Marco Antonio Ferreira Gomes

Monitoramento e avaliação do risco de contaminação por pesticidas em água superficial e subterrânea na região de Guaíra

The objective of this work was to determine the level of occurrence of pesticides in water, with the purpose of preserving from contamination risk by these pesticides the potable water of the region of Guaira, SP, Brazil. Preliminary hypothesis was that the intensive use of pesticide in the Guaira region is an important factor in the potential contamination of the surface water and groundwater. To identify physical properties and water dynamics in soil, the Fazenda Macauba was selected because of its soil and topography typical of the region. About 80% of the soil of the farm is Oxisol. The plowed layer of the soil has no natural structure and below it there is a compacted layer, both of which derived from agricultural activities. With the goal to evaluate the risk of contamination, the Jardim river, one of its tributary and the groundwater of the Guarani Aquifer were monitored for 2.5 years. The pesticides which were used for the irrigation activities (trifluralin, endosulfan, lambda cyhalothrin, dicofol (4,4 dichlorobenzofenone), captan, parathionmethyl, chlorothalonil and chlorpyriphos) were searched for. Water was analyzed by multiresidue method and the results of this study showed that there is not contamination, except by direct of the surface water. The absence of water contamination is interpreted in relation to the structural characteristics of the soils like thickness, grain size, and field capacity.

HPLC screening and GC-MS confirmation of triazine herbicides residues in drinking water from sugar cane area in Brazil

The extensive use of chlorotriazines as selectiveherbicides in agriculture and their relatively highpersistence imply that these compounds are now presentin the environment, contaminating surface and groundwater. In European countries, United States andCanada, the drinking water ordinance demands a limitedconcentration of 0.5 μg L-1 for the sum of allpesticides and 0.1 μg L-1 with respect to eachcompound, implying on the necessity of sensitive andselective analytical methods. In the present study wedescribe two methods for the analysis of atrazine,simazine and ametryn residues in surface and groundwater collected from the Espraiado Stream watershed,Ribeirão Preto region, SP, Brazil. The HPLC methodused for sample screening was based on herbicideextraction with dichloromethane:isopropanol (9:1, v/v)followed by reversed-phase chromatography (RP-8) withdetection at 220 nm. The presence of herbicides wasconfirmed by GC-MS after ethyl acetate extraction. Atotal of 250 samples collected at different sites fromOctober 1995 to July 1996 were analyzed. Ametrynresidues were detected in 17 samples but almost alwaysat concentrations below those maximum levels recommended by international agencies of environmental control.

Sorption, Degradation, and Leaching of Tebuthiuron and Diuron in Soil Columns

Abstract A study in small outdoor lysimeters was carried out to determine the leaching of the herbicides tebuthiuron and diuron in different soil types, using undisturbed soil columns. Soil sorption and degradation for both herbicides were also studied in the laboratory. The multi-layered AF (Attenuation Factor) model was evaluated for predicting the herbicides leaching in undisturbed soil columns. Tebuthiuron leached in greater amounts than diuron in both soils. Sorption was well represented by linear and Freundlich equations, however parameters from the linear equations were used in the AF model. In general, both herbicides presented very low sorption, with diuron presenting lower values of sorption coefficient than tebuthiuron in the two soils. Chromatographic data indicated rapid late degradation of diuron and tebuthiuron in both soil types at two different depths. Simple exponential equation was not able to represent degradation, thus a bi-exponential equation was used, and some model adjusting was needed. Average measured amounts of each herbicide were compared with amounts predicted by the multi-layered-soil AF model. The AF model was able to predict leaching amounts in the sandy soil, especially for diuron, however it did not perform well in the clayey soil.A study in small outdoor lysimeters was carried out to determine the leaching of the herbicides tebuthiuron and diuron in different soil types, using undisturbed soil columns. Soil sorption and degradation for both herbicides were also studied in the laboratory. The multi-layered AF (Attenuation Factor) model was evaluated for predicting the herbicides leaching in undisturbed soil columns. Tebuthiuron leached in greater amounts than diuron in both soils. Sorption was well represented by linear and Freundlich equations, however parameters from the linear equations were used in the AF model. In general, both herbicides presented very low sorption, with diuron presenting lower values of sorption coefficient than tebuthiuron in the two soils. Chromatographic data indicated rapid late degradation of diuron and tebuthiuron in both soil types at two different depths. Simple exponential equation was not able to represent degradation, thus a bi-exponential equation was used, and some model adjusting was needed. Average measured amounts of each herbicide were compared with amounts predicted by the multi-layered-soil AF model. The AF model was able to predict leaching amounts in the sandy soil, especially for diuron, however it did not perform well in the clayey soil.

