Distribution Characteristics And Purification Effect Of REEs Of Pinus Massoniana And Dicranopteris Dichotoma In Rare Earth Mining Area,Southern China

Changting County,Fujian Province has been the main area of rare earth mining due to the extensive distribution of rare earth resources.With the exploit of rare earth ore,it has brought about huge economic profits and caused serious problems such as soil erosion,ecological environment damage,and threats to residents’ health.For this reason,how to improve the ecological environment and purify the REEs in the rare earth mining areas in the Southern China has become an important task.In this study,the Huangnikeng and Laiyoukeng in Changting County,Fujian Province were used as the research sites.Combined with the actual conditions of sites,the growth characteristics,nutrient characteristics and environmental characteristics of Pinus massoniana and Dicranopteris dichotoma were investigated.At the same time,we proposed a new method that the phytostabilisation of Pinus massoniana coupled with the phytoextraction of Dicranopteris dichotoma worked together to purify rare earth elements in rare earth mining areas.Besides,in order to enhance the ability of Pinus massoniana to fix REEs,the application of compound fertilizer and compound microbial fertilizer was used to improve the growth environment of Pinus massoniana.The main results are as follows:(1)Among the growth indicators of Pinus massoniana and Dicranopteris dichotoma,except for the negative correlation between Pinus massoniana’s plant height and the biomass of leaves and the lack of correlation between Dicranopteris dichotoma’s plant height and density.Then,there was a significant positive correlation between other growth indicators.(2)The nutrient contents of different organs of Pinus massoniana and Dicranopteris dichotoma were quite different.The Pinus massoniana’s leaves accumulated a large amount of C,N,and P elements,while its roots accumulated a large amount of K elements.Except for N/K and P/K,C/N,C/P,C/K,N/P were significantly different in different organs of Pinus massoniana.The contents of C,N,P and K in Dicranopteris dichotoma were generally highest in leaves and lowest in petioles.In terms of nutrient ecological stoichiometry,there were significant differences among leaves,petioles and roots.(3)The content of REEs under the soil of communities was higher than that of Chinese soil and Fujian soil background values.There were certain potential ecological risks.(4)The contents of REEs in different organs of Pinus massoniana and Dicranopteris dichotoma were different.Pinus massoniana: roots> barks> branchs> trunks> leaves;Dicranopteris dichotoma: leaves> roots> petioles.This was mainly due to the differences in the absorption capacity,enrichment capacity,and transfer capacity of the REEs.The absorption coefficients and accumulation of REEs in Pinus massoniana’s organs were significantly smaller than those in Dicranopteris dichotoma’s organs.First,it indicated that the transfer of REEs from soil to Pinus massoniana in this area was not as good as that of Dicranopteris dichotoma.The ability of Pinus massoniana’s organs to accumulate REEs was not as good as that of Dicranopteris dichotoma.However,both of them had stronger ability to enrich light rare earth than heavy rare earth.(5)In the rare earth mining area,Southern China,the combined use of Pinus massoniana and Dicranopteris dichotoma purified rare earth mining areas.With one year of castration of Dicranopteris dichotoma,repairing the content of REEs in the mining area to the national standard for soil required 35,30,and 30 years.Then,it took 48,55,and44 years to repair the content of REEs in the mining area to the national standard of soil under the circumstance of two years of castration.(6)The change of the content of REEs in the annual rings of Pinus massoniana trees indicated that with the change of the ecological environment,the capacity of Pinus massoniana to absorb rare earth elements was getting better and better.Therefore,in order to promote the absorption of rare earth elements in Pinus massoniana,we needed to take further measures to control the ecological environment of the rare earth mining areas,Southern China.So,in the rare earth mining areas,Southern China,the application of compound fertilizer and compound microbial fertilizer to the roots soill of Pinus massoniana had been improved,and its organic matter content,FDA content,and available nutrient content had been improved to varying degrees.The effect was as follows: compound microbiome> compound Fertilizer group> untreated group.