ANALYSIS OF SUSPENDED SEDIMENT DISTRIBUTIONS IN THE SURFACE WATERS OF DELAWARE BAY USING REMOTE SENSING OF OPTICAL PROPERTIES.

摘要

The color of coastal water can be expressed as a vector in an n-dimensional color space, a space defined by the radiance detected in different wavelengths or bands. In waters dominated by sediment, the expression, a(,xi)/a(,xj) = G(,s)C(,ji)(' 1/2), relates the orientation, C(,ji), of the vector to the water's absorption coefficients, a(,x), in the bands, i,j. Sediment variations enter this expression through G(,s).;The model provides a physical relationship between reflectance and suspended sediment concentration, n(,s), allowing correction for composition and season. In Delaware Bay, n(,s) was found to correlate highly (r > 0.94) with the mean wind stress for 0-2 days prior to the overpass. The correlation suggests that wind stress, not tidal phase, controls suspended sediment concentrations in the bay.;In Delaware Bay, there are two water units having relatively constant color, one over the platform ( 9m). The vector model shows the same differences in the units' pigments and productivity as is observed from ship. The platform (P*) unit associates with greater pigment quantities, the central bay (C-) unit with smaller quantities. The more productive P* unit is most extensive in the spring, corresponding with bloom conditions; C- is largest in winter. River discharge varies the upbay limit of C-. Wind induced transport and tides affect the baymouth but were not observed to associate with variations in the distribution of units within the bay. The wind data, however, had little variation. The P* unit overlies the areas of mud deposition and its higher productivity may be related to outwelling of nutrients from the salt marshes. Sharp boundaries and fronts between P* and C- occur often, suggesting that P* may be closely coupled to the marsh and shoreline than to the central bay.;From the absorption coefficients, one can estimate mean pigment concentrations. Using a physical estimate of G(,s) for Delaware Bay, the vector model underpredicts dissolved organic carbon and slightly overpredicts chlorophyll-a. The Delaware value of G(,s) gave similar results in the lower Chesapeake Bay, but gave anomalous results for the Susquehanna freshet. The freshet had sediment 3-4 times larger than normal, confirming the need for a different value of G(,s).