Diurnal variation of methane emission from a paddy field in Brazilian Southeast / Variação diurna da emissão de metano em arroz irrigado no Sudeste do Brasil

ABSTRACT: This study aimed to investigate the diurnal variation of methane (CH4) emission in a flooded-irrigated rice field at different stages of the plant development under tropical climate in three growing seasons, in order to determine the most appropriate time for gas sampling in the Brazilian Southeast region. It aimed also to verify correlations between CH4 flux and air, water and soil temperatures, and solar radiation. The CH4 emissions were measured every 3-hour interval on specific days in different development stages of the flooded rice in the Experiment Station of the Agência Paulista de Tecnologia dos Agronegócios (APTA), Pólo Regional Vale do Paraíba, at Pindamonhangaba, State of São Paulo (22°55' S, 45°30' W), Brazil. Different CH4 emission rates were observed among the plant growth stages and also among the growing seasons. The CH4 emission showed high correlation with the soil temperature at 2cm depth. At this depth, the CH4 emission activation energy in response to soil temperature was higher in the stage R2. Emission peaks were observed at afternoon, while lower fluxes were recorded at the early morning. The most appropriate local time for gas sampling was estimated at 12:11:15a.m.±01:14:16 and 09:05:49p.m.±01:29:04.

RESUMO: Este estudo teve como objetivo investigar a variação diurna de emissões de metano (CH4) em uma lavoura de arroz irrigado por inundação em diferentes estágios de desenvolvimento de plantas de arroz irrigado, sob clima tropical, em três estações de crescimento, para determinar o período de tempo mais apropriado à amostragem de gás na região Sudeste do Brasil. O trabalho objetivou também verificar correlações entre o fluxo de CH4 e as temperaturas do ar, da água e do solo e a radiação solar. As emissões diurnas de CH4 foram medidas a cada intervalo de três (3) horas em dias específicos em diferentes estágios de desenvolvimento da planta de arroz inundado na Estação Experimental da Agência Paulista de Tecnologia dos Agronegócios (APTA), Pólo Regional Vale do Paraíba, em Pindamonhangaba, Estado de São Paulo (22°55' S, 45°30' W), Brasil. Diferentes taxas de emissão foram observadas entre os estágios de desenvolvimento da planta avaliados e também entre as estações de cultivo. A emissão de CH4 mostrou alta correlação com a temperatura do solo a 2cm de profundidade. Nesta profundidade, a energia de ativação da emissão de CH4 em resposta à temperatura do solo foi maior no estágio R2. Os picos de emissão foram observados no período da tarde, enquanto que menores fluxos foram registrados no início da manhã. O horário mais apropriado para amostragem de gás foi estimado em 12:11:15a.m.±01:14:16 and 09:05:49p.m.±01:29:04.

Estimation of herbicide bioconcentration in sugarcane (Saccharum officinarum L.) / Modelagem de bioconcentração de herbicidas em cana (Saccharum officinarum L.)

Sugarcane is an important crop for sugar and biofuel production in Brazil. Growers depend greatly on herbicides to produce it. This experiment used herbicide physical-chemical and sugarcane plant physiological properties to simulate herbicide uptake and estimate the bioconcentration factor (BCF). The (BCF) was calculated for the steady state chemical equilibrium between the plant herbicide concentration and soil solution. Plant-water partition coefficient (sugarcane bagasse-water partition coefficient), herbicide dilution rate, metabolism and dissipation in the soil-plant system, as well as total plant biomass factors were used. In addition, we added Tebuthiuron at rate of 5.0kg a.i. ha-1 to physically test the model. In conclusion, the model showed the following ranking of herbicide uptake: sulfentrazone > picloram >tebuthiuron > hexazinone > metribuzin > simazine > ametryn > diuron > clomazone > acetochlor. Furthermore, the highest BCF herbicides showed higher Groundwater Ubiquity Score (GUS) index indicating high leaching potential. We did not find tebuthiuron in plants after three months of herbicide application.

A cana de açúcar é uma cultura importante para produção de açúcar e biocombustíveis no Brasil e exige elevada utilização de herbicidas. Utilizamos modelo matemático para ajudar na compreensão da absorção de herbicida dessa cultura. Propriedades físico-químicas dos herbicidas e propriedades fisiológicas das plantas de cana foram usados para estimar a absorção e também o fator de bioconcentração, bioconcentration factor (BCF), calculado para o equilíbrio químico entre a concentração do herbicida na planta e na solução do solo. O coeficiente de partição planta/água, a taxa de diluição de herbicida, o metabolismo e a dissipação no sistema solo-planta e biomassa total das plantas foram adicionados ao modelo. O herbicida tebuthiuron aplicado ao solo na dose de 5,0kg ha-1 i.a. foi utilizado para testar o modelo. A absorção dos herbicidas mostrada pelo modelo indicou em ordem o seguinte: sulfentrazone> picloram> tebuthiuron> hexazinone> metribuzin> simazina> ametryn> diuron> clomazone> acetochlor. Esses herbicidas com alto índice (BCF) também apresentaram alto índice de potencial de lixiviação para água subterrânea "Groundwater Ubiquity Score" (GUS). Tebuthiuron não foi encontrado nas plantas após três meses de aplicação.

