No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 157-176).

No description available.

The work presented investigates various aspects of glutathione-dependent electrophile metabolism in bacteria. First, we studied the response of <I>Staphyloccocus aureus</I> to the electrophile methylglyoxal. We found that under our experimental conditions, this organism is incapable of methylglyoxal metabolism by either glutatione-dependent or independent mechanisms. Glutatione was found to sensitise <I>S. aureus</I> to methylglyoxal. Furthermore, the sulphydryl group of glutathione is essential in this process. This implies that a glutathione conjugate may be involved in the increased sensitivity. Methylglyoxal does not activate K⁺ efflux from <I>S. aureus</I> cells, suggesting that the KefB K⁺ efflux system is absent from this organism. NEM activates a slow release of K⁺ indicating that the KefC system may be present. We investigated the response of <I>E. coli</I> and <I>Pseudomonas</I> sp. to the electrophilic herbicide alachlor. This compound activates a release of K⁺ from <I>E.coli</I> but not from any Pseudomona tested. K⁺ efflux is not mediated by KefB, KefC or the major mechanosensitive channels. In addition to the K⁺ efflux, alachlor stimulated an increase in the absorbance at 265 nm of media containing <I>E. coli</I>. It is not fully understood what this absorbance increase represents but it may reflect an increase in the solubility of alachlor over time. Despite its potential toxicity, alachlor did not affect the growth of either <I>E. coli</I> or <I>P. fragi</I>. However, when <I>E. coli</I> were treated with EDTA they became sensitive to alachlor. This result and data obtained using ¹⁴C-labelled alachlor indicated that alachlor does not normally enter <I>E. coli</I> cells. Finally, we investigated the response of <I>E. coli</I> expressing <I>dcm</I>A from <I>Methylophilus</I> sp. DM11 to DCM. Addition of DCM resulted in immediate cessation of growth, which was not due to formaldehyde accumulation. Cells washed free of DCM after a short incubation resume growth at the pre-addition rate, indicating DCM dehalogenation causes no permanent damage to the cell.

A cana-de-açúcar e uma das principais culturas agrícolas do pais, ocupando mais de oito milhões de hectares. Recentemente, o seu sistema de colheita passa pela substituição da queima para a não queima da palhada por ocasião da colheita, gerando de 8 a 20 Mg ha-1 de resíduos na superfície do solo. Alem disso, o aproveitamento de resíduos gerados no beneficiamento para produção do álcool ou açúcar e cada vez mais frequente. Estas medidas minimizam a erosão, levam a ciclagem de nutrientes e aumento nos teores de carbono orgânico do solo, reduzindo os custos de produção. Em decorrência destas praticas, alterações no comportamento ambiental de moléculas pesticidas são esperadas, pois se sabe que o seu potencial de sorção pode variar com o teor de carbono orgânico do solo, adição de resíduos e o tempo de residência no solo (\'aging\'). Alem disso, pode ocorrer interceptação dos herbicidas pelos resíduos aplicados ao solo reduzindo sua lixiviação. Por isso, os objetivos desta pesquisa foram: (i) avaliar o efeito da adição de três resíduos orgânicos (composto, palha e cinzas da palha da cana-de-açúcar) e do tempo de residência (\"envelhecimento\") no potencial de sorção dos herbicidas (14C) alachlor e diuron, e o efeito da adição destes resíduos na lixiviação do alachlor; (ii) determinar os coeficientes de sorção do alachlor e diuron (14C) em amostras de solos coletadas em regiões produtoras de cana-de-açúcar do estado de São Paulo, e verificar o efeito do sistema de colheita (com e sem queima) sobre estes coeficientes. Os resultados mostraram que (i): a adição de composto e palha não afetou enquanto que a adição de cinza aumentou significativamente o potencial de sorção dos herbicidas. O envelhecimento (28 dias) aumentou de 1,3 a 2,3 vezes os valores de Kd. A adição de palha e de cinza diminuiu a lixiviação