Environmental Behaviour of Metolachlor and Diuron in a Tropical Soil in the Central Region of Brazil

Abstract

The environmental behaviour of metolachlor and diuron was studied in the Central-western region of Brazil, by means of a field study where six experimental plots were installed. The soil was classified as a Latosol, and the soil horizons were characterized. Sorption of metolachlor and diuron was evaluated in laboratory batch experiments. Metolachlor and diuron were applied to the experimental plots on uncultivated soil in October 2003. From this date to March 2004, the following processes were studied: leaching, runoff and dissipation in top soil. K oc of metolachlor varied from 179 to 264 mL g −1 in the soil horizons. K oc of diuron in the Ap horizon was 917 mL g −1 , decreasing significantly in the deeper horizons. Field dissipation half-lives of metolachlor and diuron were 18 and 15 days, respectively. In percolated water, metolachlor was detected in concentrations ranging from 0.02 to 2.84 μg L −1 . In runoff water and sediment, metolachlor was detected in decreasing concentrations throughout the period of study. Losses of 0.02% and 0.54% of the applied amount by leaching and runoff, respectively, were observed confirming the high mobility of this herbicide in the environment. In percolated water, diuron was detected with low frequency but in relatively high concentrations (up to 6.29 μg L −1 ). In runoff water and soil, diuron was detected in decreasing concentrations until 70 days after application, totalizing 13.9% during the whole sampling period. These results show the importance of practices to reduce runoff avoiding surface water contamination by these pesticides, particularly diuron.

Influência da temperatura, umidade e profundidade do solo na persistência do diurom e sulfato de endossulfam em um solo tropical

“…3 Para o diurom, os limites de detecção e quantificação do método foram 3 e 10 µg kg -1 , respectivamente, com intervalo de recuperação entre 84 e 102%. 4 A precisão dos métodos foi considerada satisfatória, sendo o coeficiente de variação menor do que 20%.…”

“…2 Diurom e endossulfam são dois dos pesticidas mais frequentemente utilizados nas culturas de grãos e algodão na região centrooeste do Brasil e são também comumente usados em muitas partes do mundo. [3][4][5][6][7] Devido a problemas ambientais e elevada toxicidade, o endossulfam, classificado como extremamente tóxico pela ANVISA, 8 foi proibido em alguns países, incluindo os Estados Unidos e União Europeia, 9,10 e recentemente uma consulta aos países membros do convênio está sendo realizada para classificação desta substância como poluente orgânico persistente e sua inserção na lista prioritária do Convênio de Estocolmo sobre Poluentes Orgânicos Persistentes.…”

“…5,39 Embora a literatura ressalte a necessidade da avaliação do comportamento de pesticidas em regiões tropicais, 40 poucos estudos têm sido realizados neste sentido. 3,4 Considerando a importância da avaliação do comportamento de pesticidas e produtos de degradação em regiões tropicais, o presente estudo teve por objetivo avaliar a influência da variação da temperatura e da umidade do solo sobre a degradação do herbicida diurom e do produto de degradação sulfato de endossulfam, sob condições controladas de laboratório, em diferentes profundidades de um Latossolo Amarelo coletado em uma região agrícola do Estado de Mato Grosso.…”

Environmental dynamics of pesticides in the drainage area of the São Lourenço River headwaters, Mato Grosso State, Brazil

“…4,[7][8][9][10][11][12][13][14][15][16][17] Aiming to contribute to a better understanding of pesticide behavior in tropical areas, this work presents the results of pesticides atrazine and its metabolites desethylatrazine and desisopropylatrazine, flutriafol, metolachlor, α-and β-endosulfan and its metabolite endosulfan sulfate in a vulnerable tropical environment, emphasizing dissipation processes in the field.…”

“…2 Regarding runoff, this transport can reach 1 to 2% of the applied dose during a single extreme rain event but is usually less than 0.05%. 3,4 Kinetics of these processes are influenced by the soil physical and chemical properties, climate, topography and agricultural practices as well as by chemical and physical properties of the pesticides. The complexity of such multifactorial processes renders the study of environmental fate of pesticides difficult and site-specific studies may be necessary to evaluate specific scenarios.…”