The salinated mine water found at the Talvivaara multi-metal mine operated by Terrafame has caused structural changes in the water chemistry and biotic communities of Lake Jormasjärvi, both temporally and spatially. The significance of the effects caused by mine water effluent is amplified by the fact that Lake Jormasjärvi, the focus of the study, is among the 200 largest lakes in Finland.
“The environmental effects subsequent to the beginning of mining operations are clear, even though Lake Jormasjärvi is relatively large with a surface area of 21 km2. And it’s only the fourth lake in the chain of lakes that receive the water originating in the mining area,” explains researcher Jaakko Leppänen at the Faculty of Biological and Environmental Sciences.
Only partial help from a discharge pipeline bypassing the lake
Lake Jormasjärvi is located north of the mine and it has received mine water that has run through three other lakes, Salminen, Kalliojärvi and Kolmisoppi, as well as through the rivers connecting the lakes, throughout the mining activity, which began in 2008. A discharge pipeline constructed in 2015 transports the mining water past Lake Jormasjärvi directly to the even larger Lake Nuasjärvi, a body of water with a surface area of 96 km2. Regardless, smaller amounts of mine water continue to flow into Lake Jormasjärvi even today.
The research findings clearly demonstrate a negative change in the electrical conductivity of Lake Jormasjärvi, particularly close to the River Tuhkajoki inlet. Conductivity is an indicator of the amount of minerals and salts dissolved in the water.
Furthermore, changes in species, such as diatoms, cladocerans (water fleas) and chironomid (midge) larvae, towards an improved tolerance of salinated water are the strongest near the River Tuhkajoki inlet. However, changes in both water chemistry and aquatic species decrease closer to River Jormasjoki, the outlet of Lake Jormasjärvi.
The researchers also demonstrated a significant temporal change in aquatic organisms, showing that the statistically most significant change occurred after the mine launched its operations. The change in species towards ones that better tolerate salinated water has been pronounced since mining began.
“In the future, more consideration should be given to the effect that mines have on waterways, particularly as the pressure to establish even larger mines and mines with low ore grades grows,” Docent Jan Weckström points out.
The environmental strain caused by the mine operated by Terrafame and other low-grade mines is severe, since extensive amounts of rock have to be mined to gain sufficient ore yields, increasing the amount of waste rock produced through the process.
The effluent from the Talvivaara/Terrafame mine and its effects on the surrounding waterways have been a topic of debate throughout the mine’s existence, ever since the year 2008. In 2017, the Environmental Change Research Unit ECRU carried out a waterway study a few kilometres downstream of the mine in Lake Kivijärvi, observing that the strong salinisation of the lake had caused clear physical, chemical and biological changes. See the original article:
Leppänen, J., Weckström, J. & Korhola, A. (2017) Multiple mining impacts induce widespread changes in ecosystem dynamics in a boreal lake. Scientific Reports7, doi.org/10.1038/s41598-017-11421-8
Leppänen, J., Luoto, T. & J. Weckström (2019). Spatio-temporal impact of saline mine water on Lake Jormasjärvi, Finland. Environmental Pollution247, 1078-1088. doi.org/10.1038/s41598-017-11421-8