菱镁矿区土壤污染及修复试验

Experimental study on soil pollution and restoration in magnesite area

菱镁矿在煅烧制备氧化镁过程中产生大量的氧化镁粉尘,降落到土壤表面容易形成土壤结皮,降低土壤孔隙度,减弱土壤渗透速率。采用土柱淋洗方式在室内模拟氧化镁粉尘对土壤的渗透性影响及修复过程。向土柱中的土壤加入氧化镁粉尘模拟自然条件下氧化镁粉尘对土壤渗透速率影响;以石膏作为改良剂通过与氧化镁粉尘及土壤混合考察石膏修复氧化镁粉尘污染土壤的效果,并用扫描电镜观察石膏作用前后土壤表面形态变化。结果表明:空白对照组土壤两次淋洗后渗透速率稳定在0.367 mm·min^(-1);加入氧化镁粉尘后土壤渗透速率降低至0.214 mm·min^(-1),氧化镁粉尘污染土壤渗透速率显著降低(P<0.05);加入石膏和氧化镁粉尘的土柱经两次淋洗后土壤渗透速率稳定在0.425 mm·min^(-1),与氧化镁粉尘污染土壤相比,加入石膏后土壤渗透速率显著提高(P<0.05);扫描电镜图显示,加入石膏后土壤表面呈网状结构,土壤表面的孔隙度及稳定性提高,有利于改善土壤渗透性能。

Magnesium oxide dusts produced during calcination fall to the soil surface and easily form magnesian soil crust in magnesite mining area,which would reduce soil porosity,weaken soil infiltration rate,and be harmful to soil quality. Using a soil column leaching device,an experiment was carried out to examine the influence of magnesium oxide dust on soil infiltration and the processes of soil remediation. Soil crust was formed by adding magnesium oxide dust to the soil column,gypsum was used as a modifier to inhibit the formation of crusts,and the morphological changes of soil crusts were observed by scanning electron microscope（ SEM）. The results showed that the control group after leaching for two times,the soil infiltration rate was stable at 0.367 mm·min-1. After adding magnesium oxide to the soil,the soil infiltration rate was significantly decreased to 0. 214 mm · min-1. When gypsum and magnesium oxide were combined added into soil column,the soil infiltration rate was stable at 0.425 mm·min-1 after leaching for two times,suggesting that the soil infiltration rate increased significantly after gypsum addition compared to that contaminated by magnesium oxide dust. The SEM diagram showed that the soil surface after adding gypsum exhibited a reticular structure and that the porosity and stability of the soil surface were improved,which would increase the permeability of the soil.