Jaan-Mati Punning

Impact of forest disturbance on the pollen influx in lake sediments during the last century.

The pollen accumulation rates of four lakes in different regions of Estonia were estimated in order to study the relationship between pollen influx and the character and intensity of disturbances in the pollen catchment area. The pollen influx data obtained are in accordance with model calculations on the size of the pollen source areas. The influx of arboreal pollen and that of the dominant taxa (mainly Pinus) in the lakes investigated shows that, in the case of small lakes (area 3-6ha) in a forested landscapes, the bulk of the pollen originates from an area within 100-200m around the lake. The distribution patterns of influx from two lakes situated close to each other but at different distances from forest fires show that past disturbances can be reliably detected when the disturbance occurred in the immediate vicinity of the lake and at least 25% of the local pollen source area was involved. In the case of a large lake (137ha) only fires embracing thousands of hectares can be detected in the pollen diagrams.

C/N ratio and fossil pigments in sediments ofsome Estonian lakes: an evidence of human impact andHolocene environmental change

The content of carbon (C), nitrogen(N), fossil carotenoids (TC) and chlorophyllderivatives (CD) in the sediments of five Estonianlakes was analysed. Historical records of man-inducedchanges on catchments were used for the interpretationof the obtained data. On the basis of the C/N ratiosit was estimated that the planktonic matter formed ca.25% (C/N ratio 24) to 90% (C/N ratio 8) of theorganic pool matter of lake sediments. In eutrophicLake Ruusmäe the fraction of the phytoplanktonproduced in lakes was highest, amounting toapproximately 80–95% of the deposited organic matter.Remarkable C/N changes were noted in the sedimentsfrom lakes Matsimäe and Viitna, where the contentof planktonic matter has increased during lastdecades, reflecting an increase in recreationalactivity around these lakes. The variations in pigmentconcentrations in the sediments of lakes Matsimäeand Ruusmäe could be explained by changes in theland-use that have altered the intensity of primaryproduction and conditions of TC and CD degradationbefore the final burial.

Environmental problems in the Estonian oil shale industry

In Estonia technologies for oil shale mining and consuming have been continuously developed for more than 80 years. By March 2006 one billion tonnes of oil shale had been produced in Estonia. Since the 1960s, Estonia has been the largest oil shale producer and consumer in the world. In the 1980s about two-thirds of the worlds oil shale output came from Estonia. Serious problems in the mining complex are connected with large losses of oil shale at mining and enrichment (more than 30%) and voluminous dewatering (25 m3 per tonne of oil shale). After mining and beneficiation, much limestone remains unused and is deposited in waste dumps. Oil shale waste and waste heaps may be considered a rather innocent production residue; however, from time to time they are subject to self-ignition. Following combustion of enriched oil shale, ash remains which also has to be deposited. The most toxic waste (semicoke) comes from the oil-shale chemical industry. Power stations using oil shale emit large amounts of carbon dioxide and other gases; the groundwater regime, and often also the water quality, are altered in mined-out areas. Environmental effects and the resulting immediate hazards were greatest in the 1980s, now the situation is improving.

Diatom assemblages in sediments of Lake Juusa, Southern Estonia with an assessment of their habitat

Diatom analysis of surface sediments and two sediment cores from different sedimentation areas of a small closed lake was undertaken with the aim of acquiring knowledge on the dependence of the distribution of diatom assemblages on lake bathymetry. Lake Juusa was selected for the study because we have for this lake a large data set about the lithological composition of sediments and macrofossil and cladoceran records for the Holocene. A high carbonate content (20–60%) in the sediment sequence indicates high carbonacity and relatively stable pH values during the Holocene. On the basis of comprehensive analysis, abrupt water-level fluctuations and changes in the trophic status were established. Results of this study showed that the fluctuations of the water-level were the leading factor determining the habitats of diatom assemblages in the lake. In the surface sediment samples planktonic species such as Cyclotella spp., Stephanodiscus spp. and Aulacoseira spp. had a depth optimum at 3–4 m and the most abundant periphytic taxa were distributed mostly at depths shallower than 3.5 m. The same regularity was established in sediment cores where a good correlation between planktonic species and lake water depth was found in sediments accumulated at water depths >4 m. Lake Juusa appears to be a proper site for detailed environmental reconstructions over the Holocene, and the results will give us a good opportunity to analyse the history of water-level fluctuations in other small Estonian lakes.

Historical changes in the concentrations of polycyclic aromatic hydrocarbons (PAHs) in Lake Peipsi sediments

The distribution of 11 individual polycyclic aromatic hydrocarbons (PAHs) was analysed in a 210Pb dated sediment core from the deepest area of Lake Peipsi and in four surface sediment samples taken from littoral areas. According to the concentrations in the core three groups of PAHs may be distinguished: (1) relatively stable concentrations of PAHs within the whole studied time interval; (2) very low concentrations in sediments accumulated before intensive anthropogenic impact (from 19th century up to the 1920s) following a slight increase and (3) an overall increase in PAH concentrations since the 1920s up to the present. Comprehensive analysis of PAHs in the core and monitoring data obtained in the 1980s together with the lithology of sediments show that an increase of anthropogenically induced PAHs correlates well with the history of fuel consumption in Estonia and speaks about atmospheric long-distance transport of PAHs. The continuous increase of PAH concentrations since the 1920s do not support the earlier hypothesis about the dominating impact of the oil shale fired power plants near the lake, because their emissions decreased significantly in the 1990s. The concentration of PAHs in the deep lake core sample correlates well with the content of organic matter, indicating absorption and co-precipitation with plankton in the sediment.