do alachlor (< 1,0% do aplicado) em relação ao composto e o controle (~6% do aplicado). A palha reteve ~80% do alachlor aplicado. (ii): a sorção foi mais elevada para o herbicida diuron (Kd médio = 26,5 L kg-1) em relação ao alachlor (Kd médio = 2,3 L kg-1). De modo geral, os atributos do solo que melhor se correlacionaram com os valores de Kd foram os teores de carbono orgânico, argila e CTC. Os coeficientes de sorção do alachlor e diuron foram bem correlacionados com os teores de óxidos ferro livres e amorfos (r > 0,7), respectivamente. De forma geral, a manutenção da palha no solo promoveu incrementos nos valores de Kd, mas não alterou sua classificação quanto ao potencial de mobilidade. / Sugarcane is a major crop in Brazil covering more than eight million hectares. Recently, its harvesting system has been changing from burning to not-burning of straw at harvesting, generating 8-20 Mg ha-1 of residue on the soil surface. Furthermore, the use of waste generated in sugarcane processing for the production of alcohol or sugar is more and more frequent. These measures minimize soil erosion and favor nutrient cycling and increased levels of organic carbon in the soil, reducing production costs. As a result, changes in environmental behavior of pesticide molecules are expected, since their sorption potential can vary according to the organic carbon content in the soil, the addition of waste and the residence time in the soil (\"aging\"). Moreover, the residues on the soil can intercept herbicides reducing their leaching. Therefore, the objectives of this research were: (i) to evaluate the effect of three organic wastes (compost, straw and straw ashes of sugarcane) and residence time (\"aging\") on the sorption potential of herbicides (14C) alachlor and diuron, and the effect of these wastes on the leaching of alachlor; (ii) determine the sorption of alachlor and diuron (14C) in soil samples collected from sugarcane producing regions in Sao Paulo State, Brazil, and verify the effect of the harvesting system (with and without burning) on these coefficients. The results showed that: (i) the addition of the compost and straw did not affect herbicide sorption while the addition of ash significantly increased the sorption potential of herbicides. The aging (28 days) increased 1.3 to 2.3 times the Kd values. The addition of straw and ash decreased the leaching of alachlor (< 1.0% of applied dose) in relation to compost and control (~6% of applied dose). The straw retained ~80% of alachlor applied; (ii) the sorption was higher for the herbicide diuron (average Kd = 26.5 L kg-1) in relation to alachlor (average Kd = 2.3 L kg-1). In general, the soil characteristics that best correlated with Kd values were the contents of organic carbon, clay and CEC. The sorption coefficients of alachlor and diuron were well correlated with the concentration of free and amorphous iron oxides (r > 0.7), respectively. Overall, the maintenance of straw on the soil promoted increases in Kd values, but did not change its classification regarding its the potential of mobility.

A cana-de-açúcar e uma das principais culturas agrícolas do pais, ocupando mais de oito milhões de hectares. Recentemente, o seu sistema de colheita passa pela substituição da queima para a não queima da palhada por ocasião da colheita, gerando de 8 a 20 Mg ha-1 de resíduos na superfície do solo. Alem disso, o aproveitamento de resíduos gerados no beneficiamento para produção do álcool ou açúcar e cada vez mais frequente. Estas medidas minimizam a erosão, levam a ciclagem de nutrientes e aumento nos teores de carbono orgânico do solo, reduzindo os custos de produção. Em decorrência destas praticas, alterações no comportamento ambiental de moléculas pesticidas são esperadas, pois se sabe que o seu potencial de sorção pode variar com o teor de carbono orgânico do solo, adição de resíduos e o tempo de residência no solo (\'aging\'). Alem disso, pode ocorrer interceptação dos herbicidas pelos resíduos aplicados ao solo