SPECTRAL PROPERTIES OF SUSPENDED SOLIDS, DISSOLVED ORGANIC 
CARBON, AND IRON IN WATERS FROM WETLANDS AND SUGAR-CANE FIELDS 
Dean Muirhead 
James Cruise 
Richard Miller 
Lousiana State University 
Dept. Civil and Environmental Engineering 
CEBA Building 
Baton Rouge, LA 70803, USA 
ISPRS Commission VII / Working Group 1 
ABSTRACT 
Dissolved organic carbon (DOC) originating from biogeochemical processes plays an important role in 
the global cycle of carbon and the quality of surface waters. DOC can also act as carrier of hydrophobic 
pollutants (i.e. pesticides) from land to sea. The presence of DOC alters the optical properties of water 
and interferes with the accuracy of retrieval algorithms for other water constituents, such as suspended 
solids (SS). This research improves the understanding of the contribution of DOC, suspended solids, and 
iron to the optical properties of coastal waters in Louisiana. Spectral properties are measured as a 
function of water samples with a range of DOC from wetlands and sugarcane field runoff are filtered 
(0,45 uum) to remove SS and passed through solid phase extraction columns to separate the iron and the 
DOC. DOC, iron, SS, and absorbance are measured at each step. Absorption coefficients are given as a 
function of the water constituents. The spectral interference of DOC is most pronounced during low flow 
periods. 
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