Estimation of algal and suspended sediment loads (singly and combined) using hyperspectral sensors and integrated mesocosm experiments
- Creighton Univ., Omaha, NE (United States)
- SST Development Group, Inc., Stillwater, OK (United States)
- USDA/ARS Grazinglands Research Lab., El Reno, OK (United States); and others
Most remote sensing algorithms for materials in water are based on studies on natural waters with complex and variable optical properties, or of small indoor microcosm containers. We used sunlit, cylindrical, black mesocosm tanks (80m{sup 3}, 3 m depth) and a hyperspectral radiometer to examine reflectances of algal blooms and suspended kaolin white clay. In three integrated experiments, algae and clay levels were carefully manipulated: (1) Algal bloom water in one tank was pumped to a second which began with clear water, and clear make-up water was pumped to the first to obtain a well graded series (Chl. a = 0 - 62 {mu}g/L). (2) White, kaolin clay was added stepwise to clear water, resulting in an organic seston range of 0 - 40 mg/L. (3) Algal bloom water from a single source was divided between two tanks to establish Chi. a loads of 31 and 57 {mu}g/L. Then, identical additions of clay were made to both tanks to achieve a range of 0 - 72 mg/L inorganic matter while conserving the algal loads. The first experiment revealed a strong interplay between algal scattering and absorption. Pigment absorbance dominated below 510 nm, while increasing cell scattering in regions of low pigment activity caused green and NIR peaks to form near 560 and 700 nm. In spite of strong chlorophyll absorbance near 675 nm, this region had small reflectance increases with increased algae. In the second experiment, white clay had high albedo. At seston levels above 40 mg/L, green reflectance exceeded 50% and NIR reflectance at 800 nm exceeded 9%. In the third experiment, algal pigments strongly attenuated clay reflectance in a dose dependent manner, even at green wavelengths. Clay particles greatly amplified but also preserved algal reflectance patterns. Our findings affirm the importance of high spectral resolution at diagnostic wavelengths in turbid Case 2 coastal and inland waters.
- OSTI ID:
- 478136
- Report Number(s):
- CONF-970319-; TRN: 97:002802-0029
- Resource Relation:
- Conference: 4. thematic international conference on remote sensing for marine and coastal environments: technology and applications, Orlando, FL (United States), 17-19 Mar 1997; Other Information: PBD: 1997; Related Information: Is Part Of Proceedings of the fourth international conference on remote sensing for marine and coastal environments. Technology and applications: Volume I; PB: 741 p.
- Country of Publication:
- United States
- Language:
- English
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