Date of Award

8-1990

Degree Name

Doctor of Philosophy

Department

Science Education

First Advisor

Dr. William B. Harrison III

Second Advisor

Dr. George G. Mallinson

Third Advisor

Dr. Michael E. McCarville

Fourth Advisor

Dr. Richard Passero

Abstract

This study was undertaken to: (a) determine the effect of sodium chloride concentration on mobilizing cadmium, copper, lead, nickel, and zinc from stream sediments; (b) determine if chloro-metal complexes may play a role in any such mobilization; and (c) determine the correlations between chloride ion and each of these metals in an urban stream during winter road-salting periods.

The drainage basin of the Red Run, an urban stream draining all or parts of several cities north of Detroit, Michigan, was chosen as a study site. Stream sediments containing the five heavy metals were stirred with sodium chloride or sodium nitrate solutions and heavy metal concentrations were determined in aliquots removed at specified time intervals. Cadmium concentration was found to have a high correlation (r =.90) and zinc a low correlation (r =.49) with chloride concentration. Cadmium was also found to be released into chloride solutions to a greater extent than into nitrate solutions. A similar but more subdued effect was found for zinc, but only for longer desorption periods. Copper was found to have a low, negative correlation (r = $-$.38) and nickel little, if any, negative correlation (r = $-$.29) with chloride concentration. Lead concentrations were below limits of detectability. These results indicate that the release of cadmium and, to a lesser extent, zinc, from stream sediments can be facilitated by the formation of soluble chloro-metal complexes.

Winter stream studies revealed a moderate chloride-zinc correlation (r =.57) at one of three sampling stations. Otherwise, only low to little, if any, chloride-metal correlations could be detected for cadmium, copper, nickel or zinc at any location. Lead was again generally below limits of detectability.

Deicing salt was found to contain zinc, but only at levels calculated to contribute minimally to total zinc levels at each of the three sampling sites.

Changes in stream sediment heavy metal concentrations over an entire winter road-salting period, or over a single snow and road-salting event could not be unequivocally attributed to the use of highway deicing salts. Instead, differences in sediment heavy metal concentrations appeared to be more closely related to differences in the percent of sediment finer than 0.063 or 0.125 mm.

A general decline in both total and exchangeable sediment cadimum levels was observed throughout the study. This decline was most likely a response of Red Run sediments to controls placed on metal levels entering and being discharged from a wastewater treatment plant.

Comments

Dr. W. Thomas Straw

Access Setting

Dissertation-Open Access

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