Characterization of the coastal area facing Cogoleto (Ligurian Sea): areal and historical distribution of chromium

Introduction: The marine coastal area facing the town of Cogoleto, in the Ligurian Sea, is well known for having been subject to the uncontrolled discharge of wastes containing large amounts of Cr [1]. Because of this it has been listed among the reclamation sites of national interest. This implies the design and the implementation of characterization plan according to the set of rules approved by the Italian Ministry of the Environment. This work discuss the results of the characterization campaign in comparison with those obtained from an in deep study to enlighten the detailed of input history and trends. Methods: For the characterization, 200-300 cm long sediment cores were retrieved using a vibrocorer (self-sheating-hydraulic-sampling bottom device). From 200 cm cores were sampled intervals 0-10cm, 10-30, 30-50, 100-120 and 180-200 cm; from 300 cm cores was sampled also the section 280-300 cm. For the complementary study, a gravity corer was used, especially designed to preserve an undisturbed top. In this case, the core was extruded and sectioned to obtain slices 1-4 cm thick, with higher resolution close to the interface. After collection some core were scanned for whole-core magnetic susceptibility. Sampling sites are shown in Fig. 1. Metals (Al, As, Cd, Co, Cr tot, Cr VI, Cu, Fe, Hg, Mn, Ni, Pb, V, Zn) were analyzed by AAS after complete dissolution of the samples with HNO3, HF and HCl in a microwave oven. Pb and Cs, used for dating purposes, were determined by alpha and gamma spectrometry. Grain sizes were obtained using sieves and, for silts and clays with an X-ray sedigraph.