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Multiple linear regressions showed that the pH effect on copper uptake was only significant when taking into account cation exchange capacity , or calcium and dissolved organic carbon levels in the pore water .
 Chemical: copper; Chemical: calcium; Chemical: carbon
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: copper; Chemical: calcium; Chemical: carbon