Joint effects of arsenic and cadmium on plant growth and metal bioaccumulation: a potential Cd-hyperaccumulator and As-excluder Bidens pilosa L.

Joint effects of arsenic (As) and cadmium (Cd) on the growth of Bidens pilosa L. and its uptake and accumulation of As and Cd were investigated using the field pot-culture experiment. The results showed that single Cd (<or=25 mg kg(-1)) and As (<or=50 mg kg(-1)) treatments could promote the growth of B. pilosa, resulting in 34.5-104.4% and 21.0-43.0%, respectively, increase in the dry biomass of shoots while compared with that under the control conditions. However, under the co-contamination of As and Cd, there was an antagonistic effect on the growth of the plant. The concentrations of As and Cd accumulated in tissues of the plant increased with an increase of As and Cd in soils. In particular, the levels of Cd in stems and leaves reached 103.0 and 110.0 mg kg(-1), respectively, when soil Cd was 10 mg kg(-1). Furthermore, the BF and TF values of Cd were greater than 1.0. However, the highest content of As in roots of the plant was only 13.5 mg kg(-1) when soil As was at a high level, i.e. 125 mg kg(-1), and the TF values of As were less than 0.1, indicating that B. pilosa can be considered as a potential Cd hyperaccumulator and As excluder. The presence of As had inhibitory effects on Cd absorption by the plant, in particular, the accumulation of Cd in stems, leaves and shoots decreased significantly, with 42.8-53.1, 49.3-66.4 and 37.6-59.5%, respectively, reduction when the level of soil As was up to 125 mg kg(-1) compared with that under no addition of As. Whereas, when Cd was added to soils, it could facilitate As accumulation in tissues of the plants and the As concentrations in shoots increased with increasing Cd spiked in soils. The interactive effects of Cd and As may be potential for phytoremediation of Cd and/or As contamination soils.