Adsorption Characteristics Of Dibutyl Phthalate On Black Soil And Screening Of Biological Monitoring Indexes

Dibutyl phthalate?DBP?is a common compound in the family of PAEs.It is widely used in plastic products and many other industrial products because it has a good effect on plastic modification and plasticizing.Accompanied with the consequent proliferation of DBP in the world,it has been confirmed so far that DBP has a"triple effect"and can interfere with the endocrine effects of organisms and cause endocrine disruptions.Therefore,it is important to reduce the potential hazards of the environment caused by using organic pollutants like phthalates and make it less harmful to the environment.This kind of changes and the improvement of contaminated soil resources have been increasingly concerned by the whole society.Adsorption of organic pollutants to the soil has an important influence on its migration and bioavailability.Black soil is rich in organic matter that plays an important role in adsorpting.This also indicates that black soil may have high adsorption to DBP.At the same time,DBP may be harmful to the environment after being adsorbed by the soil.It can be judged whether DBP pollution can be effectively evaluated or not through the biological monitoring indicators such as soil enzyme activity,luminescent bacteria,and DBP intermediate metabolites.The following results were obtained through experiments:According to the studies of adsorption kinetics and adsorption thermodynamics,the adsorption of DBP in soil reached equilibrium at 24 h and the first 7.5 h of reaction was a rapid adsorption period,The pseudo-second-order kinetics and pseudo-second-order kinetics and the Elovich equation were used to fit the adsorption process of DBP.The fitting results showed that the soil adsorption DBP followed a pseudo second-order kinetic model.The adsorption thermodynamics found through fitting Freundlich.that the R² value of the model reaches 0.9989and the K_F value is 2.3035.The Freundlich model can simulate the relationship between DBP adsorption in soil and water better.The effects of temperature,pH,ionic strength and DOM addition on the adsorption of DBP in soil were investigated.The results presented that temperature and DOM have a great influence on the adsorption of DBP in soil.Three temperature gradients were designed for the experiment,they are 25°C,16°C and 4°C.And the study found that as the temperature decreased,the adsorption of DBP in soil increased gradually,which proved that the adsorption of DBP on soil was exothermic.The amount of DBP adsorbed on the soil has been greatly improved,after the addition of DOM presented that DOM plays an important role in the adsorption of DBP in soil.pH may have a certain effect on the adsorption of DBP.When the pH is less than or more than 7,the adsorption of DBP in soil decreases.The ionic strength of the soil make a difference to the adsorption DBP,and when the ionic strength was less than 0.01 mol·L^-1.The adsorption capacity of DBP in soil showed an rising trendency with the increasing of ionic strength.However,when the ionic strength exceeded a certain value,the adsorption capacity decreased and began to get in the way of the adsorption carrying on.The following four soil enzyme activities were tested:soil catalase,soil sucrase,soil urease and acid phosphatase.DBP has the effect of inhibition at high concentration of catalase in the soil and totally opposite at low concentration.Catalase activity in soil began to decrease after a period of low concentration treatment,but DBP inhibited the catalase activity at high concentrations significantly.At low concentrations,DBP had little effect on the activity of urease.High concentration of DBP inhibited the activity of urease,and the activity of DBP showed a certain relationship with DBP after high concentration treatment.DBP has a great influence on soil sucrase activity.The activity will decrease significantly under low concentration treatment or high concentration treatment,and the enzyme activity will continue to decrease as time goes by.When the DBP is at a lower concentration,the change in acid phosphatase activity is not very insignificant,but when the DBP concentration rises to a certain extent,the activity of the acid phosphatase changes greatly,and after the twentieth to the thirtieth days of,enzyme activity began to fluctuate,first increase and then decrease,and eventually the activity of acid phosphatase tended to be gentle.Microorganisms in the soil was in the condition of DBP pollution after the addition of DBP to the soil,the content of MBP and PA in the soil was increasing rapidly during the whole growth period but as the decreasing of DBP content in soil,the contents of MBP and PA began to increase rapidly and kept increasing continuously.As a metabolite of DBP,MBP and PA have the characteristics of being difficult to degrade and accumulating,so it can be used as a biological monitoring indicator.