Toxicity And Bioaccumulation Of AgNPs To Daphnia Magna

Due to their widespread application, silver nanoparticles (AgNPs) will inevitably be discharged into the environment and thereby potentially pose risks to ecosystems.Many studies have reported the toxicity and bioaccumulation of nanoparticles.However, most of these studies were conducted in different culture media, and very few have been done in real water samples. The behavior and toxicity of AgNPs in real water system can be very different from the culture media, which merit more investigation. This research systematically compared toxicities and bioaccumulations of citrate-coated AgNPs (C-AgNPs) and silver ions from AgNO3 in the M4 medium and a surface water sample. Some valuable research results are obtained.(1) AgNPs and Ag+ showed dose-responsive effect on Daphnia magna. The immobility of the daphnia increased with increasing exposure concentrations. The toxicities in the surface water sample were significantly lower than those in the M4 medium. The 24 h-ECso of AgNPs and Ag+ in the M4 medium were 105 ?g/L and 2.8?g/L, respectively, while those in the water sample were 270 ?g/L and 7.5 ?g/L,respectively.(2) Both AgNPs and Ag+ exhibited chronic toxicity towards the daphnia,affecting the growth and reproduction of the daphnia. C-AgNPs and Ag+ mainly inhibited the body length, and C-AgNP at high concentrations could delay the first brood time.(3) Daphnia magna could accumulate C-AgNPs and Ag+. After exposure to 120?g/L C-AgNPs for 24 h, the body burdens in the M4 medium and the water sample were 127 ?g Ag/g and 47.3 ?g Ag/g, respectively. After exposure to 1 ?g/L Ag+ for 24 h, the body burdens in the M4 medium and the water sample were 10.1 p,g Ag/g and 7.6 ?g Ag/g, respectively. The 24 h-BCF of C-AgNPs at 120 ?g/L were calculated to be 4.22 L/g in the M4 medium and 1.3 5 L/g in the surface water.(4) Though no biological magnification phenomena were observed under the exposure concentrations, C-AgNPs and Ag+ were able to transfer from algae to the daphnia through the algae-daphnia food chain.