of > 200 ^.m, low bulk density particles made up this pycnocline feature. The turbidity maximum itself consisted of high concentrations of both large and small particles, though the median particle size at the center of the feature was >200 ^m.

Axial distributions of particle characteristics measured with the LISST on October 11,2002 during a weak flood tide are shown in Figure 10.6. October 2002 was an average month for flow, though sediment delivery was lower than average (Figure 10.2). However, this survey occurred just as the pulse of flow that made October an average month was beginning, after a long, very dry summer. Some possible indications of this pulse are the crowding of the isohalines and elevated TSS at approximately km 12. No completely fresh water was observed during this survey, and stratification was much weaker than during the May surveys. A weak turbidity maximum coincided with a near-bottom convergence in the axial salinity near km 35, with near-bottom TSS levels approximately 30 mg l-1 higher than background. TSS concentrations were in general very low in upper Chesapeake Bay. A patch of relatively high particle volume concentration was concentrated in the pycnocline just downstream of this turbidity maximum, again coincident with large, low bulk density particles. Average particle bulk densities were generally higher than during the May survey (Figure 10.5), but remained far below the densities of solid, unflocculated particles.

Time-depth distributions of various physical data from an anchor station the day before the axial survey of Figure 10.6 are presented in Figure 10.7. The anchor

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