Mining leads to soil degradation and land subsidence, resulting in decreased soil quality. However, there are limited studies on the detailed effects of mining activities on soil properties, particularly in western aeolian sand. This study, therefore, quantitatively assessed the aeolian sandy soil disturbance induced by mining activities in the contiguous regions of Shanxi, Shaanxi, and Inner Mongolia. The following soil physical quality indices were measured in the pre (May 2015), mid (October 2015), and postmining period (April 2016), such as the soil water content (SWC), particle size (PS), soil penetration (SP), and soil saturated hydraulic conductivity (SSHC). The results showed that mining activities brought irreversible effects on soil structures. In the pre-mining period, land subsidence broke up large soil particles, destroying soil structure, leading to decreased PS (218.33 vs. 194.36 mu m), SP (4615.56 vs. 2631.95 kPa), and subsequently decreased SSHC (1.12 vs. 0.99 cm/min). Rainfall during the midmining period exacerbated this fragmentation. Thereafter, low temperatures and humidity caused the soil to freeze, allowing the small soil particles to merge into larger ones. Meanwhile, the natural re-sedimentation, subsidence, and heavy mechanical crushing in the post-mining period increased PS and SP. The SSHC hence increased to 1.21 cm/min. Furthermore, the evaluation of soil indices from different stress zones showed that the external pulling stress zone always had a higher SSHC than the neutral zone in any mining period, possibly due to the presence of large cracks and high SWC. This study contributes to the understanding of the impact of mining activities on soil physical qualities, providing a theoretical basis and quantitative guidance for the surface damage caused by coal mining in the aeolian sandy area in Western China.

Quantification and evaluation ofthe spatiotemporal changes in soil quality is importantto understand soil degradation mechanisms and restore the damaged land productivity. However, the effects of coal mining subsidence on the spatial and temporal characteristics of soil quality are not well understood. We investigated the contents of pH, organic matter (OM), total nitrogen (TN), nitrate nitrogen (NN), ammonia nitrogen (AN), total phosphorus (TP), available phosphorus (AP), available potassium (AK), total potassium (TK), cation exchange capacity (CEC), sucrase activity (SA), urease activity (UA), phosphatase activity (PA), catalase activity (CA) and dehydrogenase activity (DA) in the coal mining subsided area. The results showed that the contents of TN, NN, AN, TP, AK, TK, SA, UA, PA, CA and DA exhibited significant (P < 0.05) differences among the four seasons. Compared with the upper layer (0-20 cm), the lower layer (20-40 cm) contained higher contents of AN, NN, TN, TP and TK but lower contents of SA, UA, PA, CA and DA. The NN, AP, TP, AK and UA were identified as key indicators in the minimum dataset using principal component analysis. The seasonal changes of soil quality index (SQI) were in the following order: winter (0.707), spring (0.681), summer (0.616), and autumn (0.563). The spatial changes of SQI were highest for middle slope position 3 (0.508), followed by lower slope position 4 (0.507), top slope position 1 (0.446), upper slope position 2 (0.442), and bottom slope position 5 (0.437). Based on these spatiotemporal changes in soil quality, it was suggested that the application of multiple land use types may be a useful method for land reclamation and the interest of local farmers in the coal mining subsided area.

Loess has unique physical, hydrodynamic and mechanical properties, which are influenced by both internal and external geological processes, as well as human engineering activities. Consequently, surface disasters are especially prevalent in the Loess region of China. The study area is situated in the middle part of L & uuml;liang Mountain in the middle part of the Loess Plateau, which is characterised by a typical loess landform with a complex system of gullies and hill ridges. According to current theory, the cracking boundary of the goaf profile is a straight line. However, these surface disasters are actually caused by the shear action of the deep rock layer and the original vertical joint structure of the loess. By analysing the cracking process of the 'Goaf-Overburden-Loess' in the study area, it can be found that the boundary of the movement basin presents a broken line shape, which has important implications for the accurate estimation of the area affected by loess-type surface subsidence.