## 3 Results and Discussion
### Gas Concentrations  
#### 3.2.1 Ammonia Monitoring Results  
NH\({}_{3}\) was the most abundant of the monitored gases, with internal NH\({}_{3}\) concentrations averaging 57.1 \(\pm\) 1.3 mg m\({}^{-3}\) across the entire monitoring period (excluding the two occasions when the extractor fans where disabled--these periods are discussed separately). There was substantial variation in NH\({}_{3}\) concentrations depending on the timing of the measurements. The highest average NH\({}_{3}\) concentrations were recorded during weekend daytime at 66.3 \(\pm\) 8.2 mg m\({}^{-3}\) (Table 2), although this was not significantly different (\(p\) < 0.05) from the average weekday daytime concentrations of 64 \(\pm\) 2.5 mg m\({}^{-3}\) (Figure 3). Average weekday nighttime NH\({}_{3}\) concentrations were found to be slightly lower at 54.2 \(\pm\) 2.1 mg m\({}^{-3}\), and they were statistically significantly different from the daytime concentrations. Weekend nighttime average NH\({}_{3}\) concentrations were measured to be less than 60% of the average daytime levels, at 37.9 \(\pm\) 2.6 mg m\({}^{-3}\). The differences in average concentrations of NH\({}_{3}\) during separate time periods probably reflect differences in environmental variables (i.e., temperature and humidity) and manure agitation activity between night and day, and the absence of manure agitation activities at weekends. The diurnal fluctuations in NH\({}_{3}\) concentrations and the differences in concentration patterns between weekdays and weekends were clearly seen across all four internal NH\({}_{3}\) sampling points (Figure 4). On weekdays, all internal sampling points showed concentrations peaking sharply, three times, during the daily agitation events, matching the travel of the agitator along the three manure windows (Figure 1). At weekends, a single broader NH\({}_{3}\) concentration peak was observed. It is likely that agitation itself resulted in shorter, higher magnitude NH\({}_{3}\) concentrations that were quickly cleared by the ventilation system, \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Temperature (\({}^{\circ}\)C)** & **Relative Humidity (\%)** \\ \hline Average & 22.3 & 82 \\ Min. & 16.1 & 32 \\ Max. & 34.1 & 100 \\ St. Dev. & 3.6 & 15.9 \\ Daily Max. Average & 27.1 & 98.4 \\ St. Dev. & 2.9 & 2.9 \\ Daily Min. Average & 18.3 & 60.2 \\ St. Dev. & 1.3 & 13.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of average, minimum, maximum, and standard deviation values of temperature and relative humidity, along with daily maximum and minimum averages. Figure 2: Consistent diurnal pattern of temperature and relative humidity throughout the monitoring period. Turning of the manure during agitation cycles aerates the compost and provides a supply of oxygen to the microorganisms that are performing aerobic digestion [20]. The biological oxidation of C to CO\({}_{2}\) releases heat, which raises the temperature of the compost into a thermophilic (>40 \({}^{\circ}\)C) state [20]. In addition, aeration exposes the manure to air, allowing the release of dissolved CO\({}_{2}\), which raises the pH of the manure [12]. Increases in either temperature or pH promote the emission of NH\({}_{3}\) by increasing the dissociation of NH\({}_{4}\)+ [12; 18; 19]. The process of turning/aeration itself increases the capacity for NH\({}_{3}\) utilization through air turbulence across the greatly expanded manure surface area [12], leading to the high concentrations of NH\({}_{3}\) recorded during the agitation events. However, alongside volatizing the reservoir of NH\({}_{3}\) gas in the manure, this process also temporarily lowered the temperature of the manure, which probably led to the lower NH\({}_{3}\) concentrations that were recorded directly after agitation. Following aeration, the increased availability of oxygen led to temperature increases within the compost over the next day [17].