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The authors findings imply that to prevent waterborne mercury contamination in this system from continuing for decades , remedial actions will have to control the headwater mercury source that sustains day - to - day base flow mercury concentrations and the riparian stream - bank sources that generate most of the mercury export from the system .
 Chemical: mercury; Chemical: mercury; Chemical: mercury; Chemical: mercury
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: mercury; Chemical: mercury; Chemical: mercury; Chemical: mercury