21505
Estimated lower limits of atmospheric lifetimes of biomass burning aerosol particles , 200 nm in diameter , by heterogeneous OH oxidation under fresh biomass burning plume conditions are ~ 2 days and up to ~ 2 weeks for atmospheric background conditions .
 Chemical: OH
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: OH