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重金属土壤污染是引起人类健康和生态系统严重关注的主要环境问题之一[1]。由于重金属对动物和人类具有致癌和致突变作用[2],必须对土壤中的大多数污染物质进行清除,并尽量减少潜在有毒元素进入食物链[3]。土壤中重金属的主要人为来源为采矿业[3]。通常矿物加工会产生大量废弃物,大多数废弃物被认为是有毒或有害的[4]。废弃的金属尾矿地区普遍严重缺乏植被[5],并导致了严峻的环境问题。因此,对废弃尾矿区域进行环境治理是十分紧迫的课题。
筛选合适的植物是能否在废弃尾矿库成功进行植物修复的一个关键因素[6]。与草本植物相比,木本植物特别是速生木本植物具有生物量大、根系发达的特点[7],并在一定程度上有能力富集重金属[8-9]。栓皮栎(Quercus variabilis Bl.)为壳斗科(Fagaceae)栎属(Quercus L.)高大落叶乔木,在我国分布广泛,是重要的乡土树种。研究表明栓皮栎适应性强,具有一定的重金属积累能力[10]。本项目组前期的盆栽试验结果也表明栓皮栎在重金属胁迫下有较好的耐性。目前关于该树种在废弃尾矿区对重金属吸收积累的研究较少。因此,本研究选择栓皮栎为试验材料,探讨其在铅锌尾矿环境下对重金属吸收积累特性的差异,以期筛选出具有土壤修复潜力的植物材料,为尾矿库植被恢复技术的实施提供科学依据。
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栓皮栎各家系在铅锌矿砂环境中未表现出叶片变黄、萎焉等显著毒害效应。但参试家系苗高表现出一定差异,其中泰山8号家系苗高高于其它参试材料,为145.7 cm;徂徕山5号家系苗高则低于其它家系,仅为110.7 cm(图1)。各参试材料地径在铅锌矿砂中有同样表现。徂徕山5号家系地径仅为9.8 mm,低于其它家系(图1)。
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重金属胁迫下参试栓皮栎各家系叶片生物量无显著差异(图2),其中泰山7号家系叶片生物量高于其它家系,为15.2 g·株−1。徂徕山5号家系茎生物量低于其它家系,仅为30.7 g·株−1,其它家系茎生物量无显著差异(图2)。徂徕山5号家系根系生物同样表现为低于其它家系,为45.8 g·株−1。而泰山7号家系根系生物量为63.6 g·株−1,高于其它家系。
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重金属胁迫下,栓皮栎家系体内营养元素浓度也表现出一定差异(表1)。4个家系栓皮栎叶片氮(N)浓度为18.13~20.27 g·kg−1,其中泰山2号家系叶片N浓度较高。栓皮栎茎N浓度为4.53~6.57 g·kg−1,其中徂徕山5号家系茎N浓度最高。方差分析表明徂徕山5号家系根系N浓度显著高于其它家系,为12.22 g·kg−1。各家系N吸收量无显著差异,为0.85~1.02 g·株−1。N利用效率则在家系间差异显著,为88.8~142.5 g·g−1,其中徂徕山5号家系N利用效率最低。重金属胁迫下,4个家系栓皮栎叶片磷(P)浓度为1.28~1.88 g·kg−1,其中泰山2号家系叶片P浓度最高。栓皮栎茎P浓度为0.69~0.82 g·kg−1,且在家系间无显著差异。方差分析表明泰山8号家系根系P浓度显著高于其它家系,为1.17 g·kg−1。各家系P吸收量为0.079~0.119 g·株−1,其中徂徕山5号家系P吸收量最低。各家系P利用效率则表现出相反趋势,徂徕山5号家系P利用效率为1136.5 g·g−1,高于其它家系。泰山2号家系P利用效率最低,仅为936.7 g·g−1。
表 1 铅锌矿砂环境下4个栓皮栎家系各器官中氮和磷浓度
Table 1. Average N and P concentrations in different organs of four families from Q. variabilis on Pb/Zn mine tailing
器官 Organ 家系 Family N/ (g·kg−1) P/ (g·kg−1) 叶片 Leaf T2 20.27 ± 1.16 a 1.88 ± 0.22 a T7 18.13 ± 1.33 a 1.63 ± 0.06 ab T8 19.60 ± 2.19 a 1.60 ± 0.33 ab J5 18.47 ± 2.40 a 1.28 ± 0.17 b 茎 Stem T2 5.26 ± 1.44 ab 0.82 ± 0.09 a T7 4.59 ± 1.31 ab 0.69 ± 0.08 a T8 4.53 ± 0.59 b 0.80 ± 0.07 a J5 6.57 ± 1.41 a 0.70 ± 0.10 a 根系 Root T2 7.45 ± 1.10 bc 0.76 ± 0.12 b T7 5.99 ± 0.64 c 0.88 ± 0.11 b T8 8.12 ± 0.55 b 1.17 ± 0.11 a J5 12.22 ± 1.25 a 0.88 ± 0.11 b 注:不同小写字母表示家系间差异显著(P < 0.05)。下同。
