The temporal dynamics of nitrogen (N) fractions and ammonia (NH3) volatilization were investigated over a 56-day storage period using a laboratory-scale pig slurry pit simulator. A detailed N mass balance, encompassing total N (TN), total ammonium N (TAN), organic N, and nitrate N (NO3−-N) fractions, yielded a N mass recovery of 96.5%, despite uncertainties associated with discrete emission measurements, with a TN reduction of 28.3 g vessel−1 closely matched by cumulative NH3-N emissions of 27.3 g. The NH3 emission profile exhibited a distinct two-phase pattern. During Phase I (days 1–28), emissions remained stable at 16.7–19.5 g m−2 d−1, accounting for approximately 58% of total cumulative NH3-N loss (518.6 g m−2), consistent with zero-order kinetics. Phase II (days 29–56) was characterized by first-order exponential decay (k = 0.0293 d−1, R2 = 0.982), coinciding with progressive TAN depletion. Measured emission rates were strongly correlated with theoretical free ammonia N (FAN) concentrations derived from pH and temperature (R2 = 0.74), confirming that theoretical FAN provides a useful upper bound for emission potential, although the actual gaseous flux is restricted by mass-transfer limitations at the slurry–air interface. These results demonstrate that continuous pH and temperature monitoring provides a practical basis for tracking emission dynamics and informing the timing of mitigation interventions, particularly during the high-flux initial storage phase.