Effects of coal gangue filling on drainage performance, soil fertility and heavy metal pollution in erosion gully

Abstract: In order to explore the suitable technology for the reclamation of erosion gullies in the black soil area of the Northeast China. In this paper, Xinhua farm is selected as the research area which is located in Hegang City, Heilongjiang Province, China. Aiming at the cause of erosion gullies, a new technology of filling and reclamation erosion gully with coal gangue was introduced and the post effect of the new technology was studied, including, the technological process of filling and reclamation, the influence of the thickness change of reclamation filling materials on the drainage characteristics of the gully, the fertility status and heavy metals pollution degree in the reclaimed soil. This paper aimed to explore the feasibility and breakthrough points of the technology of filling erosion gullies with coal gangue. The results showed that: 1) The increase in soil layer thickness could weaken the drainage capacity of the gully, while the increase of mixed size coal gangue thickness and large size coal gangue could increase the drainage capacity of the gully in different degrees. The interaction between the soil layer thickness and large size coal gangue layer thickness obviously influenced the drainage capacity of the gully. When the thickness of soil layer, mixed size coal gangue layer and large size coal gangue layer were 53.42, 38.51, 90 cm respectively, the shortest outflow time was 145.129 s , the drainage capacity of simulated 2 m deep gully was the strongest in this mode. 2) After 4 years of gully reclamation, the soil bulk increased, the soil acidity improved, the content of total potassium was the same as CK, but the total nitrogen, total phosphorus and organic matter content were lower than CK. And then the comprehensive fertility of soil was less than CK, which is 66.71%-80.81% of CK, and the average level only reach to 72.75%. But it was slightly higher than that of the second accumulated temperature zone in Heilongjiang Province. 3) The content of Pb was basically the same as CK and background value of local control soil; however, as for Cr and Cu, they were higher than CK and background value of local control soil in the reclaimed soil of monitoring gully. But the content of Cr, Pb, Cu are not higher than the second level standard value of national environmental quality of China. . There are slight pollution and slight enrichment of heavy metals Cr, Pb and Cu in monitored gully reclamation soil, so coal gangue can be used as a material for filling erosion gully for reclamation. However, in the long term, attention should be paid to the problem of soil heavy metal enrichment during reclamation.