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Mercury Accumulation in Soils of Depressional Wetlands in Central Pennsylvania

Author
Lawler, Daniel
Published
[University Park, Pennsylvania] : Pennsylvania State University, 2014.
Physical Description
1 electronic document
Additional Creators
Boyer, Elizabeth and Drohan, Patrick
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Open Access.
Summary
Mercury is an environmental pollutant of global concern, affecting ecosystems and human health. Emissions of mercury to the atmosphere from fossil fuel combustion and other sources can travel for long distances in the air, affecting even remote locations. Pennsylvania is located downwind of many emissions sources, and receives inputs of mercury from atmospheric deposition. In this study, I explored the accumulation of mercury in depressional wetlands, otherwise known as vernal pools. These unique wetlands are widely recognized as important ecosystems because of the critical habitat they provide for plant and wildlife communities; in particular amphibians. Vernal pools are isolated from streams and rivers, and have a seasonally fluctuating water level, typically drying out for part of the year. Given that vernal pools have large inputs of water via precipitation yet do not have any stream discharge outflows, they are likely spots within the landscape to accumulate pollutants entering via atmospheric deposition. Soil samples were collected from 12 Central Pennsylvania vernal pools, located in relatively undisturbed forested settings. Firstly, I measured the distribution of mercury with depth in the soil profile of each vernal pool. The highest mercury concentrations were found in the Oe organic soil horizon, with a majority of the mercury accumulated within the upper 15 cm of soil, suggesting relationships between mercury accumulation and organic carbon contents of the soil profiles. Secondly, I compared levels of mercury accumulation within the vernal pools to the uplands directly surrounding them. There were generally higher soil Hg concentrations within pools compared to their adjacent uplands, suggesting the importance of hydrology (i.e., the concentration of water in the concave pool settings) in affecting the distribution of mercury. Thirdly, I compared levels of mercury accumulation between the two dominant physiographic provinces of Central Pennsylvania, the Ridge and Valley and the Allegheny Plateau regions. Variations in mercury accumulation between provinces likely stem from differences in climate (e.g., more mercury accumulation in regions of higher precipitation) and differences in soils (e.g., more mercury accumulation in soils with higher organic carbon contents). Lastly, mercury concentrations measured in the vernal pools of Central Pennsylvania were compared to concentrations reported for other forested and wetland regions based on published studies, revealing that vernal pools likely act as Hg "hot spots" within forested environments.
Other Subject(s)
Dissertation Note
M.S. Pennsylvania State University 2014.
Reproduction Note
Library holds archival microfiches negative and service copy. 2 fiches. (Micrographics International, 2014)
Technical Details
The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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