Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Type
OP_PARTICLEDRAW_TYPE
Parameter: Radius
OP_PARTICLEDRAW_RADIUS
Parameter: Count
OP_PARTICLEDRAW_COUNT
Parameter: Draw Position
OP_PARTICLEDRAW_DRAWPOS
Parameter: Life Time
OP_PARTICLEDRAW_LIFE
Parameter: Life Variation
OP_PARTICLEDRAW_LIFEVAR
Parameter: Random Seed
OP_PARTICLEDRAW_SEED
Parameter: Remove
OP_PARTICLEDRAW_REMOVE
Parameter: On
OP_PARTICLEDRAW_ON
Parameter: Animation Time
OP_PARTICLEDRAW_ATIME
Parameter: Birth Count
OP_PARTICLEDRAW_OUT_PARTICLECOUNT
Parameter: Birth Num
OP_PARTICLEDRAW_OUT_PARTICLENUM