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[目的]研究紫花苜蓿(Medicago sativa L.)对河道底泥中重金属的修复作用,为利用植物修复技术解决受污染河道沉积物的重金属污染问题提供可靠依据。[方法]将过筛的底泥(以风干土计)混和均匀后装入长方形PVC箱(0.6m×0.5m×0.4m),底部设有渗流通气孔;将箱中底泥用去离子水调至30%～60%持水率(WHC)。2010年4月播入紫花苜蓿种子,生长7d后间苗,每隔30d采集植物根际土壤样品,监测底泥重金属含量、细菌及酶的活性。10月收获植物并测定植物根、茎、叶部分的重金属吸收情况。[结果]紫花苜蓿的同一部位对不同的重金属积累量不同,且同一重金属在植株的不同部位积累量也不同。紫花苜蓿对Zn的总积累量最大,且主要积累在根部;Ni、Cr、Cu和Pb也主要积累在根部;Mn在紫花苜蓿叶片中的积累最多,占植物中总积累量的42.47%;各种重金属在茎内的积累量均较低。紫花苜蓿对Ni、Cu、Pb和Cr的降解效果比较好,延长种植作物的种植时间或增加作物的播种次数有利于重金属的降解;紫花苜蓿对Mn的降解效果不明显。种植紫花苜蓿后,底泥中微生物数量显著增加,脱氢酶活性也有所提高。[结论]紫花苜蓿对Zn、Ni、Cr、Cu和Pb均有一定的修复作用,可以用于解决受污染河道底泥的重金属污染问题。
[Objective] The study aimed to study the effect of alfalfa (Medicago sativa L.) on the restoration of heavy metals in river sediments and provide a reliable basis for phytoremediation to solve the heavy metal pollution in polluted river sediments. [Method] The sieved sediment (dry clay soil) was evenly mixed into rectangular PVC box (0.6m × 0.5m × 0.4m) with seepage vent at the bottom. The sediment in the tank was washed with deionized water Adjust to 30% ~ 60% water retention (WHC). In April 2010, the alfalfa seeds were sown and the seedlings were grown for 7 days. Rhizosphere soil samples were collected every 30 days to monitor the heavy metal content, bacteria and enzyme activities in the sediment. October harvest of plants and determination of plant roots, stems, leaves part of the heavy metal absorption. [Result] The same parts of alfalfa accumulated different amounts of heavy metals, and the same heavy metals accumulated in different parts of plants. Alfalfa had the largest total Zn accumulation, and mainly accumulated in roots. Ni, Cr, Cu and Pb also mainly accumulated in roots. Mn had the highest accumulation in alfalfa leaves, accounting for 42.47% of the total accumulation in plants. The accumulation of heavy metals in stems were lower. The degradation of Ni, Cu, Pb and Cr by alfalfa was better, and the planting time of planting crops was increased or the planting times of crops were increased, which was beneficial to the degradation of heavy metals. The degradation of Mn by alfalfa was not obvious. After planting alfalfa, the number of microorganisms in sediment increased significantly, and the activity of dehydrogenase also increased. [Conclusion] Medicago sativa could restrain Zn, Ni, Cr, Cu and Pb to some extent and could be used to solve the problem of heavy metal pollution in contaminated river sediment.