Abstract
The aim of this study was to assess the toxicity and metal leachability from three dredged bottom sediments potentially stored on land. Washing out was conducted at a sediment dry mass to water mass ratio of 1:10. The method relies on washing out pollutants from the examined sample using water with third degree of purity in static/quasi-dynamic conditions. The investigations comprised three 27-h washing out cycles, including leaching in static conditions (19 h) and shaking (8 h). Bottom sediments are complex matrices; therefore laboratory tests cannot always reflect changes in physicochemical properties, which can potentially take place after a longer period of time. In spite of this, static-dynamic tests conducted under laboratory conditions provide information which enables a rough estimation of the potential threat posed by the studied sediment to the environment, at a given time. It was demonstrated that the leachability of metals during storage of polluted (Rybnik, Rzeszów) or unpolluted (Narożniki) bottom sediments does not pose a hazard to the environment. The Microtox test showed low toxicity of test water extracts. Considering their final destination, the potential and actual environmental hazards which the extracted bottom deposits pose should be assessed by determining the leachability of metals.Keywords: dredged sediments, metals, leaching, toxicity, Microtox
Highlights
Sediments accumulated in water reservoirs constitute a very important part of ecosystems, and play a crucial role in their functioning, as well as in element cycling among individual components of the water–ground system (Barbosa and De Almeida, 2001)
Metals may be immobilized in the sediments for a long time, but in variable atmospheric conditions they may be leached from the sediments and pose a hazard of returning the element to cycling in nature (Rabajczyk, 2011; Baran et al, 2011; Baran and Tarnawski, 2013)
This study showed that the highest metal leaching coefficients were obtained for the sediment from Narożniki reservoir and the lowest for the sediment from Rybnik bottom sediments
Summary
Sediments accumulated in water reservoirs constitute a very important part of ecosystems, and play a crucial role in their functioning, as well as in element cycling among individual components of the water–ground system (Barbosa and De Almeida, 2001). Sediment deposition on land in atmospheric conditions poses numerous hazards related to protection of the natural environment (Czerniawska-Kusza and Kusza, 2011; Mamindy-Pajany et al, 2011, Caille et al, 2012). Metals may be immobilized in the sediments for a long time, but in variable atmospheric conditions they may be leached from the sediments and pose a hazard of returning the element to cycling in nature (Rabajczyk, 2011; Baran et al, 2011; Baran and Tarnawski, 2013). Mobility of pollutants leached from the sediments, expressed as their susceptibility to leaching from the matrix, is the most important feature of waste from an ecological perspective, and which, apart from composition, is taken into consideration in the assessment of the waste’s harmfulness to the environment (Hardaway et al, 1999). Chemical analyses of water extracts are conducted in order to estimate the hazard of various wastes
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