The Effect Of Deltamethrin And DEHP On Earthworm Population And Soil Enzyme

In this paper deltamethrin and DEHP(Di(2-ethylhexyl)phthalate)were test pollutants,they were representative of pyrethriods pesticides and phthalate plasticizers which were two common pollutants in agriculture soil.This paper was to study the two pollutants single pollution at low concentrations of long-term exposure conditions,the population variety and reproduction of Eisenia federi and the change of soil enzyme activity were observed,the contrast of soil enzyme activity from no earthworm treatment to earthworm treatment was also observed.Whether earthworm could promote the degradation of deltamethrin and DEHP was researched through periodic sampling and testing the residual concentrations of deltamethrin and DEHP.Research indicates:Thedeltamethrin(0mg/kg-10mg/kg)and DEHP(0mg/kg-150mg/kg)in the 75-day incubation period had no significantly affect on the number of adult earthworms but had significant impact on young earthworms.In the case of deltamethrin contamination,the number of young earthworms significantly decreased with the increase of exposure concentration.Under the condition of DEHP pollution,when the exposure concentration was less than 5mg/kg,the number of young earthworms significantly increased,and the number of young earthworms did not significant differences,when the exposure to higher concentrations,the number of young earthworms decreased significantly compared with the control,the number of young earthwormshad no significant differences.The results of test that effects of two contaminants on soil enzyme activities described as follows.First were the results about deltamethrin,for soil urease,low concentrationdeltamethrininhibited the enzyme activity but high concentration activated it,and the inhibition was the main effect.For soil phosphatase,low concentration inhibitedthe enzyme activaty well high concentration activated it,but the effect were not significant.For soil dehydrogenase,Deltamethrin activated dehydrogenase activity in most cases.Next were the results about DEHP.For soil urease,DEHP inhibitedthe enzyme activity significantly,the inhibition rate increases first and then decreases with the prolongation of time,and the concentration and urease activity show a significant dose-response relationship.The effect of DEHP on the activity of phosphatase fluctuated,and it showed activation-inhibition-activation during the culture process,but there was still inhibition in the later stage of culture.DEHP was mainly activated the soil dehydrogenase activity,and activated significantly,with the longer incubation time,the activation rate decreased gradually.In the deltamethrin polluted soil,Earthworm makes soil urease,phosphatase and dehydrogenase activity significantly lower than that without earthworm.During the middle and later stages of culture,the higher the concentration of deltamethrin,the lower the inhibition rate form earthworms of urease and phosphatase activity,and the greater the inhibition of urease and phosphatase activity over time.The effect of earthworms on soil dehydrogenase in the early stages of culture were fluctuations,20 days later,the inhibition was the main effect and the inhibition rate first increased and then decreased.In the DEHPpolluted soil,earthworm group in a variety of soil enzyme activity both higher than in the absence of earthworm group and lower than the group without earthworms.For urease,the addition of earthworms in the early stage of culture resulted in the urease activity was significantly higher than that without earthworm group,followed by earthworm group urease activity in most cases was lower than that no earthworm group,after 20 days of incubation,the inhibitory effect was enhanced and reached a significant level.For phosphatase,in the first 35 days of culture,compared no earthworm group with earthworm group,there was no obvious regularity of inhibition or activation.After 35 days of culture,earthworm mainly inhibited the activity of phosphatase.For dehydrogenase,earthwormsgroup dehydrogenase activity in most cases decreased compared with no earthworm group,in the entire culture process showed a fluctuating state of inhibition.Degradation of deltamethrin and DEHP wereboth in accordance with the first-order kinetic equation,and the half-life increases with increasing concentration.The degradation of the two pollutants showed the characteristics of rapid degradation in the early stage and slow degradation in the late stage,and the addition of earthworms had no obvious effect on the degradation of the two pollutants.The results showed that adding only earthworms to deltamethrin or DEHPcontaminated soils did not affect thedegradation rate significantly.However,the use of earthworms to degrade deltamethrin and DEHP remains to be further studied.