Study On Residual Profiles Of Two Formulations Of Dinotefuran In Paddy Ecosystem And Their Processing Factors

To reduce the environmental and dietary risk in paddy field system, study on residual profiles of two dinotefuran formulations (granule and soluble powder) in three southern paddy fields was conducted and the influence of processing factors on dinotefuran residues in brown rice was investigated as well. Our work aimed to clarify the appropriate pesticide formulation and application method during the initial application period for acceleration of degradation and reduction of residues in chaff and rice originally. Besides, processing factor was introduced to evaluate dietary risk, thus the risk was further expected to be lowered by the prospective processing means.Environmental behavior of dinotefuran in soil and water was primarily elucidated, such as degradation and migration et al. The results indicated that dinotefuran was difficult to absorb, volatilize and photo-degrade in soil with the feature of easily-degradation and medium leaching. It was hard to be degraded and volatilized and easy to be degraded with illumination in water. Half life of dinotefuran in the water-sediment system was from18.3d to35.4d. These data provided a basis for defining residual profiles of dinotefuran in the rice paddy field.Furthermore, residual profiles of two formulations of dinotefuran in the rice paddy fields located in three different regions in south China were compared. Both formulations depleted quickly in the paddy soil, water and rice plant (half life,1.1d-11.5d), but the rate and dynamics curve were different between two formulations. The dynamics curves of granules (G) of dinotefuran showed a rising tendency first and then fell in water and plant, which was different from the soluble powder (SP) with a continuous declination tendency. Half life of G was2.2d-6.2d in water,3.2d-11.5d in plant, which of SP was1.1d-2.2d and1.6d-4.4d, respectively. It is obvious that SP depleted more quickly than G in water and plant. Curves of both formulations in soil presented a slight rise in the early stage. However, half life of G (3.7d-6.6d) was shorter than SP (2.4d-4.3d). Residues of G and SP in chaff and coarse rice were distinguishable. The dinotefuran residues of G in chaff and rice were0.004-0.037mg/kg and0.015-0.549mg/kg. It is less than that of SP with half life of0.011-0.084mg/kg,0.073-1.172mg/kg in chaff and rice at same trial site, respectively. Distribution of both formulation followed the order rice<chaff.Finally, processing trial illustrated that rice polishment and thermal treatment with rice-cooker and microwave oven removed dinotefuran residues from coarse rice effectively with the removal rate ranging from37.8%to69.2%, and rice-cooker was the relatively effective way. Rice polishment showed a similar removal rate with thermal treatment using microwave.In conclusion, the granules of dinotefuran depleted slower than its soluble powder in the rice paddy field, while residues of granules in rice were not higher than its soluble powder. Dietary risk could be further weakened when processing factor was considered. Hence, granules of dinotefuran were recommended for the early pesticide application in the rice paddy field. Soluble powder was accessed if necessary; however, the dosage and harvest interval should be controlled.