  Multi-wavelength ultraviolet (UV) observations by the IRIS satellite in
active region NOAA 12529 have recently pointed out the presence of long-lasting
brightenings, akin to UV bursts, and simultaneous plasma ejections occurring in
the upper chromosphere and transition region during secondary flux emergence.
These signatures have been interpreted as evidence of small-scale, recurrent
magnetic reconnection episodes between the emerging flux region (EFR) and the
pre-existing plage field. Here, we characterize the UV emission of these
strong, intermittent brightenings and we study the surge activity above the
chromospheric arch filament system (AFS) overlying the EFR. We analyze the
surges and the cospatial brightenings observed at different wavelengths. We
find an asymmetry in the emission between the blue and red wings of the Si IV
1402 \AA{} and Mg II k 2796.3 \AA{} lines, which clearly outlines the dynamics
of the structures above the AFS that form during the small-scale eruptive
phenomena. We also detect a correlation between the Doppler velocity and
skewness of the Si IV 1394 \AA{} and 1402 \AA{} line profiles in the UV burst
pixels. Finally, we show that genuine emission in the Fe XII 1349.4 \AA{} line
is cospatial to the Si IV brightenings. This definitely reveals a pure coronal
counterpart to the reconnection event.
