2012 Summer Symposium Program - Middlebury College

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Avery Shawler ‘13
Major: ENVS, BIOL
Bob Churchill Fund
Bill Hegman
GIS Specialist
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Annika Silverman ‘13
Major: ENVS, GEOL
Gretchen Augat Reilly ‘60
Environmental Studies Fund
Peter Ryan
Professor of Geology
Middlebury Summer Research Symposium 2012
Mapping Natural Communities for the Nature
Conservancy/ Vermont Natural Heritage
Program
Avery Shawler and Bill Hegman
Department of Geography, Middlebury College, Middlebury VT 05753
This summer I’m mapping natural communities for the Vermont Natural Heritage
Program. A natural community is an interacting assemblage of organisms, their
physical environment, and the natural processes that affect them. Identifying
natural communities helps ecologists understand how species interact with each
other and their physical environment. Classifying natural communities is important
for conservation, land management and land use planning. The Vermont Natural
Heritage Program has been working on mapping natural communities owned by
The Nature Conservancy. I’ve just finished mapping the High Pond Preserve in
Brandon, VT. Using a preliminary map created by Eric Sorenson, his field notes and
aerial photography I’ve been creating a final map. I’ve worked in the field identifying
species and natural communities and also in the GIS lab mapping out the natural
communities. The next site that I’m mapping is the LaPlatte River delta.
The Effect of Metamorphic Grade on Arsenic in
Bedrock and Groundwater: An Analysis of Shales,
Slates, Phyllites and Schists from the Champlain
Valley Sequence in Quebec and Vermont
Annika Silverman and Peter Ryan
Department of Geology, Middlebury College, Middlebury VT 05753
Recent research in Vermont (e.g. Ali Thompson thesis of 2011, Diego Russell thesis
of 2012) and previous work in the Himalayas (Hattori et al 2005) and California
(Bebout et al 1999) suggests that the concentration of arsenic (As) in shales
decreases as they are heated and compressed by metamorphism into slates, phyllites
and eventually schists. This clearly has potential implications for predicting the
occurrence of arsenic in groundwater. In the Taconic region of Vermont, low-grade
slates contain an average of 44 mg/kg As and 33% of bedrock water wells contain
>10 mg/L (ppb) As, the EPA maximum contaminant level for drinking water.
By comparison, higher-grade phyllites and schists from other areas of Vermont
contain an average of 3.5 ppm As and only 4% of wells contain >10 ppb As. Thus, it
appears that the rocks of Vermont contain evidence for the control of metamorphic
grade on arsenic in groundwater—the higher the grade of metamorphism, the less
naturally-occurring As in rock and in well water. In order to minimize variability