Investigation On Diphenyl Ether Herbicides Residues In Soils And Research On The Effect Of Biodegradation

Jiangsu,as a major economy and agricultural province in china,it is an important agricultural production base in the Yangtze River Delta region,which is also a gathering place for pesticide production.In order to ensure the stable and high yield of food,the production and application of herbicides increased year by year,the consequent pollution of herbicides residues has also attracted everyone's attention.Diphenyl ether herbicides have been used widely in the production and application at present.To clarify the residues of diphenyl ether herbicides in soil,the methods of point source,area source and microarea experiment were carried out.5 manufacturers which produced diphenyl ether herbicides were investigated for sampling in point source.Sampling investigation was carried out in the annular area of inside the manufacturer,100 m,100 m-200 m and 200 m-300 m outside the manufacturer.The typical farmland of diphenyl ether herbicides in Qidong,Haian,Taixing,Changshu and Lianyungang in Jiangsu were investigated in the area source.The microarea experiments were carried out based on soil investgation,sweet potato as an indicator crop.Three kinds of herbicides,fluoroglycofen,butachlor and metolachlor,were set to normal dosage and double dosage respectively.Sampled after 30 d and at harvest.The residues of fluoroglycofen,butachlor and metolachlor in the stems and leaves of sweet potato and soil were detected,and investigation of yield at harvest.The effect of herbicide application on the quality of sweet potato was clear through the residue of herbicide in sweet potato and the yield at harvest.At the same time,regarding the high efficiency degradation diphenyl ether bacterial strain SRC₁ in the early stage screening as main research object,the effect of environmental factors on the biodegradability of strain SRC₁ was studied,and indoor biodegradate experiments were carried out subsequently.The practical application of strain was evaluated through the residue of herbicides and the growth of plant.Several diphenyl ether herbicides were determined by high performance liquid chromatography?HPLC?.The main investigation and results of the research are as follows:?1?The results of point source investigation showed that:the residues of diphenyl ether herbicides in the manufacturer ranged in high level.The residues in the 5 manufacturers were mainly fluoroglycofen and fomesafen.The residual level of fluoroglycofen in four manufacturers varies from 120 mg·kg-1 to 230 mg·kg-1.Besides,the residues of fomesafen in 2 manufacturers varies from 156 mg·kg-1 to 235 mg·kg-1,indicating that pesticide residues pollution were serious.By contrast,the residues of fluoroglycofen and fomesafen outside the manufacturers had decreased in different degrees,the residues of fluoroglycofen were less than 25 mg·kg-1 and the residues of fomesafen less than 50 mg·kg-1 at 100 m distance outside the manufacturer.There were no residues detection at the 300 m from the center of the manufacturer.There was no risk in soil from 300 m away outside the manufacturer.?2?The results of area source investigation showed that the soil residues were higher in crop planting period.The residual amount of fluoroglycofen were higher than that of fomesafen.The degradation of diphenyl ether herbicides within 6 months was fast.The residues in last sampling were basically not detected.?3?The results of microarea experiment showed that:there were high residues in the soil at the early stage of planting,and more than half of the herbicides have been degraded in the soil after one month.There were no herbicides residues in the soil and sweet potato at harvest.So the normal and double-dose use of the three herbicides has no risk for sweet potato.But double-dose herbicides could inhibited the normal development of sweet potato,and decreased the yield.Fluoroglycofen,metolachlor and butachlor could reduce the yield of sweet potato by 51.6%,23.6%and 30.7%respectively.?4?The results of biodegradability study showed that:strain SRC₁ could effectively degraded fomesafen under laboratory culture conditions.After 72 hours,the degradation rate reached 84.3%.The degradation is the highest when temperature was 30? or pH was 7.0.The amount of a one-time inoculant was more,the degradation effect was better.In addition,the initial diphenyl ether within 100 mg·kg-1 got good effect,if more than this concentration,the degradation rate and growth of the strain became poor.When the initial concentration was 200 mg·kg-1,300 mg·kg-1 and 400 mg·kg-1,the degradation rate of strain were only 62%,34%,28%respectively.?5?Experimental resxults of pot experiments showed that:the effect of strain SRC₁ on the degradation of fomesafen was better than that of fluoroglycofen.In the treatment of herbicides without inoculation of degrading bacteria,the germination and growth of the plants would be significantly inhibited.There was no obvious difference in the degradation between 5%inoculant and 5%inoculant twice in the soil.One time inoculation of 10%degradation bacteria amount could achieved the best degradation effect,the degradation rate is 75%,bean sprouts grew best as well.