Spatial and seasonal variations and ecotoxicological significance of sediment trace metal concentrations in Kebir-Rhumel basin (Northeast of Algeria) Leila Sahli, Fatima-Zohra Afri-Mehennaoui, Mohamed El Hadef El Okki, Christian Blaise and Smail Mehennaoui ABSTRACT This study sought to assess sediment contamination by trace metals (cadmium, chromium, cobalt, copper, manganese, nickel, lead and zinc), to localize contaminated sites and to identify environmental risk for aquatic organisms in Wadis of Kebir Rhumel basin in the Northeast of Algeria. Water and surficial sediments (0–5 cm) were sampled in winter, spring, summer and autumn from 37 sites along permanent Wadis of the Kebir Rhumel basin. Sediment trace metal contents were measured by Flame Atomic Absorption Spectroscopy. Trace metals median concentrations in sediments followed a decreasing order: Mn > Zn > Pb > Cr > Cu > Ni > Co > Cd. Extreme values (dry weights) of the trace metals are as follows: 0.6–3.4 μg/g for Cd, 10–216 μg/g for Cr, 9–446 μg/g for Cu, 3–20 μg/g for Co, 105–576 μg/g for Mn, 10–46 μg/g for Ni, 11–167 μg/g for Pb, and 38–641 μg/g for Zn. According to world natural concentrations, all sediments collected were considered as contaminated by one or more elements. Comparing measured concentrations with American guidelines (Threshold Effect Level: TEL and Probable Effect Level: PEL) showed that biological effects could be occasionally observed for cadmium, chromium, lead and nickel levels but frequently observed for copper and zinc levels. Sediment quality was shown to be excellent for cobalt and manganese but medium to bad for cadmium, chromium, copper, lead, nickel and zinc regardless of sites. Leila Sahli (corresponding author) * Fatima-Zohra Afri-Mehennaoui Mohamed El Hadef El Okki Laboratory of Biology and Environment, University of Constantine, Algeria *Laboratory of Biology and Environment, Campus Chaab-Erssas, Biopôle, University Mentouri, Street Ain El Bey, 25000 Constantine, Algeria E-mail: sahli@univ-metz.fr; slila2006@yahoo.fr Christian Blaise Saint Lawrence Center, Environment Canada, Quebec, Canada Smail Mehennaoui Laboratory of Environment, Health and Animal Production, University of Batna, Algeria Key words | contamination, ecotoxicological significance, Kebir Rhumel basin, sediments, trace metal INTRODUCTION Countries in North Africa are facing problems of water shortage because aquatic ecosystems are submitted in much of their areas to a semi-arid climate. In Algeria, pol- lution of water resources is beginning to reach alarming proportions, especially in the north where most of these resources are located. Situated in the Northeast of Algeria, between the littoral Kabyle mountain chain and the Southern massifs of the Tell, Kebir Rhumel basin covers an area of 8,815 km 2 . Rhumel Wadi, one of the most impor- tant Wadis in Kebir Rhumel basin, supplies the Beni-Haroun dam (959,941 m 3 ), which serves as a drinking-water supply for several cities, agricultural use and the new aquaculture program in the country (Afri-Mehennaoui et al. ). Throughout the Kebir Rhumel basin, there are 100 agglomerations with a total of 1.62 million inhabitants. Con- stantine City alone holds 750,000 inhabitants. Industrial activities have significantly increased during the past cen- tury in this area. The most important effluents are located within a radius of 20 km around Constantine City. Results published by the National Agency of Water Resources (Agency of Constantinois-Seybouse-Mellegue Basin, ABH ) reveal that large sections of Wadis in Kebir Rhumel basin are polluted. Wadis receive urban effluents, industrial discharges and surface runoff, mainly from agricultural land. They are thus exposed to pollution problems that might jeo- pardize Beni Haroun dam water and therefore the drinking water of nearly all the cities served. In addition, Kebir Rhumel Wadi in the North part of the basin pours into the 1759 © IWA Publishing 2011 Water Science & Technology | 64.8 | 2011 doi: 10.2166/wst.2011.693 Downloaded from https://iwaponline.com/wst/article-pdf/64/8/1759/444773/1759.pdf by guest on 27 May 2020