Adsorption behavior of alpha -cypermethrin on cork and activated carbon

Studies were undertaken to determine the adsorption behavior of alpha -cypermethrin [R)-alpha -cyano-3-phenoxybenzyl(1S)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate, and (S)-alpha-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] in solutions on granules of cork and activated carbon (GAC). The adsorption studies were carried out using a batch equilibrium technique. A gas chromatograph with an electron capture detector (GC-ECD) was used to analyze alpha -cypermethrin after solid phase extraction with C18 disks. Physical properties including real density, pore volume, surface area and pore diameter of cork were evaluated by mercury porosimetry. Characterization of cork particles showed variations thereby indicating the highly heterogeneous structure of the material. The average surface area of cork particles was lower than that of GAC. Kinetics adsorption studies allowed the determination of the equilibrium time - 24 hours for both cork (1-2 mm and 3-4 mm) and GAC. For the studied alpha -cypermethrin concentration range, GAC revealed to be a better sorbent. However, adsorption parameters for equilibrium concentrations, obtained through the Langmuir and Freundlich models, showed that granulated cork 1-2 mm have the maximum amount of adsorbed alpha-cypermethrin (q(m)) (303 microg/g); followed by GAC (186 microg/g) and cork 3-4 mm (136 microg/g). The standard deviation (SD) values, demonstrate that Freundlich model better describes the alpha -cypermethrin adsorption phenomena on GAC, while alpha -cypermethrin adsorption on cork (1-2 mm and 3-4 mm) is better described by the Langmuir. In view of the adsorption results obtained in this study it appears that granulated cork may be a better and a cheaper alternative to GAC for removing alpha -cypermethrin from water.     

Mercury and selenium in blue shark (Prionace glauca, L. 1758) and swordfish (Xiphias gladius, L. 1758) from two areas of the Atlantic Ocean

Muscle, liver and stomach contents of 64 blue sharks and 52 swordfishes, caught between September 2004 and February 2005 near the Azores (area A) and the Equator (area E), were analysed for mercury and selenium. Levels of mercury were relatively high (blue shark: 0.032-2.5microgg(-1); swordfish: 0.031-9.8microgg(-1)) and comparable to values reported in the literature. However, mercury and organic mercury concentrations in muscle and liver of specimens from E were significantly higher than those from A. A similar trend was registered in stomach contents, suggesting higher uptake of Hg in specimens from E. This difference was also observed in the relationship between concentration in muscle and size, indicating a higher accumulation rate in specimens from E. The accumulation of Se in the liver of both species showed a positive correlation with inorganic mercury concentrations, pointing to a detoxifying mechanism of organic mercury in these species through Se-Hg liasons.     

Study of biological stabilization processes of cattle and poultry manure by thermogravimetric analysis and (13)C NMR

The biological stabilization process of cattle and poultry manure was studied using thermogravimetric analysis and (13)C nuclear magnetic resonance. The stabilization processes carried out were composting, anaerobic digestion and a mixed process (partly aerobic, partly anaerobic). It was observed from the analyzed samples that the biological stabilization processes reduce the volatile content of the bio-wastes and increase the degree of aromaticity. The stabilization of cattle manure by means of aerobic processes was able to further oxidize and enriched in aromatic compounds the bio-waste when compared with the digestion process. On the other hand, the stabilization of poultry manure resulted in a greater aromatization under the digestion process. Stabilized samples with a high degree of aromaticity presented a lower volatile content accompanied by a reduction in the intensity of the differential thermogravimetry peak registered under an inert atmosphere, indicative of the thermal decomposition of the organic matter. The thermal decomposition of all the analyzed materials (fresh and stabilized samples) commenced at around 200 degrees C but for the digested poultry manure, which decomposition initiated close to 250 degrees C. All stabilized samples yielded a lower degree of volatilization to that one observed in fresh samples.     

