Mayer Philipp, Karlson Ulrich, Christensen Peter S, Johnsen Anders R, Trapp Stefan
Department of Environmental Chemistry and Microbiology, National Environmental Research Institute, PO Box 358, 4000 Roskilde, Denmark.
Environ Sci Technol. 2005 Aug 15;39(16):6123-9. doi: 10.1021/es050556s.
Unstirred boundary layers (UBLs) often act as a bottleneck for the diffusive transport of hydrophobic organic compounds (HOCs) in the environment. Therefore, a microscale technique was developed for quantifying mass transfer through a 100-microm thin UBL, with the medium composition of the UBL as the controllable factor. The model compound fluoranthene had to (1) partition from a contaminated silicone disk (source) into the medium, (2) then diffuse through 100 microm of medium (UBL), and finally (3) partition into a clean silicone layer (sink). The diffusive mass transfer from source to sink was monitored over time by measuring the fluoranthene content of the source and sink disks. The diffusive flux of fluoranthene was slightly higher for air than for water. Cyclodextrin, humic acids, and micelles of sodium dodecyl sulfate (SDS) enhanced the diffusive flux of fluoranthene in water by more than 1 order of magnitude. These results demonstrate that medium constituents, which normally are believed to bind hydrophobic organic chemicals, actually can enhance the diffusive mass transfer of HOCs in the vicinity of a diffusion source (e.g., contaminated soil particles). The technique can be used to evaluate the effect of natural fluids on diffusive mass transfer, as it integrates the different processes, partitioning and diffusion, in one laboratory model.
静止边界层（UBLs）通常是环境中疏水性有机化合物（HOCs）扩散传输的瓶颈。因此，开发了一种微尺度技术，用于量化通过100微米厚的静止边界层的传质，将静止边界层的介质组成作为可控因素。模型化合物荧蒽必须（1）从受污染的硅盘（源）分配到介质中，（2）然后扩散通过100微米的介质（静止边界层），最后（3）分配到干净的硅层（汇）中。通过测量源盘和汇盘的荧蒽含量，随时间监测从源到汇的扩散传质。荧蒽在空气中的扩散通量略高于在水中的扩散通量。环糊精、腐殖酸和十二烷基硫酸钠（SDS）的胶束使荧蒽在水中的扩散通量提高了1个多数量级。这些结果表明，通常被认为会结合疏水性有机化学物质的介质成分，实际上可以增强扩散源（如受污染的土壤颗粒）附近HOCs的扩散传质。该技术可用于评估天然流体对扩散传质的影响，因为它在一个实验室模型中整合了不同的过程，即分配和扩散。
