Advanced oxidation of commercial herbicides mixture: experimental design and phytotoxicity evaluation.

In this work, the suitability of the UV/H2O2 process for commercial herbicides mixture degradation was studied. Glyphosate, the herbicide most widely used in the world, was mixed with other herbicides that have residual activity as 2,4-D and atrazine. Modeling of the process response related to specific operating conditions like initial pH and initial H2O2 to total organic carbon molar ratio was assessed by the response surface methodology (RSM). Results have shown that second-order polynomial regression model could well describe and predict the system behavior within the tested experimental region. It also correctly explained the variability in the experimental data. Experimental values were in good agreement with the modeled ones confirming the significance of the model and highlighting the success of RSM for UV/H2O2 process modeling. Phytotoxicity evolution throughout the photolytic degradation process was checked through germination tests indicating that the phytotoxicity of the herbicides mixture was significantly reduced after the treatment. The end point for the treatment at the operating conditions for maximum TOC conversion was also identified.

Efeito de misturas de herbicidas na dessecaçao pré-semeadura e no desenvolvimento inicial do milho safrinha / Effect of herbicide mixtures in burndown pre-planting and development of initial winter maize

Inadequate weed control is one of the factors that limit the productivity of maize. Thus the present study aimed to evaluate the effect of residual herbicides association (atrazine and flumioxazyn) to glyphosate in corn pre-seeding burdown and its effect on weed control during the early development of corn. The treatments were: control without weeding, control with weeding, glyphosate (1080 g ha-1 ), glyphosate (1080 g ha-1 ) / paraquat (400 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ), glyphosate (1080 g ha-1) + flumioxazyn (75 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazine (1500 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazine (3000 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ) + atrazine (3000 g ha-1 ) all applied 28 days before sowing, except to paraquat was applied on the same day of seeding. The design was a randomized complete block with four replications. The variables evaluated were the percentage of control at 7, 14, 21 and 28 days after application, the number of plants of Bidens pilosa, Euphorbia heteropylla and Urochloa plantaginea, regrowth percentage of U. plantaginea, stand and height of corn plants to 30 days after sowing. It was observed that the early development of corn was not affected by application of herbicides atrazine and flumioxazyn mixed with glyphosate. All mixtures of herbicides provided satisfactory control in burndown. However, there was obtained a higher speed drying with glyphosate in mixture with flumioxazyn. The combination of atrazine and glyphosate flumioxazyn promoted residual weed control Weed and E. heterophylla. Whereas when did the association of the three herbicides found residual control U. plantaginea.

O controle inadequado de plantas daninhas é um dos fatores que limitam a produtividade do milho. Assim o presente trabalho teve como objetivo avaliar o efeito da associação de herbicidas residuais (atrazina e flumioxazyn) ao herbicida glyphosate na dessecação pré-semeadura do milho e o seu efeito no controle de plantas daninhas durante o desenvolvimento inicial da cultura do milho. Os tratamentos avaliados foram: testemunha sem capina, testemunha com capina, glyphosate (1080 g ha-1 ), glyphosate (1080 g ha-1 ) / paraquat (400 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (75 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazina (1500 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazina (3000 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ) + atrazina (3000 g ha-1 ) todos aplicados 28 dias antes da semeadura, com exceção do paraquat que foi aplicado no mesmo dia da semeadura. O delineamento utilizado foi o de blocos casualizados com 4 repetições. As variáveis avaliadas foram a porcentagem de controle aos 7, 14, 21 e 28 dias após a aplicação o número de plantas de Bidens pilosa, Euphorbia heteropylla e Urochloa plantaginea, porcentagem de rebrota da U. plantaginea, estande e altura de plantas de milho aos 30 dias após semeadura. Observou-se que o desenvolvimento inicial do milho não foi afetado pela aplicação dos herbicidas flumioxazyn e atrazina em mistura com glyphosate. Todas as misturas de herbicidas promoveram controle satisfatório na dessecação. No entanto, obteve-se uma maior velocidade de dessecação nos tratamentos com glyphosate em mistura com flumioxazyn. A associação de atrazina e flumioxazyn ao glyphosate promoveu controle residual das plantas de B. pilosa e E. heterophylla. Enquanto que quando fez a associação dos três herbicidas verificou controle residual de U. plantaginea.

