Lixiviação de atrazina em solo em área de recarga do Aquífero Guarani.

No Aqüífero Guarani, o maior e mais importante lençol de água subterrânea de toda a região centro-sul do país, encontra-se a microbacia do Córrego do Espraiado, um dos seus pontos de recarga. Nesta área, existe predomínio de culturas, nas quais são utilizados herbicidas da família das triazinas e a presença de solo arenoso, que tornam a área vulnerável à lixiviação. Entre os produtos aplicados encontra-se a atrazina (2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine). Devido as suas características físico-químicas, esse herbicida tem alto potencial de risco de movimentar-se para água subterrânea. Para avaliar a lixiviação da atrazina foram feitas amostragens de solo para análise física e de água superficial e subterrânea, durante os anos de 2000 a 2002, para análise de resíduo através de cromatografia líquida HPLC (High Performance Liquid Chromatography), e confirmadas com GC-MS (Gas chromatography-mass spectrometry). Apenas quatro amostras de água superficial apresentaram resíduos de atrazina. Destas, duas com 0,04; e as outras com 0,05 e 0,09 ug/L. Nas amostras de água subterrânea os resultados indicaram uma amostra contendo 0,03 ug/L de atrazina. Entretanto, nenhuma delas foi confirmada pelo GC-MS, não indicando resíduos. A presente avaliação contou também com o uso do simulador de sistemas CMLS-94 (Chemical Movement in Layered Soils). O simulador também mostrou que a atrazina não atinge profundidades comprometedoras para a qualidade do aquífero

Herbicide and nitrate residues in surface and groundwater from sugarcane area in Brazil.

Various studies have demonstrated the presence at high levels of pesticides and nitrate in soil, surface, and groundwater. Prior studies have identified a watershed area in Brazil with a high risk of soil, surface, and groundwater contamination by pesticides at the region of Riberao Preto, SP. Surface and groundwater were collected at the area during the period of October 1995 to November 1998. By means of gas chromatography-mass spectrometry (GC-MS) technique the herbicides tebuthiuron, diuron, simazine, atrazine, and ametryne, and nitrate were analyzed according to the protocols established in literature. The recovery obtained in the extraction procedure was higher than 95% for all herbicides except simazine for which the recovery was 85,6%. Due to the enrichment in the extraction procedure and the sensitive detection at two wavelengths it was possible to obtain a quantification limit of 0.02 ug/L for the herbicides studied. The method was linear over the range of 0.02 to 2.0 ug/L. Soil data showed a higher level of the herbicide tebuthiuron, at the levels of 59.6 ppb; than the other applied during all the months. The results have shown the hercicide tebuthiuron as the one with higher concentrations in groundwater and in January of 1996 the concentration found was 0.08 ug/L, close to the maximum allowed, 0.1 ug/L, but this fact was not consistent during the other months. No residue of the other herbicides was detected. In case of nitrates, with maximum level allowed of 10 mg/L, it was found the maximum of 0.9 mg/l, but in a shallow well inside the area. Commercial wells at the edge of the watershed showed low levels of nitrate, below the risk level, but with potential for dangerous contamination.bitstream/item/199623/1/Cerdeira-Herbicide.pd

Presence of Atrazine in Water in a Recharge Area of Guarany Aquifer in Brazil

The region of Ribeirao Preto City located in Sao Paulo State, southeastern Brazil, is an important sugarcane, soybean and corn producing area. This region is also an important recharge area for groundwater of the Guarany aquifer, a water supply source of the city and region. The cultivation of grain and sugar cane in thes area demands the frequent use of the herbicide atrazine (2-chloro-4- (ethylamino)-6-(isopropylamino)-S-triazine). This research was conducted to characterize the potential contamination of groundwater with atrazine. Surface water samples were collected in the Espraiado stream in a selected watershed on the area, during the years of 1995-1998. Groundwater was also collected in wells located at the edge of the watershed during the years of 1999 to 2002. The water samples were analyzed by HPLC (High Performance Liquid Chromatography) procedure followed by GC-MS form confirmation. To predict the atrazine leaching in the area, the CMLS-94 (Chemical Movement Layered Soil) simulation model was also used. Only four atrazine detections in surface water were found, however, none of them were confirmed with GC-MS. No atrazine was detected in groundwater samples. The results obtained by the CMLS-94 simulations predicted that atrazine, after four years from the application date, would not have reached the depth of the confined aquifer (40m)

Herbicide leaching on a recharge área of Guarany Aquifer, Brazil.

