Effects of Seven-Year Fertilization Reclamation on Bacterial Community in a Coal Mining Subsidence Area in Shanxi, China

The restoration of soil fertility and microbial communities is the key to the soil reclamation and ecological reconstruction in coal mine subsidence areas. However, the response of soil bacterial communities to reclamation is still not well understood. Here, we studied the bacterial communities in fertilizer-reclaimed soil (CK, without fertilizer; CF, chemical fertilizer; M, manure) in the Lu’an reclamation mining region and compared them with those in adjacent subsidence soil (SU) and farmland soil (FA). We found that the compositions of dominant phyla in the reclaimed soil differed greatly from those in the subsidence soil and farmland soil (p < 0.05). The related sequences of Acidobacteria, Chloroflexi, and Nitrospirae were mainly from the subsided soil, whereas those of Alphaproteobacteria, Planctomycetes, and Deltaproteobacteria were mainly derived from the farmland soil. Fertilization affected the bacterial community composition in the reclaimed soil, and bacteria richness and diversity increased significantly with the accumulation of soil nutrients after 7 years of reclamation (p < 0.05). Moreover, soil properties, especially SOM and pH, were found to play a key role in the restoration of the bacterial community in the reclaimed soil. The results are helpful to the study of soil fertility improvement and ecological restoration in mining areas.

A new approach to increase land reclamation rate in coal mining subsidence area: A case study of Guqiao Coal Mine, China

Underground coal mining will inevitably cause land ponding in high groundwater table, which will affect the land sustainable development. However, the traditional reclamation (TR) is poor in land rate. Thus, finding a suitable reclamation approach is crucial to alleviate the conflicts between coal exploitation and land protection. In this paper, taking Guqiao Coal Mine of China was seriously affected by mining-induced ponding as an example. Firstly, dynamic distribution of surface subsidence and land damage from 2007 to 2017 was revealed base on concurrent mining and reclamation (CMR). Second, the land-water layout of five reclamation schemes (no reclamation, TR, CMR I, CMR II and CMR III) were simulated. Then, and the dynamic filling elevation model and filling thickness model were constructed. Finally, the sequence of earthwork allocation was optimized. The results revealed that: 1) reclaimed land area: CMR III > CMR II > CMR I > TR > no reclamation; 2) The digging depth is directly proportional to earthwork volume and land area, and inversely proportional to water area, but with increase of digging depth, the increase in the reclaimed land area relatively slowed down; 3) CMRs had reclaimed 426.31~637.82 ha and 259.62~471.13 ha more than the no reclamation and TR respectively. Compared with the no reclamation and TR, CMRs can increase the proportion of reclaimed land by 33.77~50.52% and 20.57~37.32% respectively. The research results provide a reference to increase the reclamation rate of mining areas in the high phreatic table.

Spatial Variability of Soil Moisture in Mining Subsidence Area of Northwest China

The current research only investigates the impact of coal mining on deep soil moisture from the perspective of the absolute value of soil moisture. This study applied the combined method of classical statistics and multi-dimensional geo-statistics to analyze the temporal and spatial changes of soil moisture from 0-10m in the mining face of Nalin River No.2 Mine in Northwest China from the perspective of spatial variability. The results of the study showed that in time distribution, on the whole, the soil moisture in the partial areas of the 1-year and the 2-year subsidence area was lower than that in the control area, and the variability increased, but as the subsidence entered a stable period, the degree of variability decreased; vertically observed, in space distribution, the 0-10m soil moisture in the control area had obvious distribution rules with low spatial variability. However, the spatial variability of soil moisture in the 1-year subsidence area and the 2-year subsidence area increased, and the variability showed a trend of increasing continuously with the increase of depth. During the principal component analysis, it was found that the change of soil texture caused by coal mining subsidence, the change of soil pores microstructure caused by geotechnical deformation, as well as the preferential flow caused by changes in groundwater level were the main reasons for the increasing spatial variability of soil moisture. This study revealed the principles of spatial variability of soil moisture in coal mining subsidence areas in Northwest China, which can provide a scientific basis for the restoration of mining areas.

Spatial Variability of Soil Moisture in Mining Subsidence Area of Northwest China

The current research only investigate the impact of coal mining on deep soil moisture from the perspective of the absolute value of soil moisture. This study applied the combined method of classical statistics and multi-dimensional geo-statistics to analyze the changes of soil moisture of time and space from 0-10m in the mining face of Nalin River No.2 Mine in Northwest China from the perspective of spatial variability. The results of the study showed that in time distribution, on the whole, the soil moisture in the partial areas of the 1-year and the 2-year subsidence area was lower than that in the control area, and the variability increased, but as the subsidence entered a stable period, the degree of variability decreased; vertically observed, in space distribution, the 0-10m soil moisture in the control area had obvious distribution rules with low spatial variability. However, the spatial variability of soil moisture in the 1-year subsidence area and the 2-year subsidence area increased, and the variability showed a trend of increasing continuously with the increase of depth. During the principal component analysis, it was found that the change of soil texture caused by coal mining subsidence, the change of microstructure of soil pores caused by geotechnical deformation, as well as the preferential flow caused by changes in groundwater level were the main reasons for the increasing spatial variability of soil moisture. This study revealed the principals of spatial variability of soil moisture in coal mining subsidence areas in Northwest China, which can provide a scientific basis for the restoration of mining areas.