Because the cumulative effects and toxicity of mercury,products that can remove mercury contamination in food are clearly needed.Nanoscale formulation of selenium has small size and large specific surface characteristics,and has strong affinity for mercury.To investigate the influence of nano-selenium on mercury phytotoxicity,bioaccumulation and transportation in plants,the garlics were hydroponicly cultivated in Hoagland solutions containing different dosages of nanoselenium(particle size 50 nm)and mercury.The biomass was used to indicate the phytotoxicity of nano-selenium and mercury,and then both elements in different garlic tissues were quantified with inductively coupled plasma-mass spectrometry(ICP-MS).The speciation were investigated with X-ray absorption near edge structure(XANES).The results showed that nanoselenium treatment at lower levels(< 1 mg/L)is significantly beneficial for garlic growth,while at higher levels(> 10 mg/L)the mild inhibitive effect is exhibited.On the other hand,the mercury phytotoxicity was observed to occur even at lower exposure levels(0.1 mg/L).For the garlic co-exposed to nano-selenium and mercury at higher levels(> 1 mg/L),an antagonistic effect between both elements was observed.The ICP-MS result shows that,for the garlic exposed to lower level of mercury,nano-selenium treatment at lower levels(< 0.1 mg/L)can hardly affect the content of mercury in plant,and at higher levels(> 10 mg/L)it does not promote mercury accumulation in root,bulb and leaf as Se(Ⅳ)and Se(Ⅵ)do.when Hg2+ exposure level was higher than 1 mg/L,nano-selenium treatment can significantly inhibit the absorption and transportation of Hg in different garlic tissues which was previously observed in garlic exposed to Hg and Se(Ⅳ)/Se(Ⅵ)simultaneously.XANES analysis showed that Hg was mainly present in the forms of inorganic mercury and S-Hg-S bonding as in Hg(GSH)2 and Hg(Met)2.Nano-selenium supplement can hardly affect the chemical forms of mercury located in root,bulb and leaf.Instead,it can noticeably reduce the mercury absorption by garlic and retard the transportation of mercury to the upside of the whole plant.Extensively,the nano-selenium sorbents may be intended for use in protective barrier cloths that can efficiently stop the release and accumulation of Hg in the food chain,and protect human health.