Date of Award

12-2013

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. Alan E. Kehew

Second Advisor

Dr. Patrick M. Colgan

Third Advisor

Dr. Duane R. Hampton

Fourth Advisor

Dr. Carla M. Koretsky

Access Setting

Masters Thesis-Open Access

Abstract

Groundwater from wells located in and around Hemlock Crossing Park in Ottawa County, Michigan has elevated levels of ammonium. High ammonium concentrations in potable water wells are a common indicator of anthropogenic impact, such as landfill leachate or agricultural activity. Ammonium can also occur in groundwater through the decay of natural organic material. Along with the retrieval of a complete glacial sediment core via rotasonic drilling, numerous chemical and isotopic parameters were used to determine the source of ammonium in the impacted aquifer.

Buried organic material, deposited during the Athens subepisode interglacial period, is in contact with groundwater containing elevated concentrations of ammonium and iron. High methane concentrations (20 to 41 mg/L) signify methanogenic conditions in the aquifer system and indicate very reducing conditions. A multi-isotopic approach, involving 3H and δ18O/δ2H, provides evidence that the aquifer system is not receiving recent recharge influenced by agricultural activity. Nitrogen isotopes support that the ammonium most likely originated from in situ organic material and not from anthropogenic sources. Potable wells in the confined aquifer system are at risk from the potential impact of methane migration and nitrification of ammonium, along with the aesthetic impact of high chloride concentrations.

Comments

Dr. Rama V. Krishnamurthy is the 5th advisor.

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