Bioconcentration factor estimates of polycyclic aromatic hydrocarbons in grains of corn plants cultivated in soils treated with sewage sludge.

This study presents a model to simulate the organic substance concentrations in corn grains assuming that the substances in soil solution are absorbed via the transpiration stream by plants growing in soils fertilized with sewage sludge (SS). The model was applied and validated using soil and corn grain samples from a long-term field experiment with six successive yearly applications of SS to the soil. The following polycyclic aromatic hydrocarbons (PAHs) were simulated and evaluated in soil and grain samples: acenaphthene, acenaphthylene, anthracene, benz(a)anthracene, benz(a)pyrene, benz(b)fluoranthene, benz(g,h,i)perylene, benz(k)fluoranthene, chrysene, dibenz(a,h)anthracene, fluoranthene, fluorene, indeno(1,2,3-c,d)pyrene, naphthalene, phenanthrene and pyrene. The PAH bioconcentration factors (BCF) in corn grains ranged from 1.57 to 10.97 L kg(-1). Polycyclic aromatic hydrocarbons with low soil distribution coefficients and high values of transpiration stream concentration factors (TSCF) are more likely to be absorbed by corn plants and accumulated in grains. It was possible to estimate and observe that highly lipophilic PAH molecules (heavy PAHs) show lower accumulative potential in corn grains than the less lipophilic ones (light PAHs). Sewage sludges containing significant concentrations of light PAHs with two, three or four benzene rings should be avoided as fertilizers in alimentary field crops.

Algae acid phosphatase affected by ten metals and enzymatic parameters determination in presence of mercury and copper

Acid phosphatases play important roles in algae metabolism such availability/recycling of inorganic phosphate and autophagic digestive processes. Chemicals released into the environment from agricultural activities and through industrial and urban wastes, may impair algae enzyme activity. The aim of this work was to evaluate the in vitro activation/inhibition effect of ten metals, commonly present as contaminants in soil and water, on the acid phospahatase extracted from the green algae Pseudokirchneriella subcapitata. Results demonstrated that Hg, Al, Mo, Pb, Se, and Cd inhibited the enzyme activity in 56.3, 54.5, 30.6, 25.5, 23.1 and 11.5 per cent respectively. This corresponds to the maximum percentage of effect attained at the metal concentration tested (0.02-2.0 mM). On the other hand, Cu, Zn, Ni and Cr exhibited an increment on phosphatase activity equal to 95.5, 87.6, 87.6, 77.6 and 42.8 per cent, respectively. Kinetic parameters values were calculated for the metals that showed hisghest effects. Thus, Ki ( inhibition constant) and Kd (dissociation constant) values equal to 0.0400 and 0.0016 mM were determined for Hg and Cu, respectively. A non-competitive inhibition mechanism was attributed to the former. Results improved the understanding of the basic events of the impact of metals at biochemical lebels in primary producers organisms.

Insecticide distribution model in human tissues viewing worker's health monitoring programs

This work aimed at evaluating the characteristics of thirty nine insecticides on tissue distribution and accumulation, using their physico-chemical characteristics and the tissues lipid contents to calculate the compounds distribution among the tissues. The insecticides evaluated were selected among those registered in Brazil for agriculture use. The level I fugacity model was used for the calculations of insecticide distribution among the tissues of muscles, viscera, skin, fat, blood, liver, kidneys and gut. The octanol-water partition coefficient, water solubility and tissue lipid contents showed an insecticide distribution in human tissues. Cluster analysis was performed aiming the identification and separation of insecticides groups based on their physico-chemical characteristics as compounds with similar distribution within tissues and at the same time tissues with similar distribution of various insecticides. Cluster analysis pointed out three insecticide groups: in the first, 70 - 86 percent of insecticide accumulation was found in lipid tissues; in the second, 44 - 58 percent; and in the third, 9 -19 percent. These results could contribute to health monitoring programs of farmworkers.

