Influence of Technological Process on Biodegradation of PVA/Waxy Starch Blends in an Aerobic and Anaerobic Environment

Improving biodegradability of PVA/starch blends is a reality already documented by a number of works. Admittedly, mechanical properties of products (for example, tensile strength) are somewhat worse, but suitable composition optimizing or chemical modifying of starch may eliminate the problem to a large degree. This work is an attempt to find another potential effect influencing biodegradability, that of technological procedure for producing films from these blends on an extruder. The procedure with a so-called pre-extrusion step (two-stage) and dry-blend (single-stage) produced blends of slightest differences in achieved biodegradability (virtually within limits of experimental error) in aerobic (76 vs. 79%) as well as anaerobic breakdown (48 vs. 52%). Conversely, morphological analysis exhibited superior homogeneity of films prepared by the two-stage process; their tensile strength was also higher.     

Comparison of leaching tests to determine and quantify the release of inorganic contaminants in demolition waste

The changes in waste management policy caused by the massive generation of waste materials (e.g. construction and demolition waste material, municipal waste incineration products) has led to an increase in the reuse and recycling of waste materials. For environmental risk assessment, test procedures are necessary to examine waste materials before they can be reused. In this article, results of column and lysimeter leaching tests having been applied to inorganic compounds in a reference demolition waste material are presented. The results show a good agreement between the leaching behaviour determined with the lysimeter unit and the column units used in the laboratory. In view of less time and system requirements compared to lysimeter systems, laboratory column units can be considered as a practicable instrument to assess the time-dependent release of inorganic compounds under conditions similar to those encountered in a natural environment. The high concentrations of elements in the seepage water at the initial stage of elution are reflected by the laboratory column leaching tests. In particular, authorities or laboratories might benefit and have an easy-to-use, but nevertheless reliable, method to serve as a basis for decision-making.     

Bioremediation of Chromate by Sulfate-Reducing Bacteria, Cytochromes c3 and hydrogenases

The treatment of soils and ground waters polluted by heavy metals is of economical and environmental interest. Reduction of Cr(VI) to the less toxic Cr(III) associated to its precipitation is a potentially useful process for bioremediation. In order to develop ecological processes using micro-organisms, we have compared various sulfate-reducing bacteria for enzymatic reduction of chromate. The best Cr(VI) reductase activity was obtained with Desulfomicrobium norvegicum. Despite morphological changes induced by the presence of chromate, this strain can grow in the presence of up to 500 M Cr(VI) and can decontaminate waters polluted by Cr(VI) when seeded in bioreactors. We have demonstrated the ability of several metalloenzymes (cytochromes c ₃ and hydrogenases) to reduce chromate. Biophysical investigations of the chromate/protein interaction in order to get further informations on the mechanism of metal reduction by cytochromes c ₃ are under the way.     

The rarity of twins: a result of an evolutionary battle between mothers and daughters—or do they agree?

The aim of this study was to test the hypothesis that parent–offspring conflict over parental investment might have led to the rarity of dizygotic twins in humans. We explored the theoretical prediction that twins maximize their inclusive fitness by the death of a co-twin, while mothers of twins maximize fitness by raising both twins to independence. We used life history data (1700–1900) from two parishes in Central Norway to compare differences in inclusive fitness (measured as number of children reared to the age of 16 years, using Hamilton's rule) between twins and mothers of twins. Our results show that twins maximize their inclusive fitness by the death of a co-twin, while mothers of twins raise more children by rearing both twins to adulthood. However, because twins growing up as singletons may produce higher or at least equal number of offspring than the sum of the two twins growing up together, mothers might gain more grandchildren by allowing twins to grow up as singletons. To conclude, both selfish twins and their mothers might benefit by the death of a co-twin, indicating that there is no parent–offspring conflict responsible for the rareness of twins in these human populations. Finally, we discuss the results in the light of “The Insurance Egg Hypothesis” and “The Natural Selection Hypothesis”.     

Impact of repeated irrigation of lettuce cultures with municipal wastewater on soil bacterial community diversity and composition

Environmental Science and Pollution Research - The effect of wastewater irrigation on the diversity and composition of bacterial communities of soil mesocosms planted with lettuces was studied over...     

Testing the extraction of 12 mycotoxins from aqueous solutions by insoluble beta-cyclodextrin bead polymer

Environmental Science and Pollution Research - Mycotoxins are toxic metabolites of filamentous fungi; they are common contaminants in numerous foods and beverages. Cyclodextrins are ring-shaped...     

