Sérgio Luiz de Oliveira Machado

Rice herbicide monitoring in two Brazilian rivers during the rice growing season

Irrigated rice production can involve environmental contamination with pesticides due to the proximity of the fields to rivers and to management problems. During three years (2000 to 2003) the rice herbicides clomazone, propanil and quinclorac were quantified in water during the rice growing season, in the Vacacai and Vacacai-Mirim Rivers, located in Rio Grande do Sul (RS) State, Brazil. Water samples were taken at several locations in each river, selected by their importance in terms of rice drainage area. The samples were analyzed by HPLC-UV. At least one herbicide was detected in 41% of the samples from the Vacacai River and 33% from the Vacacai-Mirim River. The most frequent herbicide in both rivers and in each year was clomazone. The amount of herbicides in the river water was dependent on the rainfall regime. River water contamination by rice herbicides is probably caused by the rice water management used in the fields. The maintenance of flooded areas makes herbicides prone to contaminate the environment. To reduce the environmental contamination risk it is necessary to adopt measures to avoid overflow of flooded rice fields, keeping paddy water in the field for time enough to reduce the herbicide concentration before its release and enhancing the quality of the levees to reduce the probability of paddy rice overflow.

Toxicological responses of Cyprinus carpio after exposure to a commercial herbicide containing imazethapyr and imazapic

Cyprinus carpio was exposed to imazethapyr and imazapic at laboratory and at field conditions. The laboratory experiment was carried out for 7 days and at rice field for 7, 30 and 90 days. Oxidative stress parameters and antioxidant profile were studied as well as metabolic parameters. After 7 days, brain AChE activity increases in laboratory and field, but in muscle, reduction was observed only in laboratory. At the same period, brain and muscle TBARS and liver CAT increase in the laboratory. Metabolic parameters showed changes in both conditions and exposure periods. After 30 days in rice field, brain AChE activity decreases and in muscle it was enhanced. After 90 days in field, only muscle AChE activity was reduced. The disorders in oxidative stress parameters and metabolism remained, indicating mainly a protein catabolism. This study pointed out short- and long-term effects of rice herbicides at environmentally relevant concentrations on toxicological parameters in tissues of C. carpio.

Acetylcholinesterase enzyme activity in carp brain and muscle after acute exposure to diafuran

Exposicao a inseticidas em concentracoes elevadas no ambiente podem ocasionar efeitos adversos subletais em organismos aquaticos. Alevinos de carpa hungara (Cyprinus carpio, Linnaeus, 1758), carpa capim (Ctenopharyngodon idella, Valenciennes, 1844) e carpa cabeca grande (Aristichthys nobilis, Richardson, 1845) foram expostos ao diafuran, um inseticida utilizado na cultura do arroz no sul do Brasil. O objetivo deste estudo foi verificar a relacao entre concentracao letal mediana (CL50) do diafuran e a atividade da enzima acetilcolinesterase (AChE) em cerebro e musculo dessas especies, como um possivel biomarcador inicial da exposicao a este inseticida. A CL50 foi determinada com peixes expostos a concentracoes de diafuran em 96 h: carpa hungara: controle; 0,5; 1,0; 1,5; 2,0; 2,5 e 3,0 mg L-1; carpa capim: controle; 1,0; 2,0; 3,0 e 3,5 mg L-1 e carpa cabeca grande: controle; 0,5; 1,0; 1,5; 2,0; 3,0 e 4,0 mg L-1, bem como a determinacao da AChE em concentracoes proximas da CL50 para essas especies. Valores de CL50 (concentracoes nominais) foram de 1,81 mg L-1 para carpa hungara, 2,71 mg L-1 para carpa capim e 2,37 mg L-1 para carpa cabeca grande. Todas as carpas expostas ao diafuran estavam letargicas (menores concentracoes) ou imoveis. Diafuran inibiu significativamente a atividade da AChE em cerebro (~38 %) e musculo (~50 %) de todas as especies estudadas. Atividade da AChE em musculo para carpa cabeca grande foi mais alta que cerebro (14,44 contra 5,94 µmol min-1 g proteina-1, respectivamente). Este estudo demonstrou que concentracoes de diafuran utilizadas na cultura do arroz podem afetar o comportamento de Cyprinus carpio, Ctenopharyngodon idella e Aristichthys nobilis, e a atividade da acetilcolinesterase cerebral e muscular pode ser um biomarcador inicial de toxicidade deste inseticida.Exposicao a inseticidas em concentracoes elevadas no ambiente podem ocasionar efeitos adversos subletais em organismos aquaticos. Alevinos de carpa hungara (Cyprinus carpio, Linnaeus, 1758), carpa capim (Ctenopharyngodon idella, Valenciennes, 1844) e carpa cabeca grande (Aristichthys nobilis, Richardson, 1845) foram expostos ao diafuran, um inseticida utilizado na cultura do arroz no sul do Brasil. O objetivo deste estudo foi verificar a relacao entre concentracao letal mediana (CL50) do diafuran e a atividade da enzima acetilcolinesterase (AChE) em cerebro e musculo dessas especies, como um possivel biomarcador inicial da exposicao a este inseticida. A CL50 foi determinada com peixes expostos a concentracoes de diafuran em 96 h: carpa hungara: controle; 0,5; 1,0; 1,5; 2,0; 2,5 e 3,0 mg L-1; carpa capim: controle; 1,0; 2,0; 3,0 e 3,5 mg L-1 e carpa cabeca grande: controle; 0,5; 1,0; 1,5; 2,0; 3,0 e 4,0 mg L-1, bem como a determinacao da AChE em concentracoes proximas da CL50 para essas especies. Valores de CL50 (concentracoes nominais) foram de 1,81 mg L-1 para carpa hungara, 2,71 mg L-1 para carpa capim e 2,37 mg L-1 para carpa cabeca grande. Todas as carpas expostas ao diafuran estavam letargicas (menores concentracoes) ou imoveis. Diafuran inibiu significativamente a atividade da AChE em cerebro (~38 %) e musculo (~50 %) de todas as especies estudadas. Atividade da AChE em musculo para carpa cabeca grande foi mais alta que cerebro (14,44 contra 5,94 µmol min-1 g proteina-1, respectivamente). Este estudo demonstrou que concentracoes de diafuran utilizadas na cultura do arroz podem afetar o comportamento de Cyprinus carpio, Ctenopharyngodon idella e Aristichthys nobilis, e a atividade da acetilcolinesterase cerebral e muscular pode ser um biomarcador inicial de toxicidade deste inseticida.

