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 Pb 2+ ,Zn 2+ ,Hg 2+ ,Cu 2+ ,Cd 2+ and Cr(Ⅵ) for the growth of photosynthetic bacterium Rhodopseudomonas palustris were y=-2.9504x+13.234,R 2=0.9906c(Pb 2+ );y=-1.1866x+ 8.1605 ,R 2=0.9827c(Zn 2+ );y=1.4736x+3.9692,R 2=0.9894c(Hg 2+ );y=1.7267x+8.7004,R 2=0.9655 c(Cu 2+ ),y=1.1551x+8.9996,R 2=0.9252 c(Cd 2+ ) and y=1.3427x+10.785,R 2=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 Hg 2+ > Cu 2+ > Cd 2+ >Cr(Ⅵ)>Zn 2+ > Pb 2+ .With orthogonal experiment of L 8(2 6),another result showed that inhibition of compound pollution of Pb 2+ ,Zn 2+ ,Hg 2+ ,Cu 2+ ,Cd 2+ and Cr(Ⅵ) on the growth of this strain showed cooperative effect.
