Study On The Toxicity Of 25 Pesticides To Chorella Ellipsoidea And Anabaena Spiroides

Chlorrella ellipsoidea and Anabaena spiroides were used as test organism to reseach the influence of pesticides to the primary producer in freshwater.Dry weight,chlorophyll a content and cell density of two algae were compared with their absorbance at 680nm in this paper, and then the 10-15 days'continual toxicity of 25 popularly used pesticides were investigated by spectrophotometric method. We draw conclusions as follows:1.Three are good linear correlation between dry weight,chlorophyll a content or cell density and absorbance at 680nm(OD680) of the two algae,all of the correlation coefficient were beyond 0.99. It indicated that OD680 is a good indicator to calculate the biomass, and this makes it possible by using the data acquired through OD680 to monitor the environment and the environmental pollution caused by pesticides.2.There is a regularity of the mid-long term toxicity of pesticides to algae. Firstly, it gradually rises to the maximum, then drops continually, at last, the growth of the algae was stimulated to some extent when pesticides are at low concentrations.3.The toxicity of 17 pesticides to Anabaena spiroides are greater than that of them to Chlorrella ellipsoidea, but the other 8 kinds—Bismerthiazol, Hexaconazole, Bromoxynil octanoate ,Simetryn, Pendimethalin, Beta-cyfluthrin, Metolcarb and Triazophos, are on the contrary.4.It also has difference in the toxicity of insecticide, herbicide and fungicide to the algae used in the experiment ,the toxicity order as follows: herbicide>fungicide>insecticide.5.Pesticides at low concentration can accelerate the growth of the two algae.23 of 25 pesticides used in this work proved it, excluding Hexaconazole and Pyridaben, the minimum of enhancing rate is 0.03 per cent caused by Pendimethalin under 0.1mg/L to green alga on 12th day ,the maximum of enhancing rate is 45.64 per cent caused by Diazinon under 0.5mg/L to cyanobacteria on 10th day.6.Besides organic phosphorus insecticides, there also exists the risk inducing Water blooms by other kinds of pesticides, pesticides with high toxicity may do so. The enhancing rate of the growth of Anabaena spiroides by Benalaxyl, Propiconazol, Fenbutatin oxide at low concentrations can reach to 14.07%,29.03% and 29.63%. Simetryn, Prometryn and Triclopyr, the enhancing rate of which are over 20%,also show that, especially for Prometryn, whose toxicity to cyanobacteria is high, it can cause 36.63% growth enhancement at 0.02mg/L , Metolcarb also enhances the growth of the alga by 14.74% on 10th day ,even at 1mg/L.