O objetivo desse trabalho foi avaliar as características de 39 inseticidas quanto a sua distribuição e acumulação em tecidos humanos como também avaliar o grau de similaridade entre os inseticidas quanto a sua distribuição nos tecidos. Para tanto, foram utilizadas as características físico-químicas dos compostos e o conteúdo de lipídeos teciduais para calcular a distribuição dos inseticidas entre os tecidos estudados. Os inseticidas selecionados para o presente trabalho foram alguns daqueles que se encontram registrados no Brasil para uso agrícola. No cálculo da distribuição dos inseticidas entre os tecidos foi utilizado o modelo de fugacidade nível I em músculos, vísceras, pele, gordura, sangue, fígado, rins e intestinos. As características físico- químicas dos inseticidas e os conteúdos de lipídio dos tecidos foram usados para calcular a distribuição dos inseticidas entre os tecidos. O coeficiente de partição octanol-água, a solubilidade em água e o conteúdo de lipídio dos tecidos determinaram a distribuição de um inseticida entre tecidos humanos. Foram realizadas análises de agrupamento, para identificar grupos de inseticidas com distribuição similar nos tecidos. 90 por cento dos 39 inseticidas apresentaram distribuição em gordura maior do que 50 por cento. A análise de agrupamento indicou três grupos de inseticidas: no primeiro o percentual acumulado na gordura variou de 70 - 86 por cento, no segundo de 44 - 58 por cento e no terceiro de 9 - 19 por cento. Os resultados obtidos podem contribuir para os programas de monitoramento da saúde do trabalhador rural.

Metals and linear alkylbenzene sulphonate as inhibitors of the algae Pseudokirchneriella subcapitata acid phosphatase activity.

Sewage sludge applied to soils as a fertilizer often contains metals and linear alkylbenzene sulphonate (LAS) as contaminants. These pollutants can be transported to the aquatic environment where they can alter the phosphatase activity in living organisms. The acid phosphatase of algae plays important roles in metabolism such as decomposing organic phosphate into free phosphate and autophagic digestive processes. The order of in vitro inhibition of Pseudokirchneriella subcapitata acid phosphatase at the highest concentration tested was LAS > Hg2+ = Al3+ > Se4+ = Pb2+ > Cd2+. A non-competitive inhibition mechanism was obtained for Hg2+ (Ki = 0.040 mM) and a competitive inhibition for LAS (Ki = 0.007 mM). In vivo studies with treated algae cultures showed that the inhibition of specific activity was observed in algae exposed during 7 days, in contrast to short term (24 h) treatments with both these chemicals. Our results suggest that the inhibition parameters in vitro did not markedly differ between the two chemicals. On the other hand, in vivo evaluations showed strong differences between both pollutants regarding the concentration values and the degree of response.

Nitrate in groundwater in Ribeirão Preto city area in Brazil

The region of Ribeirão Preto City, southeastern Brazil, is an important sugar cane and recharge area for grounwater of the Guarany aquifer. This research was conducted to evaluate the potential contamination of groundwater with nitrates in the area and in surrounding municipal wells. No significant amount of nitrate was found in the recharge agricultural area. However, nitrate levels were detected at concentrations higher than the Maximum Concentration Level (MCL) of 6.0 mg/L in a downtown, urban, well located away from agriculture, which had no history of nitrogen application, reaching values higher than the maximum risk coefficient for infants (RC) of 1.0.

Model approach for estimating potato pesticide bioconcentration factor.

We presented a model that estimates the bioconcentration factor (BCF) of pesticides in potatoes supposing that the pesticide in the soil solution is absorbed by the potato by passive diffusion, following Fick's second law. The pesticides in the model are nonionic organic substances, traditionally used in potato crops that degrade in the soil according to a first-order kinetic equation. This presents an expression that relates BCF with the pesticide elimination rate by the potato, with the pesticide accumulation rate within the potato, with the rate of growth of the potato and with the pesticide degradation rate in the soil. BCF was estimated supposing steady state equilibrium of the quotient between the pesticide concentration in the potato and the pesticide concentration in the soil solution. It is suggested that a negative correlation exists between the pesticide BCF and the soil sorption partition coefficient. The model was built based on the work of Trapp et al. [Trapp, S., Cammarano, A., Capri, E., Reichenberg, F., Mayer, P., 2007. Diffusion of PAH in potato and carrot slices and application for a potato model. Environ. Sci. Technol. 41 (9), 3103-3108], in which an expression to calculate the diffusivity of persistent organic substances in potatoes is presented. The model consists in adding to the expression of Trapp et al. [Trapp, S., Cammarano, A., Capri, E., Reichenberg, F., Mayer, P., 2007. Diffusion of PAH in potato and carrot slices and application for a potato model. Environ. Sci. Technol. 41 (9), 3103-3108] the hypothesis that the pesticide degrades in the soil. The value of BCF suggests which pesticides should be monitored in potatoes.

