『Abstract
Environmental legislation has reduced the anthropogenic loadings
of Pb and Cd to the Great Lakes region over the past 3 decades.
However, the accumulation rates of these metals still remain above
background values. Because environmental legislation was targeted
at major sources (e.g., Pb in gasoline) whose influence on the
environment was on a regional scale, local sources (e.g., watershed
scale) for the metals may now play a more significant role. The
relative importance of regional versus local scale influences
on metal inputs to the environment is poorly understood. In this
study, sediment chronologies of Pb and Cd were examined from 12
inland lakes that cover the broad geographic area of the State
of Michigan. These chronologies were compared temporally and spatially
and to watershed population densities and metal production records
to gain an understanding of local and regional influences on metal
inputs to the Great Lakes region. Results show that anthropogenic
Pb loading during the 1930s and 1970s was dominated by regional
sources, such as coal burning and use of leaded gasoline. Current
loadings are now more related to local influences such as watershed
population densities, rather than atmospheric deposition. Anthropogenic
Cd loadings to the Great Lakes region have been dominated by both
regional and local sources over time. Lead may also have shown
the influence of local sources over time, if the influence of
emissions from gasoline had not been present. This work shows
that Pb and Cd loadings in the Great Lakes region are strongly
related to watershed population densities, however, the specific
sources and pathways for the metal cycling are unclear.』
1. Introduction
2. Methodology
3. Results and discussion
3.1. 210Pb results
3.2. Temporal patterns
3.2.1. Lead
3.2.2. Cadmium
3.3. Spatial patterns
3.3.1. Lead
3.3.2. Cadmium
3.4. Population density
3.4.1. Lead
3.4.2. Cadmium
3.5. Production records
4. Conclusions
Acknowledgements
References