Habitat selection by breeding waterbirds at ponds with size-structured fish populations

Fish may significantly affect habitat use by birds, either as their prey or as competitors. Fish communities are often distinctly size-structured, but the consequences for waterbird assemblages remain poorly understood. We examined the effects of size structure of common carp (Cyprinus carpio) cohorts together with other biotic and abiotic pond characteristics on the distribution of breeding waterbirds in a seminatural system of monocultured ponds, where three fish age classes were separately stocked. Fish age corresponded to a distinct fish size gradient. Fish age and total biomass, macroinvertebrate and amphibian abundance, and emergent vegetation best explained the differences in bird density between ponds. Abundance of animal prey other than fish (aquatic macroinvertebrates and larval amphibians) decreased with increasing carp age in the ponds. Densities of ducks and smaller grebes were strongly negatively associated with fish age/size gradient. The largest of the grebes, the piscivorous great crested grebe (Podiceps cristatus), was the only species that preferred ponds with medium-sized fish and was positively associated with total fish biomass. Habitat selection by bitterns and most rallids was instead strongly influenced by the relative amount of emergent vegetation cover in the ponds. Our results show that fish size structure may be an important cue for breeding habitat choice and a factor affording an opportunity for niche diversification in avian communities.     

Finite element analysis of knee injury risks in car-to-pedestrian impacts

In vehicle-pedestrian collisions, lower extremities of pedestrians are frequently injured by vehicle front structures. In this study, a finite element (FE) model of THUMS (total human model for safety) was modified in order to assess injuries to a pedestrian lower extremity. Dynamic impact responses of the knee joint of the FE model were validated on the basis of data from the literature. Since in real-world accidents, the vehicle bumper can impact the lower extremities in various situations, the relations between lower extremity injury risk and impact conditions, such as between impact location, angle, and impactor stiffness, were analyzed. The FE simulation demonstrated that the motion of the lower extremity may be classified into a contact effect of the impactor and an inertia effect from a thigh or leg. In the contact phase, the stress of the bone is high in the area contacted by the impactor, which can cause fracture. Thus, in this phase the impactor stiffness affects the fracture risk of bone. In the inertia phase, the behavior of the lower extremity depends on the impact locations and angles, and the knee ligament forces become high according to the lower extremity behavior. The force of the collateral ligament is high compared with other knee ligaments, due to knee valgus motions in vehicle-pedestrian collisions.     

Model studies of zinc bonding with humic acid in the presence of UV-VIS-NIR radiation

Model experiments were performed to determine the influence of UV-VIS-NIR radiation on zinc bonded with humic acid (HA). The samples of HA or HA-65Zn radioisotope were overlayed on quartz sand in a glass column and subjected to elution that simulated natural conditions. The zinc concentration was chosen to that occurring in the sewage of the Central Sewage Work in Poznań. Zinc was washed with water to simulate the influence of rain. The recovery of injected radiotraces ions in the eluates was found to depend on pH, zinc and HA concentrations and on radiation exposure. The results help to evaluate the migration behavior of zinc in the presence of HA and UV-VIS-NIR radiation. From the first part of the investigation appears that radiation induces a degradation of HA-Zn layer and that the degradation process depends on pH of the environment. A decrease in pH causes an increase in photodegradation and the degree of zinc binding in the humic layer. Simultaneously, the ultra-weak luminescence (UWL) of plants was monitored to estimate the influence of zinc and HA on their development. The results show effects of HA and zinc on UWL and growth of bean and watercress which characterize the rate of plants metabolism and perturbation of their homeostasis. It was observed that high concentrations of zinc ions and HA considerably affect the development process of the plants.     

Biosorption of Pb(II) and Cr(III) from aqueous solutions: breakthrough curves and modeling studies

The sorption capacity parameters obtained for batch studies provide useful information about biosorption system. However, such data fail to explain the process under continuous-flow conditions. The present study is an attempt to explore the biosorption of Pb(II) and Cr(III) by straw from local wheat (Triticum aestivum). The biosorbent has been characterized by using Fourier transform infrared spectroscopy and surface area and elemental analyses and found to be porous and polyfunctional. S-shaped breakthrough curves were obtained at different column heights for the both metal ions. Various breakthrough parameters and saturation times have been determined. The column data have been successfully used to study the Bohart–Adams' bed depth service time (BDST) model and Yoon and Nelson's model. It was found that BDST model quite efficiently explained the whole column data whereas Yoon and Nelson model could explain it below 90 % breakthrough concentration. The predicted and calculated BDST parameters were in agreement with each other. Yoon and Nelson's constant decreased with an increase in the column height for both metal ions. Effect of change in flow rate on the Pb(II) biosorption has also been discussed with respect to BDST approach.     

Catalytic wet-air oxidation of a chemical plant wastewater over platinum-based catalysts.