Combining limnological and palaeolimnological approaches in assessing degradation of Lake Pskov

Limnological monitoring data and palaeorecords from large shallow Lake Pskov were used to study the long-term dynamic pattern of the lake ecosystem and to identify the start of its degradation. Lake Pskov is the southern part of Lake Peipsi s.l., the largest transboundary lake in Europe. The limnological monitoring data collected in the years 1956–2005 show that the water quality of L. Pskov has deteriorated and caused adverse changes in the whole ecosystem (e.g. excessive growth of algae, increased cyanobacterial blooms, silting of the lake bottom, fish kills). Doubled total phosphorus (Ptot), dissolved inorganic P (PO4-P) and chlorophyll a (Chl-a) contents, increased total alkalinity (HCO3 −) and pH, as well as decline in water transparency and oxygenation conditions, indicate a clear increase in the trophic level of the lake. However, the limnological studies do not show when the degradation started. To understand long-term dynamics of the lake ecosystem, a 52 cm sediment core taken from one monitoring station of L. Pskov was studied and dated by the 210Pb method. Palaeodata show that substantial changes in the L. Pskov ecosystem started already in the 1930s when mesotrophic conditions in the lake turned increasingly eutrophic. Since that time, the content of P, nitrogen (N), carbon (C) and relative abundance (RA%) of planktonic diatoms in the sediment have increased significantly (P 0.9 or r <-0.9, P < 0.001) were observed between the contents of P, N, C and sulphur (S) in the sediment and the mean water level (WL) and temperature (WT) registered one to five years earlier in the lake. The C content of the sediment showed a negative relationship with WL and a positive correlation with WT. A significant positive relationship was recorded also between WT, and N and P content in the sediment. It is hypothesized that a higher WT and lower WL result in an increased organic mater accumulation in the sediment in the coming years.

Human impact on the history of Lake Nômmejärv, NE Estonia: a geochemical and palaeobotanical study

A comprehensive geochemical and palaeobotanical study of the lacustrine sediments of Lake Nôm mejärv from industrialized NE Estonia establishes the links between the nature and intensity of human activities and their impacts on the state and structure of the lake ecosystem. In cores of sediment formed during the last century, five zones can be distinguished, each reflecting a pattern of human activity and characterized by a particular diatom community and sediment composition. Using reliable geochronological data it is possible to compare these zones with the known industrial load on the lake and its catchment area. The information obtained is of practical value for planning the rehabilitation of this severely impacted lake.

The Spatial Distribution of Characterised Fly-Ash Particles and Trace Metals in Lake Sediments and Catchment Mosses: Estonia

The concentrations of fly-ash particles were studied in the surface sediments of 42 lakes in Estonia. Concentrations of both spheroidal carbonaceous particles (SCPs) and inorganic ash spheres (IASs) were determined and the particles chemically characterised to different fuel types. This was accompanied by trace metal analyses from lake surface sediments and catchment mosses in order to determine the distribution of atmospheric pollutants. The obtained spatial distribution data for fly-ash particles varied to a great extent, partly due to differences in sedimentation rates but mainly due to higher deposition in industrial areas. The distribution patterns of the different particle types in lake sediments, as well as the trace metals in mosses, show that the deposition of airborne particulates is of local origin around pollution sources and that the share of long-range transported atmospheric impurities is high along the main cyclonic routes in Estonia.

Changes in lake-sediment structure and composition caused by human impact: repeated studies of Lake Martiska, Estonia

This research uses a comparison of the sediment record of Lake Martiska (NE Estonia) with well-documented historical changes in human impact to identify the factors dominantly affecting the sediment lithological composition, and the accumulation of heavy metals and other microelements into the sediments. To this end, comprehensive lithological-geochemical studies of the upper sediment were undertaken in 1986 and repeated in 2003 and 2005. Oil shale mining and processing heavily impacted the area via atmospheric pollution and groundwater extraction. As a result of the fly-ash deposition clear marker horizons of chemical compounds were formed. Historical water-level fluctuations are clearly reflected in the lithological composition and grain-size variations of the studied sediment cores. During regression and transgression phases displacement of the erosion-transport-accumulation limits caused redistribution of previously accumulated sediments and their return into the biogeochemical matter cycling of the lake. The210Pb chronology of the sediment records is in contradiction with the historical records of fly-ash emissions, suggesting that changes in 210Pb flux and focusing of sediments caused by lake-level change have invalidated the dating models.

Vulnerability and Adaptation Assessments for Estonia

Because of its geography, wide coastal areas, water resources, forests, and wetlands, the environment of Estonia is sensitive to climate change and sea level rise. Therefore, the vulnerability and adaptation assessments focused on these sectors. This chapter gives preliminary results of our study. The CERES-Barley and SPUR2 models were used to assess crop productivity. A sea level rise of 1.0 m was used to evaluate the responses of the physical and natural systems in the low-lying coastal territories in the West Estonian Plain and the West Estonian Archipelago. To estimate the responses of forests to proposed climate change scenarios, two case study areas with different types of climate (continental and maritime) were selected and a modified forest gap model was used. In addition, an analysis was conducted using paleogeographical data from Estonia and neighboring areas. These data indicate that between 7,000 and 5,000 years ago (Holocene “climatic optimum’) the temperatures in Estonia were similar to predicted future temperatures. Thus we can compare the state of ecosystems in the past with those predicted for future global climate change.