Jinman Wang

Multi-fractal characteristics of the particle distribution of reconstructed soils and the relationship between soil properties and multi-fractal parameters in an opencast coal-mine dump in a loess area

Soil reconstruction is at the core of mine land reclamation. Reconstructed soil from an opencast mine dump in a loess area is a complex composite that was assembled by humans, using multiple reconstruction technologies. The soil is composed of varied soil particles with irregular shapes and has self-similar structure. To better quantify the characterization of reconstructed soil in this dump, the soil particle-size distribution from four modes of soil reconstruction in the Shanxi Pingshuo Antaibao opencast coal-mine dump was analyzed using multi-fractal theory. Soil reconstruction modes included loess material containing gravel (LG), loess material containing coal gangue (CG), total loess material (AL) and loess material containing ginger stone (LGS). Soil particle composition, gravel content, field water capacity, soil bulk density, soil organic matter, total nitrogen (TN), soil pH and electrical conductivity (EC) of different soil layers from different reconstruction modes were measured. A generalized dimension spectrum D(q), multi-fractal singularity exponent α(q) and multi-fractal spectrum function f(α(q)) were calculated. Relationships between soil properties and fractal parameters were analyzed. The results led to the following conclusions: (1) the soil particle distribution of reconstructed soil had significant multi-fractal characteristics in an opencast coal-mine dump in a loess area. D(0), D(1), D(1)/D(0), Δα and Δf can reflect the non-uniform particle-size distribution characteristics. D(0), D(1)/D(0) and Δf (or D(0), D(1)/D(0) and Δα) can be simplified as three parameters to quantify the multi-fractal characterization of the reconstructed soil particle distribution. (2) After reclamation, the soil quality from different layers of different profiles in different reconstruction modes shows some improvement. (3) There were strong correlations between multi-fractal parameters and soil properties. D(1) and Δα increased and D(1)/D(0) and Δf decreased with increasing gravel content, soil bulk density, organic matter, TN and soil EC; however, it was opposite for pH and field water capacity. Gangue and gravel have a definite impact on the dispersion degree of soil particles in reconstruction. This study provides a theoretical basis for land reclamation and quantitative expression of reconstructed soil particles’ distribution in opencast coal-mine dumps in loess areas.

Effect of byproducts of flue gas desulfurization on the soluble salts composition and chemical properties of sodic soils.

The byproducts of flue gas desulfurization (BFGD) are a useful external source of Ca2+ for the reclamation of sodic soils because they are comparatively cheap, generally available and have high gypsum content. The ion solution composition of sodic soils also plays an important role in the reclamation process. The effect of BFGD on the soluble salts composition and chemical properties of sodic soils were studied in a soil column experiment. The experiment consisted of four treatments using two different sodic soils (sodic soil I and sodic soil II) and two BFGD rates. After the application of BFGD and leaching, the soil soluble salts were transformed from sodic salts containing Na2CO3 and NaHCO3 to neutral salts containing NaCl and Na2SO4. The sodium adsorption ratio (SAR), pH and electrical conductivity (EC) decreased at all soil depths, and more significantly in the top soil depth. At a depth of 0–40 cm in both sodic soil I and sodic soil II, the SAR, EC and pH were less than 13, 4 dS m−1 and 8.5, respectively. The changes in the chemical properties of the sodic soils reflected the changes in the ion composition of soluble salts. Leaching played a key role in the reclamation process and the reclamation effect was positively associated with the amount of leaching. The soil salts did not accumulate in the top soil layer, but there was a slight increase in the middle and bottom soil depths. The results demonstrate that the reclamation of sodic soils using BFGD is promising.

Sodic Soil Properties and Sunflower Growth as Affected by Byproducts of Flue Gas Desulfurization

The main component of the byproducts of flue gas desulfurization (BFGD) is CaSO4, which can be used to improve sodic soils. The effects of BFGD on sodic soil properties and sunflower growth were studied in a pot experiment. The experiment consisted of eight treatments, at four BFGD rates (0, 7.5, 15 and 22.5 t ha−1) and two leaching levels (750 and 1200 m3 ha−1). The germination rate and yield of the sunflower increased, and the exchangeable sodium percentage (ESP), pH and total dissolved salts (TDS) in the soils decreased after the byproducts were applied. Excessive BFGD also affected sunflower germination and growth, and leaching improved reclamation efficiency. The physical and chemical properties of the reclaimed soils were best when the byproducts were applied at 7.5 t ha−1 and water was supplied at 1200 m3·ha−1. Under these conditions, the soil pH, ESP, and TDS decreased from 9.2, 63.5 and 0.65% to 7.8, 2.8 and 0.06%, and the germination rate and yield per sunflower reached 90% and 36.4 g, respectively. Salinity should be controlled by leaching when sodic soils are reclaimed with BFGD as sunflower growth is very sensitive to salinity during its seedling stage.

Evaluating relationships between soil chemical properties and vegetation cover at different slope aspects in a reclaimed dump

Conducting research about the relationships between soil chemical properties and vegetation coverage at different slope aspects is especially important in reconstructed ecosystems of vulnerable ecological regions. This study was conducted in the first reclaimed dump within the Pingshuo mining area of Shanxi Province, China, to analyze patterns of soil chemical properties (soil organic matter (SOM), soil total nitrogen (STN), soil available phosphorus (SAP) and soil available potassium (SAp) and vegetation coverage (NDVI) and their correlations at different slope aspects. In the reclaimed dump, 26 quadrats were established along four slope aspects (i.e., shady, semi-shady, sunny and semi-sunny slopes). There was no significant difference in SOM or STN among different slope aspects, while SAP differed between shady slopes compared to semi-shady, sunny and semi-sunny slopes; SAP differed significantly between semi-shady and semi-sunny slopes. The NDVI of semi-sunny slopes differed significantly from that of the other three aspects. There was variation in the relationships between NDVI and soil chemical properties, depending on the slope aspects. The logarithm of SOM and NDVI was related linearly on shady and semi-shady slopes, while NDVI was inversely related to the natural logarithm of the logarithm of SOM on sunny and semi-sunny slopes. STN and NDVI had a first-order function relationship on shady and semi-shady slopes, yet a quadratic function relationship on sunny and semi-sunny slopes. The relationships between SAP and NDVI were inverse on all types of slopes. On shady and semi-shady slopes, NDVI had a quadratic relationship with the logarithm of SAp, but it was well fitted by using a cubic function on sunny and semi-sunny slopes. The sensitivity coefficients of soil chemical properties and NDVI were different, and soil chemical properties changed differently depending on changes in NDVI at different slope aspects.