Effect of Environmental Factors on Soil Nutrient Loss under Conditions of Mining Disturbance in a Coalfield

Underground coal mining can result in land deformation (e.g., land subsidence and ground fissures), and may consequently change the soil nutrients. Soil organic matter (SOM), total nitrogen (TN), and available phosphorus (AP) are critical indicators of soil fertility and eco-restoration in mining areas. In this study, soil samples (depth: 0–20 cm) were collected twice from 20 sampling points in pre-mining and post-mining in the No.12 panel of Caojiatan coalfield, in the Loess Plateau of China. SOM, TN, and AP in soil samples were measured, and the nutrient loss was evaluated. Ten environmental factors affecting soil nutrient loss were identified from a 5-m resolution digital elevation map (DEM). The paired t-test was utilized to evaluate the differences between SOM, TN, and AP in pre-mining and post-mining soil. The mechanisms of the effects of environmental factors on soil nutrient loss were revealed based on multiple linear regression, redundancy analysis (RDA), and the random forest algorithm (RF). Ordinary kriging and RF were utilized to predict and optimize the spatial distribution of the soil nutrient loss. The results showed that significant differences existed between the SOM, TN, and AP in the pre-mining and post-mining soil. The model established by RF provided a higher accuracy in terms of fitting the correlation between soil nutrient loss and environmental factors compared to the model established by multiple linear regression, and the feature importance obtained by RF showed that profile curvature, distance to working panel margin, and surface roughness were the most significant factors affecting the loss of SOM, TN, and AP, respectively. This study provides a theoretical reference for eco-restoration, as well as soil and water conservation, in subsided lands in coalfields

Application of the two-group - one-region and two-region - one-group Feynman-alpha formulas in safeguards and accelerator-driven system (ADS)

The applicability of the two-group (one-region) and two-region (one-group) Feynman-alpha (variance to mean) formulas was assessed with regards to applications in safeguards and accelerator-driven system (ADS) considered as an option for transmutation of nuclear wastes. Since two-group calculations with the master equation technique when both thermal and fast fissions are included, have not been performed earlier, investigation of this problem has a methodological value of its own. The potential applications of the two-group - one-region and two-region - one-group Feynman-alpha approaches in nuclear safeguards were evaluated and compared to the results of Monte-Carlo simulations

Gully Morphological Characteristics and Topographic Threshold Determined by UAV in a Small Watershed on the Loess Plateau

Gully erosion is an important sediment source in small watershed, and causes severe land degradation, particularly in semi-arid regions. Accurately measuring gully morphological characteristics, and determining its topographic threshold, are vital for gully erosion simulation and control. In this study, 910 gullies were visually interpreted by unmanned aerial vehicle (UAV) technology combined with field measurement. Ten gully morphological characteristics were extracted from the digital orthophoto map (DOM) and digital elevation model (DEM) generated by UAV images, including gully length (L), circumference (C), plane area (PA), surface area (SA), volume (V), depth (D), top width (TW), mean width (MW), cross-sectional area (CSA), and ratio of top width to depth (TW/D). The morphological characteristics of 30 reachable gullies were measured by a real time kinematic (RTK) to validate the parameters extracted from the UAV images. The topographic thresholds were determined based on the local slope gradient (S) and upland drainage area (A), using a dataset of 365 gully heads and their corresponding land-use types. The results show that the mean absolute percentage errors (MAPE) of the 2D and 3D gully characteristics are less than 10% and 20%, respectively, demonstrating a high accuracy of gully characteristic extraction from UAV images. Gully V is significantly related to the other nine parameters. Significant power functions were fitted between V, and L, C, PA, and SA. The gully volume could be well-estimated by SA (V = 0.212 SA0.982), with a R2 of 0.99. For all land-use types, the topographic threshold could be described as S = 0.61 A0.48, implying that water erosion is the dominant process controlling gully erosion in this region. The topographic threshold is land-use-dependent, and shrubland is hardest for gully incision, followed by grassland and cropland. The results are helpful to rapidly estimate gully erosion, and identify the areas for gully erosion mitigation in small watershed