Note: Lowercase letters in the same row meant significant difference among families at 0.05 level. The same below. -
4个栓皮栎家系对不同重金属的吸收和转运表现出一定差异(表2)。由表2 可知,4个栓皮栎家系体内铅(Pb)浓度表现为根系 > 叶片 > 茎,而镉(Cd)浓度则表现为根系 > 茎 > 叶片(徂徕山5号家系除外)。相比Cd和Pb,栓皮栎各家系体内锌(Zn)和铜(Cu)浓度表现为叶片 > 根系 > 茎。研究表明徂徕山5号家系体内各重金属浓度最高(叶片Zn除外);泰山8号家系体内重金属浓度较低(叶片Zn和茎 Cu除外)。
表 2 铅锌矿砂环境下4个栓皮栎家系各器官中重金属浓度
Table 2. Average heavy metal concentrations in different organs of four families from Q. variabilis on Pb/Zn mine tailing
器官 Organ 家系 Family Cd/(mg·kg−1) Pb/(mg·kg−1) Zn/(mg·kg−1) Cu/(mg·kg−1) 叶片 Leaf T2 0.39 ± 0.17 b 14.01 ± 1.35 b 81.00 ± 8.63 a 13.70 ± 1.23 a T7 0.35 ± 0.05 b 7.17 ± 0.79 c 52.03 ± 5.88 c 14.23 ± 1.25 a T8 0.29 ± 0.04 b 4.59 ± 0.86 c 58.37 ± 2.75 bc 14.33 ± 1.59 a J5 0.87 ± 0.17 a 18.07 ± 2.77 a 68.13 ± 8.56 ab 16.30 ± 3.18 a 茎 Stem T2 0.50 ± 0.07 b 4.97 ± 0.29 b 35.00 ± 1.08 a 4.38 ± 0.91 a T7 0.42 ± 0.04 bc 6.87 ± 0.79 a 34.37 ± 4.35 a 4.72 ± 0.65 a T8 0.34 ± 0.05 c 3.27 ± 0.92 c 29.10 ± 3.67 a 4.43 ± 0.41 a J5 0.69 ± 0.07 a 7.18 ± 0.54 a 36.67 ± 7.49 a 4.60 ± 0.73 a 根系 Root T2 0.71 ± 0.08 b 29.73 ± 3.72 b 43.60 ± 2.46 a 6.62 ± 1.09 b T7 0.60 ± 0.13 b 30.87 ± 7.16 b 47.67 ± 12.48 a 6.39 ± 0.69 b T8 0.65 ± 0.12 b 18.07 ± 1.31 c 42.80 ± 3.66 a 5.72 ± 1.06 b J5 0.93 ± 0.09 a 43.60 ± 5.38 a 58.40 ± 11.78 a 8.64 ± 1.19 a 方差分析表明泰山8号家系地上部Cd和Pb含量显著低于其它家系,分别为0.020和0.21 mg。尽管徂徕山5号家系地上部生物量低于其它家系,但其体内重金属浓度较高,因而其地上部Cd和Pb含量较高,每株分别为0.032和0.45 mg。各家系地上部Zn和Cu含量无显著差异,每株分别为2.02~2.72 mg和0.36~0.41 mg,其中徂徕山5号家系体内含量最低。泰山8号家系根系各重金属含量均低于其它家系,Cd、Pb、Zn和Cu含量分别为0.033、0.92、2.19和0.29 mg。
由图3可知,徂徕山5号家系各重金属富集系数(BCF)均最高,表现出较强的重金属富集能力。泰山8号家系各重金属BCF值均低于其它家系,较难富集各重金属。通常各家系较容易富集Cu,而较难富集Pb。参试材料重金属BCF值均小于0.100,特别是铅BCF值均小于0.012。栓皮栎家系对各重金属表现出不同的转移能力(图3),其中徂徕山5号和泰山2号家系对Cd和Pb有较强的转移能力。泰山2号家系对Zn的转移能力较强,其重金属转移系数(TF)为1.06,显著高于其它家系。泰山8号和泰山7号家系对Cu的转移能力较强,其TF值分别为1.16和1.12。总体而言,参试材料较容易转移Cu和Zn,较难转移Pb,其TF值均小于0.25。
