| Diquat (1, 1-ethylene-2, 2-dipyridyl two bromines salts) is one kind of BipyHerbicide which is high-efficient and can be popularized to use all over the world today, butvery little information about its chemical behaviors in aquatic biology is available. In order tosupply some scientific evidences for diquat's reasonable application ,the evaluation of itsenvironmental security and the predication of the pollution degree of diquat in the river, thispaper aims to study the hydrolysis behaviors including the effects of environmental factorsand many organic and inorganic materials towards the natural water, and also build up thedegradation of diquat in river. The main conclusions are as follows:Chapter one was introduction, in which the basic concepts, theories and currentresearches at home and abroad were reviewed briefly on hydrolysis of pesticides. In addition,research advance of diquat was summarized concisely. The contents and significances of thisresearch were also included in this chapter.In the chapter two, it studied environmental factors' effects towards hydrolysis of diquat.The results showed that: (1) Hydrolysis of diquat in the buffer solutions of pH5, pH7 and pH9can be described by the first-order kinetics equation. Diquat was stable in acid water andneutral water, but it is resolved easily in basic water; in the buffer solutions of pH5,7, 9, itshydrolysis half life in the buffer solutions was 238.97,231.05 and 22.00d,respectively. (2)The higher the temperature was, the quicker the speed of the hydrolysis process was.Hydrolysis half-life was 36.28, 22.00 and 14.71d at temperature of 15,25 and 35℃, andtemperature effect quotient (Q) ranged from 1.50～1.64. (3) When the pH value was 7and 9, the mean activation energy(Ea)for hydrolysis of diquat was 21.33and25.89kJ·mol-1, respectively. The activation entropy(ΔS), which displayed striking relation, increased withthe increasing temperature, and the mean activation entropy was -191.83J·(mol·K)-1. (4)Compared to pH and temperature, the origin of water had little effect on diquat hydrolysis.According to the variance analysis of orthogonal experiment results, it indicated that differentsources of the water didn't show obvious disparity towards diquat hydrolysis during the whole experiment.Chapter three studied the effects of some organic and inorganic materials in aquaticenvironment. Results were observed as follows: (1) The different kinds of surfactants(SDBS,CTABand TW-80) had different effects on diquat hydrolysis. The results showedthat anion surfactant SDBS could accelerate the speed of the hydrolysis. While theconcentration of SDBS increased from 0 mg·L-1 to 300 mg·L-1, the hydrolysis rate constantK values of diquat increased by a factor of 11 (11 times), the half-life of diquat hydrolysisdecreased from 192.54d to 16.70d. However, positive-ion surfactant CTAB baffledhydrolysis ofdiquat, and with the concentration of CTAB increasing from 0 mg·L-1 to 1200mg·L-1, the hydrolysis rate constant K decreased from 0.0036d-1 to 0.0018 d-1, the half-lifeincreased from 192.54d to 385.08d. The effect of non-ionicTW-80 on hydrolysis of diquatwas not obvious. (2) Add strong acid and strong base salts (NaCl, MgCl2, CaCl2, NaNO3)into diquat solution. Due to the salting-out effect which restrained hydrolysis of diquat,when the concentration of NaCl, MgCl2, CaCl2 increased from 0 mol·L-1 to 1mol·L-1, thehalf-life of diquat hydrolysis increased 2.59％, 38.34％, 43.52％, 19.69％, respectively. Addstrong base and weak acid salts (NaHCO3, Mg(HCO3)2, Ca(HCO3)2). Because dissociation ofthese salts can make water alkaline, it could accelerate the hydrolysis.While the concentrationof NaHCO3,Mg(HCO3)2,Ca(HCO3)2 increased from 0 mol·L-1 to 1mol·L-1, thehydrolysis rate constant K values of diquat increased by a factor of 23.67, 29.83, 33.67,respectively. Add strong acid and weak base salts (Mg(NO3)2, Ca(NO3)2). Becausedissociation of these salts make water acid, it could restrain the hydrolysis. While theconcentration of Mg(NO3)2, Ca(NO3)2 increased from 0 mol·L-1 to 1mol·L-1, the half-lifeof diquat hydrolysis was increased 89.12％, 49.74％, respectively.In the chapter four, rotational regression design was employed to modeling thedegradation of diquat in river and tentative analysis and verification of model were conductedpartly. The results showed that model of diquat in river is y=-13.006-0.001x12-0.006x22-0.119x32+0.003x1x2—0.015x1x3—0.005x2x3+0.118x1+0.128x2+3.500x3, variable range:x1 (T/℃)=16.60～33.40; x2(t/d)=6.70～23.30; x3 (C/mg·L-1)=6.80～13.60. Thesignificant F test: F1=2.715＜F0.05(5,8)=3.69, F2=112.011＞F0.10(9, 13)=2.16, indicatedregression equation conformed with practice preferably. The results showed that theestablished model may be used to predict the pollution of diquat in river.In the last chapter, a summary was done on the research results,and meanwhile theinnovation of the research and the projects that need to be further studied were proposed.
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