## 3 Results and Discussion
### Preprocessing of Gas Monitoring Data
#### 3.3.2 Change of Harmful Gas Concentration with Density of _Limnoperna fortunei_  
The change of NH\({}_{3}\) concentration during the purification of _Limnoperna fortunei_ is shown in Figure 11. The higher the density of _Limnoperna fortunei_, the higher the maximum release concentration of NH\({}_{3}\). Especially when the number density of _Limnoperna fortunei_ reached 5.0-7.0 \(\times\) 10\({}^{4}\) mussels/m\({}^{2}\), the maximum NH\({}_{3}\) release concentration increased linearly with the increase in _Limnoperna fortunei_ density, from 177.7673 to 307.9454 mg/m\({}^{3}\). The fluctuation of the median NH\({}_{3}\) concentration showed no obvious regularity with the change of density of _Limnoperna fortunei_, indicating that the rate of harmful gas release from the putrification of _Limnoperna fortunei_ was unrelated to the density of _Limnoperna fortunei_, which may be caused by the individual difference of _Limnoperna fortunei_ purification and the complexity of microbial reaction. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Density (\(\times\)10\({}^{4}\) Mussels/m\({}^{2}\))** & & & \\ \hline
0.5 & \(C_{NH_{3}}=-67.40+177.43-162.42^{2}+67.29t^{3}-12.10t^{4}+0.78t^{5}\) & 99.85\% & Equation (6) \\
1.0 & \(C_{NH_{3}}=-197.18+674.61t-850.64t^{2}+514.09t^{3}-155.39t^{4}+22.90t^{5}-3.13t ^{6}\) & 99.64\% & Equation (7) \\
1.5 & \(C_{NH_{3}}=-8567.57+3632.71t+11597.04t^{-1}-865.62t^{2}-8876.79t^{-2}+111.16t^{3} +\) & 99.85\% & Equation (8) \\
359.092\({}^{-3}\cdot\) & \(-6.00t^{-7}-579.90t^{-4}\) & \(-6.05t^{2}-612t^{2}-12140.38t^{-2}+\) & 99.85\% & Equation (8) \\
2.0 & \(C_{NH_{3}}=-129200.02+66496.96t+161762.11t^{-1}-19662.59t^{2}-121240.38t^{-2}+\) & 99.70\% & Equation (9) \\
3643.32\({}^{3}+49555.16t^{-3}-371.30t^{4}-8460.44t^{-4}+15.94t^{5}\) & \(-6.05t^{2}-612t^{2}-29262.01t^{-2}+\) & 99.78\% & Equation (10) \\
2.5 & \(C_{NH_{3}}=-21498.92+7629.59t+33605.65t^{-1}-1413.66t^{2}-29262.01t^{-2}+\) & 99.78\% & Equation (10) \\  & \(122.7735t^{3}+13262.65t^{-3}-3.48t^{-2}-2434.59t^{-4}\) & \(-6.05t^{2}-612t^{3}+3053.57t^{-2}-2495.84t^{3}+\) & 99.86\% & Equation (11) \\
3.0 & \(C_{NH_{3}}=-27608.84t-22319.48t^{-7}-1721.65t^{-1}+10024.78t^{2}+3053.57t^{-2}- 2495.84t^{3}+\) & 99.86\% & Equation (11) \\  & \(17374.81t^{-3}+322.14t^{-4}+68.94t^{-4}-168.5t^{-3}+1024.8t^{-2}+\) & \(-6.05t^{2}-612t^{2}-612t^{2}-612t^{2}+\) & 99.86\% & Equation (11) \\
3.5 & \(C_{NH_{3}}=-13723.15+2728.19t+29123.81t^{-1}+85.87t^{2}-31631.47t^{-2}-98.84t^{ 2}+\) & 99.91\% & Equation (12) \\
4.0 & \(C_{NH_{3}}=-62493.95+23752.51t+95396.19t^{-1}-5102.54t^{2}-83605.37t^{-2}+\) & 99.85\% & Equation (13) \\  & \(5740.2t^{3}+38844.68t^{-3}-32.22t^{-3}-795.39t^{-4}-\) & \(-6.05t^{2}-612t^{3}+\) & 99.85\% & Equation (13) \\
4.5 & \(C_{NH_{3}}=-61157.54t^{-5}+2150.84t^{-4}+96780.35t^{-3}-3376.49t^{-2}-85768.13t^{ -2}+21.78t^{3}+\) & 99.86\% & Equation (14) \\  & \(39910.72t^{-3}+96.66t^{-3}-7583.43t^{-4}-5.20t^{5}\) & \(-6.05t^{2}-612t^{3}+\) & 99.80\% & Equation (15) \\
5.0 & \(C_{NH_{3}}=-3018.26+487.21t+6684.45t^{-1}+101.21t^{2}-7447.84t^{-2}-37.13t^{3}+\) & 99.80\% & Equation (15) \\  & \(4128.66t^{-3}+2.86t^{4}-900.56t^{-4}-\) & \(-6.05t^{2}-612t^{3}+\) & \(-6.05t^{2}-612t^{3}+\) & 99.80\% & Equation (16) \\
5.5 & \(C_{NH_{3}}=-22835.36t+14906.45t^{-4}+20365.84t^{-1}-5592.57t^{-2}-10384.16t^{-2}+\) & 99.89\% & Equation (16) \\  & \(1196.90t^{3}+2795.68t^{-3}-134.94t^{-3}-307.44t^{-4}+619t^{5}\) & \(-6.05t^{2}-612t^{3}+\) & \(-6.05t^{2}-612t^{3}+\) & 99.40\% & Equation (17) \\
6.0 & \(C_{NH_{3}}=-657.51t+56241t+304.24t^{-1}-135.96t^{2}-48.10t^{-2}+11.06t^{3} +\) & 99.40\% & Equation (17) \\
6.5 & \(C_{NH_{3}}=-3202.07+3540.81t+618.63t^{-1}-1682.63t^{2}+919.91t^{-2}+413.65t^{3}-\) & 99.70\% & Equation (18) \\
6.0 & \(680.61t^{-3}-50.67t^{4}+180.60t^{-4}+24.345t^{5}-17.25t^{-5}\) & \(-7.0\) & \(-6. The change of H\({}_{2}\)S concentration released by _Limnoperna fortunei_ at different densities is shown in Figure 12. The maximum H\({}_{2}\)S release concentration was higher when the density of _Limnoperna fortunei_ was higher.