Studies On Soil Phytoremediation Of Discarded Rare Earth Mine Field By Pot Cultivation Experiment

The mountain areas of North-east Guangdong Province are rich of rare earth resources, they are also the main distribution areas and producing areas of weathered crust-eluvial rare-earth mine. Development and utilization of rare earth resources have contributed to the local development, but led to environmental and ecological problems. By means of experiment plot, plants were screen to grow well in the soil of the abandoned rare earth mine area. The stress tolerant plants were analyzed on the reducing sugar, free proline, chlorophyll, soluble protein, POD, SOD and CAT. Effects of watering, nutrition elements, inorganic elements and organic fertilizer on the soil improvement were evaluated. And the 16 s r DNA and the SRAP diversity of the soil bacteria among the control and different treatments were compared in this study. The study results were as the following:1. In this study,the survival rate of different plants grown in the soil are compared for measuring their growth potential. The results showed that Tephrosia candida, Digitaria sanguinalis, Paspalum conjugatum, Digitaria sanguinalis were dominant in growth potential, fresh weight and dry weight. But the leaves of Tephrosia candida grown in the abandoned rare earth mine soil were greener than those grown in the vegetable garden soil. Therefore, Tephrosia candida, Paspalum conjugatum, Digitaria sanguinalis were selected to measure the physiological indexes related to stress tolerance.2. The study results showed that soluble sugar, free proline, soluble protein, POD, SOD, CAT of Tephrosia candida, Paspalum conjugatum, Digitaria sanguinalis grown in the soil of the abandoned rare earth mine were greater than those grown in the vegetable garden soil. These indicated their obvious stress resistance, and Paspalum conjugatum was the most. The chlorophyll content of Paspalum conjugatum and Digitaria sanguinalis grown in the soil of abandoned rare earth mine was lower than in the vegetable garden soil, but Tephrosia candida is just the opposite. Thus Paspalum conjugatum is the best in the phytoremediation of the abandoned rare earth mine area.3. The soil microbial biomass in the abandoned rare earth mine area was great different among the different treatments, 2.45×104 cfu/g in the control, 1.78×104 cfu /g in the watering treatment, 1.90×105 cfu/g in the MS addition,2.49×106 cfu/g in the hay addition, 2.00×106 cfu/g, 9.96×107 cfu/g in the fowl manure addition. It showed that adding organic matter could improve the microbial biomass, and adding fowl manure was the best. SRAP molecular marker was used to analyze genetic diversity of the soil bacteria, and the PIC of the soil bacterial DNA in treatment of adding fowl manure was 0.903 which was the highest. It showed that soil bacteria in treatment of adding fowl manure was the most.4. Sequencing the bacterium’s 16 s r DNA and Blast analysis with NCBI Gene Bank revealed the that there were 4 bacterial genus in the control, 3 in the watering treatment, 7 in MS addition, 5 in the hay addition, in the vegetable garden soil, and 7 in the fowl manure addition.The results were in accordance with the SRAP diversity analysis.5. Growth of Paspalum conjugatum grown in the soil of different treatment was different. It showed that the leaves of Paspalum conjugatum which growed in hay addition treatment, vegetable garden soil and fowl manure addition treatment were normal, and chlorophyll content and Pn of the leaves were the highest. Growth of the watering treatment and the control showed a certain deficiency symptoms and the chlorophyll content and Pn were the lowest. Growth of the MS addition was intermediate between the above two groups.