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Trapa natans (water chestnut) is an aquatic, thermophilic plant whose decline has been observed in many localities in central Europe during the last decades. In this paper, we present a description of two new T. natans subfossil sites located outside its present northern distribution in Poland. High-resolution analysis of plant macrofossils supported by geochemical analysis were undertaken to reconstruct the palaeoecological habitat and examine the cause of the late Holocene decline of T. natans that took place ca. 4000 calibrated years before AD 1950 (cal. yr BP) in a paleolake, presently the Bagno Kusowo bog. Its disappearance was a consequence of terrestrialisation and the development of peatland. In paleolake sediments covered by the peat layer in the Mechacz Wielki bog, T. natans macrofossils were found from before ca. 3300 cal. yr BP. The decline of T. natans could have resulted from the changes and development of other plant communities where the dominant role was played by Stratiotes aloides and Nymphaea sp. In our study sites, T. natans occurred together with Potamogeton crispus, Potamogeton obtusifolius, Nymphaea alba, and Nuphar sp. in eutrophic water dominated by Ca2+, Fe3+, and Al3+ ions. Our palaeobotanical and geochemical results align with the contemporary conditions of T. natans habitat.

The aim of the study was to determine the influence of urban agglomeration on a small, natural water reservoir which, as a result of the expansion of the city of Poznań, has become an urban lake. In the vegetation period 2015, the chemistry of its water was studied, and in September additional samples of bottom sediments, plants and fish were collected for analysis in order to determine the content of heavy metals. In terms of productivity, no significant influence of the catchment was recorded. In the 1980s the lake was defined as eutrophic, and in 1996 as α-mesotrophic and such a state continues until today. This is the result of protective activity undertaken by its new owner. The adverse influence of the urbanization of the surrounding areas was reflected by the increased content of lead in particular elements of this ecosystem, that is, in bottom sediments, plants and fish muscles.

The article presents the results of preliminary geochemical and mineralogical studies of technogenic soils (Technosols) of abandoned iron ore mines on the Ławęczna Hill near Miedziana Góra in the Holy Cross (Świętokrzyskie) Mountains, southcentral Poland. The results of chemical analyses (XRF) were used to calculate the soil enrichment factors of arsenic, copper, iron, lead and zinc, and compare the element concentrations to their levels in uncontaminated soils across Poland and in the city of Kielce. The highest values of soil enrichment factors of metals (As 27.699, Ni 26.455, Cu 9.353, Zn 3.344, Pb 0.62) were recorded for the sand fraction composed of iron oxyhydroxides and hematite, whereas the lowest (Ni 0.22, Cu 0.069, Zn 0.007, Pb 0.028) for the clay–silt and sand fractions, which were primarily composed of calcite and quartz as well as for gravel fraction. The clay-silt fraction shows the highest enrichment in arsenic (27.69). The examined metals and arsenic show positive geochemical anomalies.

Urban reservoirs can receive high loads of chemicals, including persistent contaminants and eutrophication-promoting nutrients. To maintain their economic and recreational use, implementation of various restoration methods is often required. The Maltański Reservoir (Poland, Europe), a small, shallow and dammed urban water body, undergoes complete draining every four years as part of its restoration procedure. Here, we investigated the phosphorus (P) content and its fractions just before the reservoir was drained and after it had been completely filled with water again. As demonstrated, the highest accumulation of P occurred at sites through which the main water flow is directed. Calcium-bound and residual P constituted the largest proportion of P fractions. A shift in P fractions after the reservoir was drained and sediments were left without water for at least 4 months was observed. A decrease in phytoplankton utilized NH4Cl-P, Fe-P and NaOH-P fractions was found and followed a simultaneous increase in nearly biologically inaccessible HCl-P and practically biologically inactive residual P fractions. Our study demonstrates that complete drainage of the Maltański Reservoir may additionally decrease the risk of internal P loading through shifts in its fractions.