Abstract
The information about concentrations of dioxin in pore water, ecotoxicity and DOC and TOC content can be key factor for the prediction of the fate of dioxins in the aquatic environment as well as an ecological risk assessment. The aims of the study were to assess the concentration of PCDDs/PCDFs and ecotoxicity of pore water and to compare above results in relation to the dissolved organic carbon (DOC) and total organic carbon (TOC) content. The concentration of dioxins was assessed using an enzyme-linked immunoassay test, while the ecotoxicity of pore water was determined using a crustacean Daphnia magna and bacteria Aliivibrio fischeri. The studies were conducted on two different dammed reservoirs Rożnów (catchment basin of an agricultural character) and Rybnik (catchment basin of an industrial character) located in southern Poland. The concentration of dioxins in pore water was between 8.56 to 90.92 ng EQ/L, with a significantly higher concentration in the pore water from the Rożnów Reservoir than the Rybnik Reservoir. The DOC content in pore water was from 30.29 to 63.02 mg/L (Rożnów Reservoir) and from 35.46 to 60.53 mg/L (Rybnik Reservoir). Higher toxic responses were recorded for A. fischeri than for D. magna. Moreover a significantly higher toxicity for both tested organisms was indicated in pore water from the Rożnów Reservoir. Besides of TOC and DOC, the fine fractions of the sediments were particularly important in the concentration of dioxin in pore water. The other pore water parameters, such as pH and EC can influence the toxicity of water for organisms. The result indicate complex relationships between the PCDD/F, ecotoxicity and DOC, TOC concentration in pore water and confirms that these parameters are important in terms of water environmental contamination.
Highlights
Among the contaminants of the aquatic environment, a significant role is played by persistent organic pollutants (POPs), such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) (Ying et al 2009; Förstner et al 2016; Roumak et al 2018; Urbaniak et al 2016)
The Rożnów Reservoir has been functioning for almost 80 years and it encloses a mountainous catchment basin of an agricultural character, which is intensely subjected to the process of intense siltation (Baran et al 2019b)
A greater variation in the content of dissolved organic carbon (DOC) was found in pore water from the Rożnów Reservoir (CV = 25%) and a lower variation was found in pore water from the Rybnik Reservoir (CV = 16%)
Summary
Among the contaminants of the aquatic environment, a significant role is played by persistent organic pollutants (POPs), such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) (Ying et al 2009; Förstner et al 2016; Roumak et al 2018; Urbaniak et al 2016). Pore water can be an important exposure route for benthic organisms, because there is equilibrium between the phases adsorbed in the organic matter, carbon and the dissolved forms. This makes pore water a valuable tool for the assessment of the mobility, bioavailability and toxicity of different inorganic and organic contaminants (Ying et al 2009; Roig et al 2011; de Castro-Català et al 2016). In an aquatic environment, binding of Hg and MeHg to DOC can decrease the bioavailability of both forms of Hg to phytoplankton (Gorski et al 2008; Chen et al 2014). Akkanen et al (2005) reported the influence of DOC on the bioavailability of hydrophobic organic substances; the authors showed that increased binding led to decreased bioavailability
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