reduzindo sua lixiviação. Por isso, os objetivos desta pesquisa foram: (i) avaliar o efeito da adição de três resíduos orgânicos (composto, palha e cinzas da palha da cana-de-açúcar) e do tempo de residência (\"envelhecimento\") no potencial de sorção dos herbicidas (14C) alachlor e diuron, e o efeito da adição destes resíduos na lixiviação do alachlor; (ii) determinar os coeficientes de sorção do alachlor e diuron (14C) em amostras de solos coletadas em regiões produtoras de cana-de-açúcar do estado de São Paulo, e verificar o efeito do sistema de colheita (com e sem queima) sobre estes coeficientes. Os resultados mostraram que (i): a adição de composto e palha não afetou enquanto que a adição de cinza aumentou significativamente o potencial de sorção dos herbicidas. O envelhecimento (28 dias) aumentou de 1,3 a 2,3 vezes os valores de Kd. A adição de palha e de cinza diminuiu a lixiviação do alachlor (< 1,0% do aplicado) em relação ao composto e o controle (~6% do aplicado). A palha reteve ~80% do alachlor aplicado. (ii): a sorção foi mais elevada para o herbicida diuron (Kd médio = 26,5 L kg-1) em relação ao alachlor (Kd médio = 2,3 L kg-1). De modo geral, os atributos do solo que melhor se correlacionaram com os valores de Kd foram os teores de carbono orgânico, argila e CTC. Os coeficientes de sorção do alachlor e diuron foram bem correlacionados com os teores de óxidos ferro livres e amorfos (r > 0,7), respectivamente. De forma geral, a manutenção da palha no solo promoveu incrementos nos valores de Kd, mas não alterou sua classificação quanto ao potencial de mobilidade. / Sugarcane is a major crop in Brazil covering more than eight million hectares. Recently, its harvesting system has been changing from burning to not-burning of straw at harvesting, generating 8-20 Mg ha-1 of residue on the soil surface. Furthermore, the use of waste generated in sugarcane processing for the production of alcohol or sugar is more and more frequent. These measures minimize soil erosion and favor nutrient cycling and increased levels of organic carbon in the soil, reducing production costs. As a result, changes in environmental behavior of pesticide molecules are expected, since their sorption potential can vary according to the organic carbon content in the soil, the addition of waste and the residence time in the soil (\"aging\"). Moreover, the residues on the soil can intercept herbicides reducing their leaching. Therefore, the objectives of this research were: (i) to evaluate the effect of three organic wastes (compost, straw and straw ashes of sugarcane) and residence time (\"aging\") on the sorption potential of herbicides (14C) alachlor and diuron, and the effect of these wastes on the leaching of alachlor; (ii) determine the sorption of alachlor and diuron (14C) in soil samples collected from sugarcane producing regions in Sao Paulo State, Brazil, and verify the effect of the harvesting system (with and without burning) on these coefficients. The results showed that: (i) the addition of the compost and straw did not affect herbicide sorption while the addition of ash significantly increased the sorption potential of herbicides. The aging (28 days) increased 1.3 to 2.3 times the Kd values. The addition of straw and ash decreased the leaching of alachlor (< 1.0% of applied dose) in relation to compost and control (~6% of applied dose). The straw retained ~80% of alachlor applied; (ii) the sorption was higher for the herbicide diuron (average Kd = 26.5 L kg-1) in relation to alachlor (average Kd = 2.3 L kg-1). In general, the soil characteristics that best correlated with Kd values were the contents of organic carbon, clay and CEC. The sorption coefficients of alachlor and diuron were well correlated with the concentration of free and amorphous iron oxides (r > 0.7), respectively. Overall, the maintenance of straw on the soil promoted increases in Kd values, but did not change its classification regarding its the potential of mobility.

No description available.

