The paper discusses the course of air temperature in the years 1961-2014 in Chojnice (Central European Lowland), and its effect on water temperature and occurrence of ice cover on Lake Charzykowskie. An increase in mean annual air temperature was determined by 0.31°C per 10 years, and its even faster increase in the winter season (December-March), by 0.37°C per 10 years on average. An increase in mean annual water temperature in the lake by 0.24°C per 10 years also occurred. An increase in air and water temperature in winter months caused a reduction of the period of occurrence of ice cover. In the years 1961-2014, the persistence of ice cover was subject to a decrease by 3.7 days per 10 years on average, and the mean thickness of the ice cover decreased from 30 to 19 cm.
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.
Soil transformations in catchment of disappearing Sumówko Lake (Brodnickie Lake District, Poland)
Lake disappearing is a natural process which contemporarily escalates in consequence of human activity. It is estimated that within the area of Northern Poland from the last glaciation period (ca. 17 000 years ago) a half of lakes totally have disappeared. Areas exposed after water basins desiccation have become native rocks for new soils. Reduced water level results in changes of morphology and properties of the soils situated in direct vicinity of former water basins. The aim of this study was to estimate impact of the catchment groundwater level fall on morphology and properties of direct lake catchment soils, exemplified by the lake Sumowko (Northern Poland) as well as description of new soils formed of lake sediments. The analysis covered 11 soil profiles emerging within former lake basin (newly formed soils) and soils from direct vicinity of former lake (modified through ground water level fall). Obtained results prove that newly formed soils (Limnic Histosol Drainic and Haplic Gleysol) in majority are utilized as grasslands. Soils of the former lake surroundings prove relic features of gleying while they are also subject to mucking process because of dehydration.
The paper presents the current state of knowledge on dammed lakes in Poland and identifies the crucial research necessities in this area. The analysis of documents concerning dammed lakes and information obtained from institutions responsible for water management in Poland were the basis for a preliminary qualitative and quantitative assessment of dammed lakes located in north-west Poland. This allowed the identification of the necessary directions to be taken in the study of dammed lakes. In many cases, the indicated directions are innovative and have high potential for application.
The article discusses water level fluctuations in lakes and the associated changes in the lake surface and water resources in the years 1992-2011. On the basis of detailed field studies carried out in the hydrological year 2011, short-term and dynamic changes in the lakes’ hydrology were determined. Changes in hydrological lake types were evoked by unexpected hydro-meteorological situations, in particular high precipitation totals and sudden thaws in winter. The main symptom of the lake type change was the restoration, after nearly 10 years, of channels connecting the lakes. In addition, a strong interdependence was recorded in the difference between evaporation and precipitation, as well as the mean annual ranges of lake water levels in the years 1992-2010
Relationship between areal hypolimnetic oxygen depletion rate and the trophic state of five lakes in northern Poland
The oxygen content in a lake is a fundamental factor in lake ecology. In stratified lakes, deep waters are isolated from the atmosphere for several months during the summer; therefore, oxygen (substantially consumed by biological and chemical processes at this time) cannot be replaced before the autumnal mixing period. Hypolimnetic oxygen depletion has been considered an indicator of lake productivity since the early twentieth century. Many recent studies have been in opposition to this view by showing that the areal hypolimnetic oxygen depletion rate (AHOD) is poorly correlated with seston biomass and/or phosphorus concentration. The objective of this study is to show relationships between the mean values of total phosphorus (TP), total nitrogen (TN), chlorophyll a, and water transparency (Secchi disk depth, SDD) during the thermal stratification formation period and the AHOD rate. Hypolimnetic oxygen conditions in five dimictic lakes in northern Poland were examined in 2009 and 2010. Two of them were studied in the previous year. Monthly oxygen profiles taken from April to August, midsummer temperature profiles, and morphological data of the lakes were used to determine the AHOD rate. Standard water quality parameters such as concentrations of chlorophyll a, TP, and TN, as well as water transparency measured at the same time were used to calculate the trophic state indices (TSI) according to the Carlson-type formulas. On the basis of the collected data it is shown that AHOD is highly correlated with the TSI value for chlorophyll a, and poorly correlated with the TSI values for water transparency and phosphorus content. The best correlation between AHOD and TSI has been found for chlorophyll a (r2=0.702; p<0.001), as well as for overall TSI, determined by averaging separate component indices (r2=0.826; p<0.000). No correlation was found between AHOD and total nitrogen concentration. The research also confirmed previous observations, which pointed to a significant role of the hypolimnion depth in increasing oxygen deficits.
The aims of the study were to characterize shoreline soil development and evolution and to determine land use changes (19th to 20th centuries) in the direct catchment of the completely vanished Gardeja lake. The study was based on pedological research and analysis of cartographic materials. The main factor determining the current development of shoreline zone soil cover at the former Gardeja lake was human activity (lake dewatering, further drainage and human-induced erosion). Studied soil profiles were developed from mineral, non-lacustrine materials (upper parts of the slopes) and lacustrine sediments covered with colluvium. The analyzed soil catenas are representative for the undulated young glacial landscape of Northern Poland. The biggest changes of the land use were observed for the class of grasslands that is combined with shrubs (increase of cover area).