Ala Lombolo
- One of Sweden's most polluted lakes
The pollution
The investigations show that the mercury mainly origins from the state-owned mining company LKAB’s old laboratory, where they from the end of the 19th century up until 1993 used mercury salts in the iron ore analyses. Through the years, the analyses have consumed about 540 kg of mercury. Until 1967, it was flushed straight into the Luossajoki creek through the untreated municipal sewage. The Luossajoki creek flows into the smaller lake northwest of Ala Lombolo, Yli Lombolo, but due to its very shallow nature it has erosion/transport bottom and thus, instead of settling, the particles is transported onwards to Ala Lombolo. Sediment cores taken in Ala Lombolo show that an increase in mercury content is correlated with the startup of the analyses. (Kiruna kommun, 2013)
The large amounts of other metals found in the lake are considered to be weathering products from the waste rock dumping sites located next to the Kiirunavaara mine on the west brink of Ala Lombolo. The waste rock dump consists mainly of the minerals pyrite, calcite, chalcopyrite and bornite which release sulfur and metals such as copper, zinc, calcium, cobalt, molybdenum and barium during weathering. Since weathering is an ongoing process, the transportation of metals into the Luossajoki water system is a continuous event. (Kiruna kommun, 2013)
Up until 1967 when a water treatment plant was built, Ala Lombolo served as recipient of the untreated municipal wastewater, causing the lake sediment to be high in organic content and sulfur (Kiruna kommun, 2013).
The degradation of the sewage sludge uses up the oxygen, which favors the retention of metals in the sediment. Mercury may also be bound in metal sulfides and is thus also encouraged by the relatively high sulfur content and the neutral to slightly alkaline nature, originating from the weathering of the waste rock dumps (Kiruna kommun).
Current possible sources of pollution of the Luossajoki water system are the stables, the heating plant, the water treatment plant and the residential area which are all located in direct vicinity of the lake.
Luossajärvi
Ala Lombolo
Yli Lombolo
Kiruna City
Kiirunavaara iron ore mine
Torne Älv
Photo: Tham & Videgård Arkitekter
The polluted sediments are spread in the whole lake, but the mercury is most concentrated in the northeastern parts where the lake is deepest. According to Kiruna kommun (2013), the beachside sediments also contain high concentrations of mercury. Due to the internal circulation in Ala Lombolo, the lake water and the surface sediments are still very contaminated, although the release of mercury was greatly reduced for more than 30 years ago. The mercury is bound to the sediment particles and is stirred up by the circulation, making the natural recovery process very slow in Ala Lombolo. The average concentration of mercury in the lake is 28 mg/kg DM. (Kiruna kommun, 2013)
According to the Swedish Environmental Protection Agency, a mercury concentration of 5 mg/kg DM is considered high. In Ala Lombolo point values of about 40 times as much may be found (Linder, 2005, 14 October).
Most of the ammunition that was dumped in the lake lies in the north-northeastern deeper parts of the lake. However, there is also some loose ammunition and leaked nitroglycerin spread in the lake. (Linder, 2016, 8 August)
Luossajärvi
Ala Lombolo
Yli Lombolo
Kiruna City
Kiirunavaara iron ore mine
Torne Älv
Photo: Tekniska Verken i Kiruna AB
The heating plant is located on Ala Lombolo's north shore.
Iron ore has been mined in Kiirunavaara since the early 1900s and the mining is one of the main pollution sources.