| Rare earth pollution has become a peculiar problem in China because the content of rare earth elements in soil and water is higher around the mining area by unreasonable exploitation and utilization of rare earth resources.This study takes typical rare earth mines in South China as the research object to investigate the pollution status and main problems which reveal the migration and transformation rules of rare earth metals in soil,water and organisms and screen hyperaccumulator plant through analysis the enrichment characteristics of rare earth metals in different plants.Low enrichment crops were screened by analyzing the enrichment rules and mechanisms of rare earth elements in different crops.The remediation technology of rare earth contaminated soil was studied by using plant curing agent combined remediation technology.The purpose of this study is to reveal the law of environmental pollution in rare earth mining area and explore the remediation technology of rare earth mining area.(1)In this study,37 kinds of plants,15 kinds of popular vegetables,10 water samples and 9 soil samples in a rare earth mining area near the south of China were investigated and monitored to measure the content of 14 kinds of rare earth metals.The results showed that the contents of Sm and Y in soil,water,plants and vegetables are relatively high.The content of Sm is 0.00~454.48 mg/kg,0.00~7.95 mg/L,15.70~1774.80 mg/kg and 0.00~33 mg/kg,and the average content of Sm is 172.02mg/kg,1.34 mg/L,482.97 mg/kg and 79.55 mg/kg.The content of Y is 3.53~610.70mg/kg,0.00~36.95 mg/L,0.20~1553.20 mg/kg ? 0.63~231.68 mg/kg,and the average content of Y is 66.37 mg/kg,6.90 mg/L,296.54 mg/kg and 25.45 mg/kg.(2)Through soil culture experiment of the 5 kinds of plants cyclosorus parasiticus,pteris vittata,Cystoathyrium chinense,tuber fern and dicranopteris pedata in the concentration of 100 mg/kg in Sm and Y.The results showed that the content of Sm in the 5 plants is 62.08~198.5 mg/kg,and the average content is 119.98 mg/kg.The content of Y in the 5 plants is 14.86~127.73 mg/kg,and the average content is43.93 mg/kg and the content of Y in pteris vittata is highest,the content of Sm incyclosorus parasiticus is highest.Cyclosorus parasiticus has strong accumulation and transport capacity to Sm,and the enrichment factor is 0.81.The SOD activity of pteris vittata and cyclosorus parasiticus under the stress of rare earth elements Sm,Y is more active than other tested plants.At this time,the ability of plant to remove ROS is stronger,and plants can accumulate more rare earth metals.(3)Through hydroponic experiment of the 5 kinds of vegetables cabbage,lettuce,kale,sweet potato leaf lettuce in the concentration of 50 mg/L in Sm and Y.The results showed that the content of Sm in the 5 vegetables is 679.21~1067.6 mg/kg,and the average content is 849.24 mg/kg.The content of Y in the 5 vegetables is475.49~820.83 mg/kg,and the average content is 649.26 mg/kg.On edible part,Cabbage mustard accumulation of rare earth metal Sm,Y was the lowest,10.21mg/kg and 6.99 mg/kg respectively which shows the accumulation and transport ability of mustard to Sm and Y is weak and the enrichment coefficient is only 0.20 and 0.14.The amount of Sm and Y in lettuce was the highest,which was 407.60mg/kg and 304.83 mg/kg respectively.(4)Through the experiment of the concentration of 500 mg/kg single rare earth Sm contaminated soil,the concentration of 620 mg/kg single rare earth Y contaminated soil and Sm concentration of 500 mg/kg,Y concentration of 620 mg/kg compound rare earth Sm,Y contaminated soil to addind curing agent/clam powder activated carbon with concentration of 0.0,2.0,4.0,16.0,32.0,64.0 g/kg to determin5 types of occurrence of rare earth metals.If there are higher the content of iron and manganese oxides in the rare-earth metals,there are better the soil remediation effect.The results showed that the ratio of iron and manganese oxides when the concentration is 64.0 g/kg for soil Sm pollution is the largest which is 7.5%.We can think there are better the soil remediation effect to Sm contaminated soil which the concentration is 64 g/kg for clam powder.The ratio of iron and manganese oxides when the concentration is 64.0 g/kg for soil Y pollution is the largest which is 25.6%.We can think there are better the soil remediation effect to Y contaminated soil which the concentration is 64 g/kg for clam powder.The ratio of iron and manganese oxides when the concentration is both 64.0 g/kg for compound rare earth Sm,Y contaminatedsoi is the largest which is 69.7% and 62.4%.We can think there are better the soil remediation effect to compound rare earth Sm,Y contaminated soil which the concentration is 64 g/kg for clam powder.(5)Through the joint repair experiment which have different addition order between plant(Pterisvittata)and curing agent(the concentration of both 64.0g/kg clam powder).The results showed that there are higher iron and manganese oxides in the rare-earth metals when curing agent are first and then plant for single rare earth Sm contaminated soil which is 33.3%.There are higher iron and manganese oxides in the rare-earth metals when curing agent are first and then plant for single rare earth Y contaminated soil which is 24.1%.There are higher iron and manganese oxides in the rare-earth metals when plant are first and then curing agent for compound rare earth Sm,Y contaminated soil which is 36.3% and 34.5% separately.Single curing agent(clam powder)have better repair effect to single rare earth contaminated soil.Plant and curing agent combined repair have better repair effect to compound rare earth Sm,Y contaminated soi. |
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