Abstract
Sediments in ports, marinas and waterways around the world are often contaminated with metals arising from anthropogenic activities. Regular dredging is needed to achieve an appropriate water depth and reduce the environmental impact of pollutants. The aim of this study was to develop an integrated assessment method for comparing various management strategies for dredged sediments at six case study sites in Sweden. Short- and long-term environmental impacts were investigated for different management approaches, including landfilling, deep-sea disposal, metal extraction in combination with the two aforementioned, and natural recovery (no dredging). The potential value of metals in the sediments was estimated using sediment metal contents and current metal prices. Additionally, an assessment of how metal extraction could result in lower management costs was carried out. The cost of the different management approaches was calculated and evaluated together with the corresponding environmental impacts. This study shows that there is a monetary value in dredged materials, in terms of metal content, and that the materials can potentially be used for metal extraction. Metal extraction may also help to reduce the management costs, as cleaner materials are cheaper to handle. The choice of metal recovery method is important in both monetary and environmental terms, potentially contributing to a circular economy. In the future, metal recovery may become more profitable, as technologies are improved, and due to probable increases in metal prices and landfill costs.
Highlights
Dredging of ports, marinas and waterways must be performed regularly to maintain water depth but can be performed to remove contaminants (Casper, 2008; Förstner and Apitz, 2007)
The method builds on an Integrated assessment (IA) methodology developed for assessing the environmental impacts of measures to reduce climate-related risks (Andersson-Sköld et al, 2016; AnderssonSköld et al, 2014), which has here been expanded to include impacts relevant to dredged and contaminated sediment management
The sites were selected because they represent a range of activities and on the data available and the potential to perform additional sampling
Summary
Marinas and waterways must be performed regularly to maintain water depth but can be performed to remove contaminants (Casper, 2008; Förstner and Apitz, 2007). Elevated metal concentrations in sediments are often considered a problem, due to their persistence in the sediments and potential negative effects on aquatic organisms (Besser et al, 2018; Jakimska et al, 2011). Metals such as Sn, Cu and Zn, and organotin compounds (OTs) such as tributyltin (TBT) are often found in elevated concentrations in marinas and shipyards, partly due to their use in antifouling paints (Caric et al, 2016; Choi et al, 2014). Tributyltin is toxic even at trace concentrations and has been banned in the EU-15 since 2003 (2002/62/EC), but TBT and its degradation products are still present in sediments and pose a threat to marine ecosystems (Amara et al, 2018; Caric et al, 2016; Egardt et al, 2017; Filipkowska et al, 2014; HELCOM, 2009)
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