Abstract
Unregulated discharges of wastewater from pulp and paper factories resulted in the formation of relatively thick organic (cellulose) rich sediments in shallow waters along the Swedish coast. These deposits are known as fiberbanks and are contaminated by persistent organic pollutants (POPs), metals and methylmercury, which can be dispersed by diffusion and advective processes coupled to propeller wash, high river discharges, strong wind waves and submarine landslides. Based on a case study of polychlorinated biphenyls (PCBs), one group of prevalent POPs in the fiberbanks, we present a probabilistic approach to estimate the potential risk of dispersion of fiberbank contaminants. The approach allows for estimation of the dispersal pathways that dominates the risk within a given time and provides more insight about the significance of various dispersion processes. We show that it is highly likely that chemical diffusion and advection triggered by ship-induced resuspension will disperse PCBs (sum of seven congeners; Σ7PCB) above a threshold level for environmental impact, while the likelihood of river and wind-wave generated resuspension dispersion pathways are lower (∼20%, respectively). We further show that there is approximately 5% likelihood that a submarine landslide will disperse Σ7PCB above the threshold level. The study implies that the governing parameters for risk assessment specifically should include reliable data on contaminant concentration, water depth above the fiberbank, estimation of concerned fiberbank areas, time duration of erosive fluid flows and measured diffusion. The approach provides insight into the importance of various dispersion processes. We suggest that it can be applied to support risk assessment, especially when there are limited available data and/or knowledge about the system under study.
Highlights
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)
The yearly probability of exceedance is high for diffusion (100%) and advection of 7PCB fluxes triggered by ship-induced resuspension (100%)
The yearly probabilities of failure of 7PCB fluxes through advection triggered by river flow and wind-wave currents are almost equal (18 and 19%, respectively), while submarine landslide poses the lowest risk (5%)
Summary
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). Efforts are made to manage contaminated sediments, Contaminant Dispersion From Fibrous Sediments but many remediation measures are costly (Reible, 2014; Jersak et al, 2016a). Risk assessments are carried out to prioritize sites for remediation. Sediment can act both as a contaminant sink in calm accumulation areas and a contaminant source if the accumulated sediment is exposed to diffusive and advective dispersion processes (Förstner and Westrich, 2005), which can be continuous or intermittent. The sink or source perspective affects the risk scenario and the management options. Understanding and assessing the likelihood of dispersion becomes an important part of risk assessment (Reible, 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
