不同修复方式对铅锌尾矿砂微生态环境的改良作用

采用盆栽试验方法研究黑麦草、黑麦草联合改良剂等不同修复方式对铅锌尾矿砂的理化性质和微生物性状的改良作用。结果表明,不同处理使铅锌尾矿砂中有机质、碱解氮、速效磷含量显著提高,其中黑麦草联合10%菜园土和1%赤泥处理(CN1)对铅锌尾矿砂中有机质、碱解氮、速效磷含量明显提高,分别比对照提高了51.82%,300.00%和901.29%。添加改良剂显著增加了黑麦草的生物量,减少了黑麦草根部重金属的含量。不同处理使铅锌尾矿砂中微生物数量,微生物C、N含量显著增加,其中CN1处理使细菌、真菌、放线菌数量和微生物C、N含量增加效果最好,分别比对照增加了33.78,5.99,21.82,6.34,6.35倍。各处理显著提高了尾矿砂中脲酶、磷酸酶、蔗糖酶、纤维素酶活性,其中CN1处理使脲酶、磷酸酶、蔗糖酶、纤维素酶活性分别比对照提高了18.43,12.58,5.00,9.15倍。黑麦草联合10%菜园土和1%赤泥较其他处理有利于提高铅锌尾矿砂的肥力,改良尾矿砂的微生态环境,促进植物生长。     

钝化剂对铅锌尾矿砂中重金属的固化作用

铅锌尾矿砂重金属含量高,对环境危害大。为了减缓铅锌尾矿砂的重金属污染风险,采用室内培养实验方法,在铅锌尾矿砂中添加油菜秸秆、芒草秸秆、水稻秸秆、石灰和磷酸一铵等钝化剂,并通过DTPA及Tessier连续提取铅、锌、镉的化学形态,评价钝化剂对铅、锌、镉的移动性和生物有效性的影响。结果表明,油菜秸秆、芒草秸秆、水稻秸秆、石灰和磷酸一铵均显著地降低Cd的生物有效性及其迁移能力;磷酸一铵、油菜秸秆均能有效地降低尾矿砂中Pb的生物有效性及其迁移能力,尤其是磷酸一铵有极显著的效果;油菜秸秆、芒草秸秆、水稻秸秆和磷酸一铵均能有效地降低尾矿砂中Zn的生物有效性及其迁移能力。尾矿砂中DTPA态Cd、Zn与交换态、碳酸盐结合态Cd、Zn极显著正相关,DTPA态Pb与碳酸盐结合态Pb极显著正相关。从Pb、Cd、Zn生物有效态含量的减少方面考虑,油菜秸秆和磷酸一铵是较好的铅锌尾矿砂原位钝化剂。     

天然蒙脱石和沸石改良对黑麦草在铜尾矿砂上生长的影响

通过温室盆栽试验,开展了天然蒙脱石和沸石处理对黑麦草在铜矿尾矿砂上生长影响的研究。结果表明:蒙脱石和沸石改良对黑麦草的地上部生物量没有显著影响,但改变了黑麦草的根重;而施用肥料促进了黑麦草生长。蒙脱石的加入使尾矿砂的有效态锌含量显著降低,但对有效态铜的含量影响不明显;而沸石的加入均显著降低了尾矿砂的有效态铜和锌的含量;另外,矿物的加入降低了尾矿砂的pH值,但其变化与尾矿砂重金属有效态含量变化之间无相关性。矿物的加入降低了黑麦草根中的铜锌吸收,但蒙脱石增加了第一茬黑麦草地上部铜锌吸收,对第二茬黑麦草地上部铜锌吸收无影响;而沸石对两茬黑麦草地上部铜锌含量均无显著影响。不同生长期黑麦草对铜锌吸收量有差异,第二茬黑麦草的地上部锌含量明显高于第一茬,而铜含量则变化不大。     

