These releases occurred at the beginning of an ebb tide, and dispersions of the drogues and fruits were monitored for 1 tidal day. Four sentinel shellfish and fluorometer station locations were established based on the observed drogue paths and plume dispersion models developed by FDA engineers.
Shortening the duration of the dye injection from several days to 1 tidal day (24.8 h) using the superposition method made the dye amounts and the injection times acceptable.
This single tidal day (24.8 h) injection required 75 L rhodamine WT tracer dye to achieve a concentration in the WWTP effluent that would account for instrument sensitivity when measuring concentrations in the estuary.
The first approach considered the entire data set, for which the average dye concentrations per tidal day were determined.
To account for potential loss of dye from these factors, a value of 3% loss per tidal day was factored into dilution calculations, based on findings from field and laboratory studies (Hefting & O'Connell 1966, Tai & Rathbun 1988, Kilpatrick 1993).
However, dye concentrations were quickly reduced to trace amounts shortly after the dye injection concluded on the second tidal day, indicating that the dye-tagged effluent was quickly flushed from this area of Mobile Bay.
Daily tides; having a period or cycle of approximately one tidal day.
The difference in height between the two High Waters or the two Low Waters of each tidal day.
Twice daily tides; having a period/cycle of approximately one-half of a tidal day.
Tidal day. The time interval between two successive passes of the Moon over a meridian (about 24 hours, 50 minutes).
The average of the Higher High Water height on all tidal days observed during a tidal datum epoch.
The average of the Lower Low Water height of all tidal days during the tidal datum epoch.