Study On Combinedtoxicityeffectsof Halosulfuron-meth,Butachlor,Mesotrione And Atrazineon Pseudokirchneriella Subcapitata

The combined toxicity of herbicide to environment increasingly brought to the attention of the people.This paper study on Halosulfuron-methyl(HAL),But-achlor(BUT),Mesotrione(MES)and Atrazine(ATR),by the method of toxicity of 1:1,to investigate their toxic effects of single and combined on P.subcapitata.The main research as follow:1.The study of acute toxicity of four herbicides on P.subcapitata demonstrated that EC50 of HAL tested in different time points were 0.0080mg/L(24h),0.0070mg/L(48h),0.0050mg/L(72h),EC50 of BUT were 0.140mg/L(24h),0.118mg/L(48h),0.104mg/L(72h),EC50 of MES were 2.136mg/L(24h),2.748mg/L(48h),3.475mg/L(72h),and EC50 of ATR were 0.040mg/L(24h),0.020mg/L(48h),0.023mg/L(72h).With the increasing of exposure time,the toxicity increased gradually.The order of toxicity of four to P.subcapitata is HAL>ATR>BUT>MES.HAL,BUT and ATR are high-toxic herbicides to P.subcapitata,and MES is low toxic herbicide.2.The joint toxicities of binary mixtures and ternary mixtures made up of HAL,BUT,MES and ATR on P.subcapitata at in different exposure times were studied.The results showed that toxicity of binary mixtures and ternary mixtures on the algae increased with the increased exposure time and concentration.The combined toxicity of HAL+BUT showed very strong antagonism(24h),very strong antagonism(48h)and strong antagonism(72h).The mixture of HAL+MES is antagonism(24h),synergism(48h)and very strong synergism(72h).The mixture of HAL+ATR is strong antagonism at all three exposure times.The mixture of BUT+MES is antagonism(24h)and very strong synergism at 48h and 72h.The mixture of BUT+ATR is very strong antagonism(24h),strong synergism at 48h and very strong synergism at 72h.The mixture of MES+ATR is strong antagonism(24h),antagonism at 48h and nearly additive at 72h.The combined toxicity of ternary mixture of HAL+BUT+NES is slight synergism(24h),synergism(48h)and strong synergism(72h).The mixture of HAL+BUT+ATR is very strong antagonism(24h),strong antagonism(48h)and slight synergism(72h).The mixture of HAL+MES+ATR is strong antagonism(24h),antagonism(48h)and moderate antagonism(72h).The mixture of BUT+MES+ATR is strong antagonism(24h),moderate antagonism(48h)and synergism(72h).3.The effects of chlorophyll content of P.subcapitata in 72h were studied in single and binary mixed conditions.The results showed that the chlorophyll content decreased with the increase of the concentration of drugs.The six binary mixture showed antagonistic effects on the inhibition of chlorophyll content.And ternary mixtures is also antagonism,except the mixtures of HAL+BUT+MES.4.The effects of protein content of P.subcapitata in 72h were studied in single and binary mixed conditions.In the single exposure condition,the high dose of four kinds of herbicides significantly reduced the protein content,and the difference was significant.The protein content of P.subcapitata has a certain stimulating effect when mixed with low concentrations of binary mixtures of HAL and BUT.The protein was significantly inhibited in the first concentration gradient of binary mixtures of HAL and MES,and the difference was significant in the control.Thus,the binary mixture of HAL+MES has a relatively large effect on the protein relative to HAL+BUT.5.The superoxide dismutase(SOD)activity of P.subcapitata in 72h were studied in single and binary mixed conditions.In low doses of single herbicide,the activity of SOD was increased and reached a significant difference compared with the control.When the concentration increased,SOD activity will be gradually reduced.And the activity of SOD was increased significantly in low concentration of MES.And the activity of SOD increased little and decreased rapidly when exposed in HAL.In the mixed conditions,the SOD activity was increased at low concentration,but decreased in concentration increased.When the concentration of 0.086mg/L HAL was mixed with BUT,the activity of SOD was significantly lower than that of other concentration combinations and single BUT.In the mixture of HAL+MES,when the concentration of0.086mg/L HAL was mixed with MES,the activity of SOD was significantly lower than that of other concentration combinations and single MES.