Editing Tritium (section)

=== Mississippi River system ===
Trace amounts of radioactive materials from atomic weapons testing settled throughout the [[Mississippi River System]]. Tritium concentrations have been used to understand the [[residence time]]s of continental hydrologic systems such as lakes, streams, and rivers.<ref name="Mississippi">
{{cite journal
 |last1=Michel  |first1=Robert L.
 |year=2004
 |title=Tritium hydrology of the Mississippi River basin
 |journal=Hydrological Processes
 |volume=18  |issue=7  |page=1255
 |doi=10.1002/hyp.1403  |bibcode = 2004HyPr...18.1255M
 |s2cid=130033605
 |url=https://zenodo.org/record/1229196
}}
</ref> 
In a 2004 study, several rivers were taken into account during the examination of tritium concentrations (starting in the 1960s) throughout the Mississippi River Basin: [[Ohio River]] (largest input to the Mississippi River flow), [[Missouri River]], and [[Arkansas River]].<ref name="Mississippi" /> The highest tritium concentrations were found in 1963 across locations throughout these rivers.  The peak correlates with implementation of the US & Soviet atmospheric test ban treaty in 1962. The overall highest concentrations occurred in the Missouri River (1963) and were greater than 1,200&nbsp;TU while the lowest concentrations were found in the Arkansas River (never greater than 850&nbsp;TU and less than 10&nbsp;TU in the mid-1980s).<ref name="Mississippi" />

As for the mass flux of tritium through the main stem of the Mississippi River into the [[Gulf of Mexico]], data indicated that approximately 780&nbsp;grams of tritium has flowed out of the River and into the Gulf between 1961 and 1997,<ref name="Mississippi"/> an average of 21.7&nbsp;grams/yr and 7.7&nbsp;PBq/yr. Current fluxes through the Mississippi River are 1 to 2 grams, per year as opposed to the pre-bomb period fluxes of roughly 0.4&nbsp;grams per year.<ref name="Mississippi" />