Abstract
Coal mining, as one of the key drivers of land degradation worldwide, caused land subsidence problems. In this study, we conducted experimental research to explore the reclaimed mine soil (RMS) water dynamics and its sources in relation to reclaimed land use types using stable water isotopes in the Longdong coal mining area with high groundwater level in east China. We collected water samples seven times in 2017 from all of these water bodies (precipitation, surface waters (river water and water from subsidence pits (WSP)), groundwater and soil water). Our main findings are three fold: (1) the values of slope and intercept of the local meteoric water line of Craig (LMWL) of precipitation for the study area are higher than the global meteoric water line of Craig (GMWL) because of the humid monsoon climate zoon, and the values of δD and δ18O of surface waters and soil water and groundwater deviated from LMWL to some extent with a range of 5–30%, and the D and 18O of precipitation and the surface waters have higher seasonal variation than groundwater; (2) the values of δD and δ18O of RMS for the whole soil profile (0–100 cm) are lower than that of precipitation and have obvious seasonal variations and great fluctuation in the topsoil (0–30/40 cm) and decrease at depth (30/40–70 cm) and stable in deep soil layers (below 70 cm deep); (3) the RMS with forest and crop enhanced water infiltration capacity and soil water mixing strength compared with the waste RMS, so establishment of forest and crops should be encouraged in the RMS; (4) the main sources of topsoil (0–30 cm for crop and 0–40 cm for forest) of RMS are precipitation through infiltration, the main supply for deep soil water (below 70 cm deep) is groundwater, and the soil water for the middle deep soil layers (30/40–70 cm) is mainly from mixing sources of precipitation, groundwater, and river water through pant root water absorbing and groundwater upshifting.
Highlights
Soil plays an important role in the hydrology, biodiversity, geochemical cycles, and human health and produces services goods and resources for humankind.Coal mining is one of the key drivers of land degradation worldwide both in developed nations such as USA, England, Australia, and Spain and emerging economies such as China, India, and Africa [1]
Precipitation is an important link of water cycle, and its isotope composition is determined by the original conditions of vapor sources, atmospheric circulations, and moisture transport processes and pathways [3,51], especially at watershed scales, the δD and δ18 O composition of rainfall is affected by the large scale factors, such as continental effect and latitude effect, and affected by local factors, such as precipitation, temperature, topography, and landform [2,3,50,51]
Based on water stable isotope analysis, we found that the topsoil (0–30 cm for crop and 0–40 cm for forest) of reclaimed mine soil (RMS) was mainly influenced by precipitation through infiltration, the deep soil water
Summary
Coal mining is one of the key drivers of land degradation worldwide both in developed nations such as USA, England, Australia, and Spain and emerging economies such as China, India, and Africa [1]. Reclamation of disturbed soils is done with the primary objective of restoring the land. Understanding the restoration processes of reclaimed mine soil (RMS) is crucial to the global sustainable development. China is the largest producer of coal in the world, and its coal production accounts for approximately half of the global production and underground (well) mining is the major coal mining way, which produces approximately 92% of the raw coal in China [2,3]. The resulted land subsidence has emerged as the most prominent problem in coal mining areas. Land subsidence destroys large areas of arable land and threatens the local food security and water logging in the subsided land area
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