A presen&ccedil;a de defensivos agr&iacute;colas no meio ambiente, mesmo que em baixas concentra&ccedil;&otilde;es (ng L-1/ &#956;g L-1), representa uma potencial fonte de perturba&ccedil;&atilde;o end&oacute;crina para os seres vivos. Neste cen&aacute;rio, destacam-se os herbicidas alaclor e atrazina, que s&atilde;o amplamente utilizados no combate a ervas daninhas. Entretanto, a Ag&ecirc;ncia de Prote&ccedil;&atilde;o Ambiental dos Estados Unidos (EPA) classifica como carcinog&ecirc;nicos, desreguladores end&oacute;crinos e seu limite, em &aacute;gua, n&atilde;o pode ultrapassar 2 e 3 &#956;g L-1, respectivamente. O objetivo deste trabalho foi estudar a degrada&ccedil;&atilde;o eletroqu&iacute;mica do alaclor e atrazina, utilizando uma c&eacute;lula do tipo filtro-prensa, e um &acirc;nodo dimensionalmente est&aacute;vel (ADE) de composi&ccedil;&atilde;o nominal Ti/Ru0,3Ti0,7O2, pH inicial fixo em 3 e a temperatura em 25 &ordm;C, uma vez que, os m&eacute;todos convencionais de tratamento n&atilde;o s&atilde;o totalmente eficientes na remo&ccedil;&atilde;o destes compostos org&acirc;nicos nos sistemas aquosos. Inicialmente realizou-se apenas a degrada&ccedil;&atilde;o eletroqu&iacute;mica do herbicida alaclor (100 mg L-1) via planejamento fatorial de ponto central do tipo 32, tendo como vari&aacute;veis, a concentra&ccedil;&atilde;o do eletr&oacute;lito suporte cloreto de s&oacute;dio (0,05, 01 e 0,15 g L-1) e a densidade de corrente (10, 30 e 50 mA cm-2), obtendo como melhor resposta, 93,45 % de remo&ccedil;&atilde;o e 71,6 % de mineraliza&ccedil;&atilde;o, ao usar CNaCl de 0,15 g L-1 e 50 mA cm-2. Por&eacute;m, a CNaCl de 0,15 g L-1 e densidade de 30 mA cm-2 foi escolhida como a melhor condi&ccedil;&atilde;o estudada, em virtude do seu menor valor de consumo energ&eacute;tico e por apresentar a taxa de remo&ccedil;&atilde;o (93,6%) e mineraliza&ccedil;&atilde;o (71,24%) pr&oacute;ximas ao uso da maior densidade de corrente. S&oacute; ent&atilde;o, na melhor condi&ccedil;&atilde;o, obtida previamente a partir dos experimentos de degrada&ccedil;&atilde;o do alaclor, que realizou-se a oxida&ccedil;&atilde;o de 100 mg L-1 de atrazina e da mistura dos herbicidas. Tamb&eacute;m foi observado uma cin&eacute;tica de pseudo primeira ordem na oxida&ccedil;&atilde;o dos herbicidas, e, al&eacute;m disso, foi realizada a identifica&ccedil;&atilde;o dos intermedi&aacute;rios e/ou produtos de degrada&ccedil;&atilde;o do alaclor e atrazina atrav&eacute;s da t&eacute;cnica de CLAE acoplada a um espectr&ocirc;metro de massas. / The pesticides presence in environment represents a potential endocrine disturbance source for the living beings, even in low concentrations (ng L-1/ &#956;g L-1). The herbicides alachlor and atrazine are important to highlight, these herbicides are widely used to combat weeds herbs. However, the Environmental Protection Agency (EPA) classifies alachlor and atrazine as carcinogens, endocrine disruptors and their water limit may not exceed 2 and 3 &#956;g L-1, respectively. The aim of this work was to study the electrochemical degradation of alachlor and atrazine, using a filter-press cell, and a dimensionally stable anode (DSA) with a nominal composition Ti/Ru0.3Ti0.7O2, fixed initial pH of 3 and temperature of 25&ordm;C. The conventional treatment methods are not completely effective to remove these organic compounds in aqueous systems. Initially, only an electrochemical degradation of alachlor (100 mg L-1) was made by factorial design center point type 32, considering as variables: the supporting electrolyte sodium chloride concentration (0.05, 0.1 and 0.15 g L-1) and current density (10, 30 and 50 mA cm-2). In this initial degradation was obtained as better result: 93.45% of removal and 71.6% of mineralization of alachlor, using CNaCl of 0.15 g L-1 and 50 mA cm-2. However, CNaCl of 0.15 g L-1 and a density of 30 mA cm-2 was chosen as the best condition studied, in the reason of its lower energy consumption value and presents a removal rate (93.6%) and the mineralization (71.24%) closer to the use of higher current density. The electrolyses of 100 mg L-1 of atrazine and the herbicides mixture were performed only in the best condition, previously obtained with alachlor degradation experiments. In addition, a kinetic of pseudo first order for both herbicides and their mixture oxidation was observed, and besides, the identification of intermediates and/or degradation products of alachlor and atrazine was performed by liquid chromatography coupled to mass spectrometry (LC-MS).

