9614186 Shiller The composition and properties of size-fractioned riverine suspended matter will be determined, with special emphasis on particles in the sub-micron size range. This work is important because suspended particles carry much of the load of many elements in rivers and because particle surfaces can control dissolved concentrations through adsorption. However, little is known about how particle composition and adsorbing properties vary with particle size---especially in the sub-micron (or colloidal) size range. The work will utilize relatively new technologies for size fractioning suspended particles, specifically field-flow fractionation (FFF) and split-flow thin-cell lateral transport (SPLITT) fractionation. The capabilities of these methods have been demonstrated in the literature; however, their application to environmental problems is still in its infancy. Thus, a primary objective of this proposed work is the further development and quality assurance testing of environmental FFF methodology. Other objectives include the application of FFF and SPLITT to the characterization of fluvial suspended matter from a variety of fluvial environments, analysis of filtration artifacts in samples processing, investigation of bacterially-induced changes in particulate composition, and development of methodology for investigating variation of adsorption with particle size. The project will have two types of results: 1) development of FFF and SPLITT methods to the point where they can be applied more routinely for particle characterization in natural waters and 2) solution of some specific environmental questions. These specific questions include how best to filter samples for dissolved trace element analysis, what size fractions of the suspended particles contain what types of materials (and how this affects adsorption of trace elements), and how bacteria affect particle surfaces. The work will include examination and comparison of FFF results with ultrafiltration, light sca ttering, and electron microscopy. Additionally, we will do the size fractionation work using different sample pre-treatments and fractionation conditions. This will shed light on potential artifacts of the techniques. Although this is a stand alone project, the work will be pursued collaboratively with colleagues at the US Geological Survey.
