Intraspecific allometry of neonatal size in the antarctic fur seal (Arctocephalus galapagoensis)

Summary Intraspecific allometry of pup mass as a function of maternal mass was analysed in Antarctic fur seals (Arctocephalus gazella), a highly dimorphic species. The allometric exponent was 0.6, much lower than in interspecific comparisons. Slopes were the same for mother-son pairs as for mother-daughter pairs, but adjusted means were significantly higher for the former, indicating higher reproductive effort of mothers of sons. The correlation of maternal mass with pup mass explained 59% of the variance in female pup mas but only 18% of that in male pup mass. Females appeared to produce sons which were as big as possible. Relative pup mass decreased with increasing maternal mass indicating a lower reproductive effort of bigger and presumably older mothers, contrary to expectations from life history theory. Sex ratio of pups showed no relation to maternal mass.     

Pt/Mg-Ce-O catalyst for NO/H<Subscript>2</Subscript>/O<Subscript>2</Subscript> lean de-No<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> reaction

The NO/H₂/O₂ reaction was studied under oxidizing conditions in the 100-400 °C range over 0.1 wt% Pt supported on various metal oxides such as MgO, CeO₂, SiO₂, La₂O₃, CaO, Y₂O₃ and TiO₂. The Pt/MgO and Pt/CeO₂ catalysts showed good catalytic behaviours. Here, we find that the Pt/Mg-Ce-O catalyst, prepared from MgO and CeO₂ by the sol-gel method, is a very active and selective catalyst towards N₂ formation in the whole 100–400 °C range. This catalyst appears to be the most active, selective and stable one ever reported in the literature for the NO/H₂/O₂ reaction, even in the presence of 5%v H₂O or 20 ppmv of SO₂ in the feed stream.Selected article from the Regional Symposium on Chemistry and Environment, Krusevac, Serbia, June 2003, organised by Dr. Branimir Jovancicevic.     

Efficient use of Fe metal as an electron transfer agent in a heterogeneous Fenton system based on Fe0/Fe3O4 composites

In this work a novel heterogeneous Fenton system based on Fe(0)/Fe3O4 composites is described. The composites with several Fe(0)/Fe3O4 ratios were prepared by two different methods, i.e. mechanical alloying of Fe(0) and Fe3O4 powders and controlled reduction of Fe3O4 with H2. Reaction studies and detailed Conversion Electron M?ssbauer surface characterization of the composites Fe(0)/Fe3O4, Fe(0), Fe3O4, alpha-Fe2O3 and gamma-Fe2O3 suggested that Fe2+surf species are essential to produce an active Fenton system. Kinetic studies for the oxidation of the dye methylene blue, used as an organic model molecule, and for the peroxide decomposition suggest that the reactions proceed via HO* radicals generated from Fe2+surf species and H2O2 in a Fenton like mechanism. The increase in activity caused by the addition of Fe(0) is discussed in terms of a creation of Fe2+surf species during the preparation of the composite and by an electron transfer mechanism from Fe(0) to Fe3+surf during the Fenton reaction to regenerate the Fe2+surf active species.     

Methylmercury and total mercury in estuarine organisms from Rio de Janeiro, Brazil

