Transport of nitrogen in a treated-wastewater plume to coastal discharge areas, Ashumet Valley, Cape Cod, Massachusetts

Abstract

L i t t l e P o n d G r e a t P o n d G r e e n P o n d B o u r n e s P o n d Nantucket SoundCover photo. View northward from above Nantucket Sound of the narrow coastal saltwater embayments, referred to as coastal ponds, in southern Falmouth, Cape Cod, Massachusetts, and several freshwater ponds 2 to 4 miles inland from the coast. The Massachusetts Military Reservation is the tan area in the top right of the photo. Photography by Joseph R. Melanson, Aerials Only (http://www.skypic.com), used with permission. For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS. Transport of Nitrogen in a TreatedFor an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).Altitude, as used in this report, refers to distance above the vertical datum.Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25°C). Concentrations AbstractLand disposal of treated wastewater from a treatment plant on the Massachusetts Military Reservation in operation from 1936 to 1995 has created a plume of contaminated groundwater that is migrating toward coastal discharge areas in the town of Falmouth, Massachusetts. To develop a better understanding of the potential impact of the treated-wastewater plume on coastal discharge areas, the U.S. Geological Survey, in cooperation with the Air Force Center for Engineering and the Environment, evaluated the fate of nitrogen (N) in the plume. Groundwater samples from two large sampling events in 1994 and 2007 were used to map the size and location of the plume, calculate the masses of nitrate-N and ammonium-N, evaluate changes in mass since cessation of disposal in 1995, and create a gridded dataset suitable for use in nitrogen-transport simulations. In 2007, the treated-wastewater plume was about 1,200 meters (m) wide, 30 m thick, and 7,700 m long and contained approximately 87,000 kilograms (kg) nitrate-N and 31,600 kg total ammonium-N. An analysis of previous studies and data from the 1994 and 2007 sampling events suggests that most of the biologically reactive nitrogen in the plume in 2007 will be transported to coastal discharge areas as either nitrate or ammonium with relatively little transformation to an environmentally nonreactive end product such as nitrogen gas.Nitrogen-transport simulations were conducted with a previously calibrated regional three-dimensional MODFLOW groundwate...

Seasonal and Spatial Variation in the Location and Reactivity of a Nitrate‐Contaminated Groundwater Discharge Zone in a Lakebed

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Controls on mixing‐dependent denitrification in hyporheic zones induced by riverbed dunes: A steady state modeling study

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Combined use of thermal methods and seepage meters to efficiently locate, quantify, and monitor focused groundwater discharge to a sand‐bed stream

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