Sewage-Contaminated Groundwater -- Cape Cod, Massachusetts
U.S. Geological Survey (USGS
) scientists prepare a tracer solution to conduct a natural gradient tracer test to measure anammox activity in groundwater
. The tracer solution is prepared by pumping groundwater into a gas impermeable bladder to maintain the in situ dissolved oxygen concentration and then mixing in the tracer chemicals. The bladder is contained in an ice-cooled water pool to maintain the groundwater temperature until the solution is pumped back into the aquifer. Photo Credit: Deborah Repert, USGS
A diagram of the natural gradient tracer test used to detect anammox in groundwater
. The tracer solution was injected in the well on the left, and wells on the right were used to monitor the subsurface plume caused by the tracer injection. Analytical testing for the isotopic ratios of nitrogen gas (30
) helped determine rates for the denitrification of nitrate (NO3-
) to nitrogen gas (N2
) and for anammox of ammonium (New Hampshire4+
) to N2
. From Smith and others, 2015
Experimental setup for small-scale transport test designed to assess the effectiveness of the "colmation layer" at the bottom sediments of Ashumet Pond (Cape Cod, Massachusetts) for filtering out cyanobacteria and viruses
. The green color in the collapsible bag containing the colloids and a bromide tracer is caused by the presence of microbial sized fluorescent microspheres that scientists added to act as colloidal tracers. Photo Credit: Denis R. LeBlanc, USGS
Single-well tracer tests involve injecting a tracer solution into one port of a multilevel sampling well, creating a tracer cloud in the groundwater, and then monitoring the water chemistry in the tracer cloud from the same well as the tracer cloud moves away from the well. Single-well tracer tests can be used to measure chemical reactions in the subsurface such as measuring how nitrogen transforms in groundwater
scientists processing groundwater samples during a subsurface pH modification experiment
. In the foreground is a tank containing an injection solution used to create a plume of groundwater with lower pH.
A conceptual diagram of the setup of the subsurface tracer test
. A solution of bromide (conservative tracer), 17ß-estradiol, 4-nonylphenol, and sulfamethoxazole was injected into the subsurface. A series of corresponding water samples were collected from the multilevel sampler downgradient of the injection well.
Treated wastewater disposal beds on Cape Cod, Massachusetts, which created a large subsurface plume of contaminated groundwater. A team of scientists has been conducting long-term multidisciplinary research on the physical, chemical, and biological processes that control the transport of contaminants in groundwater.
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