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These analyses , coupled with observations of higher Hg in primary producers in streams with low pH , suggest that pH influences both baseline concentrations and biomagnification of Hg in these systems .
 Hg, Hg
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Hg, Hg