Resíduos de agrotóxicos na água de rios da Depressão Central do Estado do Rio Grande do Sul, Brasil

The rice-growing activity is conducted out with intensive use of agrochemicals, which, depending on the management and rainfall can reach rivers. The study aimed to determine the residues of herbicides clomazone, quinclorac, propanil, bentazone, 2,4-D and imazethapyr and insecticides carbofuran and fipronil in the Vacacai and Vacacai-Mirim rivers, located in the Central Depression of Rio Grande do Sul, in the crop of 2003/04 untill 2007/08. Samples were collected from November to February (rice growing season). Analysis of herbicides and carbofuran were performed by HPLC-DAD and fipronil by GC-ECD. During 2003/04, in both rivers, the herbicide clomazone, 2,4-D and propanil were the most frequent in water samples. In 2004/05, the quinclorac was detected in many samples and in 2005/06 and 2006/07 seasons fipronil was the most common pesticide in the samples in Vacacai and Vacacai-Mirim rivers. In the 2007/08 crop, there were less residues of pesticides in Vacacai and Vacacai-Mirim rivers. There is presence of pesticides used in rice farming in the Vacacai and Vacacai-Mirim rivers during the rice crop, especially among those analyzed, the herbicides clomazone and quinclorac and the insecticide fipronil.

Efeito do manejo de plantas daninhas no desenvolvimento inicial de Pinus taeda em várzeas na Argentina

Realizou-se um estudo sobre o efeito de cobertura e periodos de manejo de plantas daninhas em plantios no ano de 1999 de Pinus taeda, localizados na Provincia de Corrientes, Argentina. Em razao das caracteristicas da area, varzeas, foram construidos camalhoes de 1,80 m de largura por 0,60 m de altura para o plantio das mudas e, a seguir, instaladas parcelas com tres fileiras de 12 plantas em cada uma no espacamento de 1,75 m entre as mudas e 4,0 m entre o centro dos camalhoes. Foram medidas somente as 10 plantas do camalhao central, com o objetivo de avaliar o efeito de diferentes modalidades e intensidades de manejo de plantas daninhas na sobrevivencia (%), no desenvolvimento inicial em altura (cm), no diâmetro do colo (cm) e no fator de produtividade (cm3) das mudas de Pinus taeda. Avaliaram-se as modalidades de controle: controle quimico na linha do plantio (camalhao) e controle quimico em area total sendo avaliados por dois periodos: um ano e dois anos de controle, tendo ainda uma testemunha, sem nenhum controle. O delineamento estatistico do experimento foi em blocos ao acaso, com tres repeticoes. Diferencas significativas foram obtidas entre os tratamentos de controle quimico em relacao ao sem controle. Os resultados levaram a conclusao de que e benefico o controle por dois periodos e que nao houve diferenca quanto as modalidades de controle (camalhao e area total). As mudas de Pinus taeda foram submetidas ao teste de Tukey para analise da sobrevivencia e nao apresentaram diferenca significativa a 5% de probabilidade de erro nas medias.

Lethal concentration of clomazone, metsulfuron-metil, and quinclorac for silver catfish, Rhamdia quelen, fingerlings

The goal of the present work was to determine the lethal concentration (LC50) (96h) of clomazone, metsulfuron-methyl, and quinclorac, herbicides used in rice culture, for the silver catfish, Rhamdia quelen. Fingerlings were exposed to different concentrations of the herbicides. The LC50s were 7.32µL L-1 for clomazone and 395mg L-1 for quinclorac. The LC50 for metsulfuron-methyl was not obtained since all fingerlings survived even at 1200mgL-1. Probably only clomazone can lead to mortality among silver catfish reared in the rice culture system.

