Characterizations of Minerogenic Particles in Support of Modeling Light Scattering in Lake Superior Through a Two-Component Approach

摘要

The role of suspended minerogenic particles in light scattering in eastern Lake Superior and Keweenaw Bay (II sites) during July of 2006 was evaluated with an individual particle analysis technique (scanning electron microscopy interfaced with automated image and X-ray analyses, SAX), along with bulk paniculate scattering and backscattering coefficients (bp and bbp) and chlorophyll a concentration (ChI). SAX measurements provide light-scattering attributes of minerogenic particles, including chemical composition and particle size distribution (PSD). The data were use calculations for estimations of minerogenic scattering and backscattering coefficients (bm and bb,m). The bay had higher concentrations of minerogenic particles and higher values of bm, bb,m. bbp, and the backscattering ratio (bbp : bp) than the pelagic sites. Minerogenic scattering was primarily attributable particles in the size range of I -10 mm. The PSDs deviated from the (Junge) pattern of monotonic increase of particle numbers with decreasing estimates of bm and bb,m combined with those of organic particulate components, as represented by empirical Case 1 bio-optical models, showed closure with bp and bbp, supporting the credibility of the SAX -Mie approach. Variations in the bbp : bp ratio are strongly related to spatial different contributions of phytoplankton vs. minerogenic particles to scattering, with higher values observed where the minerogenic component is more important. SAX can advance the understanding of optical variability by establishing the contributions of well-defined minerogenic constituents that strongly influence optical properties.