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Nanoparticles enter soils through various pathways. In the soil, they undergo various interactions with the solution and the solid phase. We tested the following hypotheses using batch experiments: i) colloidal stability of AgNP increases through sorption of soil-borne dissolved organic matter (DOM) and thus inhibits aggregation; ii) the presence of DOM suppresses Ag oxidation; iii) surface charge of AgNP governs sorption onto soil particles. Citrate-stabilized and ...Nanoparticles enter soils through various pathways. In the soil, they undergo various interactions with the solution and the solid phase. We tested the following hypotheses using batch experiments: i) colloidal stability of AgNP increases through sorption of soil-borne dissolved organic matter (DOM) and thus inhibits aggregation; ii) the presence of DOM suppresses Ag oxidation; iii) surface charge of AgNP governs sorption onto soil particles. Citrate-stabilized and bare AgNP were equilibrated with (colloid- free) soil solution extracted from a floodplain soil for 24 hours. Nanoparticles were removed through centrifugation. Concentrations of free Ag ions and DOC, the specific UV absorbance at a wavelength of 254 nm, and the absorption ratio 945;254/945;410 were determined in the supernatant. Nanoparticle aggregation was studied using time-resolved dynamic light scattering (DLS) measurement following the addition of soil solution and 1.5 mM Ca solution. To study the effect of surface charge on the adsorption of AgNP onto soil particles, bare and citratestabilized AgNP, differing in the zeta potential, were equilibrated with silt at a solid-to-solution ratio of 1:10 and an initial Ag concentration range of 30 to 320 956;g/L. Results showed that bare AgNP sorb organic matter, with short- chained organic matter being preferentially adsorbed over long- chained, aromatic organic matter. Stabilizing effects of organic matter only come into play at higher AgNP concentrations. Soil solution inhibits the release of Ag+ ions, presumably due to organic matter coatings. Sorption to silt particles was very similar for the two particle types, suggesting that the surface charge does not control AgNP sorption. Besides, sorption was much lower than in comparable studies with sand and glass surfaces.» weiterlesen» einklappen

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