A presen&ccedil;a de defensivos agr&iacute;colas no meio ambiente, mesmo que em baixas concentra&ccedil;&otilde;es (ng L-1/ &#956;g L-1), representa uma potencial fonte de perturba&ccedil;&atilde;o end&oacute;crina para os seres vivos. Neste cen&aacute;rio, destacam-se os herbicidas alaclor e atrazina, que s&atilde;o amplamente utilizados no combate a ervas daninhas. Entretanto, a Ag&ecirc;ncia de Prote&ccedil;&atilde;o Ambiental dos Estados Unidos (EPA) classifica como carcinog&ecirc;nicos, desreguladores end&oacute;crinos e seu limite, em &aacute;gua, n&atilde;o pode ultrapassar 2 e 3 &#956;g L-1, respectivamente. O objetivo deste trabalho foi estudar a degrada&ccedil;&atilde;o eletroqu&iacute;mica do alaclor e atrazina, utilizando uma c&eacute;lula do tipo filtro-prensa, e um &acirc;nodo dimensionalmente est&aacute;vel (ADE) de composi&ccedil;&atilde;o nominal Ti/Ru0,3Ti0,7O2, pH inicial fixo em 3 e a temperatura em 25 &ordm;C, uma vez que, os m&eacute;todos convencionais de tratamento n&atilde;o s&atilde;o totalmente eficientes na remo&ccedil;&atilde;o destes compostos org&acirc;nicos nos sistemas aquosos. Inicialmente realizou-se apenas a degrada&ccedil;&atilde;o eletroqu&iacute;mica do herbicida alaclor (100 mg L-1) via planejamento fatorial de ponto central do tipo 32, tendo como vari&aacute;veis, a concentra&ccedil;&atilde;o do eletr&oacute;lito suporte cloreto de s&oacute;dio (0,05, 01 e 0,15 g L-1) e a densidade de corrente (10, 30 e 50 mA cm-2), obtendo como melhor resposta, 93,45 % de remo&ccedil;&atilde;o e 71,6 % de mineraliza&ccedil;&atilde;o, ao usar CNaCl de 0,15 g L-1 e 50 mA cm-2. Por&eacute;m, a CNaCl de 0,15 g L-1 e densidade de 30 mA cm-2 foi escolhida como a melhor condi&ccedil;&atilde;o estudada, em virtude do seu menor valor de consumo energ&eacute;tico e por apresentar a taxa de remo&ccedil;&atilde;o (93,6%) e mineraliza&ccedil;&atilde;o (71,24%) pr&oacute;ximas ao uso da maior densidade de corrente. S&oacute; ent&atilde;o, na melhor condi&ccedil;&atilde;o, obtida previamente a partir dos experimentos de degrada&ccedil;&atilde;o do alaclor, que realizou-se a oxida&ccedil;&atilde;o de 100 mg L-1 de atrazina e da mistura dos herbicidas. Tamb&eacute;m foi observado uma cin&eacute;tica de pseudo primeira ordem na oxida&ccedil;&atilde;o dos herbicidas, e, al&eacute;m disso, foi realizada a identifica&ccedil;&atilde;o dos intermedi&aacute;rios e/ou produtos de degrada&ccedil;&atilde;o do alaclor e atrazina atrav&eacute;s da t&eacute;cnica de CLAE acoplada a um espectr&ocirc;metro de massas. / The pesticides presence in environment represents a potential endocrine disturbance source for the living beings, even in low concentrations (ng L-1/ &#956;g L-1). The herbicides alachlor and atrazine are important to highlight, these herbicides are widely used to combat weeds herbs. However, the Environmental Protection Agency (EPA) classifies alachlor and atrazine as carcinogens, endocrine disruptors and their water limit may not exceed 2 and 3 &#956;g L-1, respectively. The aim of this work was to study the electrochemical degradation of alachlor and atrazine, using a filter-press cell, and a dimensionally stable anode (DSA) with a nominal composition Ti/Ru0.3Ti0.7O2, fixed initial pH of 3 and temperature of 25&ordm;C. The conventional treatment methods are not completely effective to remove these organic compounds in aqueous systems. Initially, only an electrochemical degradation of alachlor (100 mg L-1) was made by factorial design center point type 32, considering as variables: the supporting electrolyte sodium chloride concentration (0.05, 0.1 and 0.15 g L-1) and current