Phosphogypsum

Phosphogypsum refers to the gypsum formed as a by-product of processing phosphate ore into fertilizer with sulfuric acid. Phosphogypsum is radioactive due to the presence of naturally-occurring uranium and radium in the phosphate ore.

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Marine-deposited phosphate typically has a higher level of radioactivity than igneous phosphate deposits, because uranium is present in seawater.^[1]

In the United States

  The United States Environmental Protection Agency has banned most applications of phosphogypsum with a radium-226 concentration of greater than 10 picocuries/gram (pCi/g). As a result, phosphogypsum which exceeds this limit is stored in large stacks.

Florida has a large quantity of phosphate deposits, particularly in Bone Valley region. However, the marine-deposited phosphate ore from central Florida is highly radioactive, and as such, the phosphogypsum by-product is too radioactive to be used for most applications. As a result, there are about 1 billion tons of phosphogypsum stacked in 25 stacks in Florida (22 are in central Florida) and about 30 million new tons are generated each year.^[2]

Various applications have been proposed for using phosphogypsum, including using it as material for:^[1]

• road pavement
• Soil conditioner
• Cover for landfills
• roof tiles
• artificial reefs & oyster beds

References

1. ^ ^{a b} Health Physics Society. "Answer to Question #629 Submitted to "Ask the Experts"." Posted on February 9, 2001. Last accessed June 19, 2007.
2. ^ Florida Institute of Phosphate Research. "Phosphogypsum and the EPA Ban." Last accessed June 19, 2007.