Herbicide Leaching on a Recharge Area of the Guarany Aquifer in Brazil

Abstract The region of Ribeirão Preto City, located in Southeast of Brazil, São Paulo State, is an important sugarcane, soybean, and corn producing area with a high level of pesticides utilization. This region is also an important recharge area for groundwater supply of the Guarany aquifer. Since the past ten years atrazine, simazine, ametryn, tebuthiuron, diuron, 2,4-D, picloram, and hexazinone are the main herbicides used in this area. In order to study a possible leaching of some of these herbicides into the aquifer, surface, and groundwater samples were collected in a watershed during the years of 1996 to 2003, from different locations. To detect and quantify the herbicides a GC-MS (gas chromatograph/mass spectrometry) method was used. The response of the herbicides analyzed was linear over the concentration range of 0.02 to 2.0 μg/L. Analysis of groundwater revealed that the herbicides tebuthiuron, diuron, atrazine, simazine, and ametryn were not present in the samples. In the surface water collected in 1997, ametryn was present in two out of nine locations with concentrations ranging from 0.17 and 0.23 μg/L, which is above the allowable 0.1 μg/L according to the European safety level. The leaching potential of tebuthiuron, diuron, atrazine, simazine, 2,4-D, picloram, and hexazinone has been evaluated using CMLS-94, “Chemical Movement in Layered Soil,” as simulation model. No leaching into the depth of the water table at 40 m was found.

Comportamento do herbicida hexazinone em área de recarga do aqüífero Guarani cultivada com cana-de-açúcar

Sao Paulo state (Brazil) has an important area of sugarcane production, mainly for obtaining alcohol and sugar, where there is an intensive use of pesticides. An important recharge zone of Guarani aquifer, with supplies water for the local population, is located at Ribeirao Preto city, so the local behavior of pesticides must be investigated. The GUS index was obtained by using the paramenters Koc and half-life for hezazinone herbicide, determinated in representative soil of this region. This study has demonstrated that there is potential risks of hexazinone leaching to ground water, indicating that this herbicide must be monitored in ground water.

Leaching and half-life of the herbicide tebuthiuron on a recharge area of Guarany aquifer in sugarcane fields in Brazil

This study was undertaken to evaluate the degradation and mobility of the herbicide tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea) in soil under field conditions, and its potential for leaching and groundwater contamination. A watershed, Espraiado, located over a recharge area in Brazil, was chosen for soil and water studies. At Espraiado, water samples were collected from seven wells at intervals of three months from March 2004 to June 2006 and analyzed for tebuthiuron. Other samples were taken from city wells located outside of the recharge area. To assess the potential movement to the aquifer, tebuthiuron was also applied to trial plots at the recommended label rate of 1.0 kg/ha a.i. in May of 2004, with and without sugarcane coverage, on sandy soil. Soil samples were collected during the years of 2004 and 2005, at depths intervals of 20 cm from soil surface down to 120 cm and analyzed for tebuthiuron at zero, 3, 30, 60, 90, 120, 150, 180, 240, and 300 days after application. There was no clear effect of sugarcane coverage on the tebuthiuron degradation in soils, but it moved faster into the soil where there was no cover. After 180 days there were no measurable residues in the soil, and tebuthiuron was not found below 40 cm depth in any time. Tebuthiuron had a half-life of 20 days under those conditions. No tebuthiuron residue was found in ground water samples at any sampling time.

