Lourival Costa Paraíba

Bioconcentration of the insecticide pyridaphenthion by the green algae Chlorella saccharophila

A study was undertaken to examine the uptake of the organophosphate insecticide pyridaphenthion in the chlorophyta Chlorella saccharophila. Algae cultures were exposed to the initial nominal concentration 10.0 mg l(-1) pyridaphention during seven days. The insecticide bioconcentrates in the biomass to the highest level of 441.5 +/- 25.9 mg kg(-1) on the fifth day of exposure and was followed by a decrease to 76.6 +/- 5.1 mg kg(-1) on the seventh day. A model was constructed to describe the dynamic process, which estimated a bioconcentration factor (BCF) equal to 28. The study demonstrates the potential of accumulation of pyridaphenthion in aquatic organisms and helps to expand the pyridaphenthion toxicity database. The replacement of fenitrothion by pyridaphenthion concerning their use in rice flooded cultures is discussed.

Acute toxicity and bioconcentration of fungicide tebuconazole in zebrafish (Danio rerio)

This research work investigated the bioconcentration of tebuconazole [(±)‐α‐[2‐(4‐chlorophenyl)ethyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol] fungicide in zebrafish (Danio rerio) under laboratory conditions and a first‐order kinetic pesticide dissipation in the water. The concentrations of tebuconazole fitted to an equivalent nonlinear kinetic type model which allowed the calculation of the following parameters: bioconcentration factor (38.80 L kg−1), time to reach maximum fish concentration (6 days), maximum concentration in fish (0.0075 μg mg−1), half‐life in fish (24 days) and time needed for the fish to eliminate 95% of the maximum concentration (105 days). These calculations permitted the establishment of theoretical reference limit values for human consumption of fish and the establishment of safe limits for the water pesticide concentration. The data would also be useful in safe strategies associated with fishery activities that are conducted in aquatic regions close to crops using tebuconazole. The information will contribute to enlarge the tebuconazole toxicokinetics database of aquatic organisms.

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.

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 Ficks 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.

Level IV fugacity model depending on temperature by a periodic control system

Abstract A ‘level IV fugacity model’ depending on temperature, to simulate effects of periodic temperature changes on the dynamic distribution of chemical compounds in environmental systems is presented. This model is a continuous time dynamic and periodic control system of a nonsteady-state level IV fugacity model with capacity of fugacity, substance degradation rate, and substance transfer coefficients depending on temperature. Properties of this model as stability and positivity are studied. In order to evaluate the numerical results, a discretization preserving the stability and yielding the positivity of the model is used to simulate and illustrate the dynamic distribution of molinate herbicide in a hypothetical three compartmental environmental system, similar to a paddy field, consisting of air, water and bottom sediment, with four periodic temperature changes. The results show that the discretization preserves the periodicity, stability and the positivity properties. When considering a periodic temperature variation, we observed a significant temperature effect on the capacity of fugacity of compartments of the model. This temperature effect largely affect the dynamic distribution of a chemical compound in environmental systems.

Unsteady state fugacity model by a dynamic control system

Abstract A continuous time dynamic system of an unsteady state fugacity model is presented. Properties of this model as stability are studied. In order to evaluate numerical results a discretization preserving the stability and yielding the positivity property of the model is used. Finally, algorithms to determine the values of the fugacities, the concentrations and the dissipation time are given. The above study is illustrated with numerical results in a three compartmental environmental system.

Risk simulation of soil contamination by polycyclic aromatic hydrocarbons from sewage sludge used as fertilizers