The region of Ribeirao Preto city, located in Southeast of Brazil, Sao Paulo State, is an important sugarcane, soybean, and corn producing area with a high level of pesticide utilization. This region is also an important recharge area for groundwater supply of the Guarany aquifer. A survey has shown the following herbicides as the most commonly used in the area: atrazine, simazine, ametryn, tebuthiuron, diuron, and 2,4-D. In order to study a possible leaching of the herbicides into the aquifer, surface and ground water samples were collected during the years of 1996 to 2003 from different points. Groundwater samples were collected from sites near the river during the same period. It was used a GC-MS to detect and quantify the herbicides (gas chromatograph/mass spectrometry). The method was linear over the range of 0.02 to 2.0 ?g/L. Analysis of tebuthiuron, diuron, atrazine, simazine and ametryn residues showed no significance amount of these products in ground water. Only two out of nine points of surface water collected in one year, presented ametryn concentrations above (0.17 and 0.23 ug/L) the allowable 0.1 ug/L, European safety level. It was also used the simulator model CMLS-94, ?Chemical Movement Layered Soil? which indicated no leaching to the depths of the water table at 40m

GC-MS determination of chlorotriazines in aqueous environmental samples.

The extensive use of chlorotriazines as selective herbicides in agriculture and their relatively high persistence imply that these compounds are now present in the environment, contaminating surface and groundwater. In European countries, United States and Canada, the drinking water ordinance demands a limited concentration of 0.5 ug/l for the sum of all pesticides and 0.1 ug/l with respect to each compound, with the consequent need for sensitive and selective analytical methods. Gas chromatography-mass spectrometry (GC-MS) is the most reliable technique for this kind of analysis and was employed in the present study to evaluate the contamination of aqueous environmental samples by atrazine, simazine and ametryne. Surface water samples (1 liter) were collected from the Espraido watershed (Ribeirao Preto, SP, Brazil) during the period from October 1995 to July 1996, at nine different points. Groundwater samples from sites near the river were collected during the same period. The extraction procedure consisted of the addition of 100 ml of water sample, previously filtered throw 0,22 um membranes, to a separatory funnel. After the addition of 25 ul of the internal standard solution (caffeine, 5 ug/ml) and akalinization with 25 ul of 4 M NaOH aqueous solution, the samples were extracted with 15 ml ethyl acetate by shaking for 1 hour. Volumes of 5 ml of the organic phase were transferred to conic tubes and evaporated to dryness under a nitrogen flow, at the temperature of 35oC. The residues were dissolved in 25 ul acetone and 2 ul were chromatographed on a DB-5 column (J&W Scientific, 0.25 mmx30m, film of 0,25 um) using a GC-MS QP5000 Shimadzu apparatus. Helium was used as carrier gas. The operation conditions were: injector temperature 240oC; oven temperature program - start at 60oC for 1 min, increase to 150oC at a rate of 20oC/min and then to 280oC at a rate of 10oC/min; detector temperature of 230oC in the ion source of the MS. Under the chromatographic conditions selected and by extracting 100 ml of water samples, the quantification limit was estimated to be 0.02 ug/l for each triazine herbicide. The results showed traces of ametryne in surface water samples collected in December, whereas the ground water samples used for human consumption did not show contamination. The other herbicides were not detected in the samples analyzed under the condition employed

Comportamento de triazinas na bacia do Alto Taquari, Mato Grosso do Sul, Brasil.

Na Bacia do Rio Taquari, integrante da Bacia do Alto Paraguai que contempla todo o ecossistema do Pantanal, está localizada área de recarga do Aqüífero Guarani. Um levantamento do uso agrícola nas porções noroeste e oeste revelou que na região a atividade agrícola é intensiva, principalmente com soja e milho, além de forrageiras como sorgo e milheto no planalto. Como herbicidas do grupo das triazinas são utilizados na região e estes tem potencial de lixiviação para a água subterrânea, foram coletadas amostras de água de poços da área de recarga do aqüífero e analisadas para os herbicidas atrazina e simazina durante os anos de 2000 a 2002. Utilizou-se um cromatógrafo a gás Shimadzu acoplado a um espectrômetro de massas. Foram encontrados resíduos na ordem de 0,1 ppb abaixo do nível máximo aceitável de 2,0 ppb estabelecido pelo ministério da saúde. Para complementar a avaliação do potencial de lixiviação dos herbicidas foi também calculado o índice potencial de lixiviação (LPI), o que indicou que atrazina e a simazina apresentam, respectivamente, alto e moderado potencial de lixiviação

Effects of agriculture on ground water in a recharge area of Guarany Aquifer in Brazil.

