On biogeochemistry and water quality of river canals in Northern France subject to daily sediment resuspension due to intense boating activities E. Prygiel a , P.-J. Superville a , D. Dumoulin a , F. Lizon b , J. Prygiel a, c , G. Billon a, * a Laboratory LASIR (UMR 8516 CNRS e Universit e Lille 1), Cit e Scientifique, 59655 Villeneuve d'Ascq, France b Laboratory LOG, (UMR 8187 CNRS), Station Marine de Wimereux, Universit e Lille 1, 28 av. Foch, 62930 Wimereux, France c Agence de l'Eau Artois-Picardie, 200 rue Marceline, 59200 Douai, France article info Article history: Received 26 June 2014 Received in revised form 25 September 2014 Accepted 17 November 2014 Available online 3 December 2014 Keywords: Sediment Trace metal Phosphorus Resuspension Boat traffic Water framework directive River canal abstract In Northern France, channelized rivers facilitate greatly the waterway transport that should still increase in the coming years to replace as much as possible the road traffic, considered as a heavier source of pollution. These rivers are now subjected to the good potential status objectives required by the Water Framework Directive. The impact of the recurrent resuspension by the current boat traffic of polluted sediments (due to strong historical pollution) on the water quality is the main concern of this work. Our study reveals that the navigation seems to play a limited role on the enrichment of the water columns by dissolved metals and phosphorus, as well as on the oxygenation of surface waters. Conversely, the cycling of the phytoplankton over the year appears to partly control the physico-chemical and chemical evo- lutions of the overlying waters. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction The Artois-Picardie river basin (Northern France) is the smallest of the six hydrographical French basins. Because of a high inhabi- tant density, intensive agricultural activities and a strong industrial development, this basin is nowadays highly impacted by several kinds of anthropic pressures leading to the pollution of rivers with nutrients and micropollutants. Additionally, this area of low relief results in small rivers with low flows, with a consequent favored accumulation of particle-associated contaminants in the sediment. On account of its strategic location, the North of France consti- tutes an important area for commercial exchanges between the French Parisian Basin, Belgium, the Netherlands and the United Kingdom. In the 19th century, most of the greatest rivers have been channelized to facilitate commercial activities, and natural streams were strongly modified: banks have been reinforced, the beds of the rivers have been dug and channelized, and numerous locks have been built. These facilities strongly impacted the main attri- butes of these aquatic ecosystems: (i) the water columns are characterized by a regulated hydrology; (ii) as the flow is low and regulated, strong sedimentation occurs; (iii) macrophytes are often absent because of the boat traffic; and (iv) biodiversity is endan- gered by the strong competition with exogen species. River canals are thus quite different from natural streams, and are considered as “modified environments” by the European regulation. Only few studies have been carried out on the impact of boat traffic on water quality. It has previously been shown that succes- sive boat traffic can amplify the resuspension and lead to an erratic erosion of sediment and remobilization of contaminants (Neal et al., 2010; Rapaglia et al., 2011). Increase of the redox potential associated with boat traffic has been described (Lenzi et al., 2005), suggesting a better oxygenation of surface sediments and conse- quently a better mineralization of organic matter (Kleeberg et al., 2012; Lenzi, 2010), although this process was not systematically observed. However, no significant effect of resuspension events could be pointed out on dissolved phosphorus (Lenzi, 2010). Nonetheless, the oxidation of anoxic sediment should favor biogeochemical reactions that could lead to the reintroduction of * Corresponding author. E-mail address: Gabriel.billon@univ-lille1.fr (G. Billon). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol http://dx.doi.org/10.1016/j.envpol.2014.11.022 0269-7491/© 2014 Elsevier Ltd. All rights reserved. Environmental Pollution 197 (2015) 295e308