Variations in organic carbon, aggregation, and enzyme activities of gangue-fly ash-reconstructed soils with sludge and arbuscular mycorrhizal fungi during 6-year reclamation

Abstract

Mining activities can cause drastic disturbances in soil properties, which adversely affect the nutrient cycling and soil environment. As a result, many efforts have been made to explore suitable reclamation strategies that can be applied to accelerate ecology restoration. In this study, we reconstructed mine soils with fly ash, gangue, sludge, planted ryegrass, and inoculated arbuscular mycorrhizal fungi (AMF) in Pangzhuang mine of Xuzhou during 2009 to 2015. The soil aggregation process, enzyme activities (i.e., invertase, urease and acid phosphatase activities), soil organic carbon (SOC) as well as other soil nutrients such as nitrogen, phosphorus, and potassium contents of the reconstructed mine soils were monitored during 6-year reclamation. The integrated application of sludge and AMF led to a promising reclamation performance of mining areas, in which soil aggregate stability, enzyme activities, SOC, and ryegrass biomass were effectively enhanced. The micro-aggregates (< 0.25 mm) decreased with the increase of macro-aggregates (> 0.25 mm) during the reclamation, indicating that macro-aggregates were gradually formed from micro-aggregates during the pedogenesis of reconstructed mine soils. The correlation analysis shows that SOC contents in aggregate fraction of 0.25∼0.5 mm were correlated with aggregate distribution and enzyme activities. Enzyme activities, however, were not significantly correlated with aggregate distribution. The outcomes from the present study could enrich our understanding on soil property changes in pedogenesis process of reconstructed mine soils, and meanwhile, the employment of sludge combined with AMF is suggested to be an effective alternative for the mine soil reclamation.

Role of Arbuscular Mycorrhizal Fungi in Plant Growth Regulation: Implications in Abiotic Stress Tolerance

“…Very rare research reports are available in the literature demonstrating the role of AMF in mitigation of combined effects of two or more stresses. AMF symbiosis protects plants against a variety of abiotic stresses using various processes such as improved photosynthetic rate, uptake and accumulation of mineral nutrients, accumulation of osmoprotectants, up-regulation of antioxidant enzyme activity, and change in the rhizosphere ecosystem (Bárzana et al, 2015; Calvo-Polanco et al, 2016; Yin et al, 2016). Several studies have shown improved nutritional status of AMF plants under osmotic stress conditions (Augé et al, 2014; Lehmann et al, 2014; Lehmann and Rillig, 2015) resulting from deficit irrigation or salinity.…”

Fly Ash Modified Coalmine Solid Wastes for Stabilization of Trace Metals in Mining Damaged Land Reclamation: A Case Study in Xuzhou Coalmine Area

“…Trace elements like Mn and Cu were still not restricted significantly, in future works, more trace elements, more proportioning of backfill materials from different coalmines should be tested. Yin et al reported by using flay ash in reclamation, it could have influence on physical structure of reconstructed overlaying soil, by using sludge and fungi could restore the soil aggregations and the soil organic carbon [ 6 ]. Therefore in future studies we should also considered the optimization of soil quality, at the same time of contamination control.…”

“…At present, in China there are about 4.5 billion tons of coalmine solid wastes are stored in dumps: worse still is that the dumps keep increasing around 0.95 billion tons/year. At present, there are totally about 1500 coalmine waste dumps in China, which occupy more than 8 × 10 4 hm 2 land areas [ 5 , 6 , 7 , 8 , 9 ]. Mining subsidence and dumps destroy land resources and make them to be unavailable for any uses.…”

“…Coalmine wastes have huge yields in local areas e.g., in Xuzhou City, which has a coal mining history of more than 130 years; only huge amounts of gangues could fulfill the demands of backfill materials in large subsided area [ 1 , 2 , 13 , 14 , 15 ]. The subsided land reclamation could be divided into three processes: “reshaping”, “resoiling” and “replanting” [ 1 , 2 , 4 , 5 , 6 , 7 ]. For backfill reclamation, the mining solid wastes are only used for “reshaping” of subsided land, i.e., they constitute the base material of overlaying soil layers to upraise the surface to achieve ground level, on which the plants are rehabilitated.…”

“…Gangues and fly ash also contain several kinds of trace metals such like lead (Pb), cadmium (Cd), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn) etc., which are always hazardous to overlaying soil layers. In China, the “Directives of land resource reclamation” had regulated that among use types of reclaimed land, the agricultural use has the highest priority [ 2 , 4 , 5 , 6 , 7 , 13 , 14 ]. Related researchers have pointed out that there are risks of the trace metal elements releasing from mining wastes, as well as probabilities of migration into the plants and crops under certain circumstance conditions of reconstructed soil layers [ 4 , 5 , 12 , 13 , 16 , 17 , 18 ].…”