Study On Toxicity Of ?-lactam Antibiotics And Ag Nanoparticles On Chlorella Vulgaris And Daphnia Magna

Currently,?-Lactam antibiotics and Ag NPs are widely used in various fields.There are constantly reports of antibiotics and nanomaterials found in the global water environment.Their appearance may affect various organisms,especially aquatic organisms.In this study,?-lactam antibiotics,amoxicillin(AM),aztreonam(AZ)and nano silver(Ag Nanoparticles,Ag NPs)were selected to investigate the single and combined effects on Chlorella vulgaris and Daphnia magna,in order to judge the environmental toxicity of?-lactam antibiotics and nanomaterials.The results of the study are as following:After the exposure of single AM,AZ and Ag NPs in culturing Chlorella vulgaris,the growth of Chlorella vulgaris were significantly inhibited,inhibition rates increased with the exposure concentration growth,and the 96h-median effect concentration(EC₅₀)was 367.230,44.420 and 8.120 mg/L,respectively.In binary and ternary combinations,the combined effects on Chlorella vulgaris is synergistic effect.Under single and combined culture,in higher exposure concentration groups,the content of photosynthetic pigments in algal cells was significantly decreased,and the intensity of chlorophyll fluorescence was significantly weakened.The superoxide dismutase(SOD)activity,catalase(CAT)activity and malondialdehyde(MDA)content of Chlorella vulgaris cells changed to different degrees,causing different degrees of oxidative damage.After morphology observing to control group and exposure groups by SEM,it was found that the damage degree of single exposure was lower than combined exposure.The 48h-Lethal Concentration 50%(LC₅₀)for Daphnia magna was 158.29,23.977 and 0.516 mg/L for single AM,AZ and Ag NPs,respectively.Combined acute toxicity results indicated that AM/Ag NPs were additive effect,the other binary and ternary combination effect were synergistic effect.The single and combined chronic toxicity effects showed that the growth,reproduction,morphology and lifespan of Daphnia magna were affected in different degrees.In high concentration group(except AZ/Ag NPs),the first shedding time,time of first pregnancy and time of first birth were prolonged to varying degrees,and the number of reproductions in 21d,total number of birth in 21d,16d body length and lifespan were reduced to different degrees.Changes in macroflea morphology were mainly caused by Ag NPs.The results of 96h-EC₅₀of Chlorella vulgaris and the acute toxicity of 48h-LC₅₀of Daphnia magna showed that the three substances are less toxic to Chlorella vulgaris and more toxic to Daphnia magna.The single toxic effects on both Chlorella vulgaris and Daphnia magna were Ag NPs>AZ>AM,and the combined toxic effects were AM/Ag NPs>AM/AZ/Ag NPs>AM/AZ>AZ/Ag NPs.