Comparison of different probe molecules for the quantification of hydroxyl radicals in aqueous solution

We show that the transformation of benzene into phenol is a more selective probe for the hydroxyl radical than the transformation of nitrobenzene or the generation of 4-hydroxybenzoic acid from benzoic acid. The benzene to phenol system showed adequate performance as a probe upon irradiation of lake water samples and humic acids. We show that the use of nitrobenzene and benzoic acid as hydroxyl probes should be avoided because of poor selectivity. Moreover, all the tested probe molecules underwent important interference by irradiated antraquinone-2-sulphonate, and considerably overestimated the formation of the hydroxyl radicals.     

Adsorption and desorption variability of four herbicides used in paddy rice production

This investigation was performed to determine the effect of physicochemical soil properties on penoxsulam, molinate, bentazon, and MCPA adsorption–desorption processes. Four soils from Melozal (35° 43′ S; 71° 41′ W), Parral (36° 08′ S; 71° 52′ W), San Carlos (36° 24′ S; 71° 57′ W), and Panimavida (35° 44′ S; 71° 24′ W) were utilized. Herbicide adsorption reached equilibrium after 4 h in all soils. The Freundlich L-type isotherm described the adsorption process, which showed a high affinity between herbicides and sorption sites mainly because of hydrophobic and H-bonds interaction. Penoxsulam showed the highest adsorption coefficients (4.23 ± 0.72 to 10.69 ± 1.58 mL g^?1) and were related to soil pH. Molinate showed K_d values between 1.72 ± 0.01 and 2.3 ± 0.01 mL g^?1and were related to soil pH and organic matter, specifically to the amount of humic substances. Bentazon had a high relationship with pH and humic substances and its K_d values were the lowest, ranging from 0.11 ± 0.01 to 0.42 ± 0.01 mL g^?1. MCPA K_d ranged from 0.14 ± 0.02 to 2.72 ± 0.01 mL g^?1, however its adsorption was related to humic acids and clay content. According to these results, the soil factors that could explain the sorption process of the studied herbicides under paddy rice soil conditions, were principally humic substances and soil pH. Considering the sorption variability observed in this study and the potential risk for groundwater contamination, it is necessary to develop weed rice management strategies that limit use of herbicides that exhibit low soil adsorption in areas with predisposing conditions to soil leaching.     

Psychological consequences of prenatal diagnosis in a case of familial Angelman Syndrome

Angelman Syndrome (AS), characterized by mental retardation, absence of speech, seizures and motor dysfunction, is caused by genetic defects leading to loss of expression of the maternal copy of the chromosome 15q11–13 imprinted region. Most cases are sporadic, being caused by de novo deletion of maternal chromosome 15q11–13 (75%) or by paternal uniparental disomy (3–4%). Familial cases can occur, due to mutations in the UBE3A gene or in the imprinting center. We describe the case of a pregnant woman having two nephews with AS caused by a UBE3A mutation; lack of communication within the family led the woman to be completely unaware of the risk of disease recurrence until 15 weeks of gestation. UBE3A genetic testing revealed she carried the familial mutation 892–893delCT. Prenatal diagnosis was performed on amniotic fluid and demonstrated that the fetus had inherited the mutation. The unexpected diagnosis and the subsequent termination of the pregnancy caused the woman to undergo acute psychological distress showing relevant psychopathological symptoms. Nevertheless, at 2-year follow-up, adverse consequences were minimized, and the couple was planning a new pregnancy. Factors affecting the psychological outcome of abortion and the role of psychological support in reducing the risk of long-term unfavorable consequences are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Ecological bases of philopatry and cooperation in Ethiopian wolves

Ecological reasons for philopatry and cooperation are frequently invoked when kin selection is an insufficient explanation. The Ethiopian wolf (Canis simensis) is a specialised rodent hunter that forms family groups with cooperative breeding but also lives as monogamous pairs in suboptimal areas. Given the apparent absence of fitness gains to helpers from cooperative breeding, we set out to explore the benefits accrued by communal territorial defence measured as the acquisition and retention of habitats with more and most preferred rodent prey. Pairs defended relatively large territories to encompass critical amounts of key habitats within a matrix poor in rodents. Groups in optimal areas had relatively small territories and were expansionist, such that wolves in larger packs benefited per capita from increased good-quality foraging habitat. The fitness benefits of philopatry became evident after a rabies epizootic, when philopatry and expansionism prevailed in under-saturated conditions, until large groups split or provided dispersers that established locally. This study shows that high concentrations of prey can shift the balance of costs and benefits towards group living and cooperation in long-lived territorial carnivores, in so far as this dictates immediate rewards accrued from a given increment in territory size, namely greater foraging area per animal, leading to group enlargement and eventual inheritance of breeding space.     

