The measurement of heavy metals in natural waters: Zinc dynamics in the southern basin of Lake Michigan.

摘要

Analysts have attempted measurements of heavy metals in natural water systems for decades. Efforts to obtain reliable results for some elements have historically been plagued with problems related to contamination. Zinc is a case in point. Its ubiquitous nature makes it one of the most difficult elements to measure with accuracy at natural levels. This has made assessment of zinc behavior in large lakes difficult. The principal goal of this research was to develop methodology capable of measuring heavy metals at natural levels and to apply it to the study of zinc in the southern basin of Lake Michigan.;An extensive number of measurements were carried out in the southern basin of Lake Michigan to determine whether spatial and temporal variations in zinc concentrations could be observed. It appears that atmospheric inputs effect the concentrations of zinc in the surface waters during the period of thermal stratification. Concentrations in the epilimnetic waters may increase to a maximum value during the late summer months. An efficient mechanism for removal of zinc to the hypolimnetic waters may occur annually due to coprecipitation of the element during the carbonate whiting events of late summer.;The mean zinc value determined as a part of this work was 760 ;The approach taken involved the preconcentration of dithiolate-reactive elements using ammonium pyrrolidine carbodithoic acid (APDC) as a complexing ligand and cadmium ion as a carrier. The precipitates were collected onto membrane filters and analyzed as thin film samples utilizing energy dispersive X-ray fluorescence spectrometry (EDXRF). All reagents and materials used in the process were purified to insure that contamination of the samples did not occur.