Degradação de 14C-atrazina em solo sob condições semicontroladas
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Data
2000-04-01
Autores
QUEIROZ, BRIGIDA PIMENTEL VILLAR DE [UNESP]
MONTEIRO, REGINA TERESA ROSIM
Título da Revista
ISSN da Revista
Título de Volume
Editor
Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA)
Resumo
Objetivou-se neste trabalho, avaliar a mineralização e a formação de resíduos extraível e não-extraível de 14C-atrazina em um solo intensivamente utilizado para fins agrícolas no Estado de São Paulo. Atrazina radiomarcada foi aplicada (5 L ha-1 ou 2 mg kg-1 de i.a.) em um Latossolo Vermelho-Escuro, álico, A moderado, textura média. Frascos erlenmeyer contendo 200 g (peso seco) do solo assim preparado e com umidade ajustada para 2/3 da capacidade de campo foram enterrados na Estação Experimental de Lisímetros do CENA-USP, onde se iniciou, ao mesmo tempo, uma plantação de milho. O 14CO2 desprendido foi avaliado a cada 15 dias, durante 150 dias, e atingiu, no final desse período de incubação, 36% da atividade total aplicada, e meia-vida de 168 dias. Os resíduos formados no solo foram determinados, em termos de dessorção, com o uso de cloreto de cálcio, e, em termos de extração, com o sistema-solvente acetonitrila/água (80:20); os resíduos não-extraíveis foram avaliados por combustão. Durante o período de incubação, os resíduos extraíveis diminuíram para 1/3, enquanto os resíduos ligados (não-extraíveis) permaneceram ao redor de 34%. Os metabólitos foram identificados por cromatografia em camada delgada, e foram detectadas, nas frações dessorvidas, hidroxiatrazina (44%), desisopropilatrazina (3,28%) e atrazina (52,72%) e nas frações extraídas, hidroxiatrazina (16,22%), desisopropilatrazina (2,25%), desetilatrazina (2,24%) e atrazina (79,29%). Conclui-se que a mineralização ocorreu somente na fração de resíduos extraíveis e foi favorecida pelas condições de incubação, em que o principal fator foi a variação de temperatura.
The objective of this work was to evaluate the mineralization rate and residue formation in a common soil type intensively used for agriculture in São Paulo, SP, Brazil. Atrazine 14C-ring-U-R was applied to a typic Hapludox Brazilian soil (5 L ha-1 or 2 mg kg-1 of a.i.). After this procedure, samples (200 g, dry weight basis) of this soil, with moisture adjusted to 2/3 of the field capacity, were distributed in erlenmeyer flasks. The flasks were incubated buried at CENA-USP Lysimeter Station, in a started jointly corn plantation. The evolved 14CO2 was analyzed every 15 day, during a period of 150 days. The desorbed residues were extracted with 0.01M CaCl2 solution and further extracted with the organic solvent, acetonitrile-water, 80:20, and the non-extractable residues were analysed by combustion. At the end of the incubation period (150 days), the 14CO2 evolved reached up to 36% of applied activity, and half-life of 168 days. The extractable residues decreased by 1/3 during the incubation period, while the non-extractable remained unchanged, around 34% of applied activity. TLC analyses of desorbed fraction showed hydroxiatrazine (44%), deisopropylatrazine (3.28%) and atrazine (52.72%) whereas the extracted fraction presented hydroxyatrazine (16.22%), deisopropylatrazine (2.25%), desethylatrazine (2.24%), and atrazine (79.29%). It was concluded that only the extractable fraction of residues was mineralized and that variation of the incubation temperature favored atrazine mineralization.
The objective of this work was to evaluate the mineralization rate and residue formation in a common soil type intensively used for agriculture in São Paulo, SP, Brazil. Atrazine 14C-ring-U-R was applied to a typic Hapludox Brazilian soil (5 L ha-1 or 2 mg kg-1 of a.i.). After this procedure, samples (200 g, dry weight basis) of this soil, with moisture adjusted to 2/3 of the field capacity, were distributed in erlenmeyer flasks. The flasks were incubated buried at CENA-USP Lysimeter Station, in a started jointly corn plantation. The evolved 14CO2 was analyzed every 15 day, during a period of 150 days. The desorbed residues were extracted with 0.01M CaCl2 solution and further extracted with the organic solvent, acetonitrile-water, 80:20, and the non-extractable residues were analysed by combustion. At the end of the incubation period (150 days), the 14CO2 evolved reached up to 36% of applied activity, and half-life of 168 days. The extractable residues decreased by 1/3 during the incubation period, while the non-extractable remained unchanged, around 34% of applied activity. TLC analyses of desorbed fraction showed hydroxiatrazine (44%), deisopropylatrazine (3.28%) and atrazine (52.72%) whereas the extracted fraction presented hydroxyatrazine (16.22%), deisopropylatrazine (2.25%), desethylatrazine (2.24%), and atrazine (79.29%). It was concluded that only the extractable fraction of residues was mineralized and that variation of the incubation temperature favored atrazine mineralization.
Descrição
Palavras-chave
mineralização, resíduos, herbicidas, triazinas, composto orgânico de nitrogênio, adsorção, dessorção, mineralization, residues, herbicides, triazines, organic nitrogen compounds, adsorption, desorption
Como citar
Pesquisa Agropecuária Brasileira. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) Informação TecnológicaPesquisa Agropecuária Brasileira, v. 35, n. 4, p. 849-856, 2000.