Colloidal and Particulate Silver in River and Estuarine Waters of Texas

Abstract

Concentration and phase speciation of Ag in selected Texas rivers and in the Trinity River estuary were measured in order to establish the major factors that control its fate in the aquatic environment from source to sink. Concentrations of Ag in the filter-passing fractions in Texas rivers ranged from <0.01 to 62 ng/L. In the Trinity River estuary (Galveston Bay), they ranged from 0.4 to 6.4 ng/L and showed a non-conservative estuarine mixing behavior. An internal source of filter-passing (≤0.45 μm) and colloidal (1 kDa−0.45 μm) Ag was observed in the upper Trinity Bay. Silver, associated with colloidal macromolecular organic matter, which was isolated using cross-flow ultrafiltration techniques, amounted to 15−70% of the filtered (≤0.45 μm) Ag concentration, decreasing with increasing salinity. Such a trend was similar to that of dissolved and colloidal organic carbon. Estuarine distributions of colloidal Ag were also broadly similar to those of suspended particulate matter. The ratio of colloidal Ag to filter-passing Ag was similar to the ratio of colloidal organic carbon to total dissolved organic carbon, suggesting not only that Ag is complexed by organic macromolecules but also that functional groups with high affinity for Ag were evenly distributed over the different molecular weight fractions. Particulate Ag was found associated mainly with a iron−manganese oxyhydroxide/sulfide phase. The close relation between Ag and Fe in colloidal and particulate phases suggests common surface complexes, probably sulfhydryl groups. In river waters of Texas, 33−89% of the operationally defined dissolved (≤0.45 μm) Ag fraction was present in a large colloidal form (0.1−0.45 μm). The high affinity of Ag for suspended particulates in river and estuarine water was reflected by a high mean particle/water partition coefficient of log K d = 5.0 ± 0.6 (based on filtration through a 0.45-μm filter) and 5.5 ± 0.5 (based on filtration through a 0.1 μm filter). Particle/water partition coefficients for the surface-adsorbed phase showed particle concentration effects, which, however, disappeared (log K p1 = 5.0 ± 0.3) when the dissolved Ag data were corrected for the presence of a colloidal fraction.

Potential risks and benefits of nanotechnology: perceptions of risk in sunscreens

“…This includes regions with background levels or moderate contamination as well as sites with exceedingly high silver contamination from, e.g., mining activities. Typical levels in freshwater moderately affected by human activity are around 1-10 ng/L (Wen et al 1997;2002;Tappin et al 2010;Lanceleur et al 2011). Waters affected by untreated wastewaters, photographical industry or mining show higher concentrations that are in the range of 100 ng/L to 1 g/L (Wen et al 2002;Lanceleur et al 2011).…”

The influence of colloids on the geochemical behavior of metals in polluted water using as an example Yongdingxin River, Tianjin, China

“…In natural waters, metals have traditionally been subdivided into two fractions: 'dissolved' and 'particulate' according to an operationally defined limit (e.g., 0.45 lm) (Wen et al, 1997;Jackson et al, 2005;Pokrovsky et al, 2006;Azetsu-Scott et al, 2007;Hurst and Bruland, 2008). However, the 'dissolved' fraction clearly does not represent the truly dissolved metal ions.…”

Verhalten von Nanosilber in Kläranlagen und dessen Einfluss auf die Nitrifikationsleistung in Belebtschlamm

“…Die Silberkonzentrationen im gereinigten Abwasser von Kläranlagen (0,001-0,1 µg/L Ag) stehen im Einklang mit der hohen Eliminationsrate und erklären zudem die vergleichsweise geringe Sedimentbelastung in Fließgewäs-sern (Wen et al 1997;Warila et al 2001;Benn und Westerhoff 2008;Blaser et al 2008). Demnach reichert sich Silber bevorzugt im Schlamm mit 1-10 mg Ag/kg an; nur industrielle Einleitungen verbinden sich mit höheren Silbergehalten bis 100 mg Ag/kg TS (Firk 1986;Bachmann et al 1999;Howe und Dobson 2002;Blaser et al 2008).…”