| Popis: |
The objective of this study was to investigate the movement of selected contaminants (four heavy metals) and conventional limnological variables through the lower Saginaw River. We related limnological variables to concentrations of contaminants, determined if sources of these contaminants existed in the lower 8 km of the river, and calculated loadings of materials to Saginaw Bay. Concentrations of most variables changed significantly among the six sampling dates in 1990–1991, while relatively few variables were different among the six sampling stations. Causes of changes in concentrations of variables in the river over time appeared to stem from two factors, seasonality and river discharge. One phase of the sampling program was conducted on six different dates which encompassed river flows ranging from greater than 700 m 3 sec −1 to less than 25 m 3 sec −1 . The date on which the least river discharge was observed included a flow reversal when Saginaw Bay water intruded into the lower Saginaw River. Statistical analyses showed that temporal variation among variables was due, in part, to fluctuating river discharge and in part to seasonal factors. The relative importance of these two components varied among parameters. For example, total suspended solids were positively correlated with river discharge, while chlorophyll varied more seasonally. In contrast to temporal trends, few parameters varied significantly among the six sampling stations. This was especially true for dissolved and paniculate metals. Loadings of key materials to Saginaw Bay from the Saginaw River were generally positively correlated with river discharge. We concluded that most substances entered the river upstream of our study section in the lower 8 km of the Saginaw River. |
