Not OP, and I'm giving an educated guess, so bear with me.

A lot of foul odors of organic origin tend to be alkaline: ammonia, urea, sulfates, etc., and acetic acid tends to neutralize them into something we can't smell, or temporarily overpower the smell. In the case of weed, it's either an aromatic hydrocarbon or a terpene that is in charge of the smell. I presume that in the presence of acids, those molecules breakdown into something we cannot smell.