Sorption, degradation, and leaching of tebuthiuron and diuron in soil columns

A study in small outdoor lysimeters was carried out to determine the leaching of the herbicides tebuthiuron and diuron in different soil types, using undisturbed soil columns. Soil sorption and degradation for both herbicides were also studied in the laboratory. The multi-layered AF (Attenuation Factor) model was evaluated for predicting the herbicides leaching in undisturbed soil columns. Tebuthiuron leached in greater amounts than diuron in both soils. Sorption was well represented by linear and Freundlich equations, however parameters from the linear equations were used in the AF model. In general, both herbicides presented very low sorption, with diuron presenting lower values of sorption coefficient than tebuthiuron in the two soils. Chromatographic data indicated rapid late degradation of diuron and tebuthiuron in both soil types at two different depths. Simple exponential equation was not able to represent degradation, thus a bi-exponential equation was used, and some model adjusting was needed. Average measured amounts of each herbicide were compared with amounts predicted by the multi-layered-soil AF model. The AF model was able to predict leaching amounts in the sandy soil, especially for diuron, however it did not perform well in the clayey soil.     

Chemical degradation of chlorophenols with Fenton's reagent (Fe + H2O2)

Aqueous solutions of Fenton's reagent (Fe²⁺ + H₂O₂) have been used to effect the total decomposition of the chlorophenols: 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 3,4-dichlorophenol and 2,4,5-trichlorophenol. The mineralization of these chlorinated aromatic substrates to CO₂ and free Cl⁻ has been studied as a function of [Fe²⁺] and [HClO₄]. Increasing the concentration of Fe²⁺ enhances the decomposition process, while an increase in the concentration of HClO₄, inhibits the reaction. The presence of Fe³⁺ alone (without any Fe²⁺) with H₂O₂ has no effect on the degradation of the chlorophenols. In all cases, the stoichiometric quantity of free Cl⁻ was obtained at the completion of the decomposition reaction; but the rates of disappaearance of the chlorophenol and of the formation of the Cl⁻ are not similar. This suggests that some chlorinated aliphatic species may be formed as possible intemediates.     

Applying value analysis and fuzzy logic to select areas for installing waste fills

This article discusses a methodology for assessing and rankinga predefined universe of objects to assist in the selectionof suitable areas for the construction of sanitary landfills.The methodology is, in principle, for universal application. Its development was initially based on the `Value Analysis' methodology and then on the `Fuzzy Eigenvector Method', or `Fuzzy Logic' as it is sometimes referred to. The focus of thestudy herein is on the comparative appraisal of a group ofelements which are part of the guidelines to be adopted whendetermining the choice of the most suitable site for a sanitarylandfill. This set of guidelines includes technical, economical,environmental, social and political aspects. As an example of themethodology proposed, four different areas were chosen. They werestudied to determine which is the most appropriate site for thedevelopment of a new solid waste fill site. The results for thesefour areas, together with the functions chosen and functionweights, are presented here.     

Nitration and hydroxylation of benzene in the presence of nitrite/nitrous acid in aqueous solution

This paper studies the nitration and hydroxylation of benzene in the presence of nitrite/nitrous acid in aqueous solution, both in the dark upon addition of hydrogen peroxide and under 360 nm irradiation. In both cases the detected transformation intermediates were phenol (P), nitrobenzene (NB), 2-nitrophenol (2NP) and 4-nitrophenol (4NP). P and NB directly form from benzene, and the initial formation rate of P is at least an order of magnitude higher than that of NB. In our experiments nitrophenols arise from P nitration, as can be inferred by their time evolution and isomer ratio (2NP:4NP=60:40, 3NP below detection limit). Nitrophenols may also form upon hydroxylation of NB, but in a different ratio (2NP:3NP:4NP=45:30:25). The detection of 3NP is thus a marker for the hydroxylation of NB, since this isomer is not formed in P nitration processes. The formation rates of P and NB increase with decreasing pH, both in the presence of HNO₂ + H₂O₂ in the dark (which produce HOONO) and in the presence of NO₂⁻/HNO₂ under irradiation. In the former case the pH dependence reflects the formation rate of HOONO. In the case of the irradiation experiments the pH effect can be accounted for by the higher molar absorbivity and photolysis quantum yield of nitrous acid when compared with nitrite. Interestingly, benzene does not react with HNO₂ alone in the dark. An important feature of benzene nitration in the presence of NO₂⁻/HNO₂ under irradiation is that the process is not inhibited by the addition of hydroxyl scavengers, differently from the case of phenol nitration. This finding indicates that nitrite irradiation might lead to the nitration of certain aromatic compounds in natural waters even in the presence of natural hydroxyl scavenging agents, which are usually thought to limit the environmental role of many photochemical processes.     

Ground-level ozone mapping in large urban areas using multivariate statistical analysis: application to the São Paulo Metropolitan Area

A statistical study on the behavior of ground-level O3 concentration in different regions of a large urban area was carried out, with emphasis on pollutant gas concentrations and meteorological variables. The study was based on data generated by a network of measuring stations distributed throughout the S?o Paulo Metropolitan Area, in regions with different characteristics of traffic and economic activities. The combined application of principal component analysis and clustering techniques to data collected from 1997 until 2000 has led to the identification of implicit relationships between variables that have been associated with dominant processes related to O3 formation in different locations. Similarities between different regions of the city have also been detected and associated with local characteristics. The results indicate that the application of such statistical techniques to data collected in large urban areas enables the grouping of different regions according to their behavior in terms of O3 levels, as well as the identification of dominant processes in each group. These techniques are thus important in the planning of air pollution policies, especially in the case of O3, a pollutant that is not directly related to pollution levels alone.