Benthic community status and mobilization of Ni, Cu and Co at abandoned sea deposits for mine tailings in SW Norway

Morten Thorne Schaanning,Hilde Cecilie Trannum,Sigurd Øxnevad,Kuria Ndungu

doi:10.1016/j.marpolbul.2019.02.047

Morten Thorne Schaanning, Hilde Cecilie Trannum + Show 2 more

Open Access

https://doi.org/10.1016/j.marpolbul.2019.02.047

Copy DOI

Abstract

During 1960–94 tailings from an ilmenite mine in southwest Norway were placed in sea deposits in a sheltered fjord and a more exposed coastal basin. In 2015 both deposit sites were sampled to assess the state of metal contamination and macrobenthic communities 20–30 years after deposition was ended. The results showed that nickel and copper still exceeded environmental quality standards in sediment and pore water from the 0–1 cm layer, and fluxes of nickel, copper and cobalt to the overlying water was high compared to adjacent reference stations. Fauna communities were classified as good, but moderate disturbance was recorded along an environmental gradient defined by depth and tailings-induced parameters such as particle size and copper. The results were interpreted in terms of current discharges, biological sediment reworking and near-surface leaching of metal sulphides. No evidence was found for recycling of metals from tailings buried below the bioturbated surface layer.

Highlights

Mine tailings are wastes left over after the mineral product have been extracted from the crushed and grinded ore rock
The mean pH of 7.32 ± 0.04 measured in the sediment surface (0–1 cm) in the box core liners from Jøssingfjorden (JF) was lower than the range of 7.39–7.57 measured in the cores from Dyngadjupet (DD) and reference stations (REF) (Fig. 1, Table 2)
Concentrations of Ni, Cu and Co in the top 0–1 cm sediment layer were high compared to natural back-ground levels and toxicity-based environmental quality standards (EQS) values, but lower than the concentrations in currently produced tailings and deep deposit layers

Summary

Introduction

Mine tailings are wastes left over after the mineral product have been extracted from the crushed and grinded ore rock. The tailings consist of inert rock particles with trace amounts of potentially harmful substances such as bioavailable fractions of trace metals and remnants of production chemicals (Koski, 2012). The particles themselves may have detrimental effects on living organisms due to hypersedimentation, and small size and sharp edges may disturb vital habitat and physiological functions (Ramirez-Llodra et al, 2015). In Norway and other coastal countries, the scarcity of suitable land areas and availability of sea areas near the locations of the mineral ores, may favor sea deposition (Kvassnes and Iversen, 2013; Ramirez-Llodra et al, 2015; Berg et al, 2016)

Methods

Results

Discussion

Conclusion