Distribution and dispersal of metals in contaminated fibrous sediments of industrial origin

Anna Apler,Ian Snowball,Paul Frogner-Kockum,Sarah Josefsson

doi:10.1016/j.chemosphere.2018.10.010

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https://doi.org/10.1016/j.chemosphere.2018.10.010

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Abstract

Industrial emissions can impact aquatic environments and unregulated discharges from pulp and paper factories have resulted in deposits of cellulose fiber along the Swedish coast. These deposits are contaminated by metals, but due to their unique fibrous character the extent of sorption and dispersal of the metals is unclear. Fibrous sediments were sampled at two sites in the Ångermanälven river estuary, Sweden. The partitioning of metals between the sediment, pore water and bottom water was investigated and the degree of bioavailability was evaluated. The levels of metals in the sediment were high in fibrous or offshore samples, depending on the metal, whereas the levels of dissolved metals in pore water were low or below the limit of quantification. Partition coefficients (KD) showed that sorption to the sediment was stronger at one of the fibrous sites, possibly related to the type and size of organic matter. Undisturbed bottom water samples contained low levels of both dissolved and particle bound metals, but when comparing measured metal concentrations to threshold values of ecological status and ecotoxicological assessment criteria, both sediments and bottom water may be detrimental to living organisms. In-situ re-suspension experiments showed that the concentrations of particle bound metals increased whereas the dissolved concentrations decreased. The analyzed metals are probably retained by the solid phases of the fibrous sediment or adsorbed to particles in the water, reducing their bioavailability.

Highlights

The manufacture of pulp and paper is dominated by countries in North America, Northern Europe and East Asia, Australia and Latin America have significant industries (Suhr et al, 2015)
We studied two fibrous sediment sites in the vicinity of Kramfors, Sweden, examined the effect of resuspension on metal mobility in-situ, and compared the data with reference sites known to be less affected by point sources of fibrous sediment
The fiber-rich sediments in V€aja are more enriched in metals than the postglacial clay at Sandviken (SedS) and the reference station M0062, where the latter two sites contain concentrations similar to the national background

Summary

Introduction

The manufacture of pulp and paper is dominated by countries in North America, Northern Europe and East Asia, Australia and Latin America have significant industries (Suhr et al, 2015). It has been estimated that past pulp manufacturing in Sweden, until more stringent regulations in 1969, incurred a 10% net loss of cellulose fibers (SFS 1969:387; Norrstro€m, 2015) that were suspended in wastewaters. It is likely that similar losses and discharges occurred in other pulp and paper producing countries that used the same manufacturing methods. Two types of fibrous sediments are distinguished: “Fiberbank” describes a relatively thick sediment deposit that consists mainly of fibrous residues and wood chips with a smaller amount of natural existing clays, often close to the pulp and paper mills. The term “fibrous sediment” includes both fiberbanks and fiber-rich sediments. Many different contaminants have been found in the fibrous sediment, such as chemicals used in the processing of pulp (e.g. mercury (Hg)) and process by-products (e.g. polychlorinated dibenzo-p-dioxins and dibenzofurans)

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