  We have observed the clump G34.43+00.24 MM3 associated with an infrared dark
cloud in DNC $J$=3--2, HN$^{13}$C $J$=3--2, and N$_2$H$^+$ $J$=3--2 with the
Atacama Large Millimeter/submillimeter Array (ALMA). The N$_2$H$^+$ emission is
found to be relatively weak near the hot core and the outflows, and its
distribution is clearly anti-correlated with the CS emission. This result
indicates that a young outflow is interacting with cold ambient gas. The
HN$^{13}$C emission is compact and mostly emanates from the hot core, whereas
the DNC emission is extended around the hot core. Thus, the DNC and HN$^{13}$C
emission traces warm regions near the protostar differently. The DNC emission
is stronger than the HN$^{13}$C emission toward most parts of this clump. The
DNC/HNC abundance ratio averaged within a $15^{\prime\prime} \times
15^{\prime\prime}$ area around the phase center is higher than 0.06. This ratio
is much higher than the value obtained by the previous single-dish observations
of DNC and HN$^{13}$C $J$=1--0 ($\sim$0.003). It seems likely that the DNC and
HNC emission observed with the single-dish telescope traces lower density
envelopes, while that observed with ALMA traces higher density and highly
deuterated regions. We have compared the observational results with
chemical-model results in order to investigate the behavior of DNC and HNC in
the dense cores. Taking these results into account, we suggest that the low
DNC/HNC ratio in the high-mass sources obtained by the single-dish observations
are at least partly due to the low filling factor of the high density regions.
