Abstract
Abstract Temperature is an important factor affecting the leaching of contaminants from waste deposits, especially in the Nordic region where temperature change is more drastic than other areas. In this study, the impact of temperature variation in the leaching of sulphate, Co, Fe, Mn, Ni and Zn from the Ballangen tailings deposit, northern Norway, was investigated using a column leaching experiment. Unoxidized tailings were fed into four columns, which were subsequently put into four wine fridges set at 5, 10, 14 and 18 °C, respectively. The columns were filled with 600 mL of deionized water from the top every second week. Leachate was collected at the bottom and tested for pH, conductivity and concentrations of , Co, Fe, Mn, Ni and Zn. The saturation index for ferrihydrite and the activity of Fe2+ in the leachate were calculated with PHREEQC. The results showed that the conductivity and leachate concentrations of , Co, Fe, Mn and Ni were highest at 14 and 18 °C, and lowest at 5 °C, which showed high tailings oxidation and subsequent leaching of contaminants at higher temperatures. X-ray photoelectron spectroscopic (XPS) analysis of the residual material confirmed the oxidation of sulphides and leaching of many elements. Ferrihydrite was supersaturated in the leachate from the 14 and 18 °C columns, which showed the oxidation of pyrrhotite and olivine and the precipitation of ferrihydrite. The cumulative mass of Zn leached out was highest at 10 °C, which might be the threshold temperature for the leaching of Zn.
Highlights
Waste rock and tailings from mining operations can cause a potential risk to the surrounding environment when directly exposed to weathering
The top 5–10 cm of column C2 showed clear iron staining with a light brown colour, while, below 50 cm, the column was primarily grey with some areas of iron staining
Column C11, with the highest leaching temperature of 18 °C, showed red-brown staining throughout the column with spots of grey to light brown
Summary
Waste rock and tailings from mining operations can cause a potential risk to the surrounding environment when directly exposed to weathering. Waste rock and tailings containing high concentrations of sulphides are notorious for their potential production of acid rock drainage (ARD) and subsequent leaching of contaminants to the local environment (Avilla et al 2008). The leaching of contaminants from tailings deposits has been reported in many studies (Besser & Rabeni 1987; Yukselen 2002; Mendoza et al 2006). The leaching of contaminants from abandoned lead mine tailings deposits in southeast Missouri, USA, and the subsequent accumulation of contaminants in aquatic invertebrates have been studied (Besser & Rabeni 1987). The leaching of contaminants from tailings deposits to stream sediment and stream waters has been reported in previous studies (Concas et al 2006; Avilla et al 2008)
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