节节草生长对铜尾矿砂重金属形态转化和土壤酶活性的影响

Effects of the inhabitation by Hippochaete ramosissimum on heavy metal speciations and enzyme activities in copper mine tailing soil

通过盆栽模拟栽培试验,研究了节节草生长对铜尾矿砂重金属形态转化和土壤酶活性的影响。结果表明,节节草生长显著提高了尾矿砂中有机物结合态重金属比例(P<0.01),降低了交换态和残渣态重金属比例(P<0.05)。土壤过氧化氢酶、脲酶、多酚氧化酶和蔗糖酶活性均随着节节草的生长而不同程度的升高,其中过氧化氢酶和脲酶活性均与植物生长时间呈显著正相关(r过氧化氢酶=0.911,P<0.05;r脲酶=0.957,P<0.01),多酚氧化酶和蔗糖酶活性在植物生长旺盛期达到峰值,分别是对照组的2.40和2.02倍,随后迅速下降;而磷酸酶活性却显著下降(r磷酸酶=-0.923,P<0.05)。土壤酶活性与节节草地下部分干重的相关性大于地上部分;且与土壤有机物结合态重金属的含量呈显著正相关,与交换态和残渣态重金属含量呈显著负相关。节节草生长不仅促进了铜尾矿砂重金属朝螯合态方面转化,有效降低重金属的生物有效性,同时还显著地改善了铜尾矿砂的基质环境和土壤肥力。因此,节节草在铜尾矿废弃地恢复实践中具有较大的应用潜力。

Hippochaete ramosissimum is a perennially herbaceous Pteridophyta with a fast growing speed and a strong adaptability to environment. It is widely distributed in the middle and lower reaches of Yangtze River,and is often found in roadside,sand soil,wasteland and mining abandoned soil. H. ramosissimum is also a species of Cu-resistant plant due to its high capacity of absorption and accumulation of Cu. However,whether H. ramosissimum can be used as a phytoremediation to restore abandoned copper mine tailings remains unknown. The activity of soil enzyme is an important index of soil fertility,and can often be used to indicate remediation effect on polluted soils. Although the effects of inhabitation by H. ramosissimum on heavy metal speciations were reported occasionally,little is known about the effect of its inhabitation on soil enzyme activity. Determining the relationship between heavy metal speciations and soil enzyme activity is the first step towards large scale application of H. ramosissimum to the revegetation of copper mine tailings. In this study,the plant H. ramosissimum and the soils were both collected from Tongling copper mine tailings,and pot experiments were conducted in a greenhouse to assess the effects of H. ramosissimum growth on heavy metal speciation and enzyme activity in the collected soils. The main results showed that the growth of H. ramosissimum reduced insignificantly the total content of heavy metal in the soils （ P 0. 05） and the ratio of exchangeable and residual heavy metals （ P 0. 05） ,but increased significantly the ratio of the content of heavy metals bound to organic matter to the total content of corresponding heavy metals （ P 0. 01）. With H. ramosissimum growing,the activities of Catalase,Urease,Polyphenoloxidase and Invertase increased. The activities of both Catalase and Urease were significantly positive correlated with the growth time （ rCatalase = 0. 911,P 0. 05; rUrease = 0. 957,P 0. 01） ,and the activities of both Polyphenoloxidase and Invertase reached the peak during the vigorous growth periods of the plant,which were approximately 2. 40 and 2. 02 times higher than those in the controls,respectively,and then decreased rapidly. In contrast,the Phosphatase activity notably decreased （ rPhosphatase = -0. 923,P 0. 05） during the study period,which indicated the inhabitation of H. ramosissimum had the weaker promoting effect on the transformation of organophosphate matters to inorganophosphate ones in the soils. Compared with the dry weight of the aboveground parts of the plant,that of the underground parts showed a stronger correlation with the enzyme activities in copper mine tailing soil. The enzyme activities in the copper mine tailing soils were positively related to the content of heavy metals bound to organic matter,but were negatively related to that of exchangeable and residual heavy metals. In summary,the inhabitation of H. ramosissimum not only promoted transformation of heavy metals in copper mine tailing soils to chelated speciation and decreased heavy metal bioavailability,but also improved the fertility of soils,indicating revegetation in mining waste land is possible. H. ramosissimum exhibits application potential for the restoration of abandoned copper-mining lands.