土壤结构调理剂PAM对复垦铁尾矿砂物理性状的影响

聚丙烯酰胺(polyacrylamide,PAM)是一种常见的土壤结构调理剂,但在尾矿复垦中却少有应用。该文通过室内土柱模拟试验,采用干混法在铁尾矿砂中加入PAM,设置0%(对照)、0.05%、0.10%和0.20%共4种质量浓度PAM,观测PAM对铁尾矿砂物理性状的影响。结果表明:1)除总孔隙度之外,对照与混合PAM尾矿砂的容重、毛管孔度和毛管持水量差异显著(P0.05)。2)随着尾矿砂毛管水上升高度增加,PAM质量浓度越大,含水率下降的趋势越缓慢,但含水率的变异性却越大,变异系数从1.22%(10 cm)增大到7.13%(40 cm)。3)PAM会极显著抑制尾矿砂毛管水上升高度(P0.01)但PAM质量浓度不同,抑制程度不同。据此可将上升曲线分为3个阶段:第1阶段,0~5 min,上升高度相似阶段;第2阶段6~25 min,上升高度分异阶段;第3阶段30~420 min,上升高度变化规律相对稳定阶段。毛管水上升高度随时间变化呈现幂函数增加趋势,上升速率随时间变化呈现幂函数减小趋势。4)在自然通风状态下,72小时内不同PAM质量浓度尾矿砂的含水率均持续降低,纯尾矿砂含水率的降低幅度最大,从37.53%减少到35.60%;PAM质量浓度为0.20%的尾矿砂含水率降低幅度最小,从37.40%减少到36.67%。因此,PAM的合理使用能够有效改善尾矿砂的物理性状和水分运移,为无土区的植被恢复创造适宜的生长条件。     

铅锌矿废弃地尾矿砂对银合欢幼苗定居的影响

研究了广东省仁化县韶关凡口铅锌矿废弃地尾矿砂对银合欢（Leucaena glauca)幼苗定居的影响。结果表明，尾矿砂各Pb、Zn、Cu、Cd等重金属含量极高，Pb、Zn比对照土壤高100倍左右，Cu、Cd高4－5倍，植物对重金属的吸收、积累量较大，且多集中于根部。尾矿砂中硝态氮（NO3^--N)和铵态氮（NH4^ -N)含量很低，仅为对照土壤的13％－23％。银合欢幼苗在尾矿砂中能生长，但其叶片光合色素含量较少，株高、复叶数、植株干物质量等生物量显著降低，这主要是由于重金属含量过高导致根系活力降低，限制了植物对水分和营养物质的吸收，其次是土壤贫瘠的影响。     

铅锌矿废弃地尾矿砂对银合欢幼苗定居的影响

研究了广东省仁化县韶关凡口铅锌矿废弃地尾矿砂对银合欢(Leucaena glauca)幼苗定居的影响。结果表明，尾矿砂中Pb、Zn、Cu、Cd等重金属含量极高，Pb、Zn比对照土壤高100倍左右，Cu、Cd高4～5倍，植物对重金属的吸收、积累量较大，且多集中于根部。尾矿砂中硝态氮(NO^-₃-N)和铵态氮(NH⁺₄-N)含量很低，仅为对照土壤的13%～23%。银合欢幼苗在尾矿砂中能生长，但其叶片光合色素含量较少，株高、复叶数、植株干物质量等生物量显著降低，这主要是由于重金属含量过高导致根系活力降低，限制了植物对水分和营养物质的吸收，其次是土壤贫瘠的影响。     

辽宁铁矿尾矿砂水土流失形式与养分状况分析

铁矿尾矿砂是一种矿业废弃物,同时也是一种特殊的细颗粒基质。由于排弃中、排弃后的管理存在缺陷,因此风蚀、水蚀频发,是典型的人造砂源。以辽宁中东部地区、西部地区铁矿尾矿砂作为研究对象,以区域为单元分析其流失形式及养分状况,希望为铁矿尾矿库的治理与利用提供一定的参考。     

不同压实水平下铁尾矿砂和土壤的水力学特征比较

由于尾矿砂的不良结构和严重压实,水土流失严重,水分已成为其生态恢复的重要限制因素。因此以水分运移为主线,通过室内土柱模拟,研究铁尾矿砂和土壤在自然状态到最大压实状态间5个压实水平(铁尾矿砂1.50~1.70 g/cm^3,土壤1.30~1.50 g/cm^3)的水力学特征差异,为尾矿砂的合理改良提供依据。结果表明:铁尾矿砂自然容重1.50 g/cm^3的水分入渗能力低于土壤自然容重1.30 g/cm^3的水分入渗能力。随容重的增大,尾矿砂和土壤的水分运移特征均呈幂函数减小的趋势,但分别在1.60,1.40 g/cm^3处入渗能力明显降低。从水分参数入渗率、湿润锋距离、累计入渗量、饱和导水率、剖面水分分布整体来看,在较低容重范围内,土壤水分运移能力高于铁尾矿砂,但由于容重对土壤水分运移的影响大于铁尾矿砂,在较高容重范围内,土壤的水分运移能力则不如铁尾矿砂。铁尾矿砂和土壤的水分特征曲线形状也完全不同,铁尾矿砂呈现"上凸"形,表现为高吸力段缓低吸力段陡,土壤水分特征曲线均为"下凹"形,表现为高吸力段陡低吸力段缓。因此,尾矿砂中可以添加土壤或者类似土壤结构的基质来增强其不良的持水性和导水性,促进生态恢复。     

