Organic acid compounds in root exudation of Moso Bamboo (Phyllostachys pubescens) and its bioactivity as affected by heavy metals

Moso bamboo (Phyllostachys pubescens) has great potential as phytoremediation material in soil contaminated by heavy metals. A hydroponics experiment was conducted to determine organic acid compounds of root exudates of lead- (Pb), zinc- (Zn), copper- (Cu), and cadmium (Cd)-tolerant of Moso bamboo. Plants were grown in nutrients solution which included Pb, Zn, Cu, and Cd applied as Pb(NO3)(2) (200 mu M), ZnSO4 center dot 7H(2)O (100 mu M), CuSO4 center dot 5H(2)O (25 mu M), and CdCl2 (10 mu M), respectively. Oxalic acid and malic acid were detected in all treatments. Lactic acid was observed in Cu, Cd, and control treatments. The oxalic was the main organic acid exudated by Moso bamboo. In the sand culture experiment, the Moso bamboo significantly activated carbonate heavy metals under activation of roots. The concentration of water-soluble metals (except Pb) in sand were significantly increased as compared with control. Organic acids (1 mM mixed) were used due to its effect on the soil adsorption of heavy metals. After adding mixed organic acids, the Cu and Zn sorption capacity in soils was decreased markedly compared with enhanced Pb and Cd sorption capacity in soils. The sorption was analyzed using Langmuir and Freundlich equations with R (2) values that ranged from 0.956 to 0.999 and 0.919 to 0.997, respectively.