Dispersal of persistent organic pollutants from fiber-contaminated sediments: biotic and abiotic pathways

Abstract

Purpose Numerous sites contaminated with fiber emissions from pulp and paper industries are found in coastal areas of the Baltic Sea, but there is limited knowledge about the magnitude of dispersal of persistent organic pollutants (POPs) from these anthropogenic, organic-rich sediments called fiberbanks. The aim of this study was to quantify and compare different POP dispersal pathways from such fiberbanks. Dispersal mechanisms studied included abiotic and biotic routes (dissolved in water, particle-bound, and bioaccumulation). Materials and methods Contaminated fibrous sediments located in Ångermanälven River estuary in north-eastern Sweden were studied in sediment types representing different fiber content (i.e., fiberbanks, fiber-rich sediments, and less fiber impacted sediments). Sediment-to-water fluxes of dissolved contaminants (polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and dichlorodiphenyltrichloroethane (DDT)) were measured in situ using benthic flux chambers. Particle resuspension was measured by sampling bottom water, before and after disturbing the sediment surface. Benthic biota was collected to determine the body burden of contaminants and to determine biota-pore water accumulation factors (BAFPW) and biota-sediment accumulation factors (BSAFs). In addition, concentrations of dissolved POPs in the water column were measured in field using passive samplers. Instrumental analysis was performed using gas chromatography coupled to a triple quadrupole mass spectrometer (GC-MS/MS). Results and discussion The flux of dissolved Σ20PCBs was approximately two times higher from one of the investigated fiberbanks (3.4 ng m− 2 day− 1) compared to the other. The average particle burden of PCBs was also higher at this fiberbank after artificial disturbance (15 ng g−1 particle), which indicates that larger amounts of contaminants are likely to disperse via particle resuspension from this site compared to the other fiberbank (4.8 ng g− 1 particle). The difference might be associated with a layer of recently settled minerogenic material that covers one of the fiberbanks, which probably functions as a protective barrier. The lack of benthic biota implies that contaminant release by bioturbation is negligible in the studied fiberbanks. However, benthic biota from fiber-rich sediment showed bioaccumulation and biomagnification of contaminants. Conclusions The importance of diffusive flux from fiberbanks under undisturbed conditions became apparent when the different dispersal pathways were quantified. However, no dispersal pathway could be judged as irrelevant, since even under undisturbed conditions, advective particle transport was significant. Additionally, the uptake by biota and trophic transfer can be considerable. Quantification of dispersal routes and understanding of the relative importance of various pathways is critical for proper risk assessment and management of contaminated sediments.

Assessing the Risk of Contaminant Dispersion From Fibrous Sediments of Industrial Origin

“…All field measurements are presented in Apler et al (2014Apler et al ( , 2019Apler et al ( , 2020, Dahlberg et al (2020), Dahlberg et al (2021), andLöfroth et al (2021).…”

“…In addition, sediment (fiberbank) organic carbon content (% TOC), was determined. Detailed information on the chemical analyses is given in Dahlberg et al (2020), Dahlberg et al (2021).…”

“…Historical and contemporary discharges of pollutants into water have caused sediments to become polluted with toxins, such as persistent organic pollutants (POPs), metals and methylmercury, which may pose a risk to exposed ecosystems (e.g., Apitz et al, 2006;Gerbersdorf et al, 2011;Dahlberg et al, 2021;USEPA, 2021). Globally, efforts are made to manage contaminated sediments, but many remediation measures are costly (Reible, 2014;Jersak et al, 2016a).…”

“…Sediments have been (and are still) contaminated with metals and POPs by a range of point and diffuse sources. In Sweden, historically unregulated discharges of wastewater from pulp and paper factories resulted in the accumulation of sediments rich in cellulose fibers and wood chips along the Swedish coast (Apler et al, 2019(Apler et al, , 2020Dahlberg et al, 2020Dahlberg et al, , 2021. Subaqueous, relatively thick cellulose rich deposits (further denoted as fiberbanks) have been found in shallow-water coastal areas close to the mills, and on nearby deeper seabed areas, fiber-rich sediments have formed.…”

“…The fiberbanks differ from more natural, minerogenic sediments by their high fibrous organic content and low densities; some fiberbanks are almost buoyant due to inherent gas production from microbial degradation (Apler et al, 2019;Snowball et al, 2020). No organisms seem to thrive in the fiberbank deposits with the exception of some bacteria (Dahlberg et al, 2021) and the deposits are contaminated with POPs, such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and polycyclic aromatic hydrocarbons (PAHs), and many metals, including mercury (Hg) (Norrlin and Josefsson, 2017;Apler et al, 2019;Dahlberg et al, 2020). Analyses of benthic biota from fiber-rich sediments show that organisms bioaccumulate the contaminants present in their habitat, thus acting as a vector for transfer to organisms at higher trophic levels (Dahlberg et al, 2021).…”