| Dimethylammonium4-chlor-o-tolyloxyaceta is a kind of phenoxyacetic acid herbicide. At present,the report which residue and degradation of dimethylammonium4-chlor-o-tolyloxyaceta is little. The dimethylammonium4-chlor-o-tolyloxyaceta was applied in paddy field. This paper had systematically studied the residual degradation behavior of dimethylammonium4-chlor-o-tolyloxyaceta, hydrolysis and its influencing factors. The study had accurately evaluated ecological environment action and the safety of dimethylammonium4-chlor-o-tolyloxyaceta after it was applied in paddy field. The main conclusions were as follows:(1) The method of HPLC analysis of dimethylammonium4-chlor-o-tolyloxyaceta was established. The samples of paddy filed of dimethylammonium4-chlor-o-tolyloxyaceta were extracted by acidic solution. The minimum detectable amount of dimethylammonium4-chlor-o-tolyloxyaceta was2×10-10g and the lowest detectable concentration in paddy water, paddy soil, paddy straw, rice hull and brown rice were0.OOlmg/L,0.05mg/kg,0.01mg/kg,0.01mg/kg,0.01mg/kg, respectively, the average recoveries range from92.49%to98.71%and the relative standard deviation were from1.78%to9.23%in different kinds of tested samples.(2) A field experiment was conducted to reveal residual degradation of dimethylammonium4-chlor-o-tolyloxyaceta in rice and pappy system in Hunan, Changsha, Zhejiang Hangzhou and Guizhou Guiyang. The results show that:Its average degradation half-life of dimethylammonium4-chlor-o-tolyloxyaceta was6.10d in paddy water,5.92d in paddy straw, and7.08d in paddy soil. This showed that dimethylammonium4-chlor-o-tolyloxyaceta was an easily degradable herbicide (T1/2<30d). The recommended amount of usage450g/hm2and higher usage were675g/hm2advised to apply to the paddy field only one time durring the paddy growth period,the residues of dimethylammonium4-chlor-o-tolyloxyaceta in rice were less than the lowest detectable concentration(0.01mg/kg) and was lower than the corresponding MRL value (0.10mg/kg).(3) The study show that the factor of pH played an important role in which hydrolysis value is3,5,7,9,11, dimethylammonium4-chlor-o-tolyloxyaceta in buffer solution.The hydrolysis half-life is divided into:20.14,13.2,11.3,10.37,8.52d. Dimethylammonium4-chlor-o-tolyloxyaceta is easier hydrolyszed under alkaline conditions, but not easily hydrolyszed in neuter solution or acid solution.(4) The dimethylammonium4-chlor-o-tolyloxyaceta hydrolysis is an endothermic process. And the more higher of its temperature, the more faster of its rise. When the temperature was25℃, the hydrolysis half-life of was21.93d. When the temperature was35℃, the hydrolysis half-life was9.84d. When the temperature was45℃, the hydrolysis half-life was only5.9d that narrowed4times which compared with25℃(5) The result showed that dimethylammonium4-chlor-o-tolyloxyaceta hydrolysis was inhibited due to salting-out effect when strong acidic and strong alkaline salts (NaCl, KC1, CaCl2, NaNO3) had been added in. When the concentration of NaCl, KC1, CaCl2, NaNO3increased from0.05mol/L to1mol/L, the hydrolysis half-life of dimethylammonium4-chlor-o-tolyloxyaceta increased121%,81%,90%,79%. However, dimethylammonium4-chlor-o-tolyloxyaceta could be hydrolyszed faster when the strong alkaline and weak acidic salt (NaHO3) was added into its solution. Because dissociation of this salt can make water alkaline.(6) The study on which dimethylammonium4-chlor-o-tolyloxyaceta in the farmland of common chemical fertilizer (N, P, K) hydrolysis test shows that: The effection which compared with dimethylammonium4-chlor-o-tolyloxyaceta in pH=7hydrolysis, high concentrations urea could accelerate the hydrolysis, its half-life shorten37.16%. The KCI which acidic and alkaline are strong that hadn’t special influence on the hydrolysis rate. However, the KH2PO4was decreased the speed of the hydrolysis rate because of its weak acidic. |
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