Characteristics of the allochthonous organic matter in Finnish forest lakes and reservoirs

Alloktonisen orgaanisen aineen ominaisuuksista suomalaisissa metsäjärvissä ja tekoaltaiss

Comparative study on the estimation of humic matter in natural waters

Luonnonvesien humuspitoisuuden arviointi eri menetelmill

Recovery from acidification of lakes in Finland, Norway and Sweden 1990?1999

International audienceSulphate deposition has decreased by about 60% in the Nordic countries since the early 1980s. Nitrogen deposition has been roughly constant during the past 20 years, with only a minor decrease in the late 1990s. The resulting changes in the chemistry of small lakes have been followed by national monitoring programmes initiated in the 1980s in Finland (163 lakes), Norway (100 lakes) and Sweden (81 lakes). These lakes are partly a subset from the survey of 5690 lakes in the Northern European lake survey of 1995. Trend analyses on data for the period 1990-1999 show that the non-marine sulphate concentrations in lakes have decreased significantly in 69% of the monitored lakes. Changes were largest in lakes with the highest mean concentrations. Nitrate concentrations, on the other hand, were generally low and showed no systematic changes. Concentrations of non-marine base cations decreased in 26% of the lakes, most probably an ionic-strength effect due to the lower concentrations of mobile strong-acid anions. Acid neutralising capacity increased in 32% of the lakes. Trends in recovery were in part masked by large year-to-year variations in sea-salt inputs and by increases in total organic carbon concentrations. These changes were most probably the result of climatic variations. Nordic lakes, therefore, show clear signs of recovery from acidification. Recovery began in the 1980s and accelerated in the 1990s. Reductions in sulphur deposition are the major "driving force" in the process of recovery from acidification. Further recovery can be expected in the next 10 years if the Gothenburg protocol on emissions of acidifying pollutants is implemented. Keywords: Nordic countries, sulphur deposition, lakes, recover

Responses of headwater lakes to air pollution changes in Finland

The present work provides a national scale assessment of the trace metal contamination of small headwater lakes and the recent development of acidified lakes in Finland. The information is needed as a scientific basis for further actions in air pollution policy. The study is based on observations in a national monitoring network of lake acidification.Anthropogenic, atmospheric deposition is primarily responsible for the increase of Cd, Hg, Pb and As in headwater lake sediments. However, a decline of 20 to 40% of the accumulation of these elements within the last decades was observed, indicating a relatively fast response to the decline in the atmospheric deposition, and that the accumulated stores of atmospheric trace metals in the catchment soils are not dominating the supply of trace elements to lakes.Lake waters reflected atmospheric trace metal pollution as well, but it was not as clearly quantifiable. Acidity controls in particular the level of Cd and Zn, while organic matter (humus) controls more the level of Cr, Fe, Cu and Ni in headwater lakes. Lead, Mn and Al concentrations are affected by both these factors. Humus acts as a carrier for trace metals from catchments soils to surface waters, irrespectively of their original source.Based on comparable chemical data sets, the risks of biological effects in lakes due to trace metals are lower in Finland than in Sweden and Norway. Trace metal levels in lake waters are less critical for the biota than acidity and inorganic (labile) aluminium levels.Due to acidification, there where estimated to be 2200-4400 damaged fish populations in southern and central Finland. Most of these populations are roach in lakes smaller than ten hectares. Sulphate concentrations have declined in all types of small lakes throughout Finland in the 1990s, indicating a clear response to the sulphur emission reductions. Base cation concentrations are still declining in lakes especially in southern Finland, but to a lesser extent than sulphate.There are presently no indications of elevated nitrate levels in forested headwater lakes. The increase in buffer capacity (chemical recovery) was relatively uniform throughout the country, except that the changes were not as significant statistically and by magnitude in the dilute lakes in northern Finland.Nearly 5000 headwater lakes larger than four hectares were estimated to be recovering from acidification at present. The chemical conditions were found to be improving throughout Finland, and first perch population recoveries in southern Finland were observed.The monitoring and survey results presented here are an example of an approach, where both spatial and temporal data from several sources are aggregated. This facilitates the estimation of regional changes and quantifies the changes on national scale. The consistent monitoring provides also sound basis for further modelling of recovery processes and scenario assessment.A new challenge is the interaction of acidification/recovery processes and trace metals with possible trends in temperature and hydrology due to global climate change. This should be taken into account when assessing long-term surface water quality and developing future monitoring networks. Empirical data in space and time is needed to judge, whether the emission reduction measures have been efficient

The analysis of results of heavy metals concentrations in samples of sedimentation

Appendix 4/15 of the publication "State of the environment in the Norwegian, Finnish and Russian border area 2007" (The Finnish Environment 6/2007)

The effect of water quality on the mercury concentration of northern pike (Esox Iucius, L.) in Finnish forest lakes and reservoirs

Veden laadun vaikutus hauen elohopeapitoisuuteen Suomen metsäjärvissä ja tekoaltaiss

The origin and level of mercury in Finnish forest lakes

Elohopean alkuperä ja pitoisuustaso Suomen metsäjärviss