  We investigate quantum charge and spin pumping in armchair graphene
nanoribbons under a single ac gate voltage connected with
nonmagnetic/ferromagnetic leads via the nonequilibrium Green's function method.
In the case of nonmagnetic leads, where only part of the nanoribbon is subject
to an ac gate voltage to break the left-right spatial symmetry, we discover
that peaks of the charge pumping current appear at the Fermi energies around
the subband edges in the ac-field-free region of the nanoribbon. In the case of
ferromagnetic leads with the lead magnetizations being antiparallel to break
the left-right symmetry, similar peaks appear in the spin pumping current when
the Fermi energies are around the edges of the the majority-spin subbands in
the ferromagnetic leads. All these peaks originate from the pronounced symmetry
breaking in the transmissions with energies being around the corresponding
subband edges. Moreover, we predict a {\em pure} spin current in the case of
ferromagnetic leads with the whole graphene nanoribbon under an ac gate
voltage. The ac-field-strength and -frequency dependences of the pumping
current are also investigated with the underlying physics revealed.