间歇降雨对铁尾砂重构坡面侵蚀水动力学特性的影响

黄土高原夏季降雨集中且多暴雨,铁尾矿砂自身结构松散,堆存坡度大,雨季通常遭受多次暴雨侵蚀,严重限制植被恢复。为有效减少铁尾矿的水土流失,促进生态恢复,在干排铁尾矿砂中添加不同比例土壤和菌糠,形成6种重构坡面:松散铁尾矿砂(LT),结壳铁尾矿砂(CT),铁尾矿砂与菌糠混合物(TM),铁尾矿砂、菌糠和土壤混合物(TSM),铁尾矿砂和土壤混合物(TS),纯土(S)。采用室内人工模拟降雨技术,研究重构坡面在间歇性降雨下的侵蚀特征和水动力因素。结果表明:1)随降雨场次增加,6种坡面的产流率均持续增大,而产沙率表现出明显的分异:LT、CT和TS产沙率持续增大,表现为高产沙型,TS、TSM和S产沙率整体上是先增加后减少,表现为低产沙型;2)随降雨场次增加,6种坡面侵蚀形态也出现分异,可分为2类:LT和CT和TS坡面侵蚀形态严重,细沟发展快,演化为宽深比较小的细沟;TM和TSM和S坡面侵蚀形态轻微,细沟发展缓慢,S坡面演化为宽深比较大的细沟,TM和TSM坡面细沟很少,多为均匀分布的菌糠小坑穴。据此表征坡面侵蚀微地形变化的沟壑面积和地形起伏度,随降雨场次增加持续增大;沟壑密度则随降雨场次先急剧增加,随后由于沟壑形态差异,部分坡面减少;3)6种坡面的坡面流流型均为层流,流态大多为急流;随降雨场次增加,流速、水流功率整体表现为增大的趋势,径流剪切力无明显趋势,阻力系数、曼宁粗糙系数表现出减小的趋势;除径流剪切力,不同降雨场次间水动力学特征差异显著(P0.05)。6种坡面侵蚀产流产沙可用对数、线性或幂函数较好地模拟。纯尾矿砂坡面侵蚀最为严重,坡面覆土具有明显的减流效果,但添加菌糠的减沙效果最好,因此对于土源缺乏的铁尾矿砂复垦区,同时添加菌糠和土壤可以有效减少侵蚀,易于植被修复。     

含盐铁尾矿砂在机械沙障中的固化性能

[目的]针对荒漠区交通干线的风沙灾害问题,利用当地含盐铁尾矿砂为原料进行固化性能试验,用于制备新型机械沙障实现以废治灾。[方法]采用普通硅酸盐水泥与华夏一号离子固化剂来固化含盐铁尾矿砂,通过干湿循环、冻融循环、自然风化试验后试样抗压强度变化综合评价其耐久性,并深入分析了孔隙结构的改变对耐久性能的影响机理。[结果] 7%～10%的水泥掺量就可以使固化试样的强度达到2MPa以上,复掺0.2‰的离子固化剂后可明显改善固化试样的强度和耐久性;孔隙结构分析表明,耐久性试验中,由于水汽及盐的迁移使试样的总孔体积增大,中孔或大孔占比增加,但未出现连通超大孔洞,强度损失小。[结论]利用含盐铁尾矿砂作为一种工程材料,通过水泥与离子固化剂将其固化后可制备防风固沙用机械沙障,强度与耐久性均可满足工程要求,具有实际应用价值。     

不同改良剂对黑麦草在铜矿尾矿砂上生长的影响

Montmorillonite, rice straw, organic manure and chemical fertilizer were used as amendment materials for copper mine tailings, and their effects on mine tailing pH, nutrients and metal availability to ryegrass were investigated. Chemical fertilization was the most effective one in improving ryegrass growth in mine tailings among the amendment materials examined. It was found that montmorillonite raised biomass of ryegrass at the 1st and 2nd cuts, but it did not give further positive effects at the 3rd and 4th cuts. The effect of organic materials on ryegrass growth was not so good as expected, mainly due to their slow decomposition in mine tailings with less soil microorganisms. Available Cu and Zn contents in mine tailings decreased in the presence of montmorillonite but increased when rice straw and organic manure were used as amendments. Cu and Zn contents in ryegrass decreased with increasing the rate of montmorillonite application but increased with the rate of rice straw. Zn showed much stronger mobility from soil to ryegrass than Cu, and almost all the available N and P in mine tailings, except for the treatments with organic manure, were completely consumed after ryegrass had grown in mine tailings for more than four months and been harvested for four times. Owing to its large biomass and high metal uptake, ryegrass is a potential plant for remediation of metal contaminated soils in practice.     