Does seston size structure reflect fish-mediated effects on water quality in a degraded semiarid wetland?

This study evaluates whether the size structure of seston (the sum of living and nonliving particles in the water column) reflects the effects of fish on wetland water quality. Using enclosures, we measured water quality and zooplankton community structure in the presence and absence of two fish species with distinct foraging strategies [benthivorous carp (Cyprinus carpio) and planktivorous mosquitofish (Gambusia holbrooki)]. Seston collected from the enclosures was counted and sized automatically with a Coulter counter, and the size structure in the range of 1–60 μm was modelled using the underlying Pareto distribution of particles. Only Cyprinus contributed to a loss of water quality (increased nutrient levels, algal and non-algal turbidity, hypoxia), while both fish species changed zooplankton community composition compared to fishless controls. However, these changes were not reflected in parameters [goodness of fit (r ²) and parameter c (slopes)] of Pareto models. Multivariate statistics suggest that seston size structure responded more to environmental gradients related to water depth but the relationships were also weak. Our overall result contrasts with the regulation of size spectra constructed from living organisms. Although seston integrates many structural and functional features of the water column, the lack of strong relationships between Pareto model parameters and water quality suggests that a size-based approach to characterise seston structure has a limited potential for assessing biota-mediated effects in wetlands in a straightforward manner.     

Virological Characterization of Roof-Harvested Rainwater of Densely Urbanized Low-Income Region

Food and Environmental Virology - Roof-harvested rainwater (RHRW) is considered relatively clean water, even though the possible presence of pathogens in the water may pose human health risks. In...     

OPTIMAL LONG-TERM SCHEDULING OF STORMWATER DRAINAGE REHABILITATION1

ABSTRACT: A mathematical model is developed to optimally schedule long-term stormwater infrastructure rehabilitation activities. The model is capable of considering multiple rehabilitation projects and is driven by overall cost eensiderations. Rehabilitation activities are scheduled based on perceived reliabilities and future deterioration expected within the specified planning horizon. Future growth within the stormwater drainage basin is incorporated using chance constraints that limit the likelihood that a stormwater discharge exceeds system conveyance capacity. Model structure and development are discussed, and a hypothetical example using a drainage network is presented.     

Analysis of Products Generated from the Thermal and Catalytic Degradation of Pure and Waste Polyolefins using Py-GC/MS

The possibility of transforming waste plastics into valuable hydrocarbons via catalytic cracking and reforming is attracting increasing interest. Pyrolysis coupled with Gas Chromatographic separation and Mass Spectrometry detection (Py-GC/MS) has been used in this work to study the product selectivity of various catalysts in the conversion of pure and residual polyethylene samples into hydrocarbon products. Five acid solids of comparable aluminium contents but different textural and acid properties were tested as catalysts, including three zeolites (standard ZSM-5, nanocrystalline n-ZSM-5 and Beta) and two mesostructured solids (Al-MCM-41 and Al-SBA-15). Thermal cracking of the pure and residual polymers generated a similar range of products to each other, with a high proportion of linear paraffins and olefins of varying lengths. The presence of zeolitic materials resulted in complete elimination of heavy linear products, an increase in the light hydrocarbon fraction and a marked selectivity towards the formation of single-ring aromatic species, particularly benzene, toluene and xylene. Aromatic formation was particularly notable with the small crystal size n-ZSM-5 (aromatic selectivity up to 53.9%) and less marked in the case of standard ZSM-5 (up to 36.4%) and Beta zeolite (up to 35.0%). Mesostructured catalysts like Al-MCM-41 and Al-SBA-15 favoured the production of light C₂–C₅ hydrocarbons (up to 57.9%) while the formation of aromatic products was significantly lower than with zeolitic materials. The paper examines the extent and the causes for this product selectivity and discusses its connection with the acid and textural properties of each catalyst. It was also observed that, under the experimental conditions employed, the products generated were not significantly affected by the nature and origin of the polymers employed.