植被恢复对重金属污染土壤有机质及团聚体特征的影响

采用田间原位试验,研究了不同植被恢复3年对重金属污染土壤有机碳及团聚体结构和稳定性的影响,评价了不同植物修复效果的差异,为农田重金属污染土壤修复中,合理选择植被类型,以及建立评价标准提供理论依据。在某Cu,Cd重度污染农田建立田间小区,施加钝化材料石灰(对照除外)后种植海州香薷(ME),伴矿景天(MS)和巨菌草(MP)3种植物,3年的田间原位修复试验后,分析各处理下土壤有机质含,0.25 mm机械稳定性团聚体(DR_(0.25))和水稳定性(WR_(0.25))团聚体含量,团聚体平均质量直径(MWD),几何平均直径(GMD),团聚体稳定率(AR,%)和分形维数(D)等团聚体稳定性指标。结果表明,3年植被恢复后,3种植被处理均提高了土壤有机质含量,提高幅度为2.89%~5.39%,并提高了0.25mm机械稳定性团聚体(DR_(0.25))和水稳定性(WR_(0.25))团聚体含量,提高幅度分别为2.89%~5.39%,6.64%~10.40%和13.34%~17.48%。3种植物处理均可以显著提高土壤机械稳定性团聚体和水稳性团聚体的平均质量直径(MWD)和几何平均直径(GMD),其中以巨菌草处理提高幅度最大。在团聚体稳定性方面,3种植物处理均可以提高团聚体的稳定率(AR,%),以海州香薷处理提高幅度最大;植物处理可以显著降低土壤机械稳定性团聚体的分形维数(D),但对水稳定性团聚体的分形维数没有明显的影响。综上所述,采用钝化加原位植物修复可以提高重金属重度污染农田的有机质含量和土壤团聚体的稳定性,改善土壤结构,可以在重金属重度污染土壤修复中推广应用。

Effects of Vegetation Restoration on Soil Organic Matter and Aggregate Characteristics of Heavy Metal Contaminated Soils

In order to study the influence of vegetation restoration on soil organic carbon and soil aggregate structure and stability,a 3-year in-situ experiment was conduct.In a Cu and Cd contaminated farmland,12 plots were built,after applying the passivation materials(except the CK treatment),three kinds of plants (Elsholtzia splendens,Sedum plumbizincicola and Pennisetum sinese) were planted,three years later,the soils were collected to analyze the content of soil organic matter and aggregate composition,and then the content of ＞0.25 mm mechanical-stable (DR0.25) and water-stable (WR0.25) aggregates,aggregate mean mass diameter,geometric mean diameter,aggregate stability rate and fractal dimension (D) were analyzed too.The results showed that after the 3-year vegetation restoration,all of the 3 vegetation treatments increased soil organic matter content,and improved the contents of ＞0.25 mm mechanical-stable(DR0.25) and waterstable (WR0.25) aggregates,increased by 2.89％～5.39％,6.64~10.40％ and 13.34％～17.48％,respectively.The three kinds of plant treatments could significantly improve aggregate mean mass diameter and geometric mean diameter,the largest increase was the treatment of Pennisetum sinese.In aggregate stability,3 kinds of plant treatments could improve the aggregate stability rate,the treatment of Elsholtzia splendens with the largest increase.The vegetation restoration could significantly reduce the soil mechanical stable aggregate fractal dimension,but have no obvious influence on the water-stable aggregates fractal dimension.In summary,the content of organic matter and soil aggregate stability can be improved by adding passivation materials and in-situ phytoremediation,in this way the soil structure can be improved,the soil quality will be restored in the process.