Revegetation of copper mine tailings with ryegrass and willow

To restore vegetation on metal mine tailings is very difficult because they often contain high concentrations of heavy metals, low nutrient content and low water retention capacity. This study involved 3 experiments that evaluated the effects of 4 treatment amendments: montmorillonite, rice straw, organic manure and chemical fertilizer on the growth of ryegrass (Loliurn perenne L.) and willow (Salix virninalis L.) with Cu and Zn mine tailings from two mining areas. The results showed that ryegrass was the most tolerant of 4 crops to Cu toxicity. Also when organic manure, which contained high concentrations of inorganic salts, was added to the mine tailings, it significantly hindered ryegrass growth (P=0.05).Meanwhile, with ryegrass organic manure significantly increased (P=0.05) the extractable Cu concentration in both mine tallings. When montmorillonite was used as a mine tailings amendment with willow, the height and tress number at the 1st cut were significantly greater (P = 0.05) than a control without montmorillonite. However there was no significant difference for height, tress number, dry weight or root dry weight at the 2nd cut. So, amendment applications to reduce metal toxicity and increase nutrients retention in mine tailings were essential during revegetation of mine tailings.     

Determination of Acid Volatile Sulfides and Chromium Reducible Sulfides in Cu-Zn and Au Mine Tailings

The present study investigated the use of chemical extractions for the determination of acid volatile sulfides (AVS) and chromium reducible sulfides (CRS) in sulfidic mine tailings from Au and Cu-Zn mines. The main objectives of the study were to understand the factors affecting AVS and CRS extraction in mine tailings and to use the AVS and CRS data as indicator of biotic reactions, including microbial sulfate-reduction. Tailings from one Cu-Zn mine and two Au mines located in the Timmins area, Ontario, Canada, were extracted for AVS and CRS, along with pure metal sulfides. Tailings were also characterized by XRD and the relative abundance of pyrite and pyrrhotite in the samples was determined. Our results showed that AVS in mine tailings were generally not extractable at cold temperature, but they could be extracted from most tailings samples at ～ 80 °C. AVS extraction of pure metal sulfides showed that pure pyrrhotite was partially soluble during cold and hot extractions and that it significantly contributed to the overall AVS fraction of the tailings. Such findings complicate the use of AVS as bio-indicators of microbial activity because a large fraction of the pyrrhotite present in the tailings originated from the ore deposit. The CRS fractions were found to be unaffected by the presence of pyrrhotite and truly represented the pyrite content of the tailings. The use of AVS and CRS data from mine tailings can be helpful in assessing the distribution of metal sulfides but attention must be paid to their true significance.     

Growth and Metal Accumulation of Geyer and Mountain Willow Grown in Topsoil versus Amended Mine Tailings

Willows (Salix spp.) are an integral component in the restoration of wetland plant communities that have been impacted by the fluvial deposition of mine tailings. A greenhouse study was conducted to compare growth and metal uptake of Geyer (S. geyeriana) and mountain (S. monticola) willow grown in topsoil versus lime and biosolids amended mine tailings. Biomass, leader length, and tissue metal contents were measured after four months growth. Above and belowground biomass and leader length of Geyer willow were greater for plants grown in topsoil compared to amended mine tailings. However, soil type did not affect mountain willow growth. Analysis for five metals yielded complex results for the two willow species and soil types. As compared to mountain willow, Geyer had greater concentrations of Mn and Pb in aboveground tissues, and Cu in senesced leaves and bark-less leaders when grown in tailings; mountain willow leaves contained greater levels of Cd than Geyer when grown in tailings. Both willow species had foliar Cd levels which were above livestock toxicity tolerance values. Based on growth characteristics, mountain willow appeared better suited for restoration of mine tailings compared to Geyer willow. However, because of the high Cd uptake by both willow species, care should be taken in restoration efforts where wildlife and domestic livestock are likely to browse on the willows.     

Stabilization of Mine Tailings Using Fly Ash and Sewage Sludge Planted with Phalaris arundinacea L.

The impact of plants (Phalaris arundinacea L.) on the leakage of ammonium, cadmium, copper, nitrate, phosphate, and zinc from sulfidic mine tailings covered with wood fly ash and sewage sludge was investigated. Either ash or sludge was placed in contact with the tailings, and ash layers of either low or high compactness were used. It was revealed that an ash/sludge cover effectively decreased the metal leaching from the tailings regardless of the order in which the materials were applied. Plants decreased the amount of leachate and the concentrations of ammonium and phosphate. The presence of ash below the sludge decreased the plant uptake of copper and zinc and nitrate leakage. However, when the ash was added as a thin (1.5 cm) porous layer, roots and air reached the tailings and caused high metal leakage. The results support the use of a vegetated ash/sludge cover in the treatment of mine tailings, provided that the sealing layer is firm enough to prevent root penetration.     

