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Grøn Dyst 2016

405 90 Evaluation of environmental impacts of a submarine tailing deposit in Northern Norway M.V. Henning and M.M. Kudahl DTU Environmental Engineering, Technical University of Denmark INTRODUCTION The Norwegian company Nussir ASA has in 2015 got the permission to deposit copper mine tailings in Repparfjorden, Kvalsund, Norway, like it was done in the 1970’s. The most common way to deposit tailings are in dams on land. In Norway submarine tailing deposits (STD) are commonly used due to lack of space on land and due to the rocky surface. It is usually used for sulphide-rich tailings to avoid acid rock drainage (ARD). The deposition of tailings in fjords in Norway is against EU’s regulations on waste in the marine environments and STD is prohibited USA and Canada. Copper tailings are sulfide-rich and dissolution of copper is extremely poisonous for marine organisms. In sediment, the limit value for copper is 84 mg/kg. Four cores from around and inside the old deposit was examined by sequential extraction to evaluate the bonding of copper in the sediment. Nussir ASA argues that copper found in tailings is bonded in the fraction least willing to dissolve in water and thus poses no threat to the marine environment. This project investigated in which stage the copper is bonded and if STD would have environmental effects in Repparfjorden. METHOD Sequential extraction with four steps was used for two cores of 20 and 21 cm depth (20-21 samples) and one core of 10 cm depth (10 samples), while sequential extraction with five steps was used for one core of 216 cm depth (7 samples). Sequential extraction measures copper availability in four stages (increasing in bond strength): ion exchange, reduction of metal oxides, oxidation of organic material and residuals. The five step method includes two steps of ion exchange. RESULTS Each core showed increased levels of copper in depths of app. 4-12 cm. This indicates presence of tailings from ~40 years ago. In three cores, 50-60 % of the copper was bonded in the fraction most willing to dissolve in water (ion exchange) and only 8-10 % in residuals. The three cores had at 7-8 cm depth a content of copper of 300-500 mg/kg sediment. The last core had ~10 % bonded in the most willingly to dissolve in water fraction and 25 % in residuals. The last core had at 7-8 cm depth a content of copper of 60 mg/kg sediment. CONCLUSION The core with smallest fraction bonded in ion exchange and largest fraction in residuals was located outside the old deposits and together with the low content of copper, this indicates that the deposited tailings from the old deposit have not moved. The content of copper in the three other cores shows that approximately 90 % of copper from the tailings deposit is bonded in easy/relatively easy dissolvable fractions in opposition to the evaluation from Nussir ASA. Furthermore, the concentrations of copper in the sediment are significantly higher than the limit value. Even though sedimentation will happen naturally and encapsulate the contamination, the high concentrations and the proved availability of the copper in the sediment cause a risk to the marine environment. ENVIRONMENTAL PROBLEMS & SOLUTIONS POSTER IDEA BACHELOR FINAL ASSIGNMENT


Grøn Dyst 2016
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