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Residues of the herbicides simazine, metribuzin, metolachlor, trifluralin, atrazine, and two metabolites of atrazine, deisopropylatrazine (DIA) and deethylatrazine (DEA), are surveyed in the surface and groundwater of the Primavera do Leste region, Mato Grosso, Brazil during September and December 1998 and April 1999. Different water source sampling stations of groundwater (irrigation water well, drinking water well, and water hole) and surface water (dam and river) are set up based on agricultural land use. A solid-phase extraction procedure followed by gas chromatography-nitrogen-phosphorus detection is used for the determination of these compounds. All compounds are detected at least once in water samples. A temporal trend of pesticide contamination is observed, with the highest contamination frequency occurring in December during the main application season. Metribuzin shows the highest individual detection frequencies throughout the monitoring period, followed by metolachlor, simazine, and DEA. The maximum mean concentrations of pesticides in this study are in the range from 0.14 to 1.7 microg/L. We deduct that the contamination of water resources is predominantly caused by non-point pollution of pesticides used in intensive cash-crop cultures of the Cerrado area. Therefore, a continuous monitoring of pesticide concentrations in water resources of this tropical region is necessary to detect the longer term contamination trends and developing health risks.

Sorption of acetamiprid ((E)-N1-[(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methylacetamidine), carbendazim (methyl benzimidazol-2-ylcarbamate), diuron (N-(3,4-dichlorophenyl)-N, N-dimethyl urea) and thiamethoxam (3-(2-chloro-thiazol-5-ylmethyl)-5-methyl-[1,3,5]oxadiazinan-4-ylidene-N-nitroamine) was evaluated in two Brazilian tropical soils, Oxisol and Entisol, from Primavera do Leste region, Mato Grosso State, Brazil. To describe the sorption process, batch experiments were carried out. Linear and Freundlich isotherm models were used to calculate the K(d) and K(f) coefficients from experimental data. The K(d) values were utilized to calculate the partition coefficient normalized to soil organic carbon (K(oc)). For the pesticides acetamiprid, carbendazim, diuron and thiamenthoxan the K(oc) (mL g(- 1)) values ranged in both soils from 98 - 3235, 1024 - 2644, 145 - 2631 and 104 - 2877, respectively. From the studied pesticides, only carbendazim presented correlation (r(2) = 0.82 and p < 0.01) with soil organic carbon (OC) content. Acetamiprid and thiamethoxam showed low sorption coefficients, representing a high risk of surface and ground water contamination.

Studies conducted over a period of about 14 years in the northern part of the Pantanal of Mato Grosso revealed that there is a.pronounced seasonal succession of algal communities resulting from periodic flooding and desiccation. Generally, during the high water period, the microtlora is very sparse but species-rich and dominated by the Desmidiales, which are notably inhabitants of mineral-poor waters. During the dry season, the rapidly evaporating pools of water in the Pantanal often support extremely large concentrations of algae belonging mainly to other orders of Chlorophyta and to Euglenophyta. The seasons of rising and falling water levels are chraracterized by a mixed flora containing elements typical of both the high water and dry seasons, according to the local conditions that prevail. Dense beds of filamentous algae in the family Zygnernataceae are generally encountered only where there is inflow of nutrient-rich water or another source of local eutrophication. The algae present belong overwhelmingly to cosmopolitan or circumtropical species. Their presence and relative abundance seem to be determined primarily by the concentrations of inorganic nutrients in the water. Of the 337 species observed, most are reported for the first time from the Pantanal, and the list of species provides the only comprehensive catalog of autotrophic microorganisms yet compiled for this vast wetland. The physical and chemical characteristics of the habitats in which the various algae occur and their relationships with the macrophyte communities are discussed. One variety of desmid is redescribed and given a valid name: Stuurodesmus convergens (EHRENBERG ex RALFS) LILLIEROTH var. teilingii DE-LAMONICA-FREIRE nom. nov., and the taxonomic status of Cosmorium guficiense (GUT-WINSKI) DE-LAMONICA-FREIRE comb. nov. is revised. 254 E. M. DE-LAMONICA-FREIRE and C. W. HECKMAN contrast, during the high water period, or cheiu, extremely small amounts of vital mineral nutrients are present in the water, which is extremely clear and dominated by various aquatic macrophyte species.Preliminary studies revealed that the algal communities undergo profound seasonal changes within relatively short periods of time (HECKMAN etal., 1993). As in the case of the macrophytes, the species present are widely distributed rather than endemic to the Pantanal. The algae encountered are mainly those known to be cosmopolitan or circumtropical in distribution. However, the environmental conditions under which they develop and the communities among which they are found are often profoundly different than those in other climatic zones (HECKMAN, 1994b).This study was undertaken to determine the seasonal succession of the algae in the Pantanal of PoconC, Ciceres, and Bargo de Melgaqo, which is the northern part of that vast wetland located in the State of Mato Grosso. The goals of the study were to provide a comprehensive list of the most important algal species in the Pantanal of Mato Grosso, to determine their seasons of occurrence, and to provide basic informa...