Application of the two-group - one-region and two-region - one-group Feynman-alpha formulas in safeguards and accelerator-driven system (ADS)

The applicability of the two-group (one-region) and two-region (one-group) Feynman-alpha (variance to mean) formulas was assessed with regards to applications in safeguards and accelerator-driven system (ADS) considered as an option for transmutation of nuclear wastes. Since two-group calculations with the master equation technique when both thermal and fast fissions are included, have not been performed earlier, investigation of this problem has a methodological value of its own. The potential applications of the two-group - one-region and two-region - one-group Feynman-alpha approaches in nuclear safeguards were evaluated and compared to the results of Monte-Carlo simulations

Correlations between plant and soil for their C, N, P contents and stoichiometry on the steep gully slopes

Steep gully slope is the primary geomorphic composition on the Loess Plateau with serious soil erosion. The impact of plant (leaf, litter and root) on soil nutrients and their stoichiometric characteristics, and the correlations between them are not yet fully understood on steep gully slopes. This study was conducted to identify the correlations of carbon (C), nitrogen (N), phosphorus (P) contents and their stoichiometry between soil, and leaf, litter and root under typical plant communities on Chinese Loess Plateau's steep gully slopes. Total six communities (two shrubs and four grasses) and one farmland planted with Zea mays (control) were tested. Within the selected quadrat (shrub of 2 m × 2 m, grass of 1 m × 1 m), the fresh and mature leaves were firstly taken in different positions of the plant, and then all the surface litters were gathered. Root and soil were taken from the 0–120 cm depth, which was divided into seven soil layers (0–10, 10–20, 20–30, 30–40, 40–60, 60–80 and 80–120 cm). Our results revealed that significant differences were detected in C, N, P contents and stoichiometry of plant (leaf, litter and root) and soil among most of plant communities. For various plant communities, shrub communities had higher contents of C, N and P in leaves, litter and roots. Soil organic carbon and total nitrogen contents declined with soil depth by 61% to 87% and 45% to 77%, respectively. Total contents of soil P and root C, N, P varied irregularly along with soil. It was proved that shrub communities were relatively P-deficient, while farmland and grass communities were N-limited. Besides, partial N and P nutrients were released to soil from litter on steep gully slopes. Significant correlations between soil C, N, P contents and that of the root and litter were examined. Furthermore, the correlations became more significant when C, N and P nutrients of root and litter were quantified by their storages. This study offers a deep understanding of the interactions between soil and plant nutrients, which is conducive to future ecological environment management and improvement in the semi-arid region

Gully Morphological Characteristics and Topographic Threshold Determined by UAV in a Small Watershed on the Loess Plateau

Gully erosion is an important sediment source in small watershed, and causes severe land degradation, particularly in semi-arid regions. Accurately measuring gully morphological characteristics, and determining its topographic threshold, are vital for gully erosion simulation and control. In this study, 910 gullies were visually interpreted by unmanned aerial vehicle (UAV) technology combined with field measurement. Ten gully morphological characteristics were extracted from the digital orthophoto map (DOM) and digital elevation model (DEM) generated by UAV images, including gully length (L), circumference (C), plane area (PA), surface area (SA), volume (V), depth (D), top width (TW), mean width (MW), cross-sectional area (CSA), and ratio of top width to depth (TW/D). The morphological characteristics of 30 reachable gullies were measured by a real time kinematic (RTK) to validate the parameters extracted from the UAV images. The topographic thresholds were determined based on the local slope gradient (S) and upland drainage area (A), using a dataset of 365 gully heads and their corresponding land-use types. The results show that the mean absolute percentage errors (MAPE) of the 2D and 3D gully characteristics are less than 10% and 20%, respectively, demonstrating a high accuracy of gully characteristic extraction from UAV images. Gully V is significantly related to the other nine parameters. Significant power functions were fitted between V, and L, C, PA, and SA. The gully volume could be well-estimated by SA (V = 0.212 SA0.982), with a R2 of 0.99. For all land-use types, the topographic threshold could be described as S = 0.61 A0.48, implying that water erosion is the dominant process controlling gully erosion in this region. The topographic threshold is land-use-dependent, and shrubland is hardest for gully incision, followed by grassland and cropland. The results are helpful to rapidly estimate gully erosion, and identify the areas for gully erosion mitigation in small watershed