Pesticide bioconcentration modelling for fruit trees.

The model presented allows simulating the pesticide concentration evolution in fruit trees and estimating the pesticide bioconcentration factor in fruits. Pesticides are non-ionic organic compounds that are degraded in soils cropped with woody species, fruit trees and other perennials. The model allows estimating the pesticide uptake by plants through the water transpiration stream and also the time in which maximum pesticide concentration occur in the fruits. The equation proposed presents the relationships between bioconcentration factor (BCF) and the following variables: plant water transpiration volume (Q), pesticide transpiration stream concentration factor (TSCF), pesticide stem-water partition coefficient (K(Wood,W)), stem dry biomass (M) and pesticide dissipation rate in the soil-plant system (k(EGS)). The modeling started and was developed from a previous model "Fruit Tree Model" (FTM), reported by Trapp and collaborators in 2003, to which was added the hypothesis that the pesticide degradation in the soil follows a first order kinetic equation. The FTM model for pesticides (FTM-p) was applied to a hypothetic mango plant cropping (Mangifera indica) treated with paclobutrazol (growth regulator) added to the soil. The model fitness was evaluated through the sensitivity analysis of the pesticide BCF values in fruits with respect to the model entry data variability.

Fator de bioconcentração de poluentes orgânicos de lodos em frutos de laranjeiras / Bioconcentration factor of organic pollutants of the sewage sludge in orange fruits

Estimou-se o fator de bioconcetração de dezenove poluentes orgânicos para verificar quais devem ser monitorados em frutos de laranjeiras, cultivadas em solos tratados com lodo proveniente de estações de tratamento de esgotos. O modelo Fruit Tree Model (FTM) foi aplicado em cultivo hipotético de laranjeiras, utilizando-se a massa molar,a pressão de vapor, a solubilidade em água e o coeficiente de partição pctanol-água de poluentes (compostos orgânicos não-iônicos) que podem ser encontrados em lodos. Os coeficientes de sorção no carbono orgânico do solo, de partição caule-águas e o fator de concentração no fluxo de transpiração foram calculados por meio de expressões que correlacionam cada um desses parâmetros com o coeficiente de partição octanol-água. Obtendo-se o fator de bioconcentração e a concentração do poluente no solo é possível estimar a quantidade desses agentes químicos ingeridos diariamente pelo consumo de frutas frescas. Valores limites de poluentes em lodos podem ser calculados a partir do fator de bioconcentração do poluente em frutas. Os poluentes indicados pela estimativa para monitoramento em frutos de laranjeiras cultivadas com lodo foram: 1,2-diclorobenzeno, 2,4-dinitrofenol, 3,3-diclorobenzidina e nitrobenzeno

Bioconcentration of trichlorfon insecticide in pacu (Piaractus mesopotamicus).

Pacu (Piaractus mesopotamicus) is one of the most representative fish species of Brazilian fish culture, produced in most Brazilian States due to its importance for food diet and sport fishery. This research work investigated the bioconcentration of trichlorfon [phosphonic acid, (2,2,2-trichloro-1-hydroxyethyl)-dimethyl ester] insecticide in pacu under fish ponds culture conditions and a first-order kinetic insecticide dissipation in the water. Trichlorfon was applied at a rate of 4.62 x 10(4) mg to each of three nurseries containing 4.2 x 10(5)l of water. The fish ponds were built on the soil and supported 60 young pacus fishes. The concentrations of trichlorfon fitted to an equivalent non-linear kinetic type model, allows estimate the values of trichlorfon concentration in the water and fishes. These estimations together with the bioconcentration factor determined in the fishes, allowed establishing theoretical reference limit values for human consumption of fishes produced under cultivation systems with trichlorfon. This information will contribute to enlarge the database on pesticide use in Brazilian commercial fish farming, especially about the use of trichlorfon as chemotherapy for the control of fish ectoparasites.

Kinetics of carbosulfan hydrolysis to carbofuran and the subsequent degradation of this last compound in irrigated rice fields.

The objectives of this work were estimate the reaction rates of hydrolysis of carbosulfan to carbofuran and subsequent degradation of this last compound in irrigated rice fields, and the respective half life, in aquatic environment and soil solution, by mean of numerical solution of differential ordinary linear equations system that describes the kinetics of insecticide concentrations. The results indicated that the carbosulfan and carbofuran have low persistence in water and medium persistence in soil solution of tropical irrigated rice fields. However, both compounds can be found in laminar water and soil solution in concentration above environmental and human safety limits.

