Difference of Absorption of Pinus sylvestris in La3+and Ce3+Solutions
Pinus sylvestris is as the research object,the process of absorption of lanthanum nitrate hexahydrate,cerium nitrate hexahydrate,lanthanum chloride heptahydrate,cerium chloride heptahydrate,lanthanum sulfate octahydrate and cerium sulfate octahydrate by Pinus sylvestris under hydroponic conditions was analyzed,in or-der to reveal the mechanism of Pinus sylvestris repairing pollution by La3+and Ce3+.In this paper,the content and rate of La3+and Ce3+absorbed by Pinus sylvestris in different times were studied by using the uptake kinetic method.And the correlation between the measured and predicted values of La3+and Ce3+absorbed in Pinus syl-vestris-hydroponics system was explored through regression analysis.The concentrations of La3+and Ce3+in the hydroponic solution were set to 100,300,500 and 1000 mg·L-1,respectively.The results show that the con-tents of La3+and Ce3+in Pinus sylvestris increase with the increase of the concentration of hydroponic solution.The content ranges of lanthanum sulfate,lanthanum nitrate and lanthanum chloride are 0.0014-0.0142 g,0.0009-0.0115 g and 0.0017-0.0195 g,respectively,and the content ranges of cerium sulfate,cerium nitrate and ceri-um chloride are 0.0019-0.0119 g,0.0015-0.0141 g and 0.0022-0.0198 g,respectively.When the concentrations of rare earth ions in the hydroponic solution are the same,the absorption of Ce3+by Pinus sylvestris is greater than that of La3+,and the absorption saturation time of Ce3+laggs that of La3+.The analysis of uptake kinetic about 0-60 h of the fastest absorption rate by Pinus sylvestris in hydroponic solution shows that the absorption rate decreases significantly during the period of 3-24 h,and then decreases slowly after 24 h under different rare earth ion concentrations.When the concentration of La3+and Ce3+in hydroponic solution is 1000 mg·L-1,the absorption rate of Ce3+by Pinus sylvestris is higher than that of La3+in 0-60 h,and the absorption rates of different rare earth compounds are in the order:chlorinated state＞sulfuric acid state＞nitric acid state,which is proportional to the content of La3+and Ce3+absorbed by Pinus sylvestris at different time.Finally,through the univariate linear regression analysis between the amount of rare earth elements absorbed by Pinus sylvestris and the concentration in hydroponic solution,it is concluded that the data fitting of different La3+and Ce3+have a good prediction effect.In conclusion,Pinus sylvestris has better ability to absorb La3+than Ce3+in hydroponic so-lution,so it has high tolerance.Pinus sylvestris and other enrichment plants could be used to improve the ecolog-ical restoration efficiency of soil polluted by La3+and Ce3+.
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