Studies On Photodegradation Of Propargite And Fenpyroximate And Their Effects On Soil Dehydrogenase Activity

The photodegradation of propargite, fenproximate singly and the mixed which were put on glass slide and in different water, under sunlight, 300W and 500W high pressure mercury lamp light were studied. Also propargite, fenpyroximate singly and the mixed effected on the soil dehydrogenase under the different dosage of pesticides and soil, different incubating time were studied. The main results were summarized as follows.Under sunlight or high pressure mercury lamp light when in the solid phase or liquid phase, the photodegradation of propargite and fenpyroximate followed first-order kinetics, while the photolysis rate of fenpyroximate was quicker than that of propargite. Under sunlight, the photodegradation half-life of propargite was 4.58 times more than that of fenpyroximate in pure water.The solid phase on glass slide of propargite and fenpyroximate, their photolysis rate were in the order of 500W high pressure mercury lamp, 300W high pressure mercury lamp, sunlight. In the light treatment, their mixed showed significant photosensitizing or photoquenching effect each other. In the sunlight, propargite presented significant photosensitization to fenpyroximate, when propargite/ fenpyroximate=5, the photosensitive rate reached 176.53%; meanwhile fenpyroximate to proargite has photoquenching effect, as fenpyroximate/ propargite=5, its photoquenching effect rate was only 28.56%. Under high pressure mercury lamp light, they both were photoquencher each other. There were a positive correlation between the ratio photosensitizing or photoquenching effect and as photosensitizer or photoquencher in the pesticides, but there were negative correlation in the proportional pesticide of photosensitived or phoquenched.Under the light treatment of 300W pressure mercury lamp, in the different kind water, the photolysis rate of propargite and fenpyroximate was not dealt water> filtered water> sterilized water. The photolysis rate of propargite in different water was pond water> pure water> river water> well water, that of fenpyroximate was pure water > pond water > well water>river water. In the light treatment, the propargite and fenpyroximate as 3:1 mixture which appeared notable photosensitizing or photoquenching effect each other. Under high pressure mercury lamp, the propargite and fenpyroximate as a phtoquencher each other in the pure water. Propargite to fenpyroximate has a photoquenching in the well water, river water and pond water, but fenpyroximate to propargite appeared photosensitization effect. The acting suquence of photosensitivity or photoquenching effect decreased with the not dealt water-filtered water- sterilized water. In sunlight, propargite and fenpyroximate were as aphotosensitizer each other in pure water.It was observed that the photolysis rate of the two pesticide in phosphate buffer were quicker in pH5 and in pH9 than in pH7. The photodegradation effect on each other were stronger in pH5 and pH9 phosphate buffer than in pH7 phosphate buffer as well as.All in all, the activity of soil dehydrogenase was stimulated when added low dosage of the two pesticides, and when the added dosage exceed some threshold the activity was inhibited. The inhibited effect of propargite on NO.1 soil dehydrogenase appeared adding 8.50g/g soil The inhibited effect of fenpyroximate on NO. 1 soil dehydrogenase appeared in the beginning adding dosage exceed 4.40g/g . The background level of soil dehydrogenase of NO.2 soil was lower than that of NO.l soil, the pesticide limit that began to yield inhibiting effect on soil dehydrogenase was lower on NO.2 soil than on NO.l soil. When adding treatment as the dosage 3:1 mixture with propargite and fenpyroximate, the combination of propargite and fenpyroxmate to soil dehydrogenase was a independent effect.When incubated 30 days, the propargite and fenpyroximate and their mixed made effect on the activity of soil dehydrogenase, the variation tendency of soil dehydrogenase by adding propargite was inhibited- stimulated- revive, while adding fenpyroximate, it is in...