Abstract
Abstract. Millions of tons of bottom sediments are dredged annually all over the world. Ports and bays need to extract the sediments to guarantee the navigation levels or remediate the aquatic ecosystem. The removed material is commonly disposed of in open oceans or landfills. These disposal methods are not in line with circular-economy goals and additionally are unsuitable due to their legal and environmental compatibility. Recovery of valuables represents a way to eliminate dumping and contributes towards the sustainable extraction of secondary raw materials. Nevertheless, the recovery varies on a case-by-case basis and depends on the sediment components. Therefore, the first step is to analyse and identify the sediment composition and properties. Malmfjärden is a shallow semi-enclosed bay located in Kalmar, Sweden. Dredging of sediments is required to recuperate the water level. This study focuses on characterizing the sediments, pore water and surface water from the bay to uncover possible sediment recovery paths and define the baseline of contamination in the water body. The results showed that the bay had high amounts of nitrogen (170–450 µg L−1), leading to eutrophication problems. The sediments mainly comprised small size particle material (silt, clay and sand proportions of 62 %–79 %, 14 %–20 %, 7 %–17 %, respectively) and had a medium–high level of nitrogen (7400–11 000 mg kg−1). Additionally, the sediments had little presence of organic pollutants and low–medium concentration of metals or metalloids. The characterization of the sediments displays a potential use in less sensitive lands such as in industrial and commercial areas where the sediments can be employed as construction material or as plant-growing substrate (for ornamental gardens or vegetation beside roads).
Highlights
Ports, lakes and semi-enclosed water bodies require continuous dredging of bottom sediments to guarantee proper navigation levels and preserving the aquatic ecosystem (DelValls et al, 2004)
The characterization of sediments, pore water and surface water sampled from the Malmfjärden Bay were assessed to define pollution baselines of the water body and to determine potential beneficial uses of dredged sediments
The sediment composition was dominated by silt and clay with moderate levels of organic material and a medium–high concentration of nitrogen
Summary
Lakes and semi-enclosed water bodies require continuous dredging of bottom sediments to guarantee proper navigation levels and preserving the aquatic ecosystem (DelValls et al, 2004). Millions of tons of dredged sediments are generated around the world (Mymrin et al, 2017). The extracted sediments are classically regarded as waste and either landfilled or disposed of in open oceans (Ali et al, 2014). Environmental and legal reasons constrain these sediment management methods. Open ocean disposal affects the marine ecosystem, and several countries have already banned this action (Cesar et al, 2014); landfilling has long been responsible for spreading greenhouse gases and contaminated leachates, leading to different environmental impacts. Landfills are classified as unsustainable paths of wastes since they lack the recuperation of resources and are restricted due to high space requirements (Depountis et al, 2009)
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