## 3 Results and Discussion
### Effect of the BA Natural Weathering
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Fraction**}} & \multicolumn{6}{c}{**Element**} \\ \cline{2-9}  & \multicolumn{1}{c}{**SiO\({}_{2}\)**} & \multicolumn{1}{c}{**CaO**} & \multicolumn{1}{c}{**Fe\({}_{2}\)O\({}_{3}\)**} & \multicolumn{1}{c}{**Al\({}_{2}\)O\({}_{3}\)**} & \multicolumn{1}{c}{**K\({}_{2}\)O**} & \multicolumn{1}{c}{**TiO\({}_{2}\)**} & \multicolumn{1}{c}{**P\({}_{2}\)O\({}_{3}\)**} & \multicolumn{1}{c}{**SO\({}_{2}\)**} \\ \hline \multicolumn{9}{c}{**112-24.4 mm**} \\ \hline Untreated & 47.272 \(\pm\) 0.271 & 18.022 \(\pm\) 0.103 & 5.601 \(\pm\) 0.037 & 5.599 \(\pm\) 0.132 & 1.241 \(\pm\) 0.011 & 0.797 \(\pm\) 0.029 & 0.896 \(\pm\) 0.031 & 2.108 \(\pm\) 0.022 \\ \hline \(3\) months & 44.377 \(\pm\) 0.752 & 18.057 \(\pm\) 0.285 & 5.428 \(\pm\) 0.110 & 5.476 \(\pm\) 0.403 & 1.134 \(\pm\) 0.031 & 0.786 \(\pm\) 0.097 & 0.790 \(\pm\) 0.087 & 2.101 \(\pm\) 0.069 \\ \hline \(6\) months & 42.474 \(\pm\) 0.699 & 16.891 \(\pm\) 0.275 & 5.288 \(\pm\) 0.114 & 5.372 \(\pm\) 0.406 & 0.988 \(\pm\) 0.028 & 0.773 \(\pm\) 0.100 & 0.708 \(\pm\) 0.084 & 2.049 \(\pm\) 0.064 \\ \hline \multicolumn{9}{c}{**24.44–40.0 mm**} \\ \hline Untreated & 46.902 \(\pm\) 0.588 & 18.141 \(\pm\) 0.2682 & 6.748 \(\pm\) 0.097 & 7.612 \(\pm\) 0.350 & 1.739 \(\pm\) 0.030 & 0.737 \(\pm\) 0.074 & 1.041 \(\pm\) 0.073 & 1.949 \(\pm\) 0.050 \\ \hline \(3\) months & 43.536 \(\pm\) 0.752 & 16.359 \(\pm\) 0.268 & 6.519 \(\pm\) 0.100 & 7.404 \(\pm\) 0.457 & 1.657 \(\pm\) 0.040 & 0.731 \(\pm\) 0.072 & 1.042 \(\pm\) 0.091 & 1.652 \(\pm\) 0.056 \\ \hline \(6\) months & 36.081 \(\pm\) 0.620 & 16.753 \(\pm\) 0.252 & 6.067 \(\pm\) 0.122 & 7.958 \(\pm\) 0.441 & 1.247 \(\pm\) 0.031 & 0.715 \(\pm\) 0.071 & 0.657 \(\pm\) 0.089 & 1.470 \(\pm\) 0.056 \\ \hline \multicolumn{9}{c}{**40.0 mm natural weathering**} \\ \hline Untreated & 37.479 \(\pm\) 0.631 & 22.763 \(\pm\) 0.343 & 6.288 \(\pm\) 0.122 & 5.757 \(\pm\) 0.425 & 1.116 \(\pm\) 0.029 & 1.018 \(\pm\) 0.108 & 1.449 \(\pm\) 0.100 & 4.865 \(\pm\) 0.103 \\ \hline \(3\) months & 33.703 \(\pm\) 0.617 & 22.947 \(\pm\) 0.366 & 6.384 \(\pm\) 0.136 & 5.508 \(\pm\) 0.419 & 0.928 \(\pm\) 0.027 & 1.123 \(\pm\) 0.111 & 1.558 \(\pm\) 0.101 & 4.418 \(\pm\) 0.099 \\ \hline \(6\) months & 31.850 \(\pm\) 0.503 & 22.947 \(\pm\) 0.366 & 6.193 \(\pm\) 0.124 & 5.404 \(\pm\) 0.394 & 0.832 \(\pm\) 0.024 & 1.594 \(\pm\) 0.102 & 1.558 \(\pm\) 0.101 & 4.677 \(\pm\) 0.099 \\ \hline \multicolumn{9}{c}{**40.0 mm laboratory ageing**} \\ \hline Untreated & 37.479 \(\pm\) 0.631 & 22.763 \(\pm\) 0.343 & 6.288 \(\pm\) 0.122 & 5.757 \(\pm\) 0.425 & 1.116 \(\pm\) 0.029 & 1.018 \(\pm\) 0.108 & 1.449 \(\pm\) 0.100 & 4.865 \(\pm\) 0.103 \\ \hline \(3\) months & 34.279 \(\pm\) 0.623 & 24.263 \(\pm\) 0.160 & 6.252 \(\pm\) 0.128 & 5.487 \(\pm\) 0.406 & 1.083 \(\pm\) 0.028 & 0.101 \(\pm\) 0.106 & 1.496 \(\pm\) 0.101 & 4.800 \(\pm\) 0.103 \\ \hline \(6\) months & 33.569 \(\pm\) 0.616 & 24.641 \(\pm\) 0.163 & 6.176 \(\pm\) 0.123 & 5.418 \(\pm\) 0.395 & 1.059 \(\pm\) 0.027 & 0.980 \(\pm\) 0.101 & 1.615 \(\pm\) 0.104 & 4.847 \(\pm\) 0.103 \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._Figure 7: Amounts of heavy metals in different bottom ash fractions during natural weathering (mg/kg): Mn; Cu; Zn; Pb; Sr.