Decomposition of organic matter in the presence of the herbicide clomazone.

Clomazone (2-(2-chlorophenyl) methyl-4.4-dimethyl-3-isoxazolidinone) is a post emergence herbicide widely used in rice fields in Rio Grande do Sul (Brazil) with high activity against Gramineae at the recommended application rate of 700 g/ha. The presence of this chemical in the water may affect microorganisms responsible for the decomposition of organic matter. Thus, a disturbe in the trophic chain sustained by the decompositors could happen. In the present work the decomposition rate of organic matter (Typha latifolia) exposed to several concentrations of a clomazone formulation: 0 (control), 25.0, 62.0, 156.0, 390.0 and 976.0mg/L on the basis of the active ingredient was evaluated. Five litter bags containing about 3.0g of pieces of T. latifolia leaves wereplaced in aquariums with 15 of reconstituted water. In cach aquarium were added 500g of sediment from the same place of the plant collection, as a source of decompositors microorganisms. The results relative tothe control, showed that the decomposition rate in the highest and lowest dose was reduced in 50.05 and 1,28%, respectively, after 80 days.

Toxicity of the herbicide clomazone on duckweed Lemna valdiviana.

The duckweed Lemna valdiviana is commonly founded colonizing small shallow waters (lakes on the lowland in south Brazil. This organism may have been affected by herbicide input into lakes from aerial application and/or drainage office paddy fields. Clomazone (2- (2-chlorophenyl) methyl-4.4-dimethyl-3-isoxazolidinone) is one of the herbicides more fiequentely used as post-emergence in rice paddies. For this work assays were carried as EC50(96h) semi-statics with aseptic culture. The sterile fronds were abtained from material harvest on the paddy fields, and the concentration of Clomazone ranged from 14.0 to 229.0 mg/l. two procedures were considered: diluted in water and sprayed applicated Clomazone. The observed phytotoxic effects were evaluated by growth rate (kt), duplication time (Td), frond yield, plant yield, mortality, chlorophyll a and b and protochlorophyll concentration. The EC50 values obtained to sprayed Clomazone (Kt=31.7; Td=31.9) were significantly small than to diluted Clomazone (Kt=46.4; td=47.3). These dadta suggest that aerial route is more hazardous than diluted procedure. Presence of chlorotic, necrotic, abnormal and died frond were common at the 114.0 and 229.0 mg/l treatment. Recuperation test corroborated the evidence that the sprayed procedure were more deleterious and L. valdiviana doesn't recovery his reproductive ability at the 114.0 and 229.0 mg/l treatment.

Risk assessment of the herbicide clomazone in the aquatic life.

Clomazone (2-(2-chlorophenyl)methyl-4.4-dimethyl-3-isoxazolidinone) is a post emergence herbicide widely used in rice fields in Rio Grande do Sul (Brazil) with high activity against Gramineae at the recommended application rate(AR).of 700g/ha. The herbicide input into the aquatic ecosystem may occur by aerial application or water drainage. The presence of this chemical in the water may affect non-target organisms leading to impairments in the aquatic food chain. Studies were conducted in this work to evaluate the risk of Clomazone using the estimated mean affective concentration (EC50) for the microalgae Selenastrum capricornutum(96h), the duckweed Lemna valdiviana(96h) and the crustacean Daphnia similis(48h). The EC50 values were 11.2; 31.7 and 13.8 mg/l, respectively. According to the obtained data, and considering a direct input of the herbicide in a 10cm column water, the estimated maximum application rate that doesn't cause acute effects is 5.3 AR for S. capricornutum, 6.5 AR for D. similis and 15.0 AR for L. valdiviana. The estimated maximum application rate that doesn't cause chronic effects is 2.0 AR for D. similis, 1.6 AR for S. capricornutum and 4.5 AR for L. valviana.

Persistência do herbicida clomazone em arroz irrigado em sistema pré-germinado.

1997

Comportamento dos herbicidas propanil e clomazone em solos alagados.

