Wei Zhang - Temporal Changes in Aqu/C60 Physical–Chemical, Deposition, and Transport Characteristics in Aqueous Systems

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  Publication Details (including relevant citation   information): Isaacson, Carl, Zhang, Wei, Powell,   Tremaine, Ma, Xin, Bouchard, Dermont, Environ. Sci.   Technol., 2011, 45 (12), pp   5170-5177

  Abstract: Little is known about how temporal   changes in the physical?chemical properties of C60 aggregates   formed in aqueous systems (termed aqu/C60) can impact transport   pathways contributing to ecological exposures. In this study   three aqu/C60 suspensions of short-term (100 days),   intermediate-term (300 days), and long-term (1000 days) water   exposure were first characterized for particle size distribution,   water/toluene phase distribution, and surface chemistry. Then,   aqu/C60 deposition to a model silica surface and transport in   porous media were studied by quartz crystal microbalance (QCM)   and saturated sand columns. As suspension time increased, aqu/C60   particle size shifted to a larger size range as determined by   asymmetric flow field-flow fractionation (AF4) and the aqu/C60   distribution to toluene was reduced, likely due to surface   polarization as revealed by nuclear magnetic resonance (NMR) and   UV?visible spectroscopy of the aqu/C60 suspensions. Additionally,   the deposition to silica surfaces in both QCM and column studies   decreased with increased water exposure time. Although a small   increase in aqu/C60 aggregate size with time may partially   explain the greater transport of the long-term aqu/C60 because of   the decreased collector efficiency for larger submicrometer   particles, the polarization of the aqu/C60 (thus a more   hydrophilic surface) revealed by the toluene/water phase   distribution and confirmed by NMR, is considered the determining   factor.

  Address (URL): http://dx.doi.org/10.1021/es1041145