Pollutants in lake sediments
Last updated 5 August 2016
Pollutant levels in lake sediments are generally low in the Arctic. They are classified as insignificantly to moderately polluted. Sediment cores from Ellasjøen, a lake on Bjørnøya, show an increase in PCBs and DDT from the 1930s to the 1970s, followed by a reduction. The brominated flame retardants, PBDEs and HBCDs, show an increase from 1940 to 2000. No reduction is seen for these, but recent data are lacking.
What is being monitored?
Organic pollutants in lake sediments in Ellasjøen and Richardvatnet
The figure shows the trend in the sums of PCBs, DDT, PBDEs and HBCDs in lake sediments from Ellasjøen, Bjørnøya. The data show a rise in the concentration of PCBs and DDT from the 1930s to the 1970s, followed by a reduction. The brominated flame retardants, PBDEs and HBCDs, show a rise from 1940 to 2000.
(Cite these data: Akvaplan-niva (2022). Pollutants in lake sediments in Ellasjøen. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://www.mosj.no/en/influence/pollution/forurensning-innsjosedimenter.html)
The figure shows a point for the sums of PCBs, DDT and PBDEs, HCB and toxaphene 50 in lake sediments from Richardvatnet, a lake in Spitsbergen.
(Cite these data: Akvaplan-niva (2022). Pollution in lake sediments in Richardvatnet. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://www.mosj.no/en/influence/pollution/forurensning-innsjosedimenter.html)
The figure shows the trend in the heavy metal, mercury (Hg), in lake sediments from Ellasjøen, Bjørnøya.
(Cite these data: Akvaplan-niva (2022). Mercury (Hg) in lake sediments from Ellasjøen. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://www.mosj.no/en/influence/pollution/forurensning-innsjosedimenter.html)
Details on these data
|Last updated||5 August 2016|
|Update interval||Every 5th year|
|Commissioning organization||Norwegian Polar Institute|
|Contact persons||Guttorm Christensen|
The samples are processed in the laboratory using a variety of techniques to permit the analysis of several groups of pollutants. The following is performed to analyse organic, fat-soluble herbicides, PCBs and some brominated flame retardants (BFRs):
About 10g of sediment are freeze dried, an internal standard solvent is added which contains carbon-13 (13C) marked standards of DDT, PCBs and PBDEs. The pollutants are extracted to 150ml toluene by Soxhlet extraction with a reflux of 8 hours. The solvent is steamed down to 0.5ml using Turbovap (Zymark, Hopkinton, MA, USA). The solvent is changed first to dichloromethane, sulphur is removed by Gel Permeation Chromatography before the sample is concentrated to 0.5ml (Turbovap) and the solvent is changed to cyclohexane. The extract is cleaned in a florisil column to which water-free sodium sulphate is added.
The sample is analysed with an interlinked, high-resolution, gas chromatograph (GC) and mass spectrometer (MS). The concentrations are calculated by quantifying internal standards with known concentration and comparing these with the response (chromatogram) from the samples.
Detection limits for the individual compounds are three times the noise level of the instrument. The detection limit varies between each analysis and different types of samples, but the typical detection limit is 0.01–0.03 ng/g dry weight.
Analysis of mercury (Hg)
The samples are dried (50°C, 48 hours), mixed with 7M HNO3 and sealed in Teflon containers to be degraded in a microwave oven (10 min at 375W and 55 min at 275W). Cooled samples are transferred to test tubes and diluted to 10ml. Metals are quantified by spectrometry (ICP-AES) and mass spectrometry (ICP-QMS). Reference material (LGCPromochem) is analysed simultaneously for quality assurance. Detection limits vary from 0.01 to 2.0 mg/kg dry weight for the different metals and the analytical uncertainty varies from 16 to 50%.
Fieldwork is carried out using the best available methods to avoid sample contamination. Chemical analyses are performed by an accredited laboratory using internationally published and approved methods. To avoid contamination, only superclean equipment is used. A blank sample and a standard reference sample are analysed for each tenth sample. In addition to the accreditation, the laboratory regularly takes part in international intercalibration tests.
The samples of lake sediments are either the uppermost sediment (Richardvatn) or a sediment core (Ellasjøen). At Ellasjøen, 4 sediment cores were taken at the same station, one for each of the tasks, dating, organic pollutants, metals and organic carbon. The cores are divided into 1cm thick slices in the field and each of these was frozen immediately. Since the core contains material that fell to the bottom in different datable periods, it contains a natural archive of the pollution status and can be brought up and analysed whenever required.
Reference level and action level
Since persistent organic pollutants are anthropogenic pollutants which are not found in a natural state, the reference level for an unaffected state will be zero (in reality, the detection limit).
Serious efforts have been made to limit the spread of persistent organic pollutants. The Stockholm Convention regulates an international ban on the manufacture and use of PCBs, several herbicides, brominated flame retardants and some fluorine compounds.
Standards have been drawn up for environmental classification of sediments. Lake sediments from Svalbard are classified as insignificantly to moderately polluted with respect to most metals and organic pollutants.
