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Delineating ion‐ion interactions by electrostatic modeling for predicting rhizotoxicity of metal mixtures to lettuce Lactuca sativa
Author(s) -
Le T. T. Yen,
Wang Peng,
Vijver Martina G.,
Kinraide Thomas B.,
Hendriks A. Jan,
Peijnenburg Willie J.G.M.
Publication year - 2014
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.2643
Subject(s) - chemistry , toxicity , lactuca , metal , copper , metal ions in aqueous solution , metal toxicity , ion , adsorption , copper toxicity , membrane , environmental chemistry , inorganic chemistry , analytical chemistry (journal) , biochemistry , botany , biology , organic chemistry
Effects of ion–ion interactions on metal toxicity to lettuce Lactuca sativa were studied based on the electrical potential at the plasma membrane surface ( ψ 0 ). Surface interactions at the proximate outside of the membrane influenced ion activities at the plasma membrane surface ({M n+ } 0 ). At a given free Cu 2+ activity in the bulk medium ({Cu 2+ } b ), additions of Na + , K + , Ca 2+ , and Mg 2+ resulted in substantial decreases in {Cu 2+ } 0 . Additions of Zn 2+ led to declines in {Cu 2+ } 0 , but Cu 2+ and Ag + at the exposure levels tested had negligible effects on the plasma membrane surface activity of each other. Metal toxicity was expressed by the {M n+ } 0 –based strength coefficient, indicating a decrease of toxicity in the order: Ag + > Cu 2+ > Zn 2+ . Adsorbed Na + , K + , Ca 2+ , and Mg 2+ had significant and dose‐dependent effects on Cu 2+ toxicity in terms of osmolarity. Internal interactions between Cu 2+ and Zn 2+ and between Cu 2+ and Ag + were modeled by expanding the strength coefficients in concentration addition and response multiplication models. These extended models consistently indicated that Zn 2+ significantly alleviated Cu 2+ toxicity. According to the extended concentration addition model, Ag + significantly enhanced Cu 2+ toxicity whereas Cu 2+ reduced Ag + toxicity. By contrast, the response multiplication model predicted insignificant effects of adsorbed Cu 2+ and Ag + on the toxicity of each other. These interactions were interpreted using ψ 0 , demonstrating its influence on metal toxicity. Environ Toxicol Chem 2014; 33:1988–1995. © 2014 SETAC