| Dibutyl-phthalate (DBP) has become an important organic pollutants in the world as a widely used synthetic organic compounds.DBP has been widely detected in the basin of Three Gorges Reservoir and had a greater security risk to the water environment of reservoir. There has been a large fluctuating zone around the reservoir due to the special scheduling of Three Gorges reservoir, as a special flooding soil, the soil in fluctuating zone not only can become the source of DBP but also can become the sink of DBP in the reservoir because of the periodical flooding,erosion,and siltation by the reservoir water. The pH, dissolved oxygen, temperature, microorganisms and organic matter of the soil in fluctuating zone will take place a series of changes after flooding. Whether these changes will have an impact on the migration and release processes of DBP in the soil of fluctuating zone, What kind of impact will happen? Research in these areas is extremely lacking. Accordingly, this study has simulated the regular pattern of the migration and release processes of DBP in the soil of fluctuating zone using the soil collected from Chongqing kaixian in Three Gorges Reservoir as studying object and examined the impacts on the migration and release processes of DBP in different background concentrations、different water properties (ion content, DBP content, organic matter content)、and different environmental conditions (DO, temperature, light, coexistence DEHP, microbial activity) during the soil in fluctuating zone flooded. The results are as follows:1、the characteristics of the migration and release processes about DBP after the soil of fluctuating zone flooded is:DBP migrate from the soil to the water in the early days after flooding, the release behavior of DBP is the main migration process.Release process is divided into two phases:one is quick release whose releasing time is relatively short with a rapid releasing rate; another is slow release whose releasing time is relatively slow and long with a slow releasing rate. In the interim (12d) after flooding the capacity of release reached a maximum; the DBP which released from the soil into the water will migrated from the water to the soil again after continued flooding; eventually in the later period after flooding, the content of DBP in soil and water reached equilibrium. The process that DBP released from soil into the overlying water after flooding can be well fitted by two-compartment first-order kinetics:it showed the rate of quick release is much greater than the the rate of slow release during the process that DBP released from soil into the overlying water, but the amount of slow release had accounted for99.12%in the entire release process. That indicate slow release is the main act during the process that DBP released from soil into the overlying water. The process that DBP migrated from the overlying water to soil after the content of DBP in overlying water reaching the maximum was fitted with double constant equation, the level of significance is good.2、The characteristics that DBP migrated and released from soil into overlying water after soil with different DBP concentrations flooded is basically the same. But the rate of quick release kd,rap that DBP released into the overlying water increased following the added DBP concentrations in soil; on the other hand, the rate of slow release kd.slow that DBP released into the overlying water slowed following the added DBP concentrations in soil. The greater initial content of DBP in soil, the amount of DBP released into the overlying water would be greater during the process flooded.3、The water conditions of Overlying water can impact the process that DBP migrates and releases during the soil in fluctuating zone flooded(1) Ionic strength in the water can effect the process of release:when ionic strength in the water was increased, the amount of DBP released into the overlying water would increase. The increased ionic strength in the water can enhance the quick release of DBP, but there is not apparent impact on the slow release of DBP.(2) The concentration of DBP in the overlying water has a little effect on the migration and release of DBP in the soil.however, high concentrations of DBP in the overlying water could change the migration behavior of DBP. In the early days after flooding, the high concentrations of DBP in the overlying water would inhibit the release of DBP from the soil; when the flooding time lengthened, DBP still keepped releasing from the soil to the water; On the other hand, the high concentrations of DBP in the overlying water would delay the time when the amount of DBP released from the soil reached maximum. Overall it did not affect the fate of DBP in the soil-water environment. (3) The concentration of organic matte in the overlying water has a big effect on the migration and release of DBP in the soil. The higher concentration of organic matter existed in overlying water, the amount of DBP releasing into the overlying water would greater. Meanwhile, the rate of quick release kd,rap that DBP released into the overlying water would increase, the rate of slow release kd,slow would slow down correspondingly. But high concentrations of organic matter could slow down the quick release of DBP in the soil.4、The external environmental conditions can impact the process that DBP migrates and releases during the soil in fluctuating zone flooded(1) When the temperature of Overlying water increased, the intensity of releasing into the water about DBP would increase following the increasing temperature. When the environmental temperature rosed from15℃to35℃, the percentage that quick release and slow release accounted the entire release phase only occurred minor changes, but the rate of quick release kd,rap had a great appreciation and the rate of slow release kd,slow had a small decline. This indicates that the changes of environmental temperature primarily produce some impacts to the quick release of DBP, high temperature can significantly accelerated the rate of quick release at the same time.(2) Illumination can impact the process that DBP migrates and releases during the soil in fluctuating zone flooded:The concentrations of DBP released into the water was different with different light source. The overall effect is that the concentration of DBP in the overlying water with natural light is higher than using ultraviolet light as the light source. After the amount of DBP in the overlying water reached maximum, the content of DBP in overlying water decreased relatively fast under the ultraviolet light, the process decreased relatively slow under the natural light.(3) The oxygen content in the overlying water can slightly impact the process that DBP migrates and releases during the soil in fluctuating zone flooded. However the largest release content of DBP and the times reached the largest release content were different with different oxygen content. Overall, the content of DBP in the overlying water under high oxygen study> the content of DBP in the overlying water under natural state study> the content of DBP in the overlying water under low oxygen study. The time when the concentration of DBP in overlying water reached maximum brought forward at the8days after flooding in the high oxygen and low oxygen studies, and the time was at12days in natural study.(4) When the phthalate-bis (2-ethylhexyl)-ester (DEHP) simultaneously existed in the soil, there would be some significant effects to the release of DBP. The study added DBP and DEHP could release more DBP than the study added single DBP, and kd,rap, kd,slow were bigger than the study added single DBP also.It Indicated the amount of DBP releasing into the overlying water and the rate of release could be increased when there was some DEHP in the soil at the same time.(5) The microbial activity could take some impacts to the process that DBP migrates and releases during the soil in fluctuating zone flooded. However the effect is not obvious, due to the lack of microorganisms existed in the soil originally and those microorganisms were not domesticated during the study. The content of migrated DBP under sterilization treatment was slightly less than non-sterile treatment. |
PDF Full Text Request