MOVEMENT AND LOADINGS OF INORGANIC CONTAMINANTS THROUGH THE LOWER SAGINAW RIVER

The objective of this study was to investigate the movement of selecte d contaminants (four heavy metals) and conventional limnological varia bles through the lower Saginaw River. We related limnological variable s to concentrations of contaminants, determined if sources of these co ntaminants existed in the lower 8 km of the river, and calculated load ings of materials to Saginaw Bay. Concentrations of most variables cha nged significantly among the six sampling dates in 1990-1991, while re latively few variables were different among the six sampling stations. Causes of changes in concentrations of variables in the river over ti me appeared to stem from two factors, seasonality and river discharge. One phase of the sampling program was conducted on six different date s which encompassed river flows ranging from greater than 700 m(3) sec (-1) to less than 25 m(3) sec(-1). The date an which the least river d ischarge was observed included a pow reversal when Saginaw Bay water i ntruded into the lower Saginaw River. Statistical analyses showed that temporal variation among variables was due, in part, to fluctuating r iver discharge and in part to seasonal factors. The relative importanc e of these two components varied among parameters. For example, total suspended solids were positively correlated with river discharge, whil e chlorophyll varied more seasonally. In contrast to temporal trends, few parameters varied significantly among the six sampling stations. T his was especially true for dissolved and particulate metals. Loadings of key materials to Saginaw Bay from the Saginaw River were generally positively correlated with river discharge. We concluded that most su bstances entered the river upstream of our study section in the lower 8 km of the Saginaw River.