Abstract:

A short-term exposure experiment of 19 native plant species was carried out from May 2006 to August 2008 at two sites with different stresses of acid rain pollution (HP: Guangzhou Petrochemical Factory in Huangpu represents a contaminated area; LXH: Liuxihe National Forest Park represents a relative clean area). Total 76 soil samples, collected from rhizospheres of those tested plants and the nearby bulk soil, were analyzed to investigate chemical behaviors of rhizosphere soil under the different acid rain pollution. Meanwhile, soil samples of rhizosphere of Schima superba and the nearby bulk soil under a longer-term pollution were also collected and analyzed for further confirmation. The results showed: (1) Soil major ions (H⁺, Al³⁺, Cl^-, NO₃^-, SO₄^2-, K⁺, NH₄⁺) contents in the serious acid rain stress area were higher than that in the relative clean area and the serious acid rain stress induced an increase in leaching Ca²⁺, however promoted Ca²⁺ transfer from bulk soil to rhizosphere soil. (2) The nutrient content of rhizosphere soil was in general higher than that of bulk soil. (3) There were antagonistic actions and negative correlations between Ca²⁺ (as well as organic matter) and Al³⁺ in rhizosphere soil. (4) Acid rain significantly caused Al release, the ratio of exchangeable Al and exchangeable Ca (Al/Ca) of the soil in serious acid rain pollution area was larger than that in the relative clean area. (5) There was a close correlation between Al³⁺ and organic acid in the soil, which suggested that the plant roots would excrete more organic acid with the enhancing acid stress for complexing Al³⁺ in the root sphere to lessen the toxicity of aluminum.

Key words: acid rain stress, rhizosphere soil, chemical behavior, Guangzhou