Toxic Effects Of AgNPs On Daphnia Magna Under Different Exposure Routes

Nano silver（AgNPs）has been industrially developed and applied to various consumer products due to its excellent antibacterial properties in recent years,but it is inevitable that AgNPs will enter the water during the production and consumption of AgNPs products.There have been many literatures on the aquatic toxicity of AgNPs mainly focusing on the toxic effects of water exposure.There are few studies on the toxic effects of dietary exposure of AgNPs,and the result and mechanism of aquatic toxicity are not clear.Not conducive to the development of AgNPs environmental risk assessment.This thesis studied the effects of AgNPs on the growth,reproduction,bioaccumulation and other indicators of Daphnia magna under water exposure（AgNPs）and diet exposure（AgNPs-incubated algae and AgNPs-laden liposomes）.Combined with the blank control experiment,analyze the toxic mechanism of AgNPs to Daphnia magna,and provide more accurate toxicity data for the environmental water risk assessment of AgNPs.And got the following main research results:（1）Under water exposure,the acute 24h-EC₅₀ of AgNPs on Daphnia magna is35.51μg/L.When the concentration is higher than 12μg/L,AgNPs will inhibit the reproduction and growth of Daphnia magna.The cumulative amount in the body decreases with the increase in concentration.（2）AgNPs can inhibit the growth of algal.AgNPs-incubated algae under dietary exposure can significantly inhibit the reproduction and growth of Daphnia magna,and the cumulative amount in Daphnia magna increases with the increase in concentration;the acute 24h-EC50 of AgNPs-laden liposomes on Daphnia magna is 58.92μg/L by diet exposure.At 14 days,the toxicity to Daphnia magna is not obvious,and the trend of accumulation in Daphnia magna is not obvious,but it significantly inhibits the reproduction of Daphnia magna at 21 days.（3）In the 14-day sub-chronic experiment,the effect concentration EC₅ of AgNPs under water exposure,AgNPs-incubated algae and AgNPs-laden liposomes on the number of molts of Daphnia magna were 2.24,0.02 and 0.86μg/L,respectively;The effect concentration EC₅ on the total reproduction of Daphnia magna were 3.1,0.005and 0.31μg/L,respectively;The effect concentration EC₅ on the number of first brood of Daphnia magna were 23.91,0.119 and 1.55μg/L,respectively;The effect concentration EC₅ on the body length of Daphnia magna is 4.08,0.14 and 1.07μg/L respectively;the subchronic toxicity result is AgNPs-incubated algae>AgNPs-laden liposomes>AgNPs,diet exposure toxicity>water exposure toxicity,and AgNPs toxicity of intake through algae enrichment>toxicity of dietary intake through liposome encapsulation.（4）In the 14 days bioaccumulation experiment,the 14-day bioconcentration factor BCF was 6.01 g/L when the concentration of AgNPs under water exposure was 1.5μg/L.The 14 days biomagnification factor BMF was 46.19 g/L when the concentration of AgNPs-incubated algae under diet exposure was 1.11μg/L.The 14 days biomagnification factor BMF was 0.68 g/L when the concentration of AgNPs-laden liposomes under diet exposure was 1.5μg/L.The bioaccumulation effect of AgNPs-incubated algae is far greater than AgNPs and AgNPs-laden liposomes,and dietary intake of AgNPs may be one of the main reasons for inhibiting the reproduction and growth of Daphnia magna.There are 27 figures,13 tables,and 178 refences during this paper.