Abstract:

Ecological restoration is difficult to construct in the Pb/Zn tailings due to the low nutrient concentrations, poor physical structure and high heavy metal (cadmium, Cd; lead, Pb; zinc, Zn) concentrations. Amendments are used to improve the suitability of the tailings, which is an important method for the ecological restoration of tailings ponds. In this experiment, fermented sheep manure, sludge and coconut shell biochar with different mass fractions (1%, 2.5%, 5%) were used to investigate the effects of fertility and physical structure and heavy metal (Cd, Pb, Zn) bioavailability of Pb/Zn mine tailings and then the improvement effects were verified by pot experiment of ryegrass. The results showed that the available nitrogen, phosphorus, potassium and organic matter increased by 0.87?9.56 times, 1.87?37.7 times, 1.87?43.7 times and 0.85?7.28 times, respectively. The most significant effects on hydraulic conductivity, total porosity and water retention of tailing sand were observed at the addition rate of 2.5% and showed that fermented sheep manure>biochar>sludge. Furthermore, bioavailability of heavy metals was significantly (P<0.05) reduced by 28.6%?64.6% (Cd), 30.4%?70.6% (Pb), and 14.4%?45.5% (Zn), and coconut shell biochar had the most significant effect. Ryegrass’s germination, height and total dry mass had been increased by 16.1%?20.3%, 10.8%?48.9% and 7.55%?19.5%, respectively, and fermented sheep manure is the best. Thus, fermented sheep manure, sludge and coconut shell biochar could be used as amendments to improve the suitability of Pb/Zn tailings and promote plant growth. Furthermore, Pearson’s correlation analysis showed that aboveground dry mass and height were highly significantly (P<0.01) and positively correlated with cation exchange capacity and available potassium, but significant (P<0.01) negative correlations were observed with saturated hydraulic conductivity and available state heavy metal. Plant root dry mass and root length were observed to be significantly and positively correlated with saturated water content; in contrast, they were significantly and negatively correlated with the percentage of grain size (1?2 mm). This work can provide a theoretical basis for substrate improvement and revegetation of tailings pond with low nutrients, poor physical structure and high heavy metal pollution.

Key words: Pb/Zn tailings, amelioration, organic amendments, nutrients, physical properties

摘要：

铅锌矿尾砂由于肥力低、物理结构差且重金属镉（Cd）铅（Pb）锌（Zn）浓度高，植物难以生长，从而严重制约了尾砂库的生态恢复。利用改良剂改善尾砂的适生性是尾砂库生态恢复的重要方法。通过基质改良试验探究添加不同质量分数（1%、2.5%、5%）的发酵羊粪、污泥和椰壳生物炭对铅锌矿尾砂养分、物理结构的改良效果和对重金属镉铅锌的固定效果，再通过黑麦草（Lolium perenne L.）盆栽试验验证对适生性的改善效果。结果表明，添加改良剂使有效态氮、磷、钾以及有机质分别提高了0.87－9.56、1.87－37.7、1.87－43.7和0.85－7.28倍。添加质量分数为2.5%时，3种改良剂对尾砂的导水性、总孔隙度和持水性的积极影响最为显著，表现为发酵羊粪>生物炭>污泥。此外，3种改良剂显著（P<0.05）降低有效态重金属质量分数，Cd、Pb、Zn分别降低了28.6%－64.6%、30.4%－70.6%、14.4%－45.5%。其中，椰壳生物炭对3种重金属的固定效果最好。添加改良剂显著提高了黑麦草的发芽率、总高度和总干质量分别提高了16.1%－20.3%、10.8%－48.9%和7.55%－19.5%，其中发酵羊粪效果最好。因此，发酵羊粪、污泥和椰壳生物炭可作为改良剂改善铅锌矿尾砂的适生性并促进植物生长。Pearson相关性分析表明，植物地上部分干质量和株高与阳离子交换量和速效钾呈极显著（P<0.01）正相关，与饱和导水率和有效态重金属呈极显著（P<0.01）负相关。植物根干质量和根长均与饱和含水量呈显著正相关，而与1－2 mm的粒径呈显著负相关。该文可为养分贫瘠、物理结构差和高重金属污染尾砂库的植被恢复提供理论依据。

关键词: 铅锌尾砂, 基质改良, 有机改良剂, 养分, 物理性质