Efeito de misturas de herbicidas na dessecaçao pré-semeadura e no desenvolvimento inicial do milho safrinha / Effect of herbicide mixtures in burndown pre-planting and development of initial winter maize

Inadequate weed control is one of the factors that limit the productivity of maize. Thus the present study aimed to evaluate the effect of residual herbicides association (atrazine and flumioxazyn) to glyphosate in corn pre-seeding burdown and its effect on weed control during the early development of corn. The treatments were: control without weeding, control with weeding, glyphosate (1080 g ha-1 ), glyphosate (1080 g ha-1 ) / paraquat (400 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ), glyphosate (1080 g ha-1) + flumioxazyn (75 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazine (1500 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazine (3000 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ) + atrazine (3000 g ha-1 ) all applied 28 days before sowing, except to paraquat was applied on the same day of seeding. The design was a randomized complete block with four replications. The variables evaluated were the percentage of control at 7, 14, 21 and 28 days after application, the number of plants of Bidens pilosa, Euphorbia heteropylla and Urochloa plantaginea, regrowth percentage of U. plantaginea, stand and height of corn plants to 30 days after sowing. It was observed that the early development of corn was not affected by application of herbicides atrazine and flumioxazyn mixed with glyphosate. All mixtures of herbicides provided satisfactory control in burndown. However, there was obtained a higher speed drying with glyphosate in mixture with flumioxazyn. The combination of atrazine and glyphosate flumioxazyn promoted residual weed control Weed and E. heterophylla. Whereas when did the association of the three herbicides found residual control U. plantaginea. (AU)

O controle inadequado de plantas daninhas é um dos fatores que limitam a produtividade do milho. Assim o presente trabalho teve como objetivo avaliar o efeito da associação de herbicidas residuais (atrazina e flumioxazyn) ao herbicida glyphosate na dessecação pré-semeadura do milho e o seu efeito no controle de plantas daninhas durante o desenvolvimento inicial da cultura do milho. Os tratamentos avaliados foram: testemunha sem capina, testemunha com capina, glyphosate (1080 g ha-1 ), glyphosate (1080 g ha-1 ) / paraquat (400 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (75 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazina (1500 g ha-1 ), glyphosate (1080 g ha-1 ) + atrazina (3000 g ha-1 ), glyphosate (1080 g ha-1 ) + flumioxazyn (50 g ha-1 ) + atrazina (3000 g ha-1 ) todos aplicados 28 dias antes da semeadura, com exceção do paraquat que foi aplicado no mesmo dia da semeadura. O delineamento utilizado foi o de blocos casualizados com 4 repetições. As variáveis avaliadas foram a porcentagem de controle aos 7, 14, 21 e 28 dias após a aplicação o número de plantas de Bidens pilosa, Euphorbia heteropylla e Urochloa plantaginea, porcentagem de rebrota da U. plantaginea, estande e altura de plantas de milho aos 30 dias após semeadura. Observou-se que o desenvolvimento inicial do milho não foi afetado pela aplicação dos herbicidas flumioxazyn e atrazina em mistura com glyphosate. Todas as misturas de herbicidas promoveram controle satisfatório na dessecação. No entanto, obteve-se uma maior velocidade de dessecação nos tratamentos com glyphosate em mistura com flumioxazyn. A associação de atrazina e flumioxazyn ao glyphosate promoveu controle residual das plantas de B. pilosa e E. heterophylla. Enquanto que quando fez a associação dos três herbicidas verificou controle residual de U. plantaginea. (AU)

Genotoxic and biochemical effects of atrazine and Roundup(®), alone and in combination, on the Asian clam Corbicula fluminea.

The present study aimed to evaluate biochemical and genotoxic effects of the herbicides atrazine (ATZ) and Roundup(®) (RD) separately, as well as their mixture, on the freshwater clam Corbicula fluminea after 96 h exposure. Animals were exposed to 2 and 10 ppb of ATZ (ATZ2 and ATZ10), 2 and 10 ppm of RD (RD2 and RD10) and the following mixtures: 2 ppb ATZ+2ppm RD (AR2) and 10 ppb ATZ+10 ppm RD (AR10). Activities of ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR), as well as the multixenobiotic resistance mechanism (MXR), reduced glutathione concentrations (GSH) and lipid peroxidation (LPO) were measured in gills and digestive gland. DNA damage was determined in clams hemocytes through the comet assay. The gills were more susceptible to the action of the herbicides and the results showed that ATZ2 and ATZ10 caused a significant reduction in EROD and the mixture leads to a significant decrease in EROD and MXR. No significant change in the biotransformation parameters was observed in the digestive gland. Regarding the primary antioxidant defenses, SOD activity increased in the gills of clams exposed to ATZ10 and RD10 and in the digestive gland of animals exposed to RD2 and RD10, CAT activity was significantly reduced only in digestive gland of clams exposed RD10 while GPX increased in the gills after exposure to ATZ2 and RD10. The exposure to RD10 caused a significant increase in LPO in both gills and digestive gland. While the exposure to ATZ and RD separately did not increase DNA damage, the exposure to AR2 and AR10 caused a significant increase in the occurrence of DNA damage. In conclusion, this study showed that both herbicides applied alone caused effects on C. fluminea; ATZ interfered mostly in biotransformation while RD interfered mainly in antioxidant defenses leading to lipid peroxidation. The herbicides mixture showed antagonistic effects on the gills EROD and on lipid peroxidation in gills and digestive gland and synergistic effects on the gills MXR and on DNA damage in the hemocytes.