Effect of peat on heavy metal bioavailability in soil system and flowering Chinese cabbage

A pot experiment with flowering Chinese cabbage（Brassica campestris L. ssp. chinensis Var. utilis Tsenet Lee） was conducted to study the effect of amended peat rates on the bioavailability and chemical form distribution of heavy metals in soil. The pots were added with 3 sets of soil amended with Cu 200 mg/kg, Cr 300 mg/kg and Pb 1000 mg/kg. One set of soil was amended with 6 peat treatments, i.e. 0%, 0.5%, 1%, 2%, 4% and 5%, respectively. Each treatment of one heavy metal set had four replications. With the increase of peat rates, the distribution of heavy metals, content of the DTPA-exchangeable heavy metals in the soil and in the root, stem and leaf of the plants changed significantly. On the contrary, the content of organically bounded heavy metals in the soil and the yield of flowering Chinese cabbage were enhanced greatly as a whole, but the yield decline occurred in the treatment with 4% or 5% peat rate. In a word, the 0%#8722;5% peat rates reduced the bioavailability of the heavy metals Cu, Cr, Pb and 0%#8722;3% peat rates enhanced the vegetable yield in the soil polluted by heavy metals.