Degradação do pesticida Padron® por processos fotoquímicos utilizando luz artificial e solar

Destruction of Padron® (dye and picloram) was evaluated using a photoreactor and a solar reactor. Photolysis was observed using only a germicide lamp (GL). Black light (BL) and H2O2 (172 mmol L-1) promoted a conversion of 49% and 6% of dye and picloram, respectively. Photocatalytic processes were more efficient using TiO2/GL (96%-dye; 60%-picloram) than TiO2/BL (44%-dye; 40%-picloram). Photolysis using sunlight was not observed during PadronÒ recirculation in the reactor constructed with four borosilicate tubes. Meanwhile, adding H2O2 resulted in 12% conversion of dissolved organic compounds. Finally, the most efficient mineralization (60%) was obtained using the Fenton reaction ( H2O2-176 mmol L-1; FeSO4x6H2O-90 mmol L-1) and sunlight.

Investigation of the occurrence of pesticide residues in rural wells and surface water following application to tobacco

In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cropping, was assessed. Water consumption wells and surface water flows were sampled at different times. After a preconcentration step with solid phase extraction (SPE), the selected pesticides were determined by gas chromatography with electron capture detection (GC-ECD) or high performance liquid chromatography with diode array detection (HPLC-DAD). No pesticides were detected in the well water samples and surface water flow in the winter season. However, in the spring and summer higher concentrations of chlorpyrifos and imidacloprid were found in the water source samples. Atrazine, simazine and clomazone were also found. The occurrence of pesticides in collected water samples was related with the application to tobacco.

Avaliação da contaminação por organofosforados em águas superficiais no município de Rondinha - Rio Grande do Sul

Water pollution is a serious environmental problem. In Rondinha, Rio Grande do Sul, on a small area planted with tobacco, it has been using organophosphates pesticides. The purpose of this study was to evaluate the organophosphates pesticides contamination of the superficial water in this municipality. The samples collected in fifteen places were evaluated by the method of organophosphates acethylcolinestherase inhibition. In five samples the organophosphates levels were above the limit established by CONAMA, indicating the necessity of arrangements that allow reducing the risk of the population and the environment contamination.

Estimativa de risco de contaminação das águas por pesticidas na região sul do estado do RS

Pesticides can be quite useful in agricultural production, however, some pesticides after application can reach and contaminate the hydric resource. Pesticide monitoring must be careful because it is expensive and lengthy. Thus, in this work, a theoretical prediction was made using the approaches suggested by EPA-USA, the Groundwater Ubiquity Score index (GUS) and the Goss method associated with physicochemical properties of 27 pesticides used in a region in the south of Brazil. The results of this work led to the identification of the pesticides that should be prioritized in the environmental monitoring due to their high potential for contaminating water resources.

Análise de resíduos de agrotóxicos em tomates empregando dispersão da matriz em fase sólida (DMFS) e cromatografia gasosa

This work was aimed on optimization of the matrix solid-phase dispersion (MSPD) technique using gas chromatography for analyzing residues of chlorpyriphos, λ-cyhalothrin, cypermethrin and deltamethrin in tomatoes. The results showed that silica was more efficient for the clean up of extracts, but florisil provided the highest recovery rates. A 2³ complete factorial design was carried out to evaluate the absorbent/sample ratio, presence of co-column (silica) and ultrasonic bath on the extraction rate. The percentage of extraction of the pesticides chlorpyriphos, λ-cyhalothrin, cypermethrin and deltamethrin were 64.7, 88.3, 99.2 and 89.2%, respectively, with relative standard deviations below 5%.

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

São 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 Ribeirão 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.

Database of the Amazon aromatic plants and their essential oils

The aromatic flora of the Amazon has been inventoried for 30 years. In this sense, were made over 500 field trips to collect over 2500 plants and to obtain more than 2000 essential oils and aroma concentrates, all of them submitted to GC and GC-MS. This work led to the creation of a database for the aromatic plants of the Amazon, which catalogs general information about 1250 specimens. The database has allowed the publication of the chemical composition of the oils and aromas of more than 350 species, associated with a larger number of chemical types. The essential oils of many species offer optimum conditions for economic exploitation and use in national and international market of fragrances, cosmetics, agricultural and household pesticides.

Feromônios de insetos: tecnologia e desafios para uma agricultura competitiva no Brasil

Pheromones are chemical compounds used by species to communicate intra and inter specifically. As strategy of integrated pest management (IPM), the use of these compounds allows the monitoring of target insects that results in more reliable interventions and consequently avoiding unnecessary use of pesticides. In certain crops these compounds are used as a control measure, not only monitoring. The Brazilian agriculture has a portfolio of 49 major crops that are attacked by 447 species of insects. Of this total, 103 species have already been the subject of study in the research with pheromones. Currently, in the Brazilian market, 28 pheromone products are indicated for the control of 19 insect pests. However, these products are not used regularly in major crops of the country. This stems from the lack of implementation of IPM of these crops. While the research focused on the main species of agribusiness pests, marked of pheromones products is serving to more marginal crops like apples and peaches at the expense of major crops like soybean and corn.

