Trial On The Time Characteristics And Mechanism Of Joint Toxicity Of Some Heavy Metals And Pesticides To Chlorella Pyrenoidosa

Heavy metal and herbicide pesticide contaminants universally exist in the aquatic environments.Heavy metal pollution has become a major problem in environmental protection management due to its'characteristics of enrichment and refractory degradation.The pesticides in the environment have a series of negative effects on the natural environment due to their persistence and fluidity generally,which raises many concerns.In addition,these two types of pollutants may become a threat to human health through the food chain and other ways.Therefore,analysis of the pollution laws and mechanisms of heavy metals and pesticides,which can provide a method and data references for the evaluation of envrionmental risks of pollutants existing in environmen.Therefore,chlorella pyrenoidosa?C.pyrenoidosa?was used as the test organism,and five heavy metals copper?Cu?,manganese?Mn?,cadmium?Cd?,zinc?Zn?,and lead?Pb?and three pesticides:methamizin?Met?,Bladex?Bla?,and Terbumeton?Ter?together with their combined toxicity of binary and multi-component systems to C.pyrenoidosa were investigated.Concentration additive?CA?model was used to analyze toxicity interaction within mixtures.At the same time,combining with time-concentration-effect?CRC?curve,the chlorophyll contents of C.pyrenoidosa in different concentration levels of pollutants in different exposure time were also determined.The main results are as follows:?1?Five heavy metals and three pesticides have time-dependence on C.pyrenoidosa,but the toxicity of different pollutants varies in the same exposure time,and the toxicity orders also change with time extending.Selecting the negative logarith of the mean effect concentration(EC₅₀),pEC₅₀,as the toxicity index,the toxicity orders of the five heavy metals are as follows:for the exposure time of 48 h and 72 h,Cu>Cd>Zn>Pb>Mn;96 h,Cu>Zn>Cd>Pb>Mn.The toxicity orders of the three pesticides are the same in the whole exposure time:Bla>Ter>Met.?2?In the five heavy metal mixture systems,CA prediction lines of the most mixture rays fall below the 95%confidence intervals,i.e additive addition,and the variety of addition is not obvious with time.CA prediction lines of some mixture rays fall above the 95%confidence intervals,i.e.antagonism,with the extension of time,the antagonism gradually weakened?eg.Zn-Cd mixture system?.?3?In the three pesticide mixture systems,CA prediction lines of most binary pesticide mixture rays fall below the 95%confidence intervals,and exhibite synergism.With the extension of time,synergism gradually augments.While CA prediction lines of the pesticide ternary mixture rays basically falls within the 95%confidence interval and appear additive effects and the variety of addition is not obvious with time,totally different toxic effects from the binary mixture.?4?In the binary mixture systems of five heavy metals and three pesticides,CA prediction lines of most mixture rays fall above and within the 95%confidence intervals diplaying antagonism and additive action.With the extension of time,the antagonism gradually weakened while additive action keeps constant.CA prediction lines of the Bla-Cu mixture rays fall below the 95%confidence interval displaying synergism.With the extension of time,synergism gradually augments.?5?In the octagonal mixture system of five heavy metals and three pesticides,CA prediction lines of mixture ray R5,R6 and R7 fall above the 95%confidence interval,and show antagonism.CA prediction lines of the mixture ray R1,R2,R8 and R10 fall below the 95%confidence interval and show synergistic effects.CA prediction lines of R3,R4 and R9 mostly fall within the 95%confidence interval and display additive action.Toxicity interaction of all the mixture rays chang little with time lengthening.?6?The changing trends of chlorophyll a concentrations of C.pyrenoidosa treated by single heavy metals and pesticides,and the mixture of these components at different inhibition rates and in different exposure time are also consistent with the changing trends of their toxic effect.Inhibition effect increase,and the corresponding cholorophyll a content gradually decrease.Compared with the control group,with the extension of time,the chlorophyll content reduction rate of each inhibition effect reached the maximum in 96 h.However,the variations of various pollutants in different exposure time and different inhibition effects is not the same.