Rapid and accurate hplc-dad method for the determination of the herbicide bispyribac-sodium in surface water, and its validation

A new method is described for the determination of the herbicide bispyribac-sodium in surface water, especially from river and irrigated rice water samples. The method involves extraction in solid phase and quantification by high performance liquid chromatography with diode array detection (HPLC-DAD). After optimization of the extraction and separation parameters, the method was validated. The method presented average recoveries of 101.3 and 97.7%, under repeatability and intermediate precision conditions, respectively, with adequate precision (RSD from 0.9 to 7.5%). The method was applied for the determination of bispyribac-sodium in surface water samples with a limit of detection of 0.1 μg L-1.

Lixiviação do imazethapyr em solo de várzea sob dois sistemas de manejo

Imazethapyr has been widely used in Rio Grande do Sul since the development of Clearfield TechnologyTM(CL) on rice, in a formulated mixture of imazethapyr + imazapic (75 + 25g L-1). However, the use of such technology raised the problem of herbicide carryover, which might affect non-tolerant crops in rotation with different intensities. The plant injury is related, among other factors, with the herbicide position in the soil profile. The present work had the objective of determining the depth positioning of imazethapyr on a lowland soil cultivated with rice in two soil tillage system: conventional system (CS) and no till system (NT), in an area where CL rice had been cultivated for two years followed by non tolerant rice in the third year. Herbicide concentration in soil samples was analyzed by HPLC-DAD. There is a higher concentration of imazethapyr in the topsoil (0-5cm) on the CS, when compared to the NT, while it leached until 20cm in both systems. In the CS, imazethapyr were uniformly distributed in the first 15 cm of soil, whereas in NT, imazethapyr were accumulated in 5-10 and 10-15cm layers.

Red rice seed bank evolution under different systems of lowland utilization

Num ecossistema agricola, a reducao do banco de sementes e um dos aspectos mais importantes no manejo de plantas daninhas; e em solos de varzeas, o arroz vermelho (Oryza sativa L.) e atualmente considerado a principal planta daninha. Nesse sentido, conduziu-se um experimento com o objetivo de avaliar a evolucao do banco de sementes de arroz vermelho no solo em diferentes sistemas de semeadura de arroz irrigado e em alternativas de manejo do solo de varzea. O experimento foi instalado em campo por dois anos consecutivos na mesma area (safras agricolas 1996/97 e 1997/98) em Santa Maria, RS, em solo classificado como Planossolo, com infestacao media de 516 sementes viaveis de arroz vermelho/m². A estimativa do banco de sementes de arroz vermelho foi realizada atraves de 10 coletas de solo, utilizando um cilindro com 0,10m de diâmetro a 0,10m de profundidade. Apos a coleta, os graos foram separados do solo e realizado teste de tetrazolio para determinar a quantidade de sementes viaveis na amostra. As coletas foram realizadas antes da instalacao do experimento (set/1996), apos a colheita do primeiro ano (mai/1997) e apos a colheita do segundo ano (mai/1998). Os resultados mostraram que o cultivo do arroz no sistema convencional promove aumento no banco de sementes de arroz vermelho, enquanto que a semeadura de arroz em solo inundado (mix de pre-germinado, pregerminado ou transplante de mudas) e tao eficiente na reducao do banco de sementes de arroz vermelho quanto a rotacao com o sorgo, o pousio do solo sem a presenca de animais e tambem o preparo de verao.

Persistência na água e influência de herbicidas utilizados na lavoura arrozeira sobre a comunidade zooplanctônica de Cladocera, Copepoda e Rotifera

In the rice paddy field it is used a large amount of agrochemical that, depending on their field persistence and toxicity, can contaminate water bodies and may affect living organism. With the objective of determining the effect of field concentrations of Clomazone, Quinclorac, Metsulfuron-methyl and Propanil herbicides on zooplankton community (Cladocers, Copepods and Rotifers), it was carried an experiment in aquaculture ponds, during March to May 2005, in autumn season. In the 1st, 2nd, 3rd, 7th, 10th, 18th, 31th and 51th days after the herbicides application, water samples were collected to evaluate the physical chemical water parameters, herbicides concentration and zooplankton community. The water physical chemical parameters means were: dissolved oxygen (3.5mg L-1), temperature (20.1°C), pH (6.0), total hardness (18mg L-1 CaCO3) and total alkalinity (9mg L-1 CaCO3). The decreasing of herbicides persistence in water was: Clomazone = Quinclorac > Propanil > Metsulfuron-methyl with average of 31, 31, 10 and 7 days, respectively. The results indicated that the herbicides provoke little alteration in density of Rotifers and, Copepods (Adults and Nauplii). The Cladocers group density remained low for the whole experiment period.