Ambient compensation for PM is quite difficult, as it depends on the particle composition. Besides PM measurements from monitoring stations are taken at 20C and 50%rH (the weighing part of the measurement), if I remember correctly.
The PMS3003 (aka G3) sensor gives you 2 sets of values.The datasheet describes the 1st set as "Read the to value is a TSI For standard data" and the 2nd one as "Reading to the value of value is an atmosphere as the standard". After looking at the data coming from from my unit, I interpret the 1st set as "at ambient conditions" and the 2nd one as "at standard atmosphere". Therefore, if you want to compare with a measurement station you can use the 2nd set.
Please let me know how your experiment goes.