Characterization of dredged sediments: a first guide to define potentially valuable compounds – the case of Malmfjärden Bay, Sweden

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).

Management of dredged marine sediments in southern France: main keys to large-scale beneficial re-use

“…They are solid particles of sand, silt, clay and other substances that result from the erosion of rocks, soils and any continental solids and from the precipitation by biochemical processes in aquatic environments ). Natural and human activities are the vectors for the production and transport of sediments that settle to the bottom of water bodies, hindering navigation and the physicochemical balance of these water bodies (Ferrans et al 2019; Mehdizadeh, Guo, et Ling 2021; Pal et Hogland 2022). Consequently, regular dredging is necessary to maintain adequate depths in waterways (Chen et al 2021).…”

“…The manufacture of concrete from sediment is therefore conceivable, but for non-structural applications. It would essentially be used as an underlay for tra c lanes(Ferrans et al 2019).…”

Defining potential valuables through the characterisation of lake sediments: case study in Arkelstorp bay, Sweden

“…Sediments are typically rich in beneficial compounds (like organic matter and nutrients) that could potentially be recovered to contribute to minimising the mining of resources [4]. However, dredged material is, according to European legislation 2008/98/EC, to be considered waste.…”

Recycling of bottom sediment to agriculture: effects on plant growth and soil properties

“…According to estimates by the European SedNet network, 200 million m 3 of sediment is excavated annually in Europe (SedNet 2004). Therefore, the direction of dredged material management should be chosen based on the analyses of the physicochemical properties Responsible editor: Jos Brils and the degree of contamination of the sediment (Baran et al 2016a, b;Couvidat et al 2018;Ferrans et al 2019). Spadaro and Rosenthal (2020) suggest using the circular economy model to reduce and reuse bottom sediment in the environment.…”

“…Their availability in the form of fertilisers represents a key factor in the overall question of global food security. On the other hand, high contents of potentially toxic trace elements and organic pollutants can be a barrier in the use of bottom sediments (Akcil et al 2015;Baran et al 2019c;Ferrans et al 2019).…”