River, Kaniecki 2004;Kaniecki and Brychcy 2010) and dams in river courses (e.g., the Dry Creek: Gordon and Meetenmeyer 2006).…”