Evaluation of soil temperature effect on herbicide leaching potential into groundwater in the Brazilian Cerrado.

The effect of annual variations in the daily average soil temperatures, at different depths, on the calculation of pesticide leaching potential indices is presented. This index can be applied to assess the risk of groundwater contamination by a pesticide. It considers the effects of water table depth, daily recharge net rate, pesticide sorption coefficient, and degradation rate of the pesticide in the soil. The leaching potential index is frequently used as a screening indicator in pesticide groundwater contamination studies, and the temperature effect involved in its calculation is usually not considered. It is well known that soil temperature affects pesticide degradation rates, air-water partition coefficient, and water-soil partition coefficient. These three parameters are components of the attenuation and retardation factors, as well as the leaching potential index, and contribute to determine pesticide behavior in the environment. The Arrhenius, van't Hoff, and Clausius-Clapeyron equations were used in this work to estimate the soil temperature effect on pesticide degradation rate, air-water partition coefficient, and water-soil partition coefficient, respectively. The relationship between leaching potential index and soil temperature at different depths is presented and aids in the understanding of how potential pesticide groundwater contamination varies on different climatic conditions. Numerical results will be presented for 31 herbicides known to be used in corn and soybean crops grown on the municipality of São Gabriel do Oeste, Mato Grosso do Sul State, Brazil.

Soil temperature effect in calculating attenuation and retardation factors.

The effect of annual variation of daily average soil temperature, at different depths, in calculating pesticides ranking indexes retardation factor and attenuation factor is presented. The retardation factor and attenuation factor are two site-specific pesticide numbers, frequently used as screening indicator indexes for pesticide groundwater contamination potential. Generally, in the calculation of these two factors are not included the soil temperature effect on the parameters involved in its calculation. It is well known that the soil temperature affects the pesticide degradation rate, water-air partition coefficient and water-soil partition coefficient. These three parameters are components of the retardation factor and attenuation factor and contribute to determine the pesticide behavior in the environment. The Arrhenius equation, van't Hoff equation and Clausius-Clapeyron equation are used in this work for estimating the soil temperature effect on the pesticide degradation rate, water-air partition coefficient and soil-water partition coefficient, respectively. These dependence relationships, between results of calculating attenuation and retardation factors and the soil temperature at different depths, can aid to understand the potential pesticide groundwater contamination on different weather conditions. Numerical results will be presented with pesticides atrazine and lindane in a soil profile with 20 degrees C constant temperature, minimum and maximum surface temperatures varying and spreading in the soil profile between -5 and 30 degrees C and between 15 and 45 degrees C.

Estimativa da carga contaminante de pesticidas e nitrato para as águas subterrâneas no estado de Säo Paulo / An estimating of risk contamination by pesticides and nitrate in groundwater in Säo Paulo state

Apresenta método simplificado para estimar a carga contaminante de águas subterrâneas do Estado de Säo Paulo, por pesticidas e nitrato, empregando dados secundários. As variáveis foram sistematizadas em base anual por cultura e município, integrando área cultivada, produtividade, insumos associados, tipo de solo, pluviosidade e características de mobilidade dos produtos. Os dados referentes a 563 municípios, 37 culturas, 128 princípios ativos e nitrato foram trabalhados em programa especialmente formulado para classificaçäo dos municípios, em uma escala de carga contaminante potencialmente aplicada, permitindo a definiçäo de regiöes prioritárias para monitoramento, principais produtos a serem determinados e culturas associadas. Os resultados podem ainda ser úteis para a indicaçäo de produtos com menores riscos para emprego em áreas vulneráveis

Um programa em Pascal para avaliar a cinética de agrotóxicos em organismos aquáticos / A Pascal program to evaluate the kinetics of the agrotoxics in aquatic organisms

O ambiente aquático é, freqüentemente, alvo de agressöes por compostos químicos de diversas origens que contaminam os organismos que alí habitam. Através de estudos de bioconcentraçäo de agrotóxicos na biota aquática, é possível se prever o impacto ambiental destes produtos. O presente trabalho tem por finalidade apresentar um programa computacional na linguagem PASCAL, que facilita o cálculo de alguns parâmetros toxicocinéticos, a usuários que trabalham com bioconcentraçao aquática com um modelo determinístico de um compartimento. Os parâmetros toxicocinéticos calculados pelo programa proposto auxiliam a estabelecer limites máximos de descarga de poluentes na água e oferecem subsídios para o delineamento de estudos de biomagnifiçäo.