Com os objetivos de avaliar a distribuição, persistência e degradação dos herbicidas no solo, na água e seu escape para outros corpos de água e avaliar os mecanismos de absorção/dessorção no solo, foi instalado um experimento de campo no Município de Pelotas no Rio Grande do Sul, utilizando-se os herbicidas propanil e clomazone na cultura de arroz alagado. O processo adotado para amostrar os produtos no solo foi aperfeiçoado, com a introdução de tubos de PVC perfurados que permitiam a ocorrência dos processos de troca no solo. Foram feitas as isotermas de adsorção para o propanil e clomazone, ajustadas por quatro modelos distintos. Fez-se também analise química dos grãos para os elementos N, P, K, Ca, Mg, S, Cu, Mn, Zn, determinando-se o teor de proteína bruta.Os resultados obtidos para o clomazone mostram que não houve contaminação ambiental pelo produto uma vez que nao foi detectada sua presença nas amostras de solo e agua do experimento. A ocorrência do propanil somente foi detectada nas amostras de solo coletadas com os tubos perfurados aos 30 e 120 dias após a emergência das plantas. Dos modelos de curvas de adsorção testados e comparados pelo método dos resíduos padronizados, o modelo de Freundlich foi o que melhor descreveu o comportamento dos dois produtos.

Modelagem da bioconcentração de herbicidas em plantas.

Propriedades físico-químicas de herbicidas e propriedades fisiológicas de plantas foram utilizadas para apresentar um modelo que simula a bioconcentracão e calcula o fator de bioconcentração de herbicidas em plantas. A modelagem supõe que o herbicida na solução do solo é absorvido pela planta no processo de transpiração da solução do solo. Utilizamos o modelo para estimar o fator de bioconcentração dos herbicidas 2,4-D, acetochlor, ametryn, atrazine, clomazone, diuron, hexazinone, imazapyr, metribuzin, pendimethalin, picloram, simazine, sulfentrazone, tebuthiuron e trifluralin em cana-deaçúcar. A modelagem sugere que existe uma correlação negativa entre o fator de bioconcentração e o coeficiente de sorção de herbicidas no carbono orgânico do solo.

Sugarcane herbicide leaching risk evaluation in Guarany Aquifer.

he region of Ribeirão Preto, São Paulo State, Brazil, is located over recharge area of the Guarany aquifer, the most important source of groundwater in the South Central region of the country. This region is also the most important sugarcane producing area of the country which produces a large amount of the ethanol. This study was conducted to determine the potential risk of herbicide groundwater contamination. The leaching risk potential of herbicides to groundwater was conducted using the weather simulator ?Weather Generator? (WGEN) coupled with the model ?Chemical Movement Trough Layered Soils? (CMLS94). The following herbicides were evaluated in clayey and sandy soils (Typic Haplorthox and Typic Quartzipsamment soils) found in the region: ametryn (N-ethyl-N\'-(1- methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine), atrazine (6-chloro-N-ethyl-N\'-(1-methylethyl)-1,3,5-triazine- 2,4-diamine), clomazone (2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone), diuron (3,4-dichlorophenyl)- N,N-dimethylurea), halosulfuron (3-chloro-5-[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl], hexazinone (3- cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4 (1H,3H)-dione), imazapic ((±)-2-[4,5-dihydro-4-methyl-4- (1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid), imazapyr ((±)-2-[4,5-dihydro-4-methyl- 4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid), MCPA (4-chloro-2-methylphenoxy)acetic acid), metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one), MSMA (Amonosodium salt of MAA), paraquat (1,1\'-dimethyl-4,4\'-bipyridinium ion), pendimethalin (N-(1-ethylpropyl)-3,4-dimethyl-2,6- dinitrobenzenamine), picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), simazine (6-chloro-N,N\'-diethyl- 1,3,5-triazine-2,4-diamine), sulfentrazone [N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H- 1,2,4-triazol-1-yl]phenyl]methanesulfonamide], and tebuthiuron [N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N\'- dimethylurea]. Results obtained by our simulation study have shown that the herbicides picloram, tebuthiuron, and metribuzin have the highest leaching potential, in either sandy or clayey soils, with picloram reaching the root zone of sugarcane at 0.6m in less than 150 days.

Efeito de três herbicidas usados em culturas de arroz irrigado sobre a mobilidade e crescimento de organismos aquáticos bioindicadores.

1997

Estudo da qualidade da água em culturas de arroz irrigado com aplicação de herbicidas.

1997

Impacto ambiental de herbicidas em arroz irrigado.

1997