Guanabara Bay (GB), located in the Rio de Janeiro State, is still a productive estuary on the south-eastern Brazilian coast. It is an ecosystem heavily impacted by organic matter, oil and a number of other toxic compounds, including Hg. The present study aimed to comparatively evaluate the aquatic total mercury (THg) and MeHg contamination, and the ratios of MeHg to THg (% MeHg), in 3 species of marine organisms, Micropogonias furnieri-carnivorous fish (N = 81), Mugil spp.--detritivorous fish (N = 20) and Perna perna--filter-feeding bivalves (N = 190), which are widely consumed by the population. A total of 291 specimens were collected at the bay in different periods between 1988 and 1998. THg concentrations were determined by cold vapour AAS with stannous chloride as a reducing agent. MeHg was extracted by dithizone-benzene and measured by GC-ECD. Analytical quality was checked through certified standards. All organisms presented both low THg and MeHg concentrations and they were below the maximum limit of 1,000 micrograms Hg.kg-1 wet wt. as established for human intake of predatory fish by the new Brazilian legislation. Carnivorous fish showed higher THg and MeHg concentrations, and also % MeHg in muscle tissues, than organisms with other feeding habits and lower trophic levels. The average of THg concentrations in carnivorous fish was 108.9 +/- 58.6 micrograms.kg-1 wet wt. (N = 61) in 1990 and 199.5 +/- 116.2 micrograms.kg-1 wet wt. (N = 20) in 1998, but they presented different total length and body weights. The average THg content in detritivorous fish was 15.4 +/- 5.8 micrograms.kg-1 wet wt., whereas THg concentrations ranged from 4.1 to 53.5 micrograms.kg-1 wet wt. for the molluscs. The THg and MeHg contents of mussel varied according to the sampling point and water quality. MeHg concentration in detritivorous fish was similar to MeHg concentration in molluscs, but there was a significant difference in the MeHg/THg ratio: the carnivorous fish presented higher MeHg percentages (98%) than the detritivorous fish (54%) and the molluscs (33%). Weight-normalised average concentration of THg in carnivorous fish collected in 1990 (0.18 +/- 0.08 microgram.g-1/0.7 kg wet wt.) and in 1998 (0.16 +/- 0.09 microgram.g-1/0.7 kg wet wt.) presented no significant difference (t = 1.34; P < 0.5). In conclusion, the low THg and MeHg concentrations in the organisms from the GB ecosystem, are related to its eutrophic conditions and elevated amounts of suspended matter. In this situation, Hg could be strongly complexed or adsorbed by the particulate, which would dilute the Hg inputs and reduce its residence time in the water column, with a consequent decrease in its availability to organisms.     

Evaluation of soil temperature effect on herbicide leaching potential into groundwater in the Brazilian Cerrado

The effect of annual variations in the daily average soil temperatures, at different depths, on the calculation of pesticide leaching potential indices is presented. This index can be applied to assess the risk of groundwater contamination by a pesticide. It considers the effects of water table depth, daily recharge net rate, pesticide sorption coefficient, and degradation rate of the pesticide in the soil. The leaching potential index is frequently used as a screening indicator in pesticide groundwater contamination studies, and the temperature effect involved in its calculation is usually not considered. It is well known that soil temperature affects pesticide degradation rates, air-water partition coefficient, and water-soil partition coefficient. These three parameters are components of the attenuation and retardation factors, as well as the leaching potential index, and contribute to determine pesticide behavior in the environment. The Arrhenius, van't Hoff, and Clausius-Clapeyron equations were used in this work to estimate the soil temperature effect on pesticide degradation rate, air-water partition coefficient, and water-soil partition coefficient, respectively. The relationship between leaching potential index and soil temperature at different depths is presented and aids in the understanding of how potential pesticide groundwater contamination varies on different climatic conditions. Numerical results will be presented for 31 herbicides known to be used in corn and soybean crops grown on the municipality of S?o Gabriel do Oeste, Mato Grosso do Sul State, Brazil.     

Aqueous solubility, Henry's law constants and air/water partition coefficients of n-octane and two halogenated octanes

New data on the aqueous solubility of n-octane, 1-chlorooctane and 1-bromooctane are reported between 1 degree C and 45 degrees C. Henry's law constants, K(H), and air/water partition coefficients, K(AW), were calculated by associating the measured solubility values to vapor pressures taken from literature. The mole fraction aqueous solubility varies between (1.13-1.60)x10(-7) for n-octane with a minimum at approximately 23 degrees C, (3.99-5.07)x10(-7) for 1-chlorooctane increasing monotonically with temperature and (1.60-3.44)x10(-7) for 1-bromooctane with a minimum near 18 degrees C. The calculated air-water partition coefficients increase with temperature and are two orders of magnitude lower for the halogenated derivatives compared to octane. The precision of the results, taken as the average absolute deviations of the aqueous solubility, the Henry's law constants, or the air/water partition coefficients, from appropriate smoothing equations as a function of temperature is of 3% for n-octane and of 2% and 4% for 1-chlorooctane and 1-bromooctane, respectively. A new apparatus based on the dynamic saturation column method was used for the solubility measurements. Test measurements with n-octane indicated the capability of measuring solubilities between 10(-6) and 10(-10) in mole fraction, with an estimated accuracy better than +/-10%. A thorough thermodynamic analysis of converting measured data to air/water partition coefficients is presented.     

