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

Abstract

In China, coalmine wastes, such as gangues, are used for reclamation of mining subsided land. However, as waste rocks, gangues contain several trace metal elements, which could be released under natural weathering and hydrodynamic leaching effects and then migrate into the reclamed soil layer. However, it is very difficult to find adequate other backfill materials for substitution of gangues. In this paper, we present a novel method and case study to restrict the migration ability of trace metal elements in gangues by using another kind of coalmine solid waste—fly ashes from coal combustion. In this study, fly ashes were mixed with gangues in different mass proportions 1:0.2, 1:0.4, 1:0.6 and 1:0.8 as new designed backfill materials. Due to the help of fly ash, the occurrence states of studied trace metal elements were greatly changed, and their releasing and migration ability under hydrodynamic leaching effect were also significantly restricted. In this research seven trace metal elements in gangues Cu, Zn, Pb, Cd, Cr, Mn and Ni were studied by using soil column hydrodynamical leaching method and simulated precipitation for one year. The results show that under the driving of natural precipitation trace metal elements were generally transported deep inside the reconstructed land base, i.e., far away from soil layer and most of the trace metal elements were transformed into a bonded state, or combined in inert occurrence states, especially the residual state. With this method, the migration activities of tested trace metal elements were greatly restricted and the environmental potential risk could be significantly reduced.

Assessing the ecological regime and spatial spillover effects of a reclaimed mining subsided lake: A case study of the Pan'an Lake wetland in Xuzhou

“…From 2010, Jiawang District began to carry out land reclamation and ecological restoration projects in the coal mining area. As China's first wetland park developed through the land reclamation and ecological restoration of a coal mine subsidence area, the Pan'an Lake wetland has been constructed following a four-pronged model integrating "basic farmland rectification, coal mining subsidence reclamation, ecological environment restoration and wetland landscape development", and the constructed wetland covers roughly 10 square kilometres [39,40]. Through land reclamation and ecological restoration, landscape patterns and ecological environments in the mining subsidence area have changed, and ecological functions such as those of atmospheric regulation, water conservation, entertainment, waste treatment, food production and biodiversity protection are improving [18].…”

Responses of Natural Microorganisms to Land Reclamation and Applications of Functional Microorganisms in Biorestoration of Coal Mining Area

“…Gangues and coal combustion byproducts, like fly ash, have been used for the reclamation of mining subsided land in some areas. However, it is controversial as gangues and fly ash may contain high amounts of trace elements and may threaten the surrounding environment [22].…”

Do the Reclaimed Fungal Communities Succeed Toward the Original Structure in Eco-Fragile Regions of Coal Mining Disturbances? A Case Study in North China Loess—Aeolian Sand Area

“…For degraded ecosystems in general, natural restoration with longer restoration cycles can increase vegetation cover, soil nutrients, etc. However, the coal mining disturbance is so intense and persistent that the mining area can be called an extremely disturbed site, prone to serious environmental impacts (Bian et al, 2012;Michieka, 2014;Huang et al, 2018). Self-recovery is more difficult in the short term and must be guided by artificial measures in advance, using methods such as planting ecological forests to accelerate the natural succession process, which is then known as mine site ecological restoration.…”