Fiber optic sample cells for polychromatic detection of dissolved and particulate matter in natural waters

The development of global ocean color models for remote sensing imagery with high accuracy is an important goal for Earth Science Research. Estimates of the concentration of dissolved and particulate materials in water can be derived by inversion of remote sensing imagery, that is, remote sensing reflectance based on empirical or semi-analytical models of reflectance water constituents. The efficacy of these models depends on accurate measurements of the spectral absorption of dissolved and particulate materials in natural waters. However, traditional methods using expensive laboratory spectrophotometers to measure the absorption of dissolved and particulate materials require special handling and storage prior to measurement. Further, their detection limit is often insufficient to detect the typically low dissolved and particulate matter seawater concentrations. Liquid core waveguides designed for portable instrumentation to measure the absorption of dissolved organic matter and particulate matter will be described. Traditionally, particulate matter is determined via the "quantitative filtering technique" (QFT), where particulate matter is concentrated on a Glass Fiber Filter (GFF) pad and its forward absorption measured with a laboratory based spectrophotometer and an integrating sphere. Performance and design of an inexpensive and portable fiber-optic-based GFF filter holder are discussed. Effective pathlength and numerical aperture of the sample cells are determined. Further, dissolved and particulate absorption is measured.