Geological Society of America

T19 Urban Geochemistry

Sunday, 22 September 2019
8:00 AM - 12:00 PM
Room 128AB, North Building

ISOTOPIC AND ELEMENTAL ANALYSIS OF THE ANTHROPOGENIC IMPACT IN FARMINGTON BAY

Paper number: T19-2
Program: Technical Sessions
Time: 8:15 AM – 8:30 AM

Authors

Nathan V. Gunnell Presenting Author
Brigham Young University, Provo, UT
Stephen Nelson
National Institute of Health, Rockville, MD
Daniel R. Engstrom
Science Museum of Minnesota, Marine on St. Croix, MN

Abstract

Influence of human activity on surrounding environments is an important field of research. With respect to aquatic settings, lacustrine deposits provide excellent proxies of environmental change since the sediment accumulates at a relatively constant rate, recording environmental change. This study employs isotopic, mineral, and chemical records from Farmington Bay freeze cores, in particular δ¹³C, δ¹⁵N, and ²¹⁰Pb isotopes as well as phosphorus level fluctuation. In particular, δ¹⁵N provides a record of changing nutrient sources and ²¹⁰Pb isotopes permit estimation of the age of sediment with depth.

Initial results from these ²¹⁰Pb isotopes have allowed ages to be assigned to depths along the core dating back roughly 100 years at 30 cm. At this depth, a dramatic shift in the δ¹⁵N isotope is observed. Initial δ¹⁵N levels indicated a nutrient source related to agriculture. However, beginning around 100 years ago, the δ¹⁵N shows the main nutrient source for the bay became wastewater. This may have been a result of the completion of a sewage canal in 1911 which began routing wastewater directly into the bay. Results have also shown a significant rise in phosphorus levels beginning around 1970 which may be due to the construction of the automobile causeway that isolated Farmington Bay from the rest of the Great Salt Lake.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-340106

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