[Show abstract][Hide abstract] ABSTRACT: In the Brazilian state of Rio Grande do Sul, rice (Oryza sativa) is predominantly grown using a continuous flood, which can cause herbicide runoff when fields are over-irrigated or heavy rainfall occurs. Proper irrigation and drainage management can reduce herbicide transport to the environment. The objective of this study was to evaluate the effect of different irrigation practices on water runoff and the transport and dissipation of the herbicides imazethapyr and imazapic. The experiments were conducted in the 2007/08 and 2008/09 growing seasons at the experimental area of the Universidade Federal de Santa Maria. The treatments comprised two irrigation management systems: continuous flooding of an approximate 10-cm flood depth and intermittent flooding where the flood was allowed to fully subside before being reestablished to a 10-cm height. The amount of water runoff and the rates of herbicide dissipation and transport were evaluated. Owing to increased storage of rainwater, intermittent flooding reduced water runoff by 47% and runoff of imazethapyr and imazapic by 89 and 77%, respectively, relative to the continuously flooded control. Imazapic was significantly more persistent than imazethapyr, but there was no effect of irrigation management on herbicide persistence in water.
Agricultural Water Management 05/2013; 125:26. DOI:10.1016/j.agwat.2013.04.005 · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The occurrence of pollutants in the aquatic environment can produce severe toxic effects on non-target organisms, including fish. These sources of contamination are numerous and include herbicides, which represent a large group of toxic chemicals. Quinclorac, an herbicide widely applied in agriculture, induces oxidative stress due to free radical generation and changes in the antioxidant defense system. The aim of this study was to assess if dietary diphenyl diselenide (PhSe)₂ has a protective effect in tissues of fish species Cyprinus carpio exposed to the quinclorac herbicide. The fish were fed with either a standard or a diet containing 3.0 mg/Kg of diphenyl diselenide for 60 d. After were exposed to 1 mg/L of Facet® (quinclorac commercial formulation) for 192 h. At the end of the experimental period, parameters as thiobarbituric acid-reactive substance levels (TBARS), protein carbonyl, catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), nonprotein thiols (NPSH) and ascorbic acid in the liver, gills, brain and muscle were evaluated in Cyprinus carpio. In fish exposed to quinclorac and feeding with standard diet TBARS levels increased in liver and gills. However, SOD activity decreases in liver whereas no alterations were observed in catalase activity in this tissue. Quinclorac also decrease GST activity in liver and brain, NPSH in brain and muscle and ascorbic acid in muscle. Concerning protein carbonyl exposed to herbicide the fish did not show any alterations. The diphenyl diselenide supplemented diet reversed these effects, preventing increases in TBARS levels in liver and gills. GST activity was recovered to control values in liver. NPSH levels in brain and muscle increased remain near to control values. These results indicated that dietary diphenyl diselenide protects tissues against quinclorac induced oxidative stress ameliorating the antioxidant properties.
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was to evaluate and to monitor the presence of pesticides in the waters of the São Gonçalo channel and the Piratini river located in the southern region of the State of Rio Grande do Sul. During the rice growing season, water samples were collected five times, three samples from the river Piratini and four from the São Gonçalo canal. The methodology used for the analysis of residues of quinclorac, carbofuran and clomazone was the High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD) and for residues of the pesticides fipronil and betacyfluthrin, the Gas Chromatography with Electron Capture Detection (GC-ECD) was used. Results show that from sowing to harvesting the quantity of pesticide residues in water decreased. It was also observed that, at the lowest point (Laranjal), a greater number of analyses contaminated with residues was detected (11 samples with some type of pesticide). Insecticide carbofuran and herbicide quinclorac were pesticides that presented residues more frequently (16 and 15 times, respectively). Clomazone and fipronil were present in each of the 7 samples with residues and betacyfluthrin was not detected at any site.
Revista Brasileira de Engenharia Agrícola e Ambiental 12/2008; 12(6):632-637. · 0.66 Impact Factor