三种沉水植物对Cu、Pb复合污染底泥的修复效果

利用生态缸模拟静态水体,进行底泥重金属污染的富集试验,从富集量、生物富集系数(BSAF)和去除率等指标探究苦草(Vallisneria natans)、黑藻(Hydrilla verticillata)和金鱼藻(Ceratophyllum demersum)等三种常见沉水植物对Cu、Pb复合污染底泥的修复效果。结果表明:苦草、黑藻富集效果最佳的时间段为培养生长的84~105 d,金鱼藻则为63~84 d。黑藻对Cu的BSAF达到15.2,是苦草的2.9倍、金鱼藻的2.7倍,黑藻中Cu含量与底泥中重金属含量达到显著负相关(r=-0.995,P0.05),表现出对Cu较高的富集能力。从去除率与BSAF显示,三种植物对Cu的富集能力为黑藻金鱼藻苦草;对Pb的富集能力为苦草黑藻金鱼藻;其中黑藻对Cu-Pb复合污染的综合修复效果最好。三种植物的一个生长周期结束时,底泥中Cu、Pb含量与试验开始的污染底泥相比差异均达到显著水平(P0.05),Cu-Pb复合污染程度有明显下降,经修复后的Cu-Pb复合污染底泥可达到《土壤环境质量标准》(GB15618—1995)的Ⅱ级标准;而黑藻富集作用可以使污染底泥中Cu含量达到《土壤环境质量标准》的Ⅰ级标准。

Remediation of Cu and Pb co-polluted sediments by three submerged plants

Many studies have reported that submerged plants can remove heavy metals in sediments via their root absorption, thus reducing the amount of heavy metals released from sediments into the water. Thus, submerged plants could be the important plants of phytoremediation technology. In the present study, differences in Cu and Pb accumulation by different submerged plants, Vallisneria natans, Hydrilla verticillata and Ceratophyllum demersum, in polluted sediments were investigated using an outdoor eco-cylinder static simulation test. Results indicated:The best time for the enrichment of Vallisneria natans and Hydrilla verticillata was 84~105 d after transplanting into the polluted sediments, while Ceratophyllum demersum was 63~84 d. Hydrilla verticillata showed the strongest accumulation ability for Cu, with a maximum BSAF(Biota-sediment accumulation factor, the ratio of heavy metal content in whole plant to that in sediments) of 15.2, which was 2.9 times that of Vallisneria natans, 2.7 times that of Ceratophyllum demersum. In addition, there was a significant negative correlation between the content of Cu in Hydrilla verticillata and in sediments(r=-0.995, P<0.05). Accumulation ability of three submerged plants for the same element showed significant differences. For Cu, Hydrilla verticillata had the greatest accumulation ability, followed by Ceratophyllum demersum, and Vallisneria natans was the smallest one. However, the accumulation ability for Pb was Vallisneria natans >Hydrilla verticillata >Ceratophyllum demersum. Hydrilla verticillata had the best comprehensive restoration effect for Cu-Pb pollution. There were significant decreases in Cu-Pb pollution and content at the end of one growth cycle(P<0.05). The remediated sediments met the second level of the Soil Environmental Quality Standard(GB15618-1995). Hydrilla verticillata could reduce Cu content in the sediments to the first level of the Soil Environmental Quality Standard.