Land use history of a floodplain area during the last 200 years in the Upper-Tisza region (Hungary)

Research into landscape history makes it possible to follow landscape changes in the past and support landscape management, conservation and restoration programs. Floodplain habitats are lost, isolated and fragmented on account of land use. Nowadays, these habitats are threatened by modifications in the natural water regime, as well as agricultural and forestry practices. Floodplains have great importance because they provide a transition between aquatic habitats and terrestrial biotopes. Our analysis of aerial photographs and topographical maps revealed that the major predicted changes in the study area are related to agricultural abandonment and afforestation. The comparison of land cover maps from 1784 to 2005 showed intensification of agriculture with land cover conversions from arable land and orchards to grasslands, marshes and woodlands. The land use types that are mostly responsible for the fragmentation of the landscape are arable land, economic plantations and orchards. We found that fragmentation was greater after 1956. This was caused by socioeconomic changes and showed that the habitats of floodplains have changed intensively during the last 200 years. Knowledge of this last 200 years of history contributes to a more careful and wiser management of the region through biodiversity protection and environmental development.     

House formation and feeding behaviour of<Emphasis Type="Italic"> Fritillaria borealis</Emphasis> (Appendicularia: Tunicata)

Numerous marine animals use elaborate filtration mechanisms to feed on particles suspended in the sea. Video-microscopy reveals that the common appendicularian Fritillaria borealis do so in a unique way. They live inside acellular, mucous houses, where their tail undulations act like a peristaltic pump in a close-fitting tail chamber to force water through a complex set of filters. Suspended particles, between ~0.2 and 30 µm in diameter, are retained in this process and propagated towards the mouth of the organism to be ingested. Coarser particles are back-washed out of the house during brief intervals of tail arrest, when the elastic recoil of the house walls reduces its volume to one-eighth of its inflated state. At the same time, the bifurcated tip of the animal's tail slides into a sleeve-like extension of the house. This sleeve acts like a flipper to propel the animal and collapsed house several millimetres to a few centimetres through the sea as soon as muscular activity of the tail is resumed. After a second tail arrest, a special muscular twist brings the tail out of the sleeve, whereupon undulatory pumping movements are resumed to reinflate and process particle-laden water through the house. The complete behavioural cycle lasts ~30 s. The repetitive inflation and deflation cycles of the house are probably of importance for unclogging of the coarse "inlet" filters downstream to the tail pump, as well as for agglutination of the smallest food particles trapped in the house to ease their recapture in the endostylar pharyngeal filter during the ingestion process. The unique tail sleeve and flipper at the same time enable the animal to move away from the previously filtered water and rejected coarse particles, before the house is reinflated for resumed food filtration.     

Interindividual variability in metal status in the shore crab<Emphasis Type="Italic"> Carcinus maenas</Emphasis>: the role of physiological condition and genetic variation

The relations between genetic variation, physiological condition, size and metal status in the shore crab Carcinus maenas (L.) were investigated. Shore crabs were collected at three sites around the island of Funen, Denmark, and carapace width, colour, moulting stage and major ions and protein in the haemolymph were determined. Concentrations of water, cadmium, copper and zinc in midgut glands, muscles and gills were measured, and allozyme variation at 15 loci was studied. Generally, tissue water content and copper, zinc and cadmium concentrations decreased from the moulting stages C₃ over C₄ to D crabs, whereas the opposite was true for copper and zinc concentrations in gills and muscle. However, the water content of the tissues increased with the size of the crabs. Since tissue water contents changed consistently over moulting stages, conclusions on changes in metal concentrations sometimes diverged when expressed on a dry versus wet weight basis. Regarding allozymes, esterase, malate dehydrogenase and phosphoglucomutase were polymorphic. The crabs showed a low level of genetic variability for both polymorphism (0.14) and for heterozygosity (0.07) at the three sites. Allelic frequencies showed very low levels of differentiation among the samples, no evidence of inbreeding and no population subdivision. Multilocus heterozygosity was positively correlated with size. Concentrations of copper and zinc in midgut gland, muscle tissue and gill were not correlated with genotype, whereas a weak correlation between phosphoglucomutase genotypes and concentrations of cadmium in the midgut gland was found.Communicated by M. Kühl, Helsingør