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根据主成分分析(图4),前2轴解释率为85.7%,第1主成分(PC1)占63.0%,其中高载荷且为正值的指标有植物体内镉和铅浓度、茎和根系锌和氮浓度、叶片和根系铜浓度,为负值的指标为苗高、地径、茎生物量和叶片磷浓度。说明家系间形态学指标以及茎生物量差异主要由体内重金属浓度决定。第2主成分(PC2)占22.7%,其中高载荷且为负值的指标有叶片和根系生物量,为正值的指标有叶片锌和氮浓度、茎铜和磷浓度。图4展示了标准化的主成分得分和各家系所处的位置。从第1主成分得分排序看,植物体内重金属元素较高的徂徕山5号家系得分最高,而体内重金属浓度较低的泰山8号家系得分最低。表明植物体内重金属浓度水平在第1主成分中起主导作用。从第2主成分得分排序看,植物地上部磷浓度以及叶片氮浓度较高的家系得分较高,泰山7号家系体内氮磷浓度相对较低,因此得分最低。表明植物地上部营养元素浓度在第2主成分中起主导作用。
不同栓皮栎家系对重金属的耐性和富集特性
Tolerance and Enrichment Characteristics of Different Families of Quercus variabilis to Heavy Metal
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摘要:
目的 通过野外试验,评价栓皮栎家系在铅锌尾矿环境中的生长响应、重金属积累能力及土壤修复潜力。 方法 在杭州市富阳区废弃的铅锌尾矿库进行人工植被恢复试验,分析比较4个栓皮栎家系(泰山3号、泰山7号、泰山8号和徂徕山5号)在铅锌矿砂中生长3 a的生物量及其对营养元素和重金属的吸收及转移特征。 结果 4个栓皮栎家系在矿砂环境中均能生长,未表现出毒害效应。重金属胁迫下,栓皮栎家系各器官营养元素浓度表现出一定差异,且各家系均有较高的氮磷利用效率。研究表明参试栓皮栎家系体内重金属浓度较低,且各家系重金属生物富集系数(BCF)均小于0.100。除铅外,各家系重金属转移系数(TF)均大于0.50,表现出一定的重金属转移能力。泰山8号家系平均BCF和TF值均低于其它家系。 结论 3 a的长期试验表明,参试栓皮栎家系耐性较高、重金属生物富集系数和转移系数较低,可作为有潜力的污染土壤修复树种。 Abstract:Objective A filed test was conducted to evaluate the growth response, enrichment and transfer characteristics to heavy metal and vegetation restoration prospect of four families from Quercus variabilis. Method Vegetation restoration test was carried out in the abandoned lead-zinc tailings for 3 years. The seedlings of four families (Taishan 3, Taishan 7, Taishan 8, and Julaishan 5) were transplanted into Pb/Zn mine tailing to compare their biomass, uptake and transfer characteristics of nutrient elements and heavy metals. Result The results showed that all the seedlings could survive in the Pb/Zn tailing and the toxicity symptoms was not observed. Under heavy metal stress, there were statistically significant differences among the seedlings of the four families according to the nutrient concentrations. Meanwhile, all families had high capability of utilization efficiency. Generally, the concentrations of heavy metals in different organs of Q. variabilis were low, and the values of bioconcentration factor (BCF) were less than 0.100. The values of translocation factor (TF) were more than 0.5, except Pb. The average BCF and TF values of family Taishan 8 were lower than those of the other families. Conclusion The results suggest that the families from Q. variabilis have high tolerance with the low BCF and TF, implying that they are better potential candidates for contaminated soil. -