Este trabalho investigou a presenca de 16 hidrocarbonetos policiclicos aromaticos (HPAs) em lodo de esgoto e em solo com aplicacao de lodo como fertilizante agricola e simulou o risco de contaminacao por HPAs a longo prazo. As amostras foram extraidas usando diclorometano e em seguida com n-hexano em banho ultrassonico. A limpeza do extrato foi feita em coluna de alumina. As quantificacoes dos HPAs foram obtidas por cromatografia gasosa acoplada a um espectrometro de massas (GC-MS/MS ion trap). Os resultados evidenciaram que HPAs encontrados em lodos de esgoto podem apresentar risco de contaminacao de solos. As simulacoes das concentracoes dos HPAs no solo por meio de modelos matematicos foram utilizadas para indicar uma ordem de prioridade para monitoramento da qualidade do solo: fenantreno > criseno > benzo(k)fluoranteno > benzo(a)pireno > pireno > benzo(b)fluoranteno > benzo(g,h,i)perileno > indeno(1,2,3-c,d)pireno > fluoranteno > benzo(a)antraceno > dibenzo(a,h)antraceno > fluoreno > antraceno > naftaleno > acenafteno > acenaftileno. This work investigated the presence of PAH in sewage sludge and in soil with sewage sludge applied as agricultural fertilizer and simulated a long-term risk of soil contamination by PAH. The samples were extracted using dichloromethane and then with n-hexane in ultrasonic bath. The clean-up of the extract was done on a column containing alumina. The residual PAH were obtained using a gas chromatograph coupled to a mass spectrometer (ion trap GC-MS/MS). The results evidenced that PAH concentration levels found in sewage sludge might raise potential contamination risks to the soil. Simulations of the concentrations of PAHs in soil, by mathematical modeling, allowed to indicate a priority order for monitoring soil quality in terms of these contaminants: phenanthrene > chrysene > benzo(k)fluoranthene > benzo(a)pyrene > pyrene > benzo(b)fluoranthene > benzo(g,h,i)perylene > indeno(1,2,3-c,d)pyrene > fluoranthene > benzo(a)anthracene > dibenzo(a,h)anthracene > fluorene > anthracene > naphthalene > acenaphthene > acenaphthylene.

Modelling the pesticide concentration in a rice field by a level IV fugacity model coupled with a dispersion-advection equation

The numerical simulation of a level IV fugacity model coupled to a dispersion-advection equation to simulate the environmental concentration of a pesticide in rice fields is presented. The model simulates the dynamic distribution of the pesticide in a compartmental system constituted by air, water, rice plants and bottom sediment together with saturated soil layers. The level IV fugacity model is given by a linear system of ordinary differential equations that considers the fugacities and, consequently, the concentrations of the pesticide in air, water, rice plants and bottom sediment. The dispersion-advection equation simulates the pesticide leaching in the saturated layers of the soil, considering the hydrodynamic dispersion, the pesticide degradation rate and the soil pesticide absorption in the saturated soil layer.

Level IV fugacity model by a continuous time control system

Abstract A continuous time dynamic control system of the ‘Level IV Fugacity Model’ is presented and applied to selected organic chemicals in evaluative environments system. In order to illustrate the numerical solution by this model a discretization is used to calculate the fugacity, concentration and fugacity settling time for a set of three insecticides applied in a hypothetical three compartmental environmental system. The model employs the fugacity concept and treats three bulk compartments: air, water and bottom sediment. Input to the model consists of a description of the environmental, the physical-chemical and reaction properties of the chemical, and emission rates. Expressions in matrix form are included for emissions, advections, reactions, and inter-phase transference. An algorithm to determine the values of the fugacities, concentrations and fugacity settling time is given.

Insecticide Distribution Model in Human Tissues Viewing Worker's Health Monitoring Programs

O objetivo desse trabalho foi avaliar as caracteristicas de 39 inseticidas quanto a sua distribuicao e acumulacao em tecidos humanos como tambem avaliar o grau de similaridade entre os inseticidas quanto a sua distribuicao nos tecidos. Para tanto, foram utilizadas as caracteristicas fisico-quimicas dos compostos e o conteudo de lipideos teciduais para calcular a distribuicao dos inseticidas entre os tecidos estudados. Os inseticidas selecionados para o presente trabalho foram alguns daqueles que se encontram registrados no Brasil para uso agricola. No calculo da distribuicao dos inseticidas entre os tecidos foi utilizado o modelo de fugacidade nivel I em musculos, visceras, pele, gordura, sangue, figado, rins e intestinos. As caracteristicas fisico- quimicas dos inseticidas e os conteudos de lipidio dos tecidos foram usados para calcular a distribuicao dos inseticidas entre os tecidos. O coeficiente de particao octanol-agua, a solubilidade em agua e o conteudo de lipidio dos tecidos determinaram a distribuicao de um inseticida entre tecidos humanos. Foram realizadas analises de agrupamento, para identificar grupos de inseticidas com distribuicao similar nos tecidos. 90% dos 39 inseticidas apresentaram distribuicao em gordura maior do que 50%. A analise de agrupamento indicou tres grupos de inseticidas: no primeiro o percentual acumulado na gordura variou de 70 - 86%, no segundo de 44 - 58% e no terceiro de 9 - 19%. Os resultados obtidos podem contribuir para os programas de monitoramento da saude do trabalhador rural.