Feasibility of arsenic phytostabilisation using Mediterranean shrubs: impact of root mineralisation on As availability in soils.

An incubation experiment was carried out to evaluate the rate of arsenic release from roots to soil during root mineralisation, in order to determine the viability of phytostabilisation of metal-polluted soil. Arsenic (As)-loaded roots were mixed with the soil, monitoring arsenic, phosphorus, copper and zinc solubility and pH. Arsenic dynamics in soil during root mineralisation depend on various factors such as mineralisation rate, pH and soil chemistry. After 56 days incubation, only the soil with T. gallica roots showed higher NH4(SO4)2-extractable As than soil without roots. Phosphorus release was positively correlated with extractable arsenic. Extractable Cu depended on root mineralisation but Zn solubility was controlled by soil pH. On the whole, species with high As accumulation in roots and a high mineralisation rate may release arsenic in soluble forms in the soil immediately after root addition, but the soil can partly retain arsenic subsequently. In this respect, the risk of As mobilisation due to root decomposition was found to be low, confirming the prospects for long-term phytomanagement and phytostabilisation of arsenic.