Abstract: A standard method for evaluating the toxicity of chemicals on hydrobios was applied.The results showed that 96 h linear doseresponse equations of inhibition of heavy ions Pb²⁺,Zn²⁺,Hg²⁺,Cu²⁺,Cd²⁺ and Cr(Ⅵ) for the growth of photosynthetic bacterium Rhodopseudomonas palustris were y=-2.9504x+13.234,R²=0.9906c(Pb²⁺ );y=-1.1866x+ 8.1605,R²=0.9827c(Zn²⁺ );y=1.4736x+3.9692,R²=0.9894c(Hg²⁺ );y=1.7267x+8.7004,R²=0.9655 c(Cu²⁺ ),y=1.1551x+8.9996,R²=0.9252 c(Cd²⁺ ) and y=1.3427x+10.785,R²=0.9758 c(Cr(Ⅵ),and their 96 h-EC50 were 617,460,0.200,2.172,25.66 and 392.6μmol·L^-1,respectively.The toxic sequence of these metal ions from high to low on the growth of this strain was Hg²⁺ > Cu²⁺ > Cd²⁺ >Cr(Ⅵ)>Zn²⁺ > Pb²⁺.With orthogonal experiment of L₈(2⁶),another result showed that inhibition of compound pollution of Pb²⁺,Zn²⁺,Hg²⁺,Cu²⁺,Cd²⁺ and Cr(Ⅵ) on the growth of this strain showed cooperative effect.

Key words: sulfur, form, soil, fractionation, long-term fertilization.