Derivation of two-group two-region Feynman-alpha formulas and their application to Safeguards and accelerator-driven system (ADS)

The theory of the Feynman-alpha method was extended to two-energy groups and two-regions by the use of the Chapman - Kolmogorov equation with complete description of various processes including all reaction intensities for neutrons. This paper presents a full derivation of the variance to mean formula with the forward approach, as well as quantitative evaluation of the formula with regards to applications in safeguards and accelerator-driven system. The quantitative assessment was made through MCNPX and MCNP-PoliMi simulations. The motivation for this work is related to the fact that the traditional one-group (and one-region) variance to mean formula was elaborated and used for thermal systems in which the thermal flux and the lifetime of thermal neutrons dominates. However, this approach does not fully describe the fast neutron systems, as well as heavily reflected thermal systems, since the effects of the reflector play a significant role in the latter. Thus, a two-group two-point master equation approach might lend the possibility of treating a fast multiplying material surrounded with a reflector in a more accurate way, by treating the counts separately in the fast and the thermal groups (or in the fissile and reflector regions). Investigation of this problem has a methodological value of its own since, for example, two-group calculations with the master equationtechnique when both thermal and fast fissions are included, have not been performed earlier

A general analytical solution for the variance-to-mean Feynman-alpha formulas for a two-group two-point, a two-group one-point and a one-group two-point cases

This paper presents a full derivation of the variance-to-mean or Feynman-alpha formula in a two-energy-group and two-spatial-region treatment. The derivation is based on the Chapman-Kolmogorov equation with the inclusion of all possible neutron reactions and passage intensities between the two regions. In addition, the two-group one-region and the two-region one-group Feynman-alpha formulas, treated earlier in the literature for special cases, are extended for further types and positions of detectors. We focus on the possibility of using these theories for accelerator-driven systems and applications in the safeguards domain, such as the differential self-interrogation method and the differential die-away method. This is due to the fact that the predictions from the models which are currently used do not fully describe all the effects in the heavily reflected fast or thermal systems. Therefore, in conclusion, a comparative study of the two-group two-region, the two-group one-region, the one-group two-region and the one-group one-region Feynman-alpha models is discussed

Derivation of two-group two-region Feynman-alpha formulas and their application to Safeguards and accelerator-driven system (ADS)

The theory of the Feynman-alpha method was extended to two-energy groups and two-regions by the use of the Chapman - Kolmogorov equation with complete description of various processes including all reaction intensities for neutrons. This paper presents a full derivation of the variance to mean formula with the forward approach, as well as quantitative evaluation of the formula with regards to applications in safeguards and accelerator-driven system. The quantitative assessment was made through MCNPX and MCNP-PoliMi simulations. The motivation for this work is related to the fact that the traditional one-group (and one-region) variance to mean formula was elaborated and used for thermal systems in which the thermal flux and the lifetime of thermal neutrons dominates. However, this approach does not fully describe the fast neutron systems, as well as heavily reflected thermal systems, since the effects of the reflector play a significant role in the latter. Thus, a two-group two-point master equation approach might lend the possibility of treating a fast multiplying material surrounded with a reflector in a more accurate way, by treating the counts separately in the fast and the thermal groups (or in the fissile and reflector regions). Investigation of this problem has a methodological value of its own since, for example, two-group calculations with the master equationtechnique when both thermal and fast fissions are included, have not been performed earlier