density (10, 30 and 50 mA cm-2). In this initial degradation was obtained as better result: 93.45% of removal and 71.6% of mineralization of alachlor, using CNaCl of 0.15 g L-1 and 50 mA cm-2. However, CNaCl of 0.15 g L-1 and a density of 30 mA cm-2 was chosen as the best condition studied, in the reason of its lower energy consumption value and presents a removal rate (93.6%) and the mineralization (71.24%) closer to the use of higher current density. The electrolyses of 100 mg L-1 of atrazine and the herbicides mixture were performed only in the best condition, previously obtained with alachlor degradation experiments. In addition, a kinetic of pseudo first order for both herbicides and their mixture oxidation was observed, and besides, the identification of intermediates and/or degradation products of alachlor and atrazine was performed by liquid chromatography coupled to mass spectrometry (LC-MS).

An abundance of waste products from the forestry industry (sawdust and paper pulp) lead to the concept of using them as growing media for high value crops on a field scale. However, management of subsequent weed growth posed a problem as the impact of these novel media on the performance and fate of herbicides was unknown. Three aspects of sawdust and paper pulp waste were examined and compared to two cropping soils, viz. their effect on herbicide behaviour with regard to crop selectivity, weed control efficacy and the environmental fate of selected chemicals. Cropping species such as lettuce and onions were more susceptible to alachlor and chlorpropham in sawdust than in paper pulp. The two cropping soils evaluated (Horotiu sandy loam and Mangateretere silt loam) tended to be intermediate although the former was often close to the sawdust and the latter to the paper pulp in terms of herbicide phytotoxicity to the crop plants. For the less water soluble herbicide pendimethalin, the differences in crop selectivity in the different media were not significant. The effect of the media on the efficacy of weed control was evaluated through plant species with a much lower tolerance to the herbicides evaluated in contrast to the above species. For these plants the efficacy of the herbicides was generally lower in both the sawdust and paper pulp than in the two soils. The effect was more pronounced with the more soluble alachlor, where efficacy was reduced by factors of 5 – 10, compared to pendimethalin where efficacy reduction was by factors of 0 – 3. The two high organic media had contrasting effects on the various environmental behaviour indices evaluated. Herbicide adsorption as quantified by distribution coefficient (Kd) was higher in the two novel media compared to both the Horotiu and Mangateretere soils. However, when the Kd was normalised to organic carbon (Koc), there was less variation amongst the media indicating that organic matter is an important factor in controlling sorption in these media. However, despite the high level of adsorption in the sawdust, herbicides were most prone to leaching in this medium. Conversely the paper pulp tended to be more retentive while the two soils were intermediate. The degradation as quantified by half-lives (t½) of the herbicides was generally slower in the two novel media, probably reflecting the higher sorption in these two media but also due to the lower level of microbial activity in the sawdust and paper pulp. The study shows that herbicide behaviour in these carbon based media differs significantly from that expected from soil organic matter, mainly due to the non-humified nature of the organic matter in the media and its poor biological activity.