Effects of fluoride and chloride on the growth of Chlorella pyrenoidosa.
To compare the toxic action of fluoride (F(-)) and chloride (Cl(-)) on freshwater algae, effects of F(-) and Cl(-) on Chlorella pyrenoidosa growth were investigated by determination of the algal biomass and model analysis. Results showed that the exponential growth equation (D = D0 + ae(bT)) may be used to fit the relationship between cell density (D) of C. pyrenoidosa and exposure time (T), but F(-) and Cl(-) have significantly different effects on parameters a (initial quantity of algae at the exponential growth stage) and b (growth constant). In the range of experimental concentrations, F(-) inhibited C. pyrenoidosa growth, and percent inhibition increased with increasing exposure time and F(-) concentration. By contrast, Cl(-) either inhibited or enhanced C. pyrenoidosa growth depending on Cl(-) concentration and exposure time, and percent inhibition increased with increasing Cl(-) concentration but decreased with increasing exposure time. The dose-response equation: I = min + (max - min)/(1 + 10(lgEC50-lgC)) may be used to fit the relationship between percent inhibition (I) and F(-) or Cl(-) concentration (C); however, F(-) was distinct from Cl(-) in terms of effects on parameter 'min'. The EC50 values of F(-) and Cl(-) ranged from 118 to 170 mg/L and 19.73 to 36.33 g/L, respectively; the latter is much higher than the former. Thus F(-) has higher toxicity than Cl(-).
Institute of Agricultural Engineering, Jiangsu University, Zhenjiang, China.
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D002708:Chlorella / Q000187:drug effects* / Q000254:growth & development; D002712:Chlorides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D054750:Ecotoxicology / Q000379:methods; D005459:Fluorides / Q000494:pharmacology*; D008954:Models, Biological; D014874:Water Pollutants, Chemical / Q000494:pharmacology*
D002712:Chlorides; D014874:Water Pollutants, Chemical; D005459:Fluorides