A chemical remediation technique for a nearly-total removal of arsenic and mercury from contaminated marine sediments.

After decades of industrial exploitation of the coast and consequent contamination of the sites and marine sediments, it became essential to recover the marine ecosystem by remediation methods to remove toxic contaminants. In this work, a remediation method was developed to clean marine sediments contaminated by arsenic (As) and mercury (Hg). The method can be applied to mobile platforms and is based on an environmentally friendly approach designed to minimise further contamination. The method was tested on two artificially contaminated sediments and two real samples collected from two highly contaminated sites in southern Italy, Augusta Bay and Bagnoli Gulf, characterised by high Hg and As concentrations, respectively. The method consists of four steps: washing with sodium hydroxide (NaOH) to remove metals associated with humic acid; Fenton-reaction using α-CycloDextrin (aCD) to stabilise Fe(II) at natural pH and oxidise As (III) and Hg (0 or I); complexation reaction with aCD; and complexation with sodium sulfide (Na2S) to remove Hg as soluble Hg-polysulfides. Compared to other remediation experiences in literature, this technique provides the best removal efficiency for As and Hg (ranging between 26 -71 % and 57-95 %, respectively). Considering the residual concentrations of As and Hg and the contamination threshold fixed by European Regulation for re-use, the treated sediment can be used in several civil and industrial contexts. The presented method operates in line with the principles of the circular economy to preserve natural resources, prevent secondary pollution, and promote the effective re-use of clean environmental matrices (soils, sediments and aqueous solutions), thus minimising landfill waste.

Marine pollution in the Libyan coastal area: Environmental and risk assessment.

A comprehensive assessment of the potential adverse effects on environment and human health generated by the inputs of chemicals from the most important Libyan petrochemical plant is presented. Ecotoxicological risk associated with the presence of As, Hg, Ni, Zn and PAHs in marine sediments is low or moderate, with a probability of toxicity for ecosystem <9% and <20% for heavy metals and PAHs respectively. However, surface sediments result strongly enriched in Hg and As of anthropogenic origin. Investigation of metals in fish allowed to assess potential risks for human populations via fish intake. Target hazard quotients values indicate potential risk associated to toxic metals exposure by fish consumption and lifetime cancer risk (TR) values highlight a potential carcinogen risk associated to As intake. Noteworthy, the presented results provide an unprecedented environmental dataset in an area where the availability of field data is very scant, for a better understanding of anthropogenic impacts at Mediterranean scale.

Are shipwrecks a real hazard for the ecosystem in the Mediterranean Sea?

The aim of the present study was to evaluate the hazard from shipwrecks on communities by a holistic approach taking into account different effects on biological communities. Multibeam and Remotely Operated Vehicles surveys recorded ecological assessment of fish and benthic species on three shipwrecks flooded during the Second World War on Maërl beds habitats in the strait of Sicily. Pollution levels of a wide range of chemicals of ecotoxicological concern were also measured in sediments and in fish species from different trophic levels. Statistical analysis evidenced significant differences among pollutant levels between both sediments and fish collected in shipwreck sites and controls. Concerning fish, significant effects due to the vessel's cargo type and flooding position are recorded. In spite of that, our results underline that shipwrecks are also a hotspots of biodiversity and a habitat for preservation strategies in marine ecosystems that need to be monitored.

Benthic Foraminifera as bio-indicators of anthropogenic impacts in coastal environments: Acqua dei Corsari area case study (Palermo, Italy).

This study investigates living benthic foraminiferal assemblages as bio-indicators of anthropogenic activities in a coastal area within the Gulf of Palermo (Sicily, Italy), affected by industrial and urban activities, and evaluates the environmental quality through the calibration of a Tolerant Species index (%TSstd). Sediments from 6 stations were sampled along a bathymetric transect from the coast to offshore. Sediment grain size, TOC, major, minor and trace elements and polycyclic aromatic hydrocarbons (PAHs) were compared to benthic foraminiferal assemblages and species at each station. Diversity and density of benthic foraminiferal assemblages were not affected by the presence of pollutants, while tolerant species increased with organic (TOC and PAHs) or chemical (As and Pb) concentrations. Moreover, the calibration of the %TSstd formula to >125µm foraminiferal assemblage, gives a detailed description of environmental quality along the transect, representing a good and sensitive tool to evaluate marine coastal environment.