Vertical growth in a coastal city: an analysis of Boa Viagem (Recife,Brazil)

Coastal zones around the world have experienced urban growth in the last 50 years. This landscape change brings new aspects for those zones and the environment. Real estate speculation is a decisive factor that changes landscape, with urban growth that occurs both in the extent and volume of construction. Boa Viagem (BV) beach at Recife, Northeast Brazil was just a sand bar covered by an Atlantic Forest until middle of the 1800s. Today, it has turned into a busy area of the city where residences, services and commerce co-exist in a densely packed arrangement. This work demonstrates and analyses vertical growth in BV and urban changes from 1961 to 2011. It was developed using digital image processing and visual analysis of satellite imagery and aerial photos. A GIS was created using SPRING and ArcScene, to calculate variations in area and volume creating a Volumetric Index (VI). The Minimal Mapping Area was used in sixteen census tract as samples of the area. Occupation and vertical growth were especially accentuated from 1981 to 1996 with the peak at 2011. Increases in vertical growth from shore to inland are evident in all parts of the district. This finding was confirmed by three-dimensional GIS representations of the study area and the VI during the period of this work, showing the potential of 3D GIS models for studying dense urbanization areas in coastal zones.     

Variable within-brood maternal provisioning in newly extruded embryos of Homarus gammarus

Offspring quality of decapod crustaceans has been widely studied, with special emphasis on the sources of variability determining embryonic and larval quality. Nevertheless, maternal provisioning has commonly been overlooked as a potential source of offspring within-brood variability. In the present study, the existence of variable maternal provisioning was assessed through the analysis of the fatty acid (FA) profile of newly extruded embryos from different regions of the brooding chamber of Homarus gammarus. Significant differences in the FA profile of embryos sampled from different pleopods and sides of the brooding chamber were recorded. Significant deviations of the overall mean of each surveyed female were also observed for essential FA, particularly 20:4n-6, 20:5n-3 and 22:6n-3. Lipid energy available to fuel embryogenesis also varied among embryos sampled from different regions of the brooding chamber. Results suggest variable female investment at oocyte production, which may be amplified during the incubation period of developing embryos by differential lipid catabolism. For the first time, maternal provisioning is evidenced as an additional source for within-brood variability in the FA profile of embryos.     

Comparative study of humic acids of the mound of a wood-feeding termite and of the litter directly below in the Amazon river delta

In order to determine the role of termites in the recycling of organic matter and in humification processes, organic matter from the mound of a wood-feeding termite (Nasutitermes sp.) and from the litter directly below has been studied in secondary forest on the campus of Belem University, in Brazil. The carbon content was slightly lower in the litter (just beneath the mound) than in the mound, but nitrogen was much more abundant in the mound. As a consequence, the C/N ratio of fragmented litter total organic matter is very high, which shows that the humification process is not complete. Therefore, plant debris seemed to be more degraded in the mound than in the litter, indicating a humification gradient from mound to litter. Humic acid extracted from the mound and from the litter was compared by using elemental, E4/E6 ratio, spectroscopic (FTIR) analyses, and Sephadex gel chromatography. First, humic acids were more abundant in the mound than in the litter, showing that humification processes were more advanced in the mound than in the litter. Gel-permeation chromatography showed that the humic acids of the mound contained more low-molecular-weight fractions than those of the litter. In addition, the results of infrared spectra, E4/E6 ratio and elemental composition can confirm the fulvic character of mound material and the humic character of litter material. Therefore, the plant debris seems to follow two different humification pathways in the two environments, as long as the mound is alive.