Distribution of Heavy Metals in Surface Sediments from an Antarctic Marine Ecosystem

The concentrations of lead, cadmium, copper,chromium, iron, manganese and zinc in surfacesediments collected from Potter Cove, in the 25de Mayo Island (King George Island), Antarctica, andits drainage basin, were measured by atomic absorptionspectroscopy. The obtained results were use todetermine the areal and vertical distribution of themetals of in the Cove and potential sources of thesemetals to this environment. The geochemical datasuggest that most of the metals found in Potter Coveconstitute a redistribution of autochthonous materialswithin the ecosystem. Therefore, the metalconcentrations can be considered to be present atnatural background levels in surface sediments.     

Copper and lead ion removal from wastewater using fava d’anta fodder (Dimorphandra gardneriana Tulasne)

Environmental Geochemistry and Health - The contamination of bodies of water by potentially hazardous elements has in recent decades become an environmental problem that poses serious risks to...     

Performance and stability of an anaerobic fixed bed reactor subjected to progressive increasing concentrations of influent organic matter and organic shock loads

Data on the performance of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor subjected to step increases of organic loading rates (OLR) and to organic shock loads (OSL) are presented and discussed. The tubular reactor (100 cm long and 5 cm diameter) with a useful volume of 1995 mL was filled with polyurethane foam cubic matrices holding immobilized biomass and fed with synthetic wastewater. The reactor was operated at the controlled temperature of 30+/-1 degrees C and hydraulic retention time of 7 h. After about 15 days, the HAIB reactor attained operating stability. Thereafter, it was subjected to step increases of the applied OLR that ranged from 6.8 to 18.8 kg COD/m(3)d. After steady state had been achieved at each step, OSL corresponding to approximately three times the operating OLR were applied for 7 h. No disturbance was observed due to the step increase in OLR. An increase in effluent chemical oxygen demand (COD) and volatile fatty acids (VFA) concentrations and a decrease in the percentage of methane in the biogas were observed due to OSL applications. However, stability of the monitoring parameters was always restored approximately 17 h after the application of OSL for all conditions tested.     

Speciation and quantification of mercury in Oxisol, Ultisol, and Spodosol from Amazon (Manaus, Brazil)

In order to investigate the content and distribution of Hg in soils from Amazon areas not impacted by gold mining activities, the concentration and granulometric distribution of Hg were determined in three different types of soils. Hg speciation data were obtained by a thermodesorption atomic spectrometry system and the role of physico-chemical and mineralogical characteristics on Hg content were also studied. Hg concentrations found in the soil fraction <2000 microm were similar to values found in other Amazon areas without anthropogenic sources. The fine fraction (<53 microm) of podzolized soils had a higher Hg content than clayey soils. Multivariate analysis shows that there are marking differences between Spodosols of two distinct areas (fine fraction Hg contents up to 10-fold as high) indicating the importance of pedogenic processes. All statistical data analysis indicated that organic matter plays an important role in Hg accumulation in the types of soils studied. Thermodesorption analysis revealed the presence of only Hg2+, and the predominance of organically bound Hg in the majority of the studied samples.     

Magnetic properties of the microorganism Candidatus Magnetoglobus multicellularis

Magnetotactic microorganisms use the interaction of internal biomineralized nanoparticles with the geomagnetic field to orientate. The movement of the magnetotactic multicellular prokaryote Candidatus Magnetoglobus multicellularis under an applied magnetic field was observed. A method using digital image processing techniques was used to track the organism trajectory to simultaneously obtain its body radius, velocity, U-turn diameter, and the reorientation time. The magnetic moment was calculated using a self-consistent method. The distribution of magnetic moments and radii present two well-characterized peaks at (9 ± 2) × 10⁻¹⁵ and (20 ± 3) × 10⁻¹⁵ A m² and (3.6 ± 0.1) and (4.3 ± 0.1) μm, respectively. For the first time, simultaneous determination of the distribution of the organism radii and magnetic moment was obtained from the U-turn method by a new digital imaging processing. The bimodal distributions support an organism reproduction process model based on electron microscopy observations. These results corroborate the prokaryote multicellular hypothesis for Candidatus M. multicellularis.     

Evaluation of hexavalent chromium removal in a continuous biological filter with the use of central composite design (CCD)

Hexavalent chromium is frequently found in industrial effluents as a result of the industrial applications of this compound and its anti-corrosive features. However, hexavalent chromium is extremely toxic, and its discharge in water is regulated, with a maximum limit of 0.1 mg/L in accordance with legislation established by CONAMA-Brazil (no. 397, April 3, 2008). To achieve lower discharge values, it is necessary to reduce from Cr(VI) to Cr(III), which is less toxic, and an economic alternative involves biological removal of this compound. Residence time distributions (RTDs) were measured to evaluate the behavior of actual biofilter operation conditions in a biofilter flow. The medium residence time distributions used were 8 and 24 h (recommended by the legislation). To optimize this process, a central composite design was used, considering the initial chromium concentration and pH as the independent variables and the removal of hexavalent chromium as the response. The boundary curves and surface response showed optimal behavior at 3.94 mg/L [Cr(0)] and a pH of 6.2. The removal process of hexavalent chromium is mathematically described by the Michaelis-Menten kinetic model. This model appropriately represents the variation of chromium concentration along the bioreactor.     

An abiotic typology and reference conditions for nutrients and chlorophyll-a in subtropical reservoirs (São Paulo State,Brazil)

Environmental Science and Pollution Research - The establishment of reference conditions and typology are two important steps in water resources management. The reference conditions enable the...