Wojciech Tylmann, Małgorzata Kinder, Maurycy Żarczyński and Anna Poraj-Górska
Varved lake sediments are well known archives used for paleoenvironmental reconstructions. They provide continuous, high-resolution and calendar-year chronologies of past environmental changes. From lakes Kamenduł and Perty, located in the Suwałki Landscape Park, short cores of laminated sediments were collected and investigated using microfacies analysis and X-ray fluorescence (XRF) scanning. Sediments of Lake Kamenduł form biogenic (calcite) varves with pale lamina containing precipitated calcite and dark lamina composed of mixed organic and clastic material. There is a visible difference between varves in the lower and the topmost part of the core. The varve thickness and clastic material content decrease upcore. Analysed sediments of Lake Perty also show laminated structures which are biogenic varves composed of calcite laminas interbedded with layers of mixed material and dark laminas containing mostly organic material with some clastic particles. Our study shows that further analysis of sediments from these lakes may provide valuable information about past land use changes in their catchments as well as changes in the water column, i.e. mixing regimes and redox conditions.
Wojciech Tylmann, Paulina Głowacka and Agnieszka Szczerba
Lake sediments are excellent archives of environmental and climate change. Especially important are varved sediments which can provide high-resolution (annual) records of those changes. Process studies including limnological measurements, particle flux monitoring and analyses of sediment structures give an opportunity to explain relationships between meteorological conditions, in-lake processes and varve formation. In our study, three lakes were selected in the Masurian Lakeland: Lake Żabińskie, Łazduny and Rzęśniki. These relatively small and deep lakes contain well preserved biogenic varves. The lakes are influenced by the same meteorological conditions but differ in terms of their catchment size, land use, hydrology, lake basin morphology and trophic status. To explore the relationships between different parameters and preservation/transformation of climate signals in the sediments we started systematic limnological measurements in the water column of these lakes, water sampling for hydrochemical analyses, monitoring of modern sedimentation using sediment traps and analysis of topmost varves from short sediment cores. With this comprehensive and high-resolution monitoring program scheduled for at least four years we are going to verify the potential of varves to track short-term meteorological phenomena in lake sediments.
Włodzimierz Juśkiewicz, Włodzimierz Marszelewski and Wojciech Tylmann
This paper presents the results of the study on the concentration of heavy metals and persistent organic pollutants (POPs), including PAHs and PCBs, in the bottom sediments of Lake Gopło. This lake is significantly elongated (about 25 km); its longitudinal profile is diversified, and there are deeps and thresholds impeding the flow of water. The shoreline is varied, which is characteristic of tunnel valley lakes. The catchment has a typical agricultural character with a point arrangement of industrial centres. The analysis of the diversity of the concentration of heavy metals and POPs was based on 37 samples from two representative cores: one collected in the northern part of the lake, the catchment of which shows an industrial character, and the second one in the southern part where the catchment is agricultural in character.
In the sediments, the content of the following heavy metals was analysed: Cu, Pb, Cd, Zn, Ni, Cr, Hg and As, as well as PAHs and PCBs. The sediment age was determined by the 210Pb dating method. In order to assess the contamination level of the bottom sediments with heavy metals, the contamination factor (CF) and degree of contamination (DC) were calculated. Moreover, the impact of the changes in the catchment’s land use over the past 100 years was determined. The results showed that the sediments from the industrial part of the lake significantly exceed the geochemical background for both the heavy metals from the group identified as industrial pollution and from the group of agricultural pollutants. The southern core shows only a slight increase in the amount of pollution from the agricultural group, lack of industrial pollution and a low degree of contamination. A slight increase in persistent organic pollutants is also recorded, without any apparent effect on the state of the deposited sediment. The 210PB dating enabled the main stages of human impact to be determined: the pre-industrial revolution, from the beginning of industrialisation to the 1950s, intensive human impact from the 1960s to the 1980s, and a gradual decrease in the human impact starting from the 1990s. In addition, attention was paid to the changing sedimentation rate.
Alicja Bonk, Wojciech Tylmann, Tomasz Goslar, Agnieszka Wacnik and Martin Grosjean
Varved lake sediments from Lake Zabihskie (northeastern Poland) provide a high- resolution calendar-year chronology which allows validation of 14C dating results. Microscopic analysis of the varve microfacies revealed that laminations found in Lake Zabihskie were biogenic (calcite) varves. Three independent counts indicated a good preservation quality of laminae in the 348 cm long sediment profile which contained 1000+12/-24 varves. The varve chronology was validated with the 137Cs activity peaks, the tephra horizon from the Askja eruption at AD 1875 and with the timing of major land-use changes of known age inferred from pollen analysis. 32 AMS 14C dates of terrestrial macrofossils distributed along the profile were compared with the varve chronology. After identification of outliers, the free-shape model performed with 21 14C dates provided the best possible fit with the varve chronology. We observed almost ideal consistency between both chronologies from the present until AD 1250 while in the lower part (AD 1000-1250) the difference increases to ca. 25 years. We demonstrate that this offset can be explained by too old radiocarbon ages of plant remains transported to the lake by the inflowing creek. Results of this study highlight that careful interpretation of radiocarbon age-depth models is necessary, especially in lakes where no annual laminations are observed and no independent method are used for cross-validation.
Dawid Weisbrodt, Dirk Enters, Maurycy Jacek Żarczyński, Anna Izabela Poraj-Górska and Wojciech Tylmann
Analysis of non-pollen palynomorphs supplemented by pollen analysis, microcharcoal analysis and geochemical data from laminated sediments from Lake Jaczno were used to establish different phases of land-use in the catchment between c.a. AD 1840 and AD 2013. The results show that during the first eighty years the vicinity of the lake was heavily deforested. During this period erosional inputs caused accumulation of abundant fungal spores, indicators of pastures and natural fertilizers (manure) as well as of corroded pollen grains and charcoal. Gradual regeneration of forest cover took place after World War II, when expansion of pioneer trees occurred (Betula, Salix, Carpinus, Populus). At the same time, a considerable increase in the lake trophy was observed, leading to the changes in phytoplankton and macrophyte communities: a decrease in the proportion of Botryococcus and an increase in the Nymphaea alba population. The non-pollen palynomorphs analyses indicate the substantial human impact that caused changing local environmental conditions, compatible with the results based on pollen analysis and geochemical data.