title: Toxicity of cerium and thorium on Daphnia magna.
abstract: Cerium (Ce) and thorium (Th) are always thought to be chemically similar and have comparable toxic properties on living organisms. In the present study, the acute and chronic toxicity of these two elements to freshwater crustacean Daphnia magna were investigated in the modified reconstituted water (6mg/L KCl, 123mg/L MgSO4·7H2O, and 294mg/L CaCl2·2H2O in Milli-Q water, pH 7.8). It seemed that Ce and Th had comparable acute toxicity on Daphnia: 24/48h EC50for Th and Ce were 7.3/4.7μM and 16.4/10.7μM, respectively. However, Ce was present as soluble ions while all of Th was present as particulate ThO2in the exposure medium. Considering their different chemical forms and bioavailability, the toxic mechanisms of Ce3+and ThO2on Daphnia would be totally different. To our knowledge, this is the first time to investigate the aquatic toxicity of thorium and cerium based on their actual chemical speciation in the exposure medium. The results also suggest that more attention should be paid on the detrimental effect of Th in the form of particulate ThO2.
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Jiangsu Province Metallurgical Design Institute Co., Ltd, Jiangsu, 210007, China.
authors.forename: Jingkun
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of public health, University of South China, Hunan, 421001, China.
authors.forename: Can
authors.initials: C
authors.lastname: Peng
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yayun
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: He
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Tu
authors.initials: T
authors.lastname: Lan
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Dongqi
authors.initials: D
authors.lastname: Wang
authors.affiliation: School of public health, University of South China, Hunan, 421001, China.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Fuhong
authors.initials: F
authors.lastname: Sun
authors.affiliation: Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China. Electronic address: liaohaiqing@vip.gyig.ac.cn.
authors.forename: Haiqing
authors.initials: H
authors.lastname: Liao
authors.affiliation: Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China. Electronic address: zhangzhy@ihep.ac.cn.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Zhang
keywords: Acute toxicity; Cerium; Chemical speciation; Chronic toxicity; Daphnia magna; Thorium