Sorption and Leaching Potential of Acidic Herbicides in Brazilian Soils

Abstract Leaching of acidic herbicides (2,4-D, flumetsulam, and sulfentrazone) in soils was estimated by comparing the original and modified AF (Attenuation Factor) models for multi-layered soils (AFi). The original AFi model was modified to include the concept of pH-dependence for K d (sorption coefficient) based on pesticide dissociation and changes in the accessibility of soil organic functional groups able to interact with the pesticide. The original and modified models, considering soil and herbicide properties, were applied to assess the leaching potential of selected herbicides in three Brazilian soils. The pH-dependent K d values estimated for all three herbicides were observed to be always higher than pH-independent K d values calculated using average K oc data, and therefore the original AFi model overestimated the overall leaching potential for the soils studied.Leaching of acidic herbicides (2,4-D, flumetsulam, and sulfentrazone) in soils was estimated by comparing the original and modified AF (Attenuation Factor) models for multi-layered soils (AFi). The original AFi model was modified to include the concept of pH-dependence for Kd (sorption coefficient) based on pesticide dissociation and changes in the accessibility of soil organic functional groups able to interact with the pesticide. The original and modified models, considering soil and herbicide properties, were applied to assess the leaching potential of selected herbicides in three Brazilian soils. The pH-dependent Kd values estimated for all three herbicides were observed to be always higher than pH-independent Kd values calculated using average Koc data, and therefore the original AFi model overestimated the overall leaching potential for the soils studied.

Método para a determinação de hexazinone e tebutiuron em água

METHOD FOR DETERMINATION OF HEXAZINONE AND TEBUTHIURON IN WATER. This work presents an alternative method for determination of the herbicides tebuthiuron and hexazinone in ground water. The extraction was made with dichloromethane and the analyses by high performance liquid chromatography (HPLC), using reversed-phase column, C-18, mobile phase methanol/water 50:50, v/v, detection and quantification at 247 nm. The following validation parameters were obtained: limit of detection of method 0.02 and 0.03 µg L -1 , limit of quantification of method 0.07 and 0.09 µg L -1 ; linear range limit of quantification of instrument – 300 µg L -1 (r 2 ≥ 0.998); recoveries from 90.3 to 108.2% and 90.3 to 101.6%; intermediary precision (%RSD) < 8 and < 6%, for hexazinone and tebuthiuron, respectively. The method showed to be efficient and reliable for determination of the herbicides in ground water.

Movimento do herbicida tebutiuron em dois solos representativos das áreas de recarga do aqüífero Guarani

O movimento do herbicida tebutiuron foi analisado em um Latossolo Vermelho Distrofico psamitico (LVdq) e um Neossolo Quartzarenico Ortico tipico (RQo), representativos das areas de recarga do aquifero Guarani no Brasil, tendo como fatores influenciadores, a condutividade hidraulica (K), o teor de carbono orgânico (CO) e o teor de argila (TAr). O presente estudo foi realizado em colunas de solos indeformados, com aplicacao do produto comercial contendo o herbicida em discussao. Esses parâmetros evidenciam certa influencia na movimentacao vertical do herbicida tebutiuron, particularmente no RQo, uma vez que esse herbicida e quimicamente neutro. Observou-se, por exemplo, uma diferenca significativa entre os valores K dos dois solos, sendo superior no RQo. Alem de uma relacao inversa entre teores de CO e de TAr e os valores de K dos dois solos, indicando serem aqueles parâmetros inibidores do deslocamento do tebutiuron no perfil do solo. Os resultados aqui obtidos neste trabalho visam subsidiar estudos de avaliacao de risco ambiental, sobretudo agua subterrânea, a partir de areas de recarga de aquiferos naturalmente frageis, com enfase para o aquifero Guarani.

DETERMINATION OF ANTIOXIDANT POTENTIAL AND QUANTITATION OF PHENOLIC COMPOUNDS BY HPLC IN ACCESSION OF Capsicum baccatum var. pendulum

Maria Lucy de Assisa, Marco Antônio G. B. Gomesb, Larissa L. da Cruza, Michel de S. Passosb, Silvia M. F. Pereiraa, Mariana B. S. Arantesa, Daniela B. Oliveiraa and Ivo J. C.Vieirab,* Laboratório de Tecnologia de Alimentos, Centro de Ciências e Tecnologias Agropecuárias, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes – RJ, Brasil Laboratório de Ciências Químicas, Centro de Ciências e Tecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes – RJ, Brasil