Study On The Transport Of Cr And Cd In The Soil Of Jinan Southern Mountain Area

The safety and quality of Jinan spring has become the focus of academic circles. It is the emphasis to prevent the spring from contamination. Cr(Ⅵ) and Cd are the representative of the heavy pollutants. Once they enter into the groundwater, they could cause serious consequences for human health and environmental safety. Transfering from soils into the groundwater is the main way that heavy metal Cr(Ⅵ) result in groundwater pollution. Therefore, it will obtain the benefited effect to learn about the migration regularity of Cr(Ⅵ) and Cd in soil and provide the prevent measures. research. In this article, we studied the migration regularity of heavy metal Cr(Ⅵ) and Cd in different height, different velocity and different sampling time, and the utilization proportion of different biochar, through indoor one-dimensional soil column experiment. And evaluation the control effect of biochar on Cr(Ⅵ) and Cd migration. Finally, we used mathematical method to simulate breakthrough cures, obtain the longitudinal dispersion coefficient, forecast analysis of heavy metals in the soil pollution range and degree of concentration and to provide quantitative basis for heavy metal waste management and pollution control. The main achievements and conclusions in this study showed as follows:(1)From Cr(Ⅵ) and Cd single migration curve, we observed that the migration speed of two kinds of heavy metal in three kinds of soil medium increases with the increasing flow velocity and decreases with the increasing migration distance. In the situation of high velocity, the addition of biochar in soil has also failed to block the migration of Cr(Ⅵ) and showed very strong migration ability to the deep soil and groundwater.In the situation of low velocity, the addition of biochar can significantly inhibit the migration of Cr(Ⅵ). And with the increase of biochar proportion, inhibiting effect becomes more obvious. The migration speed of Cd in three kinds of soil medium is slower than Cr(Ⅵ) in the same condition. Addition of biochar could obviously block the migration of Cd. It will tend to be controlled in the shallow soil, and the control effect increase with the migration distance increase.(2)From Cr(Ⅵ) and Cd mixed migration curve, we found that the migration velocity has been speed up in each tape of soil. It mainly because the two kinds of heavy metals using common adsorption sites, and compete with each other and restrain. Cr(Ⅵ) was affected more than Cd due to biochar and soil has stronger adsorption ability on the Cd.(3)Through the analysis of the physical and chemical properties of biochar, we concluded theexperiment mechanism is : biochar show adsorption and fixation to heavy metals depending on its huge specific surface area because itcontains a large number of negative charges; biochar has a lot of alkaline substances that can reduce the biological effectiveness of heavy metals in the soil; biochar has many organic functional groups that can coordination complexation with heavy metal ions, biochar has high cation exchange capacity(CEC), which promote the soil Cr(Ⅵ) and Cd hydrolysis precipitation formation.(4)Make use of the "three point method" formula, to obtain longitudinal dispersion coefficient of heavy metal in different condition. We found that the longitudinal dispersion coefficient of Cr(Ⅵ) and Cd was remains unchanged under the equal velocity and the same biochar addition proportion, which suggested that the soil column have been filled uniformly. In the case of other conditions unchanged, if the input of liquid flow rateincreased, the longitudinal dispersion coefficient of heavy metals will increase. The mathematical simulation of longitudinal dispersion coefficient variation law keep the consistent with the experiment phenomenon, which could prove that the accuracy of the experiment.