Monday, November 5, 2007

Environmental Monitoring of Sewage Sludge Application on Agricultural Fields Using Spectral Reflectance and LANDSAT data.

Maruthi Sridhar Balaji Bhaskar and Robert K. Vincent. Bowling Green State University, Dept of Geology, 190 Overman Hall BGSU, Bowling Green, OH 43403

The objectives of this study were to investigate the effects of sewage sludge application on the spectral reflectance properties of agricultural fields applied with sewage sludge and the potential of using LANDSAT data for monitoring the process of sewage sludge application. Information about the land application of sewage sludge has widespread utilities in monitoring the environmental quality of soil, water and atmosphere of the surroundings where it is being applied. Ground based spectral reflectance measurements and LANDSAT data were used in this study to identify the spectral regions sensitive to the sewage sludge application on agricultural fields. Bidirectional reflectance spectra (350-2500 nm) of the sludge applied and control (no sludge) fields were collected during the sewage sludge application period of summer, 2004 using a portable field spectroradiometer. The spectral reflectance of the sludge applied fields decreased significantly in the entire spectral region from 350-2500 nm as a result of sewage sludge application. The reflectance in the near-infrared (NIR) region, from 700-2500 nm and the corresponding LANDSAT bands 4, 5 and 7, which fall within this spectral region, show significant decrease in spectral reflectance as a result of sludge application on agricultural fields. The LANDSAT TM image analysis shows that the sludge-applied winter wheat stubble can be identified and mapped separately from the untreated winter wheat stubble using a non-reciprocal ratio combination of 3/2, 7/5 and 5/4. Our study shows that spectral reflectance measured in situ and remote sensing from LANDSAT TM can be used to characterize and discriminate the fields that are being applied with sewage sludge.