[r] Replace all values in a matrix <0.1 with 0

I have a matrix (2601 by 58) of particulate matter concentration estimates from an air quality model. Because real-life air quality monitors cannot measure below 0.1 ug/L, I need to replace all values in my matrix that are <0.1 with a zero/NA/null value.

Someone suggested ifelse(test, true, false) with a logical statement, but when I try this it deletes everything.