Using sedimentary archives to reconstruct pollution history and sediment provenance: The Ohře River, Czech Republic T. Matys Grygar a,b, ⁎, J. Elznicová b , T. Kiss c , H.G. Smith d a Institute of Inorganic Chemistry AS CR, v.v.i., 250 01, Řež, Czech Republic b Faculty of Environment, J.E. Purkyně University, Králova Výšina 3132/7, 400 01 Ústí nad Labem, Czech Republic c Department of Physical Geography and Geoinformatics, University of Szeged, Egyetem u. 2-6, 6722 Szeged, Hungary d School of Environmental Sciences, University of Liverpool, Liverpool L69 7ZT, United Kingdom abstract article info Article history: Received 11 August 2015 Received in revised form 3 April 2016 Accepted 6 May 2016 Available online xxxx In industrialised areas rivers and their floodplains are often highly polluted. The historic contamination of flood- plains offers an important archive of past polluting activities and fluvial sediment dynamics. It can also present a significant threat to contemporary aquatic ecosystems and water quality resulting from the remobilisation of sediment-associated pollutants from floodplain secondary sources. Therefore, knowledge of the type and level of pollutants present and their spatial distribution in floodplains is essential for supporting measures to mitigate future impacts. Here, we outline an approach for reconstructing pollution history and extent by using floodplains as archives of historic chemical contamination coupled with geochemical and geomorphological analyses to ac- count for variations in sediment provenance and depositional processes. The study is situated in the Ohře River (total catchment area of 5606 km 2 ), which provides an excellent test case given its complex pollution history, heterogeneous geology and variable deposition patterns. Most severe pollution in this river system has originated from a chemical factory in Marktredwitz, Germany (mainly Hg) and uranium processing in Nejdek, the Czech Republic (mainly U); historical lead mining and mod- ern coal combustion have also played a role. The geological/geochemical variability of the Ohře catchment re- quired extensive sampling along the river course. Variations in several major lithogenic elements, in particular Al, K, Rb, Si and Ti allowed the river course to be subdivided to geochemical river reaches using simple scatter plots (Ti against Al/Si ratio and Rb against K) or PCA; there was no need to sieve the sediment samples before analyses or perform other discrimination of sediment lithology. The geochemical river reaches reflect catchment geology and hence they exhibit distinct background functions for Cu, Pb, and Zn and varying background concen- trations of U. Titanium was the best performing reference element. The Ohře River has deposited most historical pollution in former (abandoned or laterally shifting) channels rather than in overbank fine-grained materials. The former channel sediments can be recognised by a specific surface topography, vegetation cover and sediment lithology; the use of geographic information systems (evaluating historical maps, aerial photographs and DTM by LIDAR) is indispensable in the study of the depositional patterns. The narrow floodplain limited floodplain depo- sition, and has probably allowed particulates to travel through the channel for tens of kilometres, in the case of U pollution in b 10 years. Dams constructed in the 1960s in the upper and middle river reaches have suppressed downstream transport of pollution and combined with certain channel engineering projects to prevent bank ero- sion are likely to have further limited the deposition of overbank fines. The study clearly shows that in the Ohře floodplain the fills of former channels are more suitable as pollution archives than the distal floodplain sediments (overbank fines outside the channel belt). The approach outlined here is applicable to reconstructions of pollu- tion histories for any river characterised by varied catchment geochemistry and deposition in their channel belts. © 2016 Elsevier B.V. All rights reserved. Keywords: Polluted floodplains Pollution history Fluvial archives Sediment provenance Environmental geochemistry 1. Introduction Fluvial sediments record a long history of pollution in industrialised countries (Swennen and Van der Sluys, 2002; Grosbois et al., 2012; Dhivert et al., 2015). They are valuable for the assessment of environ- mental impacts of past human actions for several reasons: (i) ancient and early industrial production and pollution were poorly documented (or not documented) in written archives, (ii) even after the first half of Catena 144 (2016) 109–129 ⁎ Corresponding author at: Faculty of Environment, J.E. Purkyně University, Králova Výšina 3132/7, 400 01 Ústí nad Labem, Czech Republic. E-mail addresses: grygar@iic.cas.cz (T. Matys Grygar), Jitka.Elznicova@ujep.cz (J. Elznicová), kisstimi@geo.u-szeged.hu (T. Kiss), Hugh.Smith@liverpool.ac.uk (H.G. Smith). http://dx.doi.org/10.1016/j.catena.2016.05.004 0341-8162/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Catena journal homepage: www.elsevier.com/locate/catena