Substantial Decrease in Contaminant Concentrations in the Sediments of the Venice (Italy) Canal Network in the Last Two Decades—Implications for Sediment Management

Roberto Zonta,Roberto Pini,Daniele Cassin,Janusz Dominik

doi:10.3390/w12071965

Abstract

The Venice canal network requires periodic intervention to remove sediments that progressively accumulate. The most recent dredging operation was carried out in the second half of the 1990s and early 2000s. These sediments had accumulated over a period of more than 30 years and were highly contaminated with Cd, Cu, Hg, Pb, Zn and PAHs. Sediments deposited after the dredging work were investigated in 2005, 2009, 2014 and 2017 by analysing sediment cores collected from three sites in the canal network. Arsenic, heavy metal and PAH concentrations were observed to be much lower than past values, although Cu, Hg and PAH levels were still relatively high. The high Cu concentrations (mean 161 mg kg−1) are partly due to the widespread use of Cu-based antifouling paint. Current Italian regulations forbid the disposal of dredged sediments with these concentrations inside the lagoon, thereby increasing the cost of canal network maintenance.

Highlights

The urban environment is a major source of pollutants, including heavy metals and polycyclic aromatic hydrocarbons (PAHs)
Nriagu and Pacyna [1] emphasised the importance of metal emissions from cities in the global pollution budget; Dat and Chang [2] recently reviewed anthropogenic sources of PAHs emitted to the atmosphere and highlighted higher PAH concentrations in urban and industrial sites than rural or remote locations
Sediment contamination in the Venice canal network is enhanced by its distinctive morphology and hydrodynamics, which trap fine particles transported from the lagoon by tidal flows

Summary

Introduction

The urban environment is a major source of pollutants, including heavy metals and polycyclic aromatic hydrocarbons (PAHs). There is, a need to identify both sources and sinks of pollutants within the urban environment, taking account of the functioning of each city. In this framework, some cities with a close relationship to water have highly distinctive features. Some cities with a close relationship to water have highly distinctive features An example of such a city is Venice (Italy), whose canal network is “marine in nature” [14] and subject to the unavoidable progressive silting up due to the accumulation of sediments, which are polluted. Water 2020, 12, 1965 ; doi:10.3390/w12071965 www.mdpi.com/journal/water

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