| Organic pollutants in agricultural soil was generated from chemical fertilizers and irrigation with wastewater.The top of agricultural soil was limited to retain pollutants,then the organic pollutants penetrated downward to groundwater and caused groundwater pollution.Therefore,to prevent and control pollutants migration to groundwater,the technical in soil solute transport is studied to find out an effective method increasing adsorption of pollutants in soil.To improve subsurface of soil for preventing organic pollutant migration to groundwater,using dodecyl dimethyl betaine(BS-12)as an amphoteric modifier,the comparison of preparation of modified soil column by two different modification methods,(1)using BS-12modified Lou soil to pack in column(pre-modified,Pre-);(2)modification by penetrating BS-12 in unmodified Lou soil column(penetrated,-p).The distribution of BS-12 in penetrated soil column was explored and the difference of phenol migration in these 2 modified columns was compared.The effect of environmental factors such as concentrations pH and ionic strength on phenol migration in the soil column was studied.(1)BS-12 modification was transported to Lou soil in column,and the different distribution of BS-12 penetrated in the different columns.The 2 levels of BS-12 ratio in 5cm depth of soil column was completely penetrated with fully BS-12 adsorption.For 20 cm depth of soil column,50%BS-12 didn't completely pass through soil column and only 100%BS-12actively penetrated.(2)Equilibrium model(EM)for non-reactive was used to fit Cl~-transport in these 2modified columns and the results showed that the retardation factor of R-value of Cl~-transport in each soil sample was smaller than 1.Non-equilibrium model(NEM)for reactive solute transport was used to describe breakthrough curves(BTCs)of phenol indicated the R-value of phenol migration was larger than 1,and R-value became larger while modification and penetration ratio increased.The R-value of phenol migration in 100%CEC of pre-100BS-12modified soil(pre-100BS-12)(7.048)was larger than 100%CEC of 100BS-12penetrated soil(100BS-12p)(6.706)caused by an increasing number of pore volume in Pre-100BS-12.The phenol retention was higher in 100-BS12p compared to Pre-100BS-12 caused by 100BS-12p contained with a high content of BS-12.As seen the result,the slower flow velocity,longer duration,high retardation factor,and phenol retention in 100BS-12p were proved that the ability to block phenol in soil was the best.(3)With an increase of phenol concentration transport,the blocking ability of phenol migration in unmodified soil(CK)was not changed,however,the blocking ability of various phenol concentration(Pre-modified soil,PMS)and(penetrated soil,PS)was enhanced.R_w of phenol washout in PMS and PS become larger with increasing modification and penetration ratio.In addition,saturated adsorption amount and retention phenol at various phenol concentration in PMS and PS were large.The blocking ability of phenol in Pre-100BS-12 and 100BS-12p didn't change in the range of pH 4 and 10,except the blocking ability of Pre-100BS-12 and 100BS-12p to phenol migration at pH 7 was higher.Even though pH of phenol migration was vary,the phenol retention in PMS and PS were still larger than CK.The flow velocity of phenol migration in CK and Pre-100BS-12 was faster with decreasing ionic strength,and the flow velocity of phenol in 100BS-12p was slower with decreasing ionic strength from 0.1 to 0.001 mol/L.The blocking ability of phenol in CK,pre-100BS-12 and 100BS-12p was weakening with decreasing of ionic strength and the phenol retention in each soil column also decreased.(4)As seen the above results,the blocking ability of phenol in subsurface soil with two modification method by BS-12 as enhanced through simulation test,the modification can significantly decrease the speed of organic pollutants infiltration with soil water.Soil modification is also a good process but the modification operation is more complicated.In this study,the main purposes are to transport or inject amphoteric surfactant to soil and the distribution of BS-12 in each soil layers is unevenly.However,the effective results are similar to the pre-modification. |
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