16520
Downgradient acetate - stimulated water samples had much higher levels of arsenic ( up to 8 mu M ) , and 4 additional thioarsenic species were present under sulfate - reducing conditions .
 Chemical: acetate; Chemical: arsenic; Chemical: thioarsenic; Chemical: sulfate
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: acetate; Chemical: arsenic; Chemical: thioarsenic; Chemical: sulfate