生物炭：一种新型改良剂能修复矿物、工业以及污水废弃物污染的土壤

Mine tailings, waste rock piles, acid mine drainage, industrial wastewater, and sewage sludge have contaminated a vast area of cultivable and fallow lands, with a consequence of deterioration of soil and water quality and watercourses due to the erosion of contaminated soils for absence of vegetative cover.High concentrations of toxic elements, organic contaminants, acidic soils, and harsh climatic conditions have made it difficult to re-establish vegetation and produce crops there. Recently, a significant body of work has focussed on the suitability and potentiality of biochar as a soil remediation tool that increases seed emergence, soil and crop productivity, above ground biomass, and vegetation cover on mine tailings, waste rock piles, and industrial and sewage waste-contaminated soils by increasing soil nutrients and water-holding capacity, amelioration of soil acidity, and stimulation of microbial diversity and functions. This review addresses: i) the functional properties of biochar, and microbial cycling of nutrients in soil; ii) bioremediation, especially phytoremediation of mine tailings, industrial waste, sewage sludge, and contaminated soil using biochar; iii) impact of biochar on reduction of acid production, acid mine drainage treatment, and geochemical dynamics in mine tailings; and iv) treatment of metal and organic contaminants in soils using biochar, and restoration of degraded land.     

Heavy metal contamination of agricultural soils around a chromite mine in Vietnam

Abstract

In Vietnam, the Co Dinh mine is the largest chromite mine in the country. Mining, ore dressing and disposal of the tailings provide obvious sources of heavy metal contamination in the mine area. The present study examined the influence of chromite mining activities on the adjacent lowland paddy field by investigating heavy metal and As levels in the mine tailings, sediments, paddy soils and water. At paddy fields located near the mine tailings, the total contents of Cr, Co and Ni were 5,750, 375 and 5,590?mg?kg^?1, and the contents of their water-extractable form were 12.7, 1.16 and 32.3?mg?kg^?1, respectively. These results revealed severe contamination of lowland paddy soils with Cr, Co and Ni as a result of mining activity, suggesting serious health hazards through agricultural products, including livestock in this area. The principal source of the pollution was sediment inflow owing to the collapse of the dike, which was poorly constructed by heaping up soil. Moreover, water flowing out from the mining area was also polluted with Cr and Ni (15.0–41.0 and 20.0–135?μg?L^?1, respectively). This might raise another problem of heavy metal pollution of watercourses in the area, indicating the need for further investigation and monitoring of fluctuations of water quality with seasonal changes.     

Adaptation, tolerance, and evolution of plant species in a pyrite mine in response to contamination level and properties of mine tailings: sustainable rehabilitation

Purpose

The impacts of mining contaminations and physico-chemical properties and geochemistry of mine tailings on the density, richness, biodiversity, evolution and succession of plant species and vegetation recovery in the mining area is very poorly reported in the literature. Therefore, the present study conducted an investigation on vegetation development and succession of plant communities at the abandoned São Domingos pyrite mining area.

Materials and methods

We conducted the field survey to estimate the vegetation development and succession of plant communities, collect vegetation (plant species, lichen and moss) and tailing (and soil) samples, and finally analyzed the physico-chemical and geochemical properties and metal levels in mine tailings, soil and vegetation samples.

Results and discussion

The results showed that the communities of low height and biomass like grass, legume, shrub, moss and lichen were dominating on the mine tailings and waste dumps at the inner sites and center of the mine, and the vegetation coverage was explicitly very poor. The reddish brown colluvia had poor soil quality, but high acidity and metal concentrations. However, at the outer edge of the mine the loamy soil and relatively lower acidity and metal contamination favored the higher vegetation cover and a gradual increase in the number of species and plant succession, where the taller, higher biomass and broad leaf trees were abundantly grown forming a dense forest and canopy. The succession of several plant communities dominating in the mining area, vegetation coverage and species richness were strongly related to the different levels of contamination, soil properties and adverse factors of mine tailings.

Conclusions

Although the high concentrations of toxic trace elements and low pH soil are important factors for limiting the plant growth, however, proper soil development with enriched nutrients and properties on mining wastes, by either natural or external soil aided process, can help to promote the high vegetation growth, mine rehabilitation and ecological restoration of the mining degraded lands.