Behavior And Effect Of Prochloraz And Its Major Metabolites In Paddy Field

Prochloraz was a new broad-spectrum fungicide developed by England Boots company (now called AgroEvo) in 1974, and launched into the market in 1977. Previous studies focused mainly on efficacy, toxicity, and fungicidal mechanism of prochloraz, little information was available about its behavior and ecological effect in paddy field. The behavior and effect of prochloraz in paddy field were studied in this thesis in order to provide some fundamental data for assessing the environment safety assessment and scientific application of prochloraz. The thesis was divided into nine chapters.Chapter 1: Current advancement on research and development of prochloraz were summarized briefly.Chapter 2 : (1) Determination method for prochloraz and its major metabolites in paddy water and soil was developed. Under the given liquid chromatography conditions (detection wavelength was 210nm, methanol-water in proper proportion was used as mobile phase, and pH was 3.0), precision, sensitivity, and repeatability can meet the basic requirements of determination of pesticide residue. (2) Prochloraz was degraded quickly in paddy water and soil after application. Its half-life varied from 3.92 to 5.95 days in water, and from 5.45 to 6.88 days in soil. The major metabolites of prochloraz included BTS44595, BTS44596 and BTS45186. The degradation of prochloraz showed some correlations with pH values, organic matter, cation exchange capacity and clay content. But this will need to be further studied and confirmed.Chapter 3: The adsorption behavior of prochloraz and its metabolites was studied in batch experiment with six kinds of paddy soils. The results showed: (1) The adsorption equilibrium times were from 5 to 14 hours. By using three kinds of sorption isotherms to model the data measured, it was found that adsorption process of prochloraz and its major metabolites could be described well with Freudlich isotherm equation, Langmuir isothermsdescribed the process with poor fitness, while BET isotherms could not describe this process. (2) When prochloraz was formulated into sportak or transformed into the three metabolites, i.e., BTS44595, BTS44596 and BTS45186, the adsorption amount decreased, and the adsorption mechanism changed. The adsorption amount of prochloraz on soils were well correlated with organic matter contents, cation exchange capacity and clay contents of the soils, and adsorption amount of sportak depended on cation exchange capacity, clay contents and pH values of the soils. (3) The Kf value decreased gradually from 73.45 to 31.70, 25.80 and 26.87 as Prochloraz was metabolized into BTS44595, BTS44596 and BTS45186, indicating that adsorption capacity of the metabolites descended sharply with the cleavage of imidazole ring in prochloraz, and adsorption mechanism changed fundamentally. Adsorption capacity of prochloraz's major metabolites was restricted by pH values of soils. The adsorption of BTS44595, BTS44596 and BTS45186 become less as pH value increased. (4) The formulation process and metabolism could obviously change adsorption behavior and adsorption mechanism of prochloraz on six kinds of paddy soils. Great attention should be paid on these aspects when prochloraz was applied to the paddy field.Chapter 4: Photo-degradation of prochloraz in aqueous solutions was discussed. Results showed: (1) Acetone, TiO2, H2O2 and FA could enhance the photo-degradation rate of prochloraz with the increasing order of acetone H2O2>TiO2>FA. (2) Photo-degradation rate of prochloraz in aqueous solutions decreased with the increasing concentration of prochloraz. (3) Photo-degradation rate of prochloraz varied with the quality of different water. The rate of photo-degradation of prochloraz was slowest in the distilled water, faster in river water, and fastest in paddy water, indicating that the water enclosures had some effects on the photo-degradation of prochloraz. (4) Photo-degradation of prochloraz increased as the pH value of the solutions changed from pH 4 to 10. (5) Triazophas, cypermethrin and iodosulfuron-methyl-sodium had some inhibition on photo-degradation of prochloraz in the aqueous solutions. The increasing order of inhibition was iodosulfuron-methyl-sodium>cypermethin>triazophos, and there were some positive correlation between the inhibition of these pesticides and their concentrations in the solutions. Pirimicarb accelerated the photo-degradation of prochlorazin the solutions, suggesting that pirimicarb exhibited a photosensitization on photo-degradation of prochloraz in solutions, and there appeared a positive correlation between degree of photo-sensitization of pirimicarb and its concentration in the solution.Chapter 5: Effect of prochloraz and its major metabolites on enzyme activity in soil was investigated. Results were as follows: (D Prochloraz, sportak, BTS44595 and BTS44596 stimulated the activity of invertase and urease in soils at the low concentration, and inhibited the activity at the high concentration. (2) Effects of prochloraz and sportak on catalase activity in soil displayed an character of "inhibition-*activation-?