模拟降雨条件下赤泥对土壤盐碱化的影响

为了解不同厚度赤泥在酸雨和雨水淋溶条件下对土壤盐碱化的影响,以山西某堆场赤泥为研究对象,采用土柱淋溶实验研究在模拟酸雨和雨水条件下,覆盖不同厚度赤泥对土壤pH、碱化度(ESP)以及电导率(EC)的影响。所用土壤为堆场附近背景土壤,其pH为8.68,有机质含量为25.66 g·kg-1,容重为1.20 g·cm-3,含水率为12.01%。结果表明:经淋溶后,土壤pH在表层0~10 cm深度显著升高,最大值达到10.18;在10~30 cm增加到8.67~9.12,与原始土壤相比升高较为明显;在30~60 cm深度没有明显变化。除覆盖5 cm厚赤泥经雨水淋溶组之外,其他实验组表层(0~10 cm)土壤ESP值均超过15.00%,土壤呈碱化状态;在10~40 cm深度土壤ESP增加到5.38%~14.70%范围,有碱化趋势,对40 cm以下深度土壤碱化影响较小。所有实验组中土壤EC值仅略有增加,对土壤盐化影响不明显。赤泥中钠、钾、镁、钙具有较强的迁移性,淋出液中最大浓度分别为125.86、2.23、57.13、209.07 mg·L-1,可能会对地下水造成潜在影响。在实验条件下,赤泥对土壤碱化影响较为明显,且碱化影响随覆盖赤泥厚度增加而增大,酸雨淋溶比雨水淋溶影响更为严重。

Effects of bauxite residue on soil salinize-alkalization under simulated rainfall conditions

To understand the influence of alkaline substances from bauxite residue under simulated acid rain and rainfall, a soil column experiment with bauxite residue of different thicknesses was conducted. The soil saline-alkali indicators included soil pH, exchangeable sodium percentage(ESP), and electric conductivity(EC). The pH, organic matter, bulk density, and water content of the soil around the bauxite residues storage facility were 8.68, 25.66 g·kg^-1, 1.20 g·cm^-3, and 12.01%, respectively. Results indicated that the pH of soil at 0~10 cm depth increased significantly, and the maximum pH was 10.18. Compared with the original soil, the soil pH at 10~30 cm depth increased to 8.67~9.12, and there were no obvious changes at 30~60 cm depth. The ESP of surface soils(0~10 cm) were lower than 15% in the condition of 5 cm bauxite residue coverage under simulated rainfall, while ESP in other conditions were higher than 15%, which indicated that the soil alkalization occurred. The soil ESP at 10~40 cm depth increased to 5.38%~14.70%, which presented a trend of alkalization. With only a slight increase of EC, the salinization of soil was not obvious. The maximum concentrations of the leachates Na, K, Mg, and Ca were 125.86, 2.23, 57.13, and 209.07 mg·L^-1, respectively, which indicate strong migration, potentially influencing the groundwater. Under trial conditions, the effects of bauxite residue on soil alkalization were more significant and increased with the thickness of the bauxite residue coverage. Moreover, the effects were more serious with the acid rain leaching than with rainfall.