Abstract
Knowledge on the fraction of trace elements in the bottom sediments is a key to understand their mobility and ecotoxicological impact. The purpose of this study was to assess the influence of the content of organic matter fractions on the mobility and ecotoxicity of trace elements in sediments from the Rybnik reservoir. The most refractory fraction of organic matter—Cnh (non-hydrolysing carbon)—dominated in the sediments. The content of organic matter fractions are arranged in the following order: Cnh (non-hydrolysing carbon) > Cfa (fulvic acid) > Cha (humic acid) > DOC (dissolved organic carbon). On the other hand, the highest value of correlation coefficients was found for different fractions of trace elements and DOC content in the bottom sediments. A higher content of TOC in the sediments significantly increased the share of elements in the potential mobile fraction and, at the same time, decreased the binding of elements in the mobile fractions. Moreover, in sediments that contain more than 100 g/kg d.m. TOC, no and medium risk of trace element release from sediments was observed. The Cu, Cd and Ni were potentially the most toxic elements for biota in the Rybnik reservoir. However, the correlation between the content of trace elements and the response of bacteria was insignificant. These results suggested that the complexation of trace elements with organic matter makes them less toxic for Vibrio fischeri. The transformation and sources of organic matter play an important role in the behaviour of trace elements in the bottom sediments of the Rybnik reservoir.
Highlights
Among the contaminants of bottom sediments, a significant role is played by trace elements, which, given certain contents and conditions, are characterised by toxicity towards living organisms, bond durability as well as the ability of activation at different stages of the food chain (Rosado et al 2016a, b; Tarnawski and Baran 2018)
We found that the most refractory fraction of organic matter—C non-hydrolysing (Cnh)—dominated in the sediments
The content of organic matter fractions are arranged in the following order: Cnh [ carbon in the fulvic acid fraction (Cfa) [ carbon in the humic acid fraction (Cha) [ dissolved organic matter (DOC)
Summary
Among the contaminants of bottom sediments, a significant role is played by trace elements, which, given certain contents and conditions, are characterised by toxicity towards living organisms, bond durability as well as the ability of activation at different stages of the food chain (Rosado et al 2016a, b; Tarnawski and Baran 2018). In order to assess the environmental threat related to trace elements accumulated in bottom sediments, it is adequate to determine the share of their forms that comprise the overall content (Martınez-Santos et al 2015). Sequential chemical extraction is considered as an important source of information on the chemical bonds in which trace elements occur in bottom sediments. This is reflected in the mechanisms of their behaviour in the environment, among others, in mobility, toxicity and potential bioavailability (Rinklebe and Shaheen 2014; Baran and Tarnawski 2015).
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