Characteristics Of Movement And Transformation Of Chromium In Underground Aquifer

As the important supply source and vital support of ecosystem, groundwater is the significant guarantee to maintain the benign cycle of water system. In recent years, along with the development of industry, more and more industrial solid castoff and waste water enter into the environment, including a mass of heavy metal chromium, and because of broad use of cadmium, the exploitation and utilization of cadmium increase steadily which have already polluted the natural environment. Pollution elements contained in the industrial waste water pollute the soil and groundwater straightway even more.We chose the method of laboratory simulation to study the characteristics of movement and transformation of chromium in underground aquifer, and the style of underground aquifer,concentration of metal,pH,ionic strength,activity of microorganism,time and concomitant cadmium were chose to be factors of which one was changed when the others were fixed basically to investigate the characteristics of movement and transformation of chromium in underground aquifer, Thomas equation was used to fit the data of varying concentration of chromium according to the volume of fluid water, and compared influence degree of different factors. The results indicated that:When the concentration of chromium in the simulation groundwater is 1mg/L and 2mg/L, the adsorption ability of medium 1 to chromium was bigger than medium 2. When the concentration of chromium in the simulation groundwater is 4mg/L, in other words, when the concentration of chromium in the simulation groundwater was a little big, the transference speed of chromium in different aquifer was close, and the style of the aquifer has little influence in movement and transformation of chromium. The chromium mainly existed as Cr6+ in the fluid water and as Cr3+ in the soil. The transform ratio of Cr6+ adsorbed by medium 2 was bigger than medium 1 and Cr3+ has diverse concentration at different distance. The concentration of chromium in the medium 1 followed the opposite order when the distance was changing greater. The pH of different fluid water all descended comparing with the pH of simulation groundwater. In the range of concentration chose in the experiment, when the concentration of chromium in simulation groundwater is different, the decreasing order of penetration in same soil is 4mg/L,2mg/L,1mg/L.When the pH of simulation groundwater change a little, namely from 5 to 6, from 7.5 to 8, it has little effect in the movement and transformation of chromium in medium 2, in the range of pH chose in the experiment, the adsorption ability of medium 2 to chromium followed the same order when the pH was changing to smaller.In the range of ionic strength chose in the experiment, the increase of concentration of NaNO3 reduced the adsorption ability of medium 2 to chromium. When concentration of NaNO3 was 0.1mol/L, the pH of fluid water aggrandized comparing with the simulation groundwater while it descended when concentration of NaNO3 was 0.5mol/L and 1.0mol/L.In the time rage chose in this experiment, at the end of 384h, the concentration of chromium in fluid water were all between 0.7~0.8mg/L comparing with the control. As same as the soil analysis result of the control, during 384h, the chromium adsorbed by medium 2 mainly existed as form of Cr3+, and the concentration of Cr6+ decreased while Cr3+ increased when the distance was changing to greater. The pH of fluid water had markedly descended trend but fluctuated in small range.When the microorganism in medium 2 was restrained, the transform speed of chromium in aquifer fell distinctly and the adsorption ability of medium 2 to chromium increased. The average pH of fluid water descended comparing with the simulation groundwater.When there was cadmium coexisted in simulation groundwater, the adsorption ability of medium 2 to chromium dropped. And at the same condition, the adsorption ability of cadmium was bigger than chromium which is inosculated with the diminishment of penetration volume when cadmium coexisted comparing with the control. The chromium adsorbed by medium 2 mainly existed as Cr3+, and the concentration followed the same order when the distance was changing to greater while the concentration of cadmium followed the opposite order. By calculating the percent of concentration of chromium in medium 2, we find that the percent of chromium in medium 2 followed the same order when the distance was changing to greater.