-re-inhibition-"-re-activation", and BTS44595, BTS44596 and BTS45186 showed a activation on catalase activity. (D Prochloraz and BTS45186 exhibited an inhibition on polyphendoxidase in soils. Sportak exhibited an activation effect, and the activation become stronger as the concentration increased. BTS44595 and BTS44596 showed a stimulation at low concentration, an inhibition at high concentration during the early stage (pre-7d), and an inhibition during the late stage. (4) Prochloraz, its formulation and its major metabolites had some effects on enzyme activity in soils, but the effect disappeared after 30d.Chapter 6: Acute toxicity of prochloraz and its major metabolites to normal aqueous animals in paddy water. Results show that: (D Wavelength of the ultraviolet absorbance spectrum changed obviously along with degradation of prochloraz. Absorption peak at 270nm disappeared along with cleavage of the imidazole ring of prochloraz. Absorption peak at 204nm has a red-sifting phenomenon, suggesting the absorption spectrum moved to the long wavelength. (2) The toxicity of prochloraz formulation is greater than that of technical grade of prochloraz. Acute toxicity of prochloraz and its formulation in the decreasing order was Tadpole, Loach, Xiangyunji. (3) The toxicity of prochloraz and its major metabolites in the decreasing order were BTS45186, prochloraz, BTS44595, BTS44596. (D It was an obvious detoxification process when prochloraz was converted to its primary metabolites BTS44595 and BTS44596, while it is an obvious intoxicating process when the primary metabolites BTS44595 and BTS44596 were converted to the secondary metabolite BTS45186. (§) Both the wavelength of the ultraviolet absorption spectrum and the acute toxicity to tested animals changed sharply along with the degradation of prochloraz. This implies some connections between them. Furtherresearches is need to prove these connectionsChapter 7: The single toxicity and the joint toxicity of fungicide prochloraz with cadmium and arsenic to tadpole of Bufo bufo were studied in the aerated river water and aeration distilled water by static experimental method. The additive index was applied to evaluate the joint toxic effects. Results indicated that: ? The single toxicity of prochloraz, cadmium, and arsenic to tadpole was : Cd2+>prochloraz>As3+> As5+; (2) The joint toxicity of prochloraz with cadmium to tadpole was synergistic, whereas the joint toxicity of prochloraz with arsenic were antagonistic, and that of cadmium and arsenic were also antagonistic; (3) Organic matter and suspended substance in the aqueous solution were found to be able to reduce the toxic impact of those compounds on tadpole in all the tested groups, especially in the tested groups of aqueous solution with cadmium only, with prochloraz and cadmium, and with cadmium and arsenic.Chapter 8: The toxicity and the effect of prochloraz and its major metabolites to Lemma paucicostata were illustrated. The results showed: (T) prochloraz, Sportak, BTS44595 ,BTS44596 and BTS45186 caused the chlophyll and carotenoid contents of L.paucicostata to decrease .The decrease accorded with the increasing of the concentration or the prolonging of the treatment time, exhibiting a negative effect. The increasing order of the negative effect was BTS45186> prochloraz>Sportak>BTS44596>BTS44595. ? Prochloraz and sportak had a great effect on the carotenoid amounts of L.paucicostata, making the chlophyll a/b value of L.paucicostata decrease. BTS44595, BTS44596 and BTS45186 had a weak effect on the carotenoid content of L.paucicostata, making the chlophyll a/b value increasing. (3) Prochloraz and sportak had a great effect on SOD, POD, CAT, MDA and soluble protein content of L.paucicostata, but there was no significant difference between them, prochloraz had a great effect on the above index at the early stage (within Id) of L.paucicostata . The effect of Sportak enhanced, and even exceeded the toxic effect of prochloraz after Id, showing that effect of prochloraz on L.paucicostata appeared earlier than that of the formulation sportak. ? At lower concentration, prochloraz, sportak, BTS44595, BTS44596 and BTS45186 activated the activity of SOD, POD and CAT from L.paucicostata, and at higher concentration they inhibited the activity. The more significant change occurred for CAT activity, suggesting that CAT could be...