Root distributions and elemental accumulations of Chinese brake (Pteris vittata L.) from As-contaminated soils

A field investigation was conducted to understand the root distributions and elemental accumulations of Chinese brake (Pteris vittata L.), an As-hyperaccumulator, grown in soils with a gradient of As concentration near an arsenic sulphide mine. The root distribution was affected not only by the levels of soil As, but also by soil texture. Plants grew better in sandy loam soils than in clay soils. Increases in the ratio of frond biomass to underground biomass were correlated with decreasing soil As concentration. Root densities of the plant decreased from 0-10 cm, 10-20 cm to 20-30 cm in the soil profiles. Most of the roots were concentrated in the upper 0-10 cm layer. Under high As conditions, As concentrations in different tissues followed the trends: pinnae > rhizomes approximate to roots of 0-10 cm > roots of 10-20 cm > roots of 20-30 cm > petioles, however, As concentrations in pinnae were higher than those in rhizomes under low As conditions. The rhizomes and pinnae were the main As pools, storing 75-86% of the total As uptaken by the plants. The rhizome, a 'buffer-storage' for plant As, maintained high concentrations of As under high soil As while the pinnae became the most important organ of storing the As under low soil As. Chinese brake might possess the ability of adjusting its As-storage under different soil As levels. The plant can not only hyperaccumulate As from the soils, but also enriched P and Ni from the soils and translocated them to the fronds. It is important to improve the root distribution for phytoremediation of As-contaminated soils using Chinese brake.