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171.
The Barigui River watershed is located in the metropolitan region of Curitiba, southern Brazil, passing through several neighboring counties. In recent years, due to growth and disorderly occupation along the river, in addition to lack of sanitation, the Basin suffered a very large inflow of untreated domestic sewage. Current programs to monitor the watershed use traditional physical-chemical parameters and generally the analysis is performed only with water samples. This study analyzes the presence of fecal sterols in sediment samples. Sediment samples were collected from six points along the river and the stanols were extracted, purified and analyzed by GC-MS. Eight compounds were analyzed, among sterols and ketones. The presence of coprostanol was also identified. Coprostanol is a stanol containing a large amount in human feces. It is found near sources of pollution and can be associated with contamination by domestic sewage. The results showed high concentrations of coprostanol, ranging from 0.25 to 196 mug g( - 1). The ratio of coprostanol and epicoprostanol, was below 0.20 at most stations, indicating that the sewage discharged into the river does not undergo prior treatment. Contamination by untreated sewage was also confirmed by ratios of isomeric forms of sterols and ketones 5beta/(5beta + 5alpha). 相似文献
172.
Soil sorption processes largely control the environmental fate of herbicides. Therefore, accuracy of sorption parameters is crucial for accurate prediction of herbicide mobility in agricultural soils. A combined experimental and statistical study was performed to investigate the small-scale spatial variability of sorption parameters for atrazine and dinoseb in soils and to establish the number of samples needed to provide a value of the distribution coefficient (K(d)) next to the mean, with a given precision. The study explored sorption properties of the two herbicides in subsurface samples collected from four pits distributed along a transect of an alluvial soil; two to four samples were taken at about 30 cm apart at each sampling location. When considering all the data, the distribution coefficients were found to be normally and log-normally distributed for atrazine and dinoseb, respectively; the CVs were relatively high (close to 50% for dinoseb and 40% for atrazine). When analyzed horizon by horizon, the data revealed distribution coefficients normally distributed for both herbicides, whatever the soil layer, with lower CVs. The K(d) values were shown to vary considerably between samples collected at very short distance (a few centimeters), suggesting that taking a single soil sample to determine sorption properties through batch experiments can lead to highly unrepresentative results and to poor sorption/mobility predictions. 相似文献
173.
Reactivity of the plant growth regulator paclobutrazol (cultar) with two tropical soils of the northeast semiarid region of Brazil 总被引:1,自引:0,他引:1
Milfont ML Martins JM Antonino AC Gouveia ER Netto AM Guiné V Mas H dos Santos Freire MB 《Journal of environmental quality》2008,37(1):90-97
The reactivity of paclobutrazol (PBZ, a plant growth retardant) with a Yellow Ultisol and a Vertisol from the semiarid northeast region of Brazil was evaluated through batch sorption experiments and modeling. Although not instantaneous, the sorption kinetic of PBZ (pure and formulated) was fast (a few hours) in both soils. The sorption kinetics were well described by a second-order (dS(t)/dt=k(2)(S(e2)-S(t))(2)) but not by a first-order model. The sorption isotherms were found to be linear and the calculated K(D) values were 8.8 +/- 0.11 and 7.4 +/- 0.2 L kg(-1) for pure PBZ in the Ultisol and the Vertisol, respectively. The corresponding K(OC) values were 1275 +/- 34 (logK(OC) = 3.11) and 1156 +/- 49 (logK(OC) = 3.06) L kg(-1), respectively. Considering the very different texture of the two soils and the similar K(OC) values determined, these results showed that in both soils, the sorption of PBZ is dominantly controlled by organic matter, although some interactions of PBZ with iron oxides (goethite) were observed in the Ultisol. Based on these sorption parameters a low leachability potential of PBZ in soils is anticipated, as they correspond to a groundwater ubiquity score (GUS) ranging from 2.0 to 2.7, i.e., moderately to not mobile, in contradiction with the actual groundwater situation in Brazil. This work stresses the need to evaluate and predict the risk associated with aquifer contamination by this widely used plant growth regulator. 相似文献
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175.
Pires JC Gonçalves B Azevedo FG Carneiro AP Rego N Assembleia AJ Lima JF Silva PA Alves C Martins FG 《Environmental science and pollution research international》2012,19(8):3228-3234
Introduction
This study proposes three methodologies to define artificial neural network models through genetic algorithms (GAs) to predict the next-day hourly average surface ozone (O3) concentrations. GAs were applied to define the activation function in hidden layer and the number of hidden neurons.Methods
Two of the methodologies define threshold models, which assume that the behaviour of the dependent variable (O3 concentrations) changes when it enters in a different regime (two and four regimes were considered in this study). The change from one regime to another depends on a specific value (threshold value) of an explanatory variable (threshold variable), which is also defined by GAs. The predictor variables were the hourly average concentrations of carbon monoxide (CO), nitrogen oxide, nitrogen dioxide (NO2), and O3 (recorded in the previous day at an urban site with traffic influence) and also meteorological data (hourly averages of temperature, solar radiation, relative humidity and wind speed). The study was performed for the period from May to August 2004.Results and discussion
Several models were achieved and only the best model of each methodology was analysed. In threshold models, the variables selected by GAs to define the O3 regimes were temperature, CO and NO2 concentrations, due to their importance in O3 chemistry in an urban atmosphere.Conclusion
In the prediction of O3 concentrations, the threshold model that considers two regimes was the one that fitted the data most efficiently. 相似文献176.
Costa Maria Angélica Martins da Silva Bruno Menezes de Almeida Sâmilla Gabriella Coelho Felizardo Marcos Paulo Costa Ana Flávia Martins Cardoso Arnaldo Alves Dussán Kelly Johana 《Environmental science and pollution research international》2023,30(4):8835-8852
Environmental Science and Pollution Research - Energy demand has increased worldwide, and biomass burning is one of the solutions most used by industries, especially in countries that have a great... 相似文献
177.
de Oliveira Maria Rayane Correia de Lima Silva Maria Gabriely Alcântara Isabel Sousa Filho Jaime Ribeiro Tintino Cícera Datiane de Morais Oliveira Magalhães Francisco Ernani Alves Martins Anita Oliveira Brito Pereira Bezerra Pessoa Renata Torres Duarte Antonia Eliene da Costa José Galberto Martins de Lima Sidney Gonçalo Coutinho Henrique Douglas Melo Capasso Raffaele de Menezes Irwin Rose Alencar 《Environment, Development and Sustainability》2021,23(10):14958-14981
Environment, Development and Sustainability - This work aimed to analyze the chemical composition and evaluate the anti-inflammatory and antinociceptive properties of the essential oil obtained... 相似文献
178.
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180.
Adriane Martins de Freitas Carla Sirtori Patricio Peralta-Zamora 《Environmental Chemistry Letters》2011,9(1):97-102
The degradation of camphor using titanium/ruthenium dioxide (TiO2/RuO2; 70:30) electrodes was investigated in a photoelectrochemical thin-film reactor under near UV light irradiation. Two different
electrolytes (Na2SO4 and NaCl) were used in this work. Camphor degradation was monitored by solvent extraction methods and gas chromatography
(GC) analysis. Comparative studies between photoelectrochemical, electrochemical, photolytic, and heterogeneous photocatalytical
process were carried out. When NaCl was used, the degradation efficiency of camphor was improved, probably on account of electrochemical
generation of active chlorine species and their photochemical conversion to chlorine radicals. Under these conditions camphor
was completely mineralized at reaction times of 30 min. 相似文献