Alleviating arsenic toxicity to plants in a simulated cover system with phosphate placement in topsoil and subsoil

摘要

Revegetation of arsenic-enriched mining wastes is challenging due to arsenic (As) toxicity to plants. Inorganic As is easily taken up by the cells of plant roots where it can disrupt plant metabolism partly due to its similarity to phosphate ions. Arsenic toxicity may be alleviated by phosphorus (P) fertilisation partly due to the analogous chemical characteristics of phosphate and arsenate ions, although this effect may vary in different plant taxa. Many mining cover systems employ a single layer, or multilayers, of soil or soil-like material directly over potential toxic waste material. We simulated this basic design in a glasshouse study by growing plants in a layered system (notionally topsoil and subsoil) where we tested how As and P interacted by assessing the effects of P fertilisation (in topsoil and subsoil) on alleviating toxicity of As placed in subsoil only (to mimic a cover system). Two contrasting plant species were used: a ryegrass (lolium multiflorumj and an Acacia species grown in the mining area (Acacia ancistrocarpaj. The growth of both plant species decreased in line with increased As concentrations in subsoil irrespective of high or low P treatments to either topsoil or subsoil. Overall we found that P application in topsoil (with As in the subsoil) was more effective than subsoil P application for sustaining improved growth of plants by alleviating As toxicity.