Foi desenvolvido um estudo sobre a presença dos herbicidas simazina, metribuzim, metolacloro, trifluralina, atrazina e seus metabólitos desisopropilatrazina (DIA) e desetilatrazina (DEA) em água superficial e subterrânea da região de Primavera do Leste, Mato Grosso, Brasil. O procedimento analítico baseou-se na extração em fase sólida com cartuchos descartáveis Sep-Pak C 18 e eluição com acetato de etila. Os níveis de resíduos foram determinados por cromatografia a gás com detector de nitrogênio e fósforo. Para a maior parte dos pesticidas, a recuperação média nos diferentes níveis de fortificação foi >70% com estimativa do desvio padrão relativo <19%. As recuperações observadas para o DIA e a trifluralina foram 25% e 56%, respectivamente. As baixas recuperações foram atribuídas à retenção incompleta do DIA e à forte retenção no sorvente e alta volatilidade da trifluralina. Os limites de detecção variaram de 0,023 a 0,088 μg L -1 . Este método foi aplicado na análise de 5 amostras de águas superficiais e 28 de águas subterrâneas, em pontos usados para abastecimento de água para consumo humano, coletadas em Primavera do Leste, Mato Grosso. O nível mais elevado encontrado nas amostras de água foi 1,732 μg L -1 de metolacloro enquanto o herbicida encontrado com maior freqüência foi o metribuzim.A study on the presence of herbicides, namely simazine, metribuzin, metolachlor, trifluralin, atrazine and two metabolites, deisopropylatrazine (DIA) and deethylatrazine (DEA), was performed in ground and surface waters from Primavera do Leste region, Mato Grosso state (Middle West of Brazil). The analytical procedure was based on solid-phase extraction (SPE) with Sep-Pak C 18 disposable cartridges and ethyl acetate for elution solvent. Residue levels were determined by gas chromatography with nitrogen-phosphorus detection. For most of the pesticides average recoveries at different fortification levels were >70% with relative standard deviation <19%. The recoveries of DIA and trifluralin in water were 25% and 56%, respectively, which were attributed to the incomplete retention of DIA and strong retention on the sorbing material and high volatility of trifluralin. Detection limits ranged from 0.023 to 0.088 μg L -1 . This method was applied for the analysis of 5 superficial water samples and 28 groundwater samples, in places used for human consumption without previous treatment, collected in Primavera do Leste, Mato Grosso, Brazil. Results indicated that the highest level of contamination in a water sample was 1.732 μg L -1 for metolachlor, while metribuzin was the most frequently detected herbicide with maximum concentration of 0.351 μg L -1 .Keywords: solid-phase extraction, water, herbicides, pesticides, GC-NPD IntroductionThe Primavera do Leste region (Mato Grosso state, Middle West of Brazil) is an area with a high agricultural production, that has expanded greatly since its start 30 years ago. As consequence of the monoculture conditions under which soybean, cotton, rice, maize and bean are grown, they are susceptible t...