## 3 Results
### Soil Microbial Community  
There were 3,722,533 valid sequences of 16S rDNA being clustered into 128,730 OTUs from all the 16 soil samples. The numbers of taxon tags ranged from 210,165 to 264,602 for the samples with Location 8 having the largest number of OTUs (166,432) and Location 3 having the smallest number of OTUs (126,439; Table 2). Alpha diversity index (Chao1 richness, ACE, Shannon and evenness) was shown in Table 2. The values of [PERSON]'s diversity index ranged from 6.79 to 7.85 and from 6.45 to 7.82 for the soils collected in July 2018 and January 2019, respectively. Both the values of Shannon's diversity index and ACE metric indicated that Location 2 and Location 4 possessed lower species richness than others did. The same was observed for the Evenness. Furthermore, the average of [PERSON]'s diversity index in July 2018 (7.37) was slightly higher than that collected in January 2019 (7.34).  
According to the sequencing results, over 90% of the reads fell within 41 bacterial phyla and the relative abundances of the bacteria at the phylum level were shown in Figure 3. On average, the five most abundant phylum-level bacteria were Proteobacteria (41.81%), Chloroflexi (11.38%), Planctomycetes (7.47%), Acidobacteria (6.86%) and Bacteroidetes (4.41%). At the class level, Deltaproteobacteria (19.75%), Gammaproteobacteria (11.16%), Alphaproteobacteria (5.40%), Anaerobic (4.01%) and Betaproteobacteria (3.97%) were the five largest bacterial classes, accounting for 44.65% of the taxon tags. At the family level, the five most dominant families were Desulfobacteraceae (7.1%), Anaerobic (4.33%), Ectothiorhodospiraceae (2.70%), Ignavibacteriaceae (1.94%) and Desulfobulbaceae (1.92%). At the genus level, _Desulfatiglas_ (1.72%), _Delalocococoides_ (1.52%), _Ignavibacterium_ (1.46%), _Acidiferrobacter_ (1.42%) and _Gp6_ (1.41%) were the five largest genera.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Time** & **Location** & **OTUs** & **ACE** & **Chao** & **Evenness** & **Shannon** & **Coverage** \\ \hline July, 2018 & 1 & 162,460 & 11,278 & 11,271 & 0.83 & 7.14 & 0.98 \\  & 2 & 154,322 & 11,990 & 11,818 & 0.79 & 7.22 & 0.98 \\  & 3 & 126,439 & 10,438 & 10,256 &  
The twenty most abundant genera were used to draw a heat map diagram (Figure 4). As shown in the heat map, Locations 2, 3 and 4 were characterized by the higher concentration of six genera, namely _Gemmatimonas_, _Thibacter_, _Nitrospira_, _Acidferrobacter_ and _GP6_, but an opposite trend was observed at Locations 5 and 6. Further, the abundance of _Dehalococcus_, _Desulfatiglans_ and _GP18_ were notably high at Locations 5 and 6, which was different from that at Locations 2 and 4. Notably, _Desulfobulus_, _Ignavibacterium_ and _GP23_ were more abundant at Locations 5, 6 and 7 during the January 2019 sampling campaign. Meanwhile, cluster analysis showed similarities between the microbial communities from the 8 sampling locations were in good agreement with their temporal characteristics except at Location 1.  
Figure 3: Bar chart of taxonomic profiles of bacterial community at the phylum level with abundance \(>\)1% in July 2018 (**a**) and January 2019 (**b**).