Key words:
- lead/zinc mine tailing
- / Quercus variabilis
- / heavy metal
- / enrichment
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表 1 铅锌矿砂环境下4个栓皮栎家系各器官中氮和磷浓度
Table 1. Average N and P concentrations in different organs of four families from Q. variabilis on Pb/Zn mine tailing
器官 Organ 家系 Family N/ (g·kg−1) P/ (g·kg−1) 叶片 Leaf T2 20.27 ± 1.16 a 1.88 ± 0.22 a T7 18.13 ± 1.33 a 1.63 ± 0.06 ab T8 19.60 ± 2.19 a 1.60 ± 0.33 ab J5 18.47 ± 2.40 a 1.28 ± 0.17 b 茎 Stem T2 5.26 ± 1.44 ab 0.82 ± 0.09 a T7 4.59 ± 1.31 ab 0.69 ± 0.08 a T8 4.53 ± 0.59 b 0.80 ± 0.07 a J5 6.57 ± 1.41 a 0.70 ± 0.10 a 根系 Root T2 7.45 ± 1.10 bc 0.76 ± 0.12 b T7 5.99 ± 0.64 c 0.88 ± 0.11 b T8 8.12 ± 0.55 b 1.17 ± 0.11 a J5 12.22 ± 1.25 a 0.88 ± 0.11 b 注:不同小写字母表示家系间差异显著(P < 0.05)。下同。
Note: Lowercase letters in the same row meant significant difference among families at 0.05 level. The same below.表 2 铅锌矿砂环境下4个栓皮栎家系各器官中重金属浓度
Table 2. Average heavy metal concentrations in different organs of four families from Q. variabilis on Pb/Zn mine tailing
器官 Organ 家系 Family Cd/(mg·kg−1) Pb/(mg·kg−1) Zn/(mg·kg−1) Cu/(mg·kg−1) 叶片 Leaf T2 0.39 ± 0.17 b 14.01 ± 1.35 b 81.00 ± 8.63 a 13.70 ± 1.23 a T7 0.35 ± 0.05 b 7.17 ± 0.79 c 52.03 ± 5.88 c 14.23 ± 1.25 a T8 0.29 ± 0.04 b 4.59 ± 0.86 c 58.37 ± 2.75 bc 14.33 ± 1.59 a J5 0.87 ± 0.17 a 18.07 ± 2.77 a 68.13 ± 8.56 ab 16.30 ± 3.18 a 茎 Stem T2 0.50 ± 0.07 b 4.97 ± 0.29 b 35.00 ± 1.08 a 4.38 ± 0.91 a T7 0.42 ± 0.04 bc 6.87 ± 0.79 a 34.37 ± 4.35 a 4.72 ± 0.65 a T8 0.34 ± 0.05 c 3.27 ± 0.92 c 29.10 ± 3.67 a 4.43 ± 0.41 a J5 0.69 ± 0.07 a 7.18 ± 0.54 a 36.67 ± 7.49 a 4.60 ± 0.73 a 根系 Root T2 0.71 ± 0.08 b 29.73 ± 3.72 b 43.60 ± 2.46 a 6.62 ± 1.09 b T7 0.60 ± 0.13 b 30.87 ± 7.16 b 47.67 ± 12.48 a 6.39 ± 0.69 b T8 0.65 ± 0.12 b 18.07 ± 1.31 c 42.80 ± 3.66 a 5.72 ± 1.06 b J5 0.93 ± 0.09 a 43.60 ± 5.38 a 58.40 ± 11.78 a 8.64 ± 1.19 a -
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