title: Influences of size-fractionated humic acids on arsenite and arsenate complexation and toxicity to Daphnia magna.
abstract: The intrinsic physicochemical properties of dissolved organic matter (DOM) may affect the mobility and toxicity of arsenic in aquatic environments. In the present study, the humic acid (HA) was ultra-filtered into five fractions according to molecular weight, and their physicochemical properties were characterized. Complexation of HA fractions with arsenite and arsenate was first determined by differential pulse polarography (DPP). The influences of HA fractions on arsenic toxicity were then examined using Daphnia magna as a model organism. As(V) had a higher affinity with HA than As(III), and their complexation was dependent on the total acidity and fluorescence characteristics of DOM. We demonstrated that the acidity and fluorescence also better explained the As toxicity to daphnids than UV absorbance and hydraulic diameter. Arsenic speciation determined by DPP significantly affected the toxicity of arsenite and arsenate. The results extended the free-ion activity model application to the case of arsenic. The present study clearly indicated that DOM with different molecular weights has distinct physicochemical properties, and could influence the speciation and toxicity of As to different extent.
authors.affiliation: School of Space and Environment, Beihang University, Beijing 100191, PR China.
authors.forename: Jinqian
authors.initials: J
authors.lastname: Ren
authors.affiliation: School of Space and Environment, Beihang University, Beijing 100191, PR China. Electronic address: fanwh@buaa.edu.cn.
authors.forename: Wenhong
authors.initials: W
authors.lastname: Fan
authors.affiliation: School of Space and Environment, Beihang University, Beijing 100191, PR China.
authors.forename: Xiangrui
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Space and Environment, Beihang University, Beijing 100191, PR China.
authors.forename: Qingquan
authors.initials: Q
authors.lastname: Ma
authors.affiliation: School of Space and Environment, Beihang University, Beijing 100191, PR China.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of Occupational Safety and Health, Beijing Municipal Institute of Labor Protection, Beijing 100054, PR China.
authors.forename: Zhizhen
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Wei
mesh_terms: D000818:Animals; D001149:Arsenates; D001151:Arsenic / Q000737:chemistry; D018053:Arsenites / Q000737:chemistry*; D003621:Daphnia; D006812:Humic Substances
chemical_list: D001149:Arsenates; D018053:Arsenites; D006812:Humic Substances; D001151:Arsenic
keywords: Complexation; DOM property; Inorganic arsenic; Molecular weight; Toxicity