Effects of Red Mud on the Remediation of Pb, Zn and Cd in Heavy Metal Contaminated Paddy Soil

[Objective] To study the remediation efficiency of red mud on Pb, Zn and Cd in the heavy metal contaminated paddy soil of mine area, to clarify its remediation mechanism and fertilizer efficiency on heavy metal contaminated soil. [Method] The soil incubation experiment was conducted to study the effect of red mud on the pH values and electrical conductivity （EC）, and the remediation efficiency of red mud on lead （Pb）, zinc （Zn） and cadmium （Cd） in heavy metal contaminated soil. [Result] Red mud addition reduced the content of exchangeable Pb, Zn and Cd in the soil significantly. Compared with the control, when incubated for 30, 60 and 90 d with the red mud dosage of 4% （W/W）, the exchangeable Pb content was decreased by 39.25%, 41.38% and 50.19%; exchangeable Zn content was decreased by 49.26%, 57.32% and 47.16%; and exchangeable Cd content was decreased by 19.53%, 24.06% and 25.70%, respectively. The application of red mud had significant impact on the share of Pb, Zn and Cd contents in five forms, and different amounts of red mud application all reduced the proportion of exchangeable Pb, Zn and Cd to the total Pb, Zn and Cd. In addition, the proportion of exchangeable Pb, Zn and Cd to total Pb, Zn and Cd decreased with the increasing amount of red mud addition. [Conclusion] The study provided references for reasonable application of red mud and reduction of heavy metal pollution in paddy soil.

Study Progress in Remediation of Soil Contaminated by Heavy Metals and Its Application Prospect

Flax is an ideal crop for remedying soil contaminated by heavy metals. It has high tolerance to heavy metals and strong adsorption to heavy metals. Through properly using or adjusting external conditions such as regulator, moisture, fertilizer, microorganisms, and pH value, it is able to improve ability of flax to absorb, trans- fer, and accumulate heavy metals. To improve the ability of flax in remediating heavy metal contaminated soil, it is recommended to strengthen cultivation of flax varieties and screening of germplasm resources, actively carry out studies on tech- nologies of fax remedying heavy metal contaminated soil, implement large-scale and mechanized planting of flax, and promote control of heavy metal contaminated soil.

Removal of heavy metals from a contaminated soilusing tartaric acid

This study reports the feasibility of remediation of a heavy metal （HM） contaminated soil using tartaric acid, an environmentally-friendly extractant. Batch experiments were performed to test the factors influencing remediation of the HM contaminated soil. An empirical model was employed to describe the kinetics of riM dissolution/desorption and to predict equilibrium concentrations of HMs in soil leachate. The changes of HMs in different fractions before and after tartaric acid treatment were also investigated. Tartaric acid solution containing HMs was regenerated by chestnut shells. Results show that utilization of tartaric acid was effective for removal of riMs from the contaminated soil, attaining 50%-60% of Cd, 40%-50% of Pb, 40%-50% of Cu and 20%-30% of Zn in the pH range of 3.5-4.0 within 24 h. Mass transfer coefficients for cadmium （Cd） and lead （Pb） were much higher than those for copper （Cu） and zinc （Zn）. Sequential fractionations of treated and untreated soil samples showed that tartaric acid was effective in removing the exchangeable, carbonate fractions of Cd, Zn and Cu from the contaminated soil. The contents of Pb and Cu in Fe-Mn oxide fraciton were also significantly decreased by tartaric acid treatment. One hundred milliliters of tartaric acid solution containing HMs could be regenerated by 10 g chestnut shells in a batch reactor. Such a remediation procedure indicated that tartaric acid is a promising agent for remediation of HM contaminated soils. However, further research is needed before the method can be practically used for in situ remediation of contaminated sites.

Studies on Heavy Metal Pollution in Soil-Plant System:A Review

Heavy metal pollution in soil-plant system is of major environmental concern on a world scale and in China in particular with the rapid development of industry. The heavy metal pollution status in soil-plant system in China, the research progress on the bioavailability of heavy metals (affecting factors, extraction methods, free-ion activity model, adsorption model, multivariate regression model, Q-I relationship, and compound pollution), and soil remediation are reviewed in the paper. Future research and monitoring is also discussed.

Evaluation of remediation process with soapberry derived saponin for removal of heavy metals from contaminated soils in Hai-Pu, Taiwan

The use of a biodegradable natural plant-based surfactant extracted from soapberry is proposed for the remediation of Ni, Cr and Mn from industrial soil site in Hai-Pu, Taiwan. Batch experiments were performed under variation of fundamental factors （saponin concentration, pH, and incubation time） for metal remediation. Removal of Ni and Mn were increased with increasing saponin concentration （0.015-0.150 g/L）, whereas the removal of Cr was increased upto 0.075 g/L saponin. The Ni, Cr and Mn were removed significantly （p 〈 0.05） at near to the neutral and slightly acidic （pH 5 to 8） conditions. Removal efficiency of Ni （99%） from the soil was found to be greater than that of Cr （73%） or Mn （25%） in the presence of saponin at a concentration of 0.150 g/L at pH 5. The removal percentage increased with incubation time where the removal of Ni was faster than that of Cr and Mn. The result indicates the feasibility of cco-friendly removal of heavy metal （Ni, Cr and Mn） from industrial soil by soil washing process in presence of plant derived saponin.

Soil heavy metal pollution from Pb/Zn smelting regions in China and the remediation potential of biomineralization

Smelting activities pose serious environmental problems due to the local and regional heavy metal pollution in soils they cause. It is therefore important to understand the pollution situation and its source in the contaminated soils. In this paper, data on heavy metal pollution in soils resulting from Pb/Zn smelting(published in the last 10 years) in China was summarized. The heavy metal pollution was analyzed from a macroscopic point of view. The results indicated that Pb, Zn, As and Cd were common contaminants that were present in soils with extremely high concentrations. Because of the extreme carcinogenicity, genotoxicity and neurotoxicity that heavy metals pose, remediation of the soils contaminated by smelting is urgently required. The primary anthropogenic activities contributing to soil pollution in smelting areas and the progressive development of accurate source identification were performed. Due to the advantages of biominerals, the potential of biomineralization for heavy metal contaminated soils was introduced. Furthermore, the prospects of geochemical fraction analysis, combined source identification methods as well as several optimization methods for biomineralization are presented, to provide a reference for pollution investigation and remediation in smelting contaminated soils in the future.

重金属-PAHs污染土壤植物微生物修复效果及机理

针对焦化厂等土壤中铬(Cr)、砷(As)重(类)金属和菲(Phe)、苯并[a]芘(BaP)等多环芳烃(PAHs)风险高、绿色低碳修复技术缺乏等突出问题,以黑麦草-玉米-食醚红球菌(Rhodococcus aetherivorans,BW2)开展植物微生物联合。结果表明,63 d后植物微生物联合修复组土壤中Cr、As、Phe和BaP浓度分别下降9.63%、5.28%、45.14%和26.87%,其中重金属的去除主要依赖于植物作用,而PAHs去除则在很大程度上取决于微生物与植物的共同作用;植物主要吸收可提取态重金属,63 d后不同修复组土壤中可交换态Cr平均下降2.19%,而As则由于降解作用使修复过程中可交换态增加;可交换态Cr和碳酸盐结合态Cr与土壤中放线菌门呈强正相关,2种形态As则与拟杆菌门、装甲菌门、FBP菌门和浮霉菌门呈正相关