Tampa Bay Study: Biogeochemical Cycles

Home | Tampa Bay Study | Data | Task 2: Water & Sediment Quality - Biogeochemical Cycles | Radionuclides

Contact: Peter Swarzenski
USGS Florida Integrated Science Center, 600 4th Street South, St. Petersburg, Florida 33701

What is a radionuclide?

A radionuclide (radioactive isotope) is an atom of specified atomic number and mass number with an unstable nucleus that can undergo radioactive decay by emitting subatomic particles. By using the quantity and decay rate of different radionuclides found in the environment, scientists can improve their understanding on the movement, sources and flow rates of water, as well as to trace and analyze pollutants.

View a decay chain for Uranium and Thorium series. A decay chain displays the series of radioactive elements until a stable isotope is reached.

Radionuclides from the Uranium (U) and Thorium (Th) decay chain were studied to increase our understanding of biogeochemical processes in Tampa Bay.

Water samples were collected from seventeen sites during both late spring and summer seasons. These samples were evaluated to determine the residence times and partitioning of radionuclide-particles between dissolved water and suspended particulate matter (SPM). The scientists also collected data on the atmospheric input of these radionuclides to determine the relationships between atmospheric deposition and the levels found within the water column of Tampa Bay.

Results indicated that partitioning of these radionuclides between the bottom and water column is enhanced by frequent summer thunderstorms, where bottom sediments are resuspended. There are lower levels of U- and Pb-particles being deposited from the atmosphere than in other Gulf coast systems, which is likely due to the effect of the Gulf on our local air masses and rainfall. Th-particles are largely affected by riverine inputs in the fall, whereas Pb-particles are more closely related to atmospheric deposition and resuspension also in the fall.

Location of data collection sites within Tampa Bay. (enlargement)

Data Sets:

Atmospheric Depositional Fluxes of Pb-210 and Be-7 for Tampa Bay, FL (metadata)

Residence Times of Th-234, Be-7, and Pb-210 for 17 sites in Tampa Bay, FL (metadata)

Salinity, concentrations of SPM (suspended particulate matter) and dissolved, particulate and total Th-234, Pb-210, and Be-7 for 17 sites in Tampa Bay, FL (metadata)

These data sets are in ArcGIS Shapefile format. To view these files, you must have ESRI ArcGIS Software or other GIS software. A freely available lightweight version of ESRI's software is ArcExplorer.

Related Products:

The Impact of Groundwater and Contaminants on Tampa Bay (USGS Open-File Report 2005-1015, January 2005)

USGS Submarine Groundwater Discharge Research Projects Website

The Tampa Bay studies in biogeochemical cycles are presented in a special volume of Marine Chemistry - an international journal for studies of all chemical aspects of the marine environment.

Refereed Publications:

Swarzenski, P.W., M. Baskaran, C.S. Henderson, and K. Yates. 2007. Tampa Bay as a model estuary for examining the impact of human activities on biogeochemical processes: An introduction. Journal of Marine Chemistry 104(1-2) : 1-3.

Baskaran, M. and P.W. Swarzenski. 2007. Seasonal variations on the residence times and partitioning of short-lived radionuclides (234Th, 7Be, 210Pb) and depositional fluxes of 7Be and 210Pb in Tampa Bay, Florida. Marine Chemistry 104 (1-2) : 27-42.

* Swarzenski, P.W., C. Reich, K.D. Kroeger, and M. Baskaran. 2007. Ra and Rn isotopes as natural tracers of submarine groundwater discharge in Tampa Bay, Florida. Marine Chemistry 104 (1-2) : 69-84.

Swarzenski, P.W. and M. Baskaran. 2007. Uranium distribution in the coastal waters and pore waters of Tampa Bay, Florida. Marine Chemistry 104 (1-2) : 43-57.

* Data on this page are presented within this journal article.