表土回覆是露天煤矿排土场生态修复的关键步骤,覆土厚度直接影响植物生长和复垦成本,为研究露天煤矿排土场不同覆土厚度对土壤水分入渗及植物水分利用的影响,采用室内土柱模拟试验,设置10,20,30,40,50 cm共5个覆土厚度,分别进行垂直入渗试验和室内盆栽试验(玉米),并结合氢氧同位素稳定示踪技术,研究不同覆土厚度土壤入渗和玉米水分利用特征,筛选研究区排土场最佳覆土厚度。结果表明:覆土厚度为10~30 cm(27.05~33.02 mm/min)的初始入渗速率显著高于40~50 cm(21.59~24.89 mm/min)的初始入渗速率(p<0.05),稳定入渗速率随覆土厚度的增加而增大,当覆土厚度高于40 cm后,随着覆土厚度的增加稳定入渗速率维持在3 mm/min左右。矸石层入渗过程受覆土层的影响较大,覆土厚度高于40 cm后,矸石层入渗速率基本稳定在土层连接面的入渗速率上。不同覆土厚度下玉米木质部水氢氧同位素值与土壤水氢氧同位素随土层变化曲线交点主要集中在覆土层,因此,玉米生长水分主要来源于覆土层。覆土厚度越大,2条线交点增多、交点分布范围增大,玉米对土壤水分的利用范围越大,当覆土厚度超过40 cm后,玉米水分利用范围基本维持在10~40 cm。结合阜新市最大降雨强度190 mm/h,该地区露天矿排土场覆土厚度应高于40 cm。
Topsoil restoration is a key step in the ecological restoration of the dump of open pit coal mine, and the thickness of soil cover directly affects plant growth and reclamation cost. In order to study the influence of the thickness of soil cover on soil water infiltration and plant water utilization in open pit mine dump, indoor soil column simulation test was adopted in this study. Five cover thicknesses of 10 cm, 20 cm, 30 cm, 40 cm and 50 cm were set up, and vertical infiltration test and indoor pot test (corn) were conducted, respectively. Combined with hydrogen and oxygen isotope stable tracing technology, soil infiltration and water use characteristics of corn with different cover thicknesses were studied to screen the optimal soil cover thickness for the waste dump in the region. The results showed that:the initial infiltration rate with a soil cover thickness of 10~30 cm (27.05~33.02 mm/min) was significantly higher than that with a soil cover thickness of 40~50 cm (21.59~24.89 mm/min) (p<0.05). The stable infiltration rate increased with the increasing of soil cover thickness. When the soil cover thickness was greater than 40 cm, the infiltration rate remained at about 3 mm/min with the increasing of the soil thickness. The infiltration process of gangue layer was greatly affected by the soil cover thickness. When the thickness of overlying soil was greater than 40 cm, the infiltration rate of gangue layer was basically stable at the infiltration rate of soil layer interface. The intersection between water hydrogen and oxygen isotope values of maize xylem and soil water hydrogen and oxygen isotope values with different soil thickness was mainly concentrated in the overlying soil layer. Therefore, the growth water of maize mainly came from the overlying soil layer. The greater the soil cover thickness was, the more intersection points of the two lines and the larger the distribution range of the intersection points, the larger the soil water utilization range of maize was. When the soil cover thickness was more than 40 cm, the water utilization range of maize was basically maintained within the range of 10~40 cm. Considering the maximum rainfall intensity of 190 mm/h in Fuxin city, the optimal reclamation thickness of open-pit dump in this area should be higher than 40 cm.