An Experimental Research On Improvement Of Abandoned Rare Earth Mine Tailings Soil And Phytoremediation

The problem of the restoration of abandoned rare earth mine soil eco-environment has beenbrought into focus. This paper sets an abandoned rare earth mine in Dingnan County, Ganzhou asan object. At first, though an analysis on physical and chemical properties of soils, we can find outthe key factor of land reclamation in abandoned rare earth mineral areas and provide the basis forsoil improvement and ecological restoration of abandoned land of rare earth. Secondly, invented anew type of soil amendments and studied the effect of the soil conditioner on abandoned rare earthmine soil; Finally, studied the growth performance of some tolerance of herbaceous plants onabandoned rare earth mine soil and grown alone or combined with soil amendments plantingimprovement and repair effect of rare earth tailing soil though Pots experiment. Main results forthis studyare as follows:（1）The abandoned rare earth mine soil was sandy soil with strongly acid (pH=4.52); theorganic matter, total nitrogen, available phosphorus and potassium of the soil were0.023%,0.103%,5.10mg/kg,40.74mg/kg, the plant nutrition of soil was overall deficiency and extremelydisproportion. The total ofthe rare earth elements in the soil exchangeable states was715.54mg/kg,under the exchangeable states in the control soil background value. The major was the compositepollution of rare earth elements which was mainlyabout Ce, Ho, La, Pr, Sm, Y.（2）Through the experiment of planting resistant plants Poa annua L., Festuca elata Kengex E. Alexeev, Pennisetum americanum×P．purpureum, orghum bicolor×S．sudanense, theresult indicated that these four plants could increase soil total nitrogen, organic matter and availablepotassium and showed a strong tolerant function. In a period of150days, the highest coverage ofvegetation could up to80%. The order of covering speed was Pennisetumamericanum×P．purpureum＞Poa annua L.＞Festuca elata Keng ex E. Alexeev＞orghum bicolor×S．sudanense. Among them, the coverage of Pennisetum americanum×P．purpureum wasmost stable, which was around80%. These four plants had some effects of absorbing the rare earthelements in the soil. Especiallyfor the absorption of Ce, Ho, La, Y, etc. was highlyobvious. On theother hand, Poa annua L. could absorb most types of rare earth elements which have11kindsincluding Ce、Dy、Er、Gd、Ho、La、Nd、Pr、Sm、Y、Yb. Particularly, the absorption forthe Ce、Ho was highest which reached112.24mg/kg,141.43mg/kg.（3）Developed a new kind of soil amendments, its modifier pH, the content of organicmatter, total nitrogen, available phosphorus and potassium were6.91,73.20%,48.32%,2.15x103mg/kg,1.68x103mg/kg. According to quality proportion between soil and fertilizer (4:1)applied soil amendment on rare earth tailings soil pH and nutrients, which have significantimprovement after150days, the content of soil total nitrogen, organic matter, available phosphorusand potassium were0.263%,4.476%,257.82mg/kg,71.17mg/kg, reached the second national soil survey in the standard of a standard. For the soil exchangeable content of rare earth elements, onlya few Holmium residues were detected.（4）The combined use of soil amendments on the abandoned rare earth mine soil, the height,root length and biomass of tolerant herbaceous plant could be improved. Vegetation coverage rateand coverage also had improved significantly. After planting20~60days, the coverage can reach100%, especially the vegetation coverage of Poa annua L., Pennisetum americanum×P．purpureum and orghum bicolor×S．sudanense can reach100%and maintain it for4~5months.