Application of phosphate-containing materials affects bioavailability of rare earth elements and bacterial community in soils

The exploitation and smelting of rare earths can cause serious pollution to the farmland around the mining area. The rare earth elements(REEs) are absorbed by crops and enter the human body through the food chain, which threatens people’s health. The effects of four phosphorus-containing materials-calcium superphosphate(SSP), phosphate rock(PR), calcium magnesium phosphate(CMP) and bone charcoal(BC) on rice growth and bacterial community structure in REE mining area of Xinfeng County were studied by pot experiment. The soil solution was collected during rice transplanting and harvest periods respectively, the rice and soil samples were collected and sequenced. The concentrations of water-soluble REEs were measured by inductively coupled plasma mass spectrometry(ICP-MS), and bacteria in soil was deeply sequenced by the Illumina Miseq sequencing platform. PR, CMP and BC promoted the growth of rice, improved the biomass of rice roots, shoots and grains, and significantly reduced absorption and accumulation of REEs in rice roots, shoots and grains. SSP treatment reduced the pH value of soil, significantly improved the concentration of REE solution in soil and improved biomass of rice roots, shoots and grains,and significantly improved the concentration of REEs in grain. The effects of phosphorus-containing materials on the absorption and accumulation of 15 REEs in rice roots, shoots and grains were very different, and significantly influenced the soil bacterial community. SSP reduced richness and diversity of bacteria. CMP improved the diversity of soil bacteria, but reduced their richness. PR and BC treatment improved the richness and diversity of soil bacteria, and significantly increased the abundance of Bacillus. The results showed that adding PR, CMP and BC to soil in the REE mining area of Xinfeng can improve food security and eco-environmental quality, and hence, are potential restorative materials;SSP is not recommended for use in acidic soils.