The Trophic Transfer And Toxic Effect Of TiO₂ Nanoparticles From Algae To Daphnia

TiO2 nanoparticles(nTiO2)are the most widely produced and used metal oxide nanoparticles at present.During the production and application,nTiO2 are inevitably released into the environment and may transfer through the food chain,posing a threat to human health.Some researchers have studied nTiO2 transfer along the food chain,but little information is available about effects of particle size and crystal content of nTi02 on their trophic transfer.In this study,5 nm anatase(nTiO2-5A),10 nm anatase(nTiO2-10A),100 nm anatase(nTiO2-100A),20 nm P25(nTiO2-P25,80%anatase and 20%rutile),and 25 nm rutile(nTiO2-25R)were selected to investigate the effects of particle size and crystal phase on the toxicity,bioconcentration,and trophic transfer of nTiO2 to algae and daphnia.The obtained results mainly include:(1)The 96 h IC50 values for algae and the 48 h LC50 values for daphnia of nTiO2-5A,nTiO2-10A,nTiO2-100A,nTi02-P25,and nTi02-25R were 10.3,18.9,43.9,33.6,and 65.4 mg/L and 10.5,13.2,37.0,28.4,and 60.7 mg/L,respectively.The acute toxicity all decreased with increasing size or rutile content of nTiO2.(2)nTiOI2 were bioaccumulated by daphnia with bioconcentration factors(BCFs)ranging from 21220 L/kg to 145350 L/kg,and nTiO2 were biomagnified when transferred from algae to daphnia with biomagnification factors(BMFs)ranging from 5.7-122.The BCFs and BMFs all decreased with increasing size or rutile content of nTiO2.(3)A preliminary analysis of the influence of nTiO2 on the daphnia metabolism was conducted.The results showed that 6 metabolic pathways were significantly disturbed in daphnia exposed to nTiO2 in the absence of algae;but in the presence of algae,only 4 metabolic pathways were significantly disturbed.This indicated that algae alleviated the impact of nTiO2 on the metabolism of daphnia.