The region of Ribeirão Preto City located in São Paulo State, southeastern Brazil, is an important and highly mechanized sugar cane producing area. It is also an important recharge area of the Guarany aquifer, which provides water to several cities and rural communities in the region. Research has been conducted in this region since 1995 to assess the behavior of herbicides, such as atrazine, simazine, ametryn, tebuthiuron, diuron, 2,4-D, picloram, and hexazinone, applied in the area. Nitrate applied as nitrogen fertilizer was also evaluated. Espraiado watershed, located over the recharge area, was chosen for this study. Water samples were collected from seven wells located inside the watershed and from surface water of Espraiado stream. Other samples were taken from city wells located at the edge of the recharge area with exception of the control samples that were collected from downtown wells. Results have shown that no residue of herbicide was found in ground water wells and only ametryn was found at levels higher than the Maximum Concentration Level (MCL) of 0.1 ?g/L in surface water of the watershed. However, nitrate was detected at levels close to the MCL of 10 mg/L in wells located in downtown, far away from the sugar cane area

Analysis of unbound plasma concentration of oxcarbazepine and the 10-hydroxycarbazepine enantiomers by liquid chromatography with tandem mass spectrometry in healthy volunteers

This study describes the development and validation of a method for the analysis of unbound plasma concentrations of oxcarbazepine (OXC) and of the enantiomers of its active metabolite 10-hydroxycarbazepine (MHD) [S-(+)- and R-(−)-MHD] using liquid chromatography with tandem mass spectrometry (LC–MS/MS). Additionally, the free fraction of the drug is described in healthy volunteers (n = 12) after the oral administration of 300 mg OXC/12 h for 5 days. Plasma aliquots of 200 μL were submitted to ultrafiltration procedure and 50 μL of the ultrafiltrate were extracted with a mixture of tert-butyl methyl ether:dichloromethane (2:1, v/v). OXC and the MHD enantiomers were separated on a OD-H chiral phase column. The method was linear in the range of 4.0–2.0 μg/mL for OXC and of 20.0–6.0 μg/mL plasma for the MHD enantiomers. The limit of quantification was 4 ng for OXC and 20 ng for each MHD enantiomer/mL plasma. The intra- and inter-day precision and inaccuracy were less than 15%. The free fraction at the time of peak plasma concentration of OXC was 0.27 for OXC, 0.37 for S-(+)-MHD and 0.42 for R-(−)-MHD. Enantioselectivity in the free fraction of MHD was observed, with a higher proportion of R-(−)-MHD compared to S-(+)-MHD

Multiresidue method for the analysis of herbicides in surface and groundwater.

The high standards for drinking water purity laid down by the European Community, United States and other coutries require the development of suitable analytical methods with high sensitivity, selectivity, accuracy and reliability, that permit the analysis of a broad variety of substances in a single run, or at least those substances that are important in a specific water catchment area. The standard method for the investigation of environmental pollutants has been gas chromatography using different selective detectors after extraction with different organic solvents. Some of that substances that are difficult to analyze by gas chromatography because of thermal instability or chemical polarity, may be analyzed by high performance liquid chromatography. In the present study we employed this technique to develop a highly sensitive method for the simultaneous analysis of atrazine, simazine, ametryne, tebuthiuron and diuron in surface and groundwater. The aqueous samples (100 ml ) were filtered through 0.22 um membranes to remove suspended matter. After adjusting the pH by the addition of 25 uL of 4M NaOH, the samples were extracted with 12 ml dichloromethane by mechanical shaking for 1 hour. After phase separation, 6 ml of the organic phases were transferred to conic test tubes and the solvent was evaporated to dryness under a stream of nitrogen at 35oC. The residues were dissolved in 200 ul of the mobile phase and 100 ul were chromatographed on a Lichrospher 100 RP-8 column (particle 5 um , 125x4mm, Merck) using 0.05 M phosphate buffer, pH 5.5, and acetonitrile (73:27, v/v) as mobile phase. The triazine herbicides were detected at 220 nm, whereas tebuthiuron and diuron were detected at 254 nm. The recovery obtained in the extration procedure was higher than 95% for all herbicides except simazine for which the recovery was 85.6%. Due to the enrichment in the extraction procedure and the sensitive detection at two wavelengths it was possible to obtain a quantification limit of 0.02 ug/L for all herbicides studied. The method was linear over the range of 0.02 to 2.0 ug/L. The method was employed for the analysis of suface and groundwater samples collected over a period of ten months (10/95 to 07/96) in the Ribeirao Preto region. Our results show that the method was suitable for the sensitive screening of these herbicides