Fertilizer and Fertilizer Production Wastes
Due to it chemical properties, phosphate rock may contain significant quantities of naturally occurring radioactive materials, including uranium (and its decay products, including radium) and thorium (and its decay products).
In the US, uranium concentrations in phosphate ore range from 200 to 300ppm (parts per million = mg/kg).
Like many other minerals, uranium was deposited on land by volcanic action, dissolved by rainfall, and in some places, carried into underground formations. In some cases, geochemical conditions resulted in its concentration into “ore bodies.” Uranium is a common element in Earth’s crust (soil, rock) and in seawater and groundwater.
The mass concentration of uranium in soil varies widely, but is typically about 3 parts per million (ppm), or 0.07 becquerels per gram (Bq g-1). A becquerel is a very small amount of radioactivity equal to one decay per second. A square kilometer of earth, 30 cm deep, will typically contain a ton or more of uranium. In the United States today, the concentration of radioactivity in uranium ore bodies is on average about 0.3% by weight, or about 78 Bq g-1.
Fertilizers are a source of uranium and other potentially toxic metals that add to the soil's natural concentration.