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Stimulating microbial growth through the use of acetate injection wells at the former uranium mill site in Rifle , Colorado , USA , has been shown to decrease dissolved uranium ( VI ) concentrations through bacterial reduction to immobile uranium ( IV ) .
 Chemical: uranium ( VI ); Chemical: uranium ( IV )
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: uranium ( VI ); Chemical: uranium ( IV )