Efeito de matriz na quantificação de agrotóxicos por cromatografia gasosa

The lack of accuracy of a chromatographic method can be associated with the matrix effect. This effect is observed in pesticide quantification by gas chromatography when the chromatographic signals of standards prepared in solvents are compared with those of the analyte in extracts of complex matrices. In the competition between the matrix components and the pesticides for the active sites of the liner, a larger amount of pesticides is transferred to the column, giving apparent extractions above 100%. In this work, we discuss factors that contribute to the matrix effect and present some attempts to overcome the problem.

Resíduos de agrotóxicos em alimentos: uma preocupação ambiental global - Um enfoque às maçãs

This paper describes the use of pesticides in agriculture. Research has shown that significant quantities of pesticide residues have been found in many types of foods. Thus, an overview is given of pesticide residue determinations in fruits and vegetables, with special attention to apples. The toxicity and the adverse effects possibly caused by the exposure of these compounds are alerting the scientific community to develop studies about the validation of analytical methods for multiresidue pesticide determination in these samples. This review shows that pesticide-residue determination in apples is becoming a very important and challenging issue.

Correlação entre parâmetros da cinética de intumescimento com características estruturais e hidrofílicas de hidrogéis de poliacrilamida e metilcelulose

In this paper, the effects of acrylamide (AAm), methylcellulose (MC) contents, pH and ionic strength on kinetic, network and hydrophilic properties of polyacrylamide and methylcellulose hydrogels were investigated. The hydrogels were characterized by evaluating of network [average molecular weight between crosslinks (M C), crosslink density (q) and the number of elastically effective chains (Ve)], and kinetic parameters [diffusional exponent (n), diffusion constant (k) and diffusion coefficient (D)]. Such properties were controlled by adjusting of the AAm, MC contents, pH and ionic strength factors. Due to high hydrophilicity and fast water-uptake, the PAAm-MC hydrogels can be considered as materials for potential applications in agricultural fields, mainly in controlled release of water or pesticides.

QuEChERS: um método moderno de preparo de amostra para determinação multirresíduo de pesticidas em alimentos por métodos cromatográficos acoplados à espectrometria de massas

This review attempts to provide an updated overview of the Quick, Easy, Cheap, Effective, Ruged and Safe (QuEChERS) multiresidue extraction method, that involves initial extraction in acetonitrile, an extraction/partition step after the addition of salt, and a cleanup step utilizing dispersive solid phase extraction. QuEChERS method is nowadays the most applied extraction method for the determination of pesticide residues in food samples, providing acceptable recoveries for acidic, neutral and basic pesticides. Several applications for various food matrices (fruits, vegetables, cereals and others) in combination with chromatographic mass spectrometry analysis were presented.

Determinação de resíduos de pesticidas em plasma bovino por cromatografia gasosa-espectrometria de massas

An analytical method for the isolation based on matrix solid-phase dispersion technique and gas chromatographic determination of pesticides in cattle plasma is presented. It was fortified 0.25 g of plasma with pesticides and blended with 1 g each C18 and Na2SO4. The homogenized matter was transferred to a SPE cartridge, which contained 1 g of activated florisil with 5 mL acetonitrile. The analites were eluted under vaccum with 15 mL acetonitrile, the extract was analyzed by gas chromatography-mass spectrometry. The limit of quantification of the method was 0.04 mg L-1 for chlorphenvinfos and fipronil and 0.02 mg L-1 for cypermethrin..

Exposição humana a substâncias químicas potencialmente tóxicas na dieta e os riscos para saúde

Humans are exposed to a variety of chemicals from the consumption of food, including undesirable compounds such as pesticides and mycotoxins. Chemical human risk assessment is a process intended to estimate the risk to a given population from the exposure to a chemical (or to a chemical group having the same mechanism of action). The process consists of four steps, namely hazard identification, hazard characterization, exposure assessment and risk characterization. Chemical dietary risk assessment is an essential procedure to establish safe food standards. In this review the tools and data sources currently used in the risk assessment process will be discussed.

Nanoestruturas em fotocatálise: uma revisão sobre estratégias de síntese de fotocatalisadores em escala nanométrica

Advanced oxidative processes (AOPs) are based on chemical processes that can generate free radicals, such as hydroxyl radicals (.OH) which are strong, non-selective oxidant species that react with the vast majority of organic compounds. Nanostructured semiconductors, especially titanium dioxide (TiO2) in the anatase phase, are well-established photocatalysts for this process, which have proved to be useful in the degradation of dyes, pesticides and other contaminants. Research in different strategies for the synthesis of nanostructured semiconductors, with particular characteristic is currently a topic of interest in many studies. Thus, this paper presents a review about various synthesis strategies of nanostructured photocatalysts.