The Development Of Rare Earth Elements Speciation Reference Materials In Mining Area Soils And A Study Of The Rare Earth Elements Environmental Geochemical Behaviors

With the increasing applications of rare earth elements and blind exploitation of rare earth mine, the amount of rare earth elements in soil environment increases every year, which had serious effects on environment. Migration, transformation and biological availability of rare earth elements in soil were not only associated with its total amount, but also with their speciations. There are two main problems in the study of rare earth elements morphology at present.First,we need to develop a standard method of speciation analysis which is broad recognized. Second, there is a lack of reference materials in rare earth elements morphological analysis. So it is necessary to develop a rare earth elements morphological analysis reference materialsand to learn more about speciations of rare earth elements in soil, in order to providea analysis value of comparison and the quality control, conduct the theoretical and experimental foundation basis for the solve of environmental problems in the development of rare earth mine.In our study, we collected soil samples from the Baotou Bayan Obo and Jiangxi Gannan typical rare earth mining area, and analyzed rare earth elements inthe samples by inductively coupled plasma mass spectrometry. According to the characteristics of its content, we selected six typical standard substance candidatesinthese two places.Andwe used BCR sequential extraction method to analysis its morphological. Finally, several laboratories cooperative analysis to determined rare earths elements in soil standard reference material, and discussed its morphological distribution characteristics and environment geochemistry effects. Main research aspects and results:(1) It is the first time in the world developed the soil REEs speciationreference materials, standard material candidates were analyzed by BCR method (acid extractable, reducible state, oxidation state, residual) to determined 16 kinds of rare earth elements. Through the candidate homogeneity test, stability test, laboratory collaborative research, and the results show that the six standard material candidates in each test items were uniformity and stability,and justified the requirements of the national standard material. We choosed 9 laboratories collaborate to determined value of 16 indicatorsin the soil speciation referencematerial, the statistical data shows that,most of the REEs morphological datas were accuracy and reliable, the reproducibility of results from different laboratories was good, most of the test project has reached the analysis value.(2) Comparing the REEs contents from Bayan Obo and GanNan the mining area surrounding soil samples, which have showed that REEs in these soils was significantly higher than the china soil background value (164μg/g).REEs in Bayan Obo mining area is the highest 15955μg/g, lowest of 207μg/gand the LREEs are enriched; REEs in GanNan mining area is highest to 1638μg/g, the lowest 585μg/g, and the HREEs are enriched. With the distance to mining area closer, the REEs content is higher, and the environment pollution became more serious.(3) From the morphological analysis of the mining surrounding soils, BTS-1、 BTS-2、BTS-3 samples form Bayan Obo rare earth tailing area, REEs mainly enriched in residual fraction,the ratio of in turn is 89.3%,71.3%,64.0%, so the bioavailability is lower, have less impact on the environment. JXS-1, JXS-2, JXS-3 samples from Jiangxi Gannan area, REEs mainly exist in acid extractable and reducible fraction, the reducible fraction proportion in turn was 62.0%,68.4%,59.0%, it is easy to transport and transformation, have a certain pollution on the surrounding environment.(4) Different forms of REEs in the soil are affected by pH value, organic matter, composition and so on, the pH value of soil is the important factor of REE speciation transformation. Through the single factor index method, multi factor index method, biological effective analysis, that the soils and crops from REEs ore district surrounding areas is serious polluted by rare earth ion.Baotou Bayan Obo mine tailing area surrounding soil should be through reduce dust diffusion to improve pollution levels; Jiangxi Gannan area surrounding soil to governance pollutionshould be use the chemical method and biological method.