Catalytic wet-air oxidation (CWAO) of wastewater (chemical oxygen demand [COD] = 1800 mg O2/dm3) from a fine chemicals plant was investigated in a fixed-bed reactor at T = 393-473 K under total pressure of 5.0 or 8.0 MPa. Catalysts containing 0.3% wt. of platinum deposited on two supports, mixed silica-titania (SM1) and carbon black composites (CBC) were used. The CBC-supported catalyst appeared to be more active than the SM1-supported one. A slow decrease of activity of the platinum on SM1 (Pt-SM1) during the long-term operation is attributed to recrystallization of titania and leaching of a support component, while the Pt-CBC catalyst is deteriorated, owing to combustion of the support component. The power-law-kinetic equations were used to describe the rate of COD removal at CWAO over the catalysts. The kinetic parameters of COD reduction for the wastewater were determined and compared with the kinetic parameters describing phenol oxidation over the same catalysts. Rates of COD removal for the wastewater were found higher than those for phenol oxidation over the same catalysts and under identical operating conditions.     

Nickel in the muscle tissues of freshwater fish from north eastern Poland should not cause human health concerns

Excessive intake of nickel (Ni) is known to produce adverse health effects in humans, including carcinogenicity and allergenicity. The main route of exposure for humans is diet, including fish. There is, however, little information concerning Ni content in freshwater fish in Poland. The aim of the study was to determine the concentrations of Ni in meat tissues of three fish species from north eastern Poland and assess toxic potential to healthy and susceptible sub-groups of individuals. The settings for the study lakes span a range of anthropogenic influence from protected areas to a basin with a town and several villages and another one influenced by a pesticide tomb leakage. Fish were netted and kept frozen until analysis. After defrosting, the fish were filleted and minced. The ashed samples were dissolved in nitric acid and analyzed for Ni by flame atomic absorption spectrometry. Roach meat contained 6.6–23 µg kg^?1 Ni, bream 9.5–178 µg kg^?1, and carp 16.5–139 µg kg^?1. These concentrations are low, indicating that the fish were not excessively contaminated with the metal. Consuming a 250 g portion of fish would result in an average nickel intake of 4 µg for roach, <10 µg for bream, and <20 µg for carp. These values represent only 0.4–2% of the maximum level that is likely to pose a risk of adverse effects as established in the USA. Consumption of fish from the study region need not necessarily pose a health threat.     

Assessment of organotin pollution along the Polish coast (Baltic Sea) by using mussels and fish as sentinel organisms

Levels of tributyltin (TBT) and its degradation products, mono- (MBT) and dibutyltin (DBT), as well as triphenyltin (TPT), were monitored in 10 stations along the Polish coast (Baltic Sea). Mussel-Mytilus edulis-and fish-Platichthys flesus-were used as sentinel organisms. The bioaccumulation patterns of butyltin and phenyltin compounds varied substantially. Butyltins were detected in mussel tissue from all the sampled stations. Among them, organisms from the Gulf of Gdansk showed the highest residues (68 ng/g w.w. as Sn) in conjunction with elevated TBT/DBT ratios, which suggest recent inputs of TBT in the area. Additionally, flatfish were sampled in the Gulf of Gdansk, and different tissues (liver, digestive tube and gills) were analyzed separately. TPT, although undetected in mussels, was always present in fish. The highest organotin concentration was observed in the liver (369 ng/g w.w. as Sn) of fish caught near Gdansk port. Relatively high concentrations were observed in digestive tube, which points out the ingestion of organotin contaminated food as an important uptake route of those compounds in P. flesus.     

Horizontal and vertical variabilities of mercury concentration and speciation in sediments of the Gdansk Basin,Southern Baltic Sea

The mercury compounds introduced to the environment because of anthropogenic activity are accumulated, mainly, in marine sediments. Both distribution of mercury in the Baltic Sea and factors affecting it are remain largely unknown. Due to its complex chemistry and variable conditions in the Baltic Sea bottom sediments, mercury may be reemitted to the overlaying water, and thus to the environment.The aim of this study was twofold. Total mercury contents were measured in sediments of the Gdansk Basin along a Vistula mouth (main source)--Gdansk Deep (deposition area) transect in order to assess spatial distribution of the element. Soft and sandy bottom sediment cores were collected and cut into slices. The mercury measurements consisted of acid digestion followed by CV-AAS determination. A five-step sequential extraction procedure involving measurements of mercury species water soluble, bound to humic substances and insoluble, was employed in order to investigate mercury speciation. On the basis of speciation results stability and remobilisation potential was assessed. The second aim was demonstrating that mercury gradients in vertical profiles of the investigated sediment cores exist.Total mercury contents varied in range from 28 ng/g x dw to 844 ng/g. Mercury associated with organic matter and sulphides, (respectively 39% and 49%) were the dominant species of the element. The results indicated that the river run-off is a source of mercury in the area. Vertical gradients of both total content and speciation of mercury in the soft sediments were attributed to both remobilisation from sediments, and decreasing trend in the anthropogenic load of the element deposited to sediments.