Temperature effect on seawater leaching of Pb, Zn, and F from waste rock at Ivittuut cryolite mine in South Greenland.

Abstract

Pollution from mining waste poses environmental risks and can adversely impact nearby communities. Understanding the weathering processes of mining waste and pollutant release is crucial for effective environmental remediation. At Ivittuut, South Greenland, cryolite was mined for 130 years. Waste rock (WR) from the mine was disposed of along the coastline of Arsuk Fjord. The WR contains sulfides such as pyrite (FeS₂), galena (PbS), sphalerite (ZnS), and chalcopyrite (CuFeS₂), with minor arsenopyrite (FeAsS) and molybdenite (MoS₂). Heavy metals, mainly Pb and Zn, leach from WR into the fjord. Monitoring over 40 years estimates the annual release of dissolved Pb into Arsuk Fjord to be 400-1000 kg. We performed a 40-week leaching experiment, using WR from Ivittuut and seawater in a Humidity Cell Test (HCT). The experiment was conducted at room temperature and 2 °C. Results show that at room temperature the concentration of Pb and Zn leached from the WR is tenfold higher than at 2 °C. Pb and Zn concentrations in leachates exceeded Greenland Water Quality Criteria (GWQC) by a factor of 20. Fluorine (F) concentrations were 10-15 times higher than GWQC. Compared to room temperature, 2 °C delayed and reduced leaching rates of Pb, Zn, and F indicate that contaminant leaching from WR in Ivittuut is slower under colder conditions, implying that Arctic climatic conditions slow down the metal mobilization, reducing Pb and Zn release at Ivittuut during winter months.