Hydrochemical parameters and trophic state of an urban lake used for recreation

Every lake located in an urban area or in the vicinity of a town is a unique element of the landscape. However, lakes situated in cities are particularly endangered as they have a role of receiving water for municipal, industrial and precipitation wastes. The load of nutrients introduced with sewage is so high that it disturbs the biological balance and disrupts biogeochemical processes in an ecosystem. The object of the study was an urban Lake Sajmino (21.6 ha, max. depth 7.8 m) used for recreation. Its catchment is smaller than the topographic catchment area because some of the precipitation water is redirected outside by a storm water drainage system. The lake is fed by 3 permanent inflows (I-III). The goal of the study was to find correlations between the hydrochemical and biological parameters of the lake water and the quality of water supplied by the inflows. Simultaneously, an attempt was made to identify the hazards, in order to undertake actions in the near future preventing deterioration of the lake’s trophic state. The amounts of pollutants flowing into the lake from various sources exceeded the acceptable levels, therefore leading to an increase in its trophy, exhibited by algal blooms and limitation in the transparency of the lake water expressed as Secchi disc visibility. A significant (p ≤ 0.05) inverse correlation between Chl a and SD (r = –0.755) was found for the lake water, and between the Chl a of the lake and the pollutants of the inflows: NNH4 (I), r = 0.786, NNO2 (I), r = 0.731, NNO2 (II), r = 0.881, suspension (III), r = –0.719. TSI indicates that the eutrophic character of the lake is still unsettled. TSI (TP) > TSI (TN) > TSI (SD) > TSI (Chl a). The SD value (2.2÷3.55 m) may be caused by dissolved organic matter, the suspension or the water’s colour. Phytoplankton (Chl a ≤ 4.840 μg dm-3) could be limited by nitrogen, zooplankton feeding or toxic compounds

Comparative study of conjugate gradient algorithms performance on the example of steady-state axisymmetric heat transfer problem

The finite element method (FEM) is one of the most frequently used numerical methods for finding the approximate discrete point solution of partial differential equations (PDE). In this method, linear or nonlinear systems of equations, comprised after numerical discretization, are solved to obtain the numerical solution of PDE. The conjugate gradient algorithms are efficient iterative solvers for the large sparse linear systems. In this paper the performance of different conjugate gradient algorithms: conjugate gradient algorithm (CG), biconjugate gradient algorithm (BICG), biconjugate gradient stabilized algorithm (BICGSTAB), conjugate gradient squared algorithm (CGS) and biconjugate gradient stabilized algorithm with l GMRES restarts (BICGSTAB(l)) is compared when solving the steady-state axisymmetric heat conduction problem. Different values of l parameter are studied. The engineering problem for which this comparison is made is the two-dimensional, axisymmetric heat conduction in a finned circular tube

Investigation of the effectiveness of the cleaning flume system applied on the Młynówka River (Lubusz voivodeship)

Przeprowadzono roczną ocenę funkcjonowania systemu filtrów wypełnionych kształtkami z polipropylenu i keramzytem, usytuowanych w korycie rzeki, których zadaniem była redukcja zawiesin ogólnych oraz biogenów w wodzie przed jej odprowadzeniem do śródmiejskiego jeziora. Wykazano, że z powodu złej konserwacji i małej ilości zabiegów czyszczących, skuteczność systemu znacznie spadła w stosunku do okresu prawidłowej eksploatacji. Dotyczyło to przede wszystkim wyczerpania możliwości zatrzymywania głównego pierwiastka biogennego – fosforu. W okresie monitorowania obiekt utrzymał zdolność do redukcji zanieczyszczeń organicznych, zawiesin i azotu.An annual assessment pertaining to the functioning of the filter systems filled with polypropylene and gravelite profiles, located in the river bed, to reduce total suspensions and biogenic compounds in the water before it was directed to the city lake, was carried out. It has been shown that due to poor maintenance and a small number of cleaning operations, the efficiency of the system has decreased considerably, comparing to the period of correct operation. This was mainly related to the exhaustion of the ability to retain the main biogenic element – phosphorus. Througout the monitoring period, the facility retained the ability to reduce organic pollutants, suspended solids and nitrogen

Data from: Rare events of massive plant reproductive investment lead to long-term density-dependent reproductive success

1. The level of reproductive investment and density and distance dependent (DDD) processes are major determinants of plant reproductive output. The reproductive investment of a plant population varies temporally, but whether and how density- and distance-dependent processes are affected by population-level reproductive investment is a puzzle. 2. We used a spatially explicit approach in order to examine DDD effects on Sorbus acuparia crop sizes for a continuous period of 16 years. Our special interest was to investigate whether and how DDD processes affect long-term individual plant reproductive success (PRS) and whether such processes vary between years of relatively high and low population-level reproductive investment, measured as fruit crop size. 3. Our study revealed that DDD processes of fruit crop relate to population level reproductive investment. In most years, including all years with low and most years with moderate reproductive investment, no positive or negative DDD was found for PRS. However, significant negative density-dependent effects were found during most years of high and some years of moderate reproductive investment. During these years, the individual reproductive success decreased with increasing density of conspecifics. 4. The overall accumulated long-term negative density-dependent pattern of PRS was determined by few sporadic years of high reproductive investment, rather than by the most frequent years of low or moderate reproductive investment, when the DDD effects were usually weak. 5. Synthesis. Our study highlights the ecological relevance of relatively infrequent processes which affect PRS, stressing thus the importance of long-term ecological research

Analysis of the impact of sex and age on the variation in the prevalence of antinuclear autoantibodies in Polish population:a nationwide observational, cross-sectional study

The detection of antinuclear autoantibody (ANA) is dependent on many factors and varies between the populations. The aim of the study was first to assess the prevalence of ANA in the Polish adult population depending on age, sex and the cutoff threshold used for the results obtained. Second, we estimated the occurrence of individual types of ANA-staining patterns. We tested 1731 patient samples using commercially available IIFA using two cutoff thresholds of 1:100 and 1:160. We found ANA in 260 participants (15.0%), but the percentage of positive results strongly depended on the cutoff level. For a cutoff threshold 1:100, the positive population was 19.5% and for the 1:160 cutoff threshold, it was 11.7%. The most prevalent ANA-staining pattern was AC-2 Dense Fine speckled (50%), followed by AC-21 Reticular/AMA (14.38%) ANA more common in women (72%); 64% of ANA-positive patients were over 50 years of age. ANA prevalence in the Polish population is at a level observed in other highly developed countries and is more prevalent in women and elderly individuals. To reduce the number of positive results released, we suggest that Polish laboratories should set 1:160 as the cutoff threshold.</p