Spreading of persistent organic pollutants from fiber bank sediments

Abstract: Discharge of untreated wastewater from paper and pulp industries have led to large environmental impacts on the coastal sediments in Västernorrland, Sweden. Dissolved fibers caused the formation of large fiber banks and fiber influenced sediment areas, which proved to be highly affected by contamination with persistent organic pollutants (POPs). Concentrations of hexachlorobenzene (HCB), 21 polychlorinated biphenyls (PCB) congeners and 6 substances of the dichlorodiphenyltrichloroethane(DDT) group were determined in sediment, pore water (extracted with polyoxymethylene (POM) strips) and two benthic biota species (Marenzelleria ssp., Saduria entomon). Contaminants were extracted using Soxhlet(sediment), shaking with acetone:n-hexane (POM) and cold column extraction(biota). Multilayer clean-up columns were used for sediment and biota, before instrumental analysis with GC-MS/MS. Several sediment samples were classified with very high contamination levels for HCB and PCB7, which is an indicator value of the seven most common PCBs in nature. Different contaminant distribution patterns at the investigated sites indicated that contaminant composition varied at different local sources. Pore water concentrations were higher for less hydrophobic contaminant groups (HCB, DDT and its derivates (DDX)). Sorption (log Kd) increased significantly with increasing hydrophobicity (log Kow) and was significantly higher in fiber bank sediments than in fiber rich sediments and less affected sediments. Bioaccumulation, measured with biota-sediment-accumulation factors (BSAF), seemed to have a bell-shaped distribution for Marenzelleria BSAFs when related to contaminant hydrophobicity; however, results observed were not significant. For Saduria entomon, bioaccumulation increased linearly with increasing contaminant hydrophobicity. Significant positive correlations between contaminant concentrations in biota and sediment for pore water was observed between concentrations in Marenzelleria on a lipid weight basis and concentrations in sediment on a dry weight basis.