## 3 Results
### Correlation between Soil Microbial Community and Soil Environmental Factors  
CCA analysis was used to further identify the soil characteristics that could contribute to microbial community variations affected by PBB addition. Both fungi and bacteria communities with BOF addition were well-separated from those in samples without PBB treatment (control). The length of the arrow represents the correlation. It can be seen from Figure 3 that the distribution of the fungi community from PBB samples was significantly positively correlated with pH, OC, N and K, while that from non-PBB samples was related to EC (Figure 3a). A similar tendency was also found in the bacterial community (Figure 3b). At the genus level, _Cumningham_, _Mucor_, _Ritzopus_, _Achromobacter_, _Chitinophag_, _Phenylobacterium_ and _Ochrobarrum_ were positively correlated with pH, OC, TN and AP, while the main influencing factor for _Trichoaderna_, _Actinomucor_, _Fussium_, _Penicillium_, _Arthrobortrys_, _Serendipita_, _Splingomonas_, _Rhodanobacter_ and _Gemmatomonas_ was EC (Figure 3).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Category**} & \multirow{2}{*}{**Genus**} & \multicolumn{2}{c}{**Relative Abundance (\%)**} \\ \cline{3-5}  & & **4\% PBB Addition** & **Control** \\ \hline \multirow{7}{*}{Fungi} & _Mucor_ & 28.8 \(\pm\) 3.60 a & 2.83 \(\pm\) 0.55 b \\  & _Rhizopus_ & 30.41 \(\pm\) 2.26 a & 0.76 \(\pm\) 0.12 b \\  & _Penicillium_ & 3.41 \(\pm\) 0.62 b & 23.13 \(\pm\) 1.27 a \\  & _Trichoderma_ & 2.32 \(\pm\) 0.40 b & 6.94 \(\pm\) 0.66 a \\  & _Fusarium_ & 0.12 \(\pm\) 0.03 b & 0.79 \(\pm\) 0.08 a \\  & _Cumningham_ & 0.41 \(\pm\) 0.001 a & 0.00 \(\pm\) 0.01 b \\  & _Serendipita_ & 0.00 \(\pm\) 0.00 b & 0.11 \(\pm\) 0.01 a \\  & _Arthrobortrys_ & 0.00 \(\pm\) 0.00 b & 0.08 \(\pm\) 0.002 a \\  & _Helvella_ & 0.00 \(\pm\) 0.001 b & 0.03 \(\pm\) 0.0001 a \\ \hline \multirow{7}{*}{Bacteria} & _Chitinophag_ & 11.77 \(\pm\) 0.03 a & 1.95 \(\pm\) 0.39 b \\  & _Splingomonas_ & 0.04 \(\pm\) 0.002 b & 0.09 \(\pm\) 0.003 a \\  & _Chitinophagaceae_ & 1.14 \(\pm\) 0.03 b & 0.06 \(\pm\) 0.01 a \\  & _Dyella_ & 2.54 \(\pm\) 0.01 a & 1.93 \(\pm\) 0.12 b \\  & _Rhodanobacter_ & 1.24 \(\pm\) 0.31 b & 4.24 \(\pm\) 0.43 a \\  & _Phenylobacterium_ & 3.51 \(\pm\) 0.73 a & 1.64 \(\pm\) 0.175 b \\  & _Bacillus_ & 4.07 \(\pm\) 0.43 a & 2.86 \(\pm\) 0.24 b \\  & _Gemmatomonas_ & 0.89 \(\pm\) 0.16 b & 2.81 \(\pm\) 0.72 a \\ \hline \hline \end{tabular}
\end{table}
Table 5: Genera with significant differences in relative abundance between BOF addition and control.  
Figure 2: Principal coordinate analysis (PCoA) of soil fungal (**a**) and bacterial (**b**) communities based on Bray–Curtis distance. PBB represents 4% of PBB addition; control, with no PBB addition.  
According to the partial Mantel test (Table S2), available potassium and EC had the most significant effect on soil fungi community structure (R\({}^{2}\) = 0.9939, \(p\) < 0.01 and R\({}^{2}\) = 0.9937, \(p\) = 0.01), followed by AN (R\({}^{2}\) = 0.9872, \(p\) = 0.0225) and OC (R\({}^{2}\) = 0.9719, \(p\) = 0.0285). The soil bacterial community was affected significantly by AK (R\({}^{2}\) = 0.9833, \(p\) < 0.01) and total N (R\({}^{2}\) = 0.9837, \(p\) < 0.01), followed by OC and EC. pH showed no significant effect on either the fungal or bacterial community. Therefore, EC, available potassium, TN, OC and EC may be important environmental factors affecting soil microorganisms.