Marine sediment contamination and dynamics at the mouth of a contaminated torrent: The case of the Gromolo Torrent (Sestri Levante, north-western Italy)

Abstract

In this study we have examined the currents and hydrological characteristics of the water column off the mouth of the Gromolo Torrent (north-western Italy) in relation to the grain-size, mineralogical characteristics and metal distribution in the marine sediment sampled. Our purpose was to quantify and map the contamination that was carried out to sea from the abandoned Libiola Fe-Cu sulphide mine that has heavily impacted the torrent. Our results show high concentrations of Cu and Zn, and relatively high concentrations of Cd and Ni inside the bay into which the Gromolo Torrent flows. However, high concentrations of As, Cr, Hg, Mn, Pb, and V found in the northern and/or eastern parts of the study area originated from other sources. The subdivision of study stations in terms of metal and mineral contents in the bottom sediments highlighted the clear influence of the currents on their dispersion and distribution in the area.

Sediment distribution on the continental shelf in relation to stream inputs and contamination: hydrodynamic, chemical, mineralogical, and sedimentological characteristics (Ligurian Sea, Italy)

“…Combining the results provided by all different analysis carried out in this study and according to results found by Capello et al (2016) and Consani et al (2019), a summary of the main characteristics of sediment and metal transport and diffusion on the continental shelf off the eastern part of the Gulf of Tigullio has been developed ( Fig. 8) and reported below:…”

“…Grain size analysis of sediments was conducted following methodology described in Capello et al ( 2016 ). Samples were wet sieved for grain size (Ø) > 63 mm (with 63, 125, 250, 500, 1000-μm steps for sand, and Ø > 2000 μm for gravel).…”

“…Other factors should be invoked to explain the distribution of metals in the sediments. The eastward principal transport of the sediments could account for the relatively high concentration of some elements (Cr, Mn, Pb, and V) observed in the sediments of the eastern part of the Tigullio Gulf by Capello et al (2016) and Consani et al (2019).…”

“…1 ) has been and still is widely studied under different points of view, but researches on metal distribution in the area and mechanisms that regulate their diffusion have only recently carried out. In fact, sea water and sediment ecology (Albertelli et al 1999 ; Capello et al 2016 ; Licandro and Ibanez 2000 ; Misic and Covazzi Harriague 2008 ; Misic et al 2016 ; Parravicini et al 2013 ), coastal and sediment geology (Barsanti et al 2003 ; Corradi et al 2003 ; De Vita et al 2012 ), and current dynamic (Capello et al 2016 ; Doglioli et al 2004 ) were deeply studied, but only Bertolotto et al ( 2005 ) have addressed the problem of sediment contamination (only with three sampling stations off the Entella mouth) in a general characterisation of the sediments of the Ligurian coast and, recently, Capello et al ( 2016 ) and Consani et al ( 2019 ) have focus their attention on the metal input to marine bottom sediments from an abandoned mine in the eastern Gulf of Tigullio. The study of Consani et al ( 2019 ) not only highlighted the presence in the coastal sediments of some metals clearly linked to the input deriving from the abandoned mine of Libiola and the geology of the area but also highlighted the presence of foreign metals of which the source is sought by the present study in the adjacent western area where another important stream for the Gulf is present (the Entella Stream).…”

“…The use of the multidisciplinary approach, which takes in consideration the relationships between sediments (grain size and minero-chemical composition) and dynamics and hydrology (coastal currents and chemico-physical characteristics of water masses), allowed to define distribution, origin, and main transport directions of sediments and associated metal dispersion and highlight outliers in metal concentrations. The study area is the Gulf of Tigullio (Ligurian Sea, north-western Italy), a marine area where heavily populated stretches of coast are closely linked to areas of great natural value, such as the Marine Protected Area of Portofino, and where recent studies of sediment contamination highlighted the presence of outliers in metal distributions (Capello et al 2016 ; Consani et al 2019 ).…”