Status and trend
Sediment is very suitable for monitoring the trend in environmental pollutants over time. A single sediment core contains the history of the environment because the age increases down the core. If the core is divided into slices and the age of the slices is determined, the trend in the amount of pollutants in the lake can be reconstructed from a single core. The figures showing the trend in PCBs, DDT, HBCDs and PBDEs from Ellasjøen on Bjørnøya are based on one sediment core sample. We see that the concentration of PCBs and DDT began to increase in the 1930s and rose until the mid-1970s, when they began to decline. Based on what we know about the manufacture and use of PCBs, the increase in the PCB concentration started a bit earlier. The reason for this is probably that some material from more recent layers contaminates the sediment further down the core when the core is pressed up through the sampling tube.
The trends of PCBs and DDT in the sediment core agree very well with the industrial history of PCBs and DDT. In Norway and many other western countries, DDT was regulated from 1969 and the early-1970s, and new uses of PCBs were banned in 1980. PCBs are still found in old building materials and some other products in Norway, and to prevent them escaping into the environment they must be delivered as hazardous waste when they become disused. The content of PCBs in the core indicates that the sediment had background concentrations (class 1) of PCBs until the 1930s, after which the content rose to class 3 – moderately polluted. The concentrations of DDT are low and correspond to class 2 – good environmental state.
The amount of the brominated flame retardants, PBDEs and HBCDs, increased from 1945 until 2001, which is the last measurement point for this series. From what we know about their manufacture and use, the rise in the PBDE and HBCD concentrations starts somewhat earlier. The reason for this is probably that some material from more recent layers contaminates the sediment further down the core when the core is pressed up through the sampling tube. The regulation of PBDE flame retardants began at the beginning of this century and the mixtures, penta- and octa-BDE, were included in the Stockholm Convention in 2009. The classification of these brominated flame retardants is incomplete.
The concentration of mercury (Hg) in the sediment is classified as class 2 – good. We see that there has been a smooth, but small, rise throughout the period from 1875 to 2001. The use of mercury is now subject to stringent restrictions, but mercury escapes from the metallurgical industry and the combustion of fossil fuels. The supply of mercury and other pollutants to Bjørnøya is mainly through long-distance transport and the sources are therefore global. Emissions of mercury in Norway have been reduced by 66% during 1995–2013. However, they are still comparatively large in relation to the targets set by Norwegian authorities. Batteries are currently the greatest source of mercury emissions in Norway. Because mercury has many small and diffuse sources ranging from combustion (natural: forest fires, volcanic activity and evaporation from the sea; and anthropogenic: industry, combustion of waste, oil, coal and gas), it takes a long time to overwin the mercury emissions.
Organic pollutants are internationally regulated through the Stockholm Convention and mercury through the Minamata Convention.
The declining concentrations of PCBs and DDT in lake sediments from Bjørnøya are a result of international regulation of the manufacture, use and emission of organic pollutants. When the sampling took place, the relatively recently regulated or non-regulated organic pollutants (i.e. the brominated flame retardants, PBDEs and HBCDs) did not show the same declining trends as the old, regulated organic pollutants. However, it is reasonable to assume that the concentration of these pollutants, too, is now declining in lake sediments.
Mercury (Hg) is regulated through the Minamata Convention. Regulations of the amounts of mercury in oil products and cleansing of gases from industry, coal-fired power stations and ships mean that mercury has been reduced in North America and Europe since the 1990s, whereas the emissions in Asia have risen greatly, mainly due to increased burning of coal in coal-fired power stations. Even so, recent data from mainland Norway indicate rising mercury concentrations in lakes. However, it is uncertain whether this trend also applies to lakes in Svalbard.
The lake sediments in Svalbard have enhanced concentrations of anthropogenic pollutants (PCBs, DDT, brominated flame retardants and mercury). They are classified from insignificantly (background) to moderately affected. Polycyclic aromatic hydrocarbons (PAHs) are not included in this assessment. The sediments may be affected by PAHs because much of the bedrock in Svalbard contains coal.
About the monitoring
Sediment is very suitable for monitoring the trend in environmental pollutants over time. A single sediment core contains the history of the environment because the age increases down the core. If the core is divided into slices and the age of the slices is determined, the trend in the amount of pollutants in the lake can be reconstructed from a single core. The lake sediment is thus an historical archive waiting there, ready for reconstruction if the need should arise.
Places and areas
Relations to other monitoring
International environmental agreements
Voluntary international cooperation
- General information on pollutants
- MOSJ report on pollutants from 2011
- General information on metals in lakes
- Christensen, G.N., Evenset, A., Rognerud S., Skjellkvåle R., Palerud R., Fjeld E., Røyset O.K. 2008. National lake survey 2004 – 2006, part III: AMAP. Status of metals and environmental pollutants in lakes and fish from the Norwegian part of the AMAP region. Statens forurensningstilsyn – SFT Oslo, report no. 2363, 171 pp.
- Evenset A., Christensen G.N., Carroll J., Zaborska A., Berger U., Herzke D., Gregor D. 2007. Historical trends in persistent organic pollutants and metals recorded in sediment from Lake Ellasjøen, Bjørnøya, Norwegian Arctic. Environmental Pollution 146, 196–205.