title: Effect of soil organic matter content and pH on the toxicity of ZnO nanoparticles to Folsomia candida.
abstract: Organic matter (OM) and pH may influence nanoparticle fate and effects in soil. This study investigated the influence of soil organic matter content and pH on the toxicity of ZnO-NP and ZnCl2 to Folsomia candida in four natural soils, having between 2.37% and 14.7% OM and [Formula: see text] levels between 5.0 and 6.8. Porewater Zn concentrations were much lower in ZnO-NP than in ZnCl2 spiked soils, resulting in higher Freundlich sorption constants for ZnO-NP. For ZnCl2 the porewater Zn concentrations were significantly higher in less organic soils, while for ZnO-NP the highest soluble Zn level (23mgZn/l) was measured in the most organic soil, which had the lowest pH. Free Zn(2+) ion concentrations were higher for ZnCl2 than for ZnO-NP and were greatly dependent on pH (pHpw) and dissolved organic carbon content of the pore water. The 28-d EC50 values for the effect of ZnCl2 on the reproduction of F. candida increased with increasing OM content from 356 to 1592mgZn/kg d.w. For ZnO-NP no correlation between EC50 values and OM content was found and EC50 values ranged from 1695 in the most organic soil to 4446mgZn/kg d.w. in the higher pH soil. When based on porewater and free Zn(2+) concentrations, EC50 values were higher for ZnCl2 than for ZnO-NP, and consistently decreased with increasing pHpw. This study shows that ZnO-NP toxicity is dependent on soil properties, but is mainly driven by soil pH.
authors.affiliation: Department of Ecological Science, Faculty of Earth and Life Sciences, VU University, Amsterdam, The Netherlands.
authors.forename: Pauline L
authors.initials: PL
authors.lastname: Waalewijn-Kool
authors.affiliation: Aquatic Ecology, Faculty of Biology, University Duisburg-Essen, Essen, Germany.
authors.forename: Svenja
authors.initials: S
authors.lastname: Rupp
authors.affiliation: Centre for Ecology and Hydrology, Lancaster Environment Centre, Lancaster, United Kingdom.
authors.forename: Stephen
authors.initials: S
authors.lastname: Lofts
authors.affiliation: Centre for Ecology and Hydrology, Wallingford, Oxfordshire, United Kingdom.
authors.forename: Claus
authors.initials: C
authors.lastname: Svendsen
authors.affiliation: Department of Ecological Science, Faculty of Earth and Life Sciences, VU University, Amsterdam, The Netherlands. Electronic address: kees.van.gestel@vu.nl.
authors.forename: Cornelis A M
authors.initials: CA
authors.lastname: van Gestel
mesh_terms: D000818:Animals; D001181:Arthropods / Q000187:drug effects*; D002712:Chlorides / Q000633:toxicity*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D053758:Nanoparticles / Q000633:toxicity*; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry / Q000633:toxicity; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000032:analysis; D017967:Zinc Compounds / Q000633:toxicity*; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D002712:Chlorides; D006812:Humic Substances; D012987:Soil; D012989:Soil Pollutants; D017967:Zinc Compounds; D014867:Water; C016837:zinc chloride; D015032:Zinc; D015034:Zinc Oxide
keywords: Bioavailability; Folsomia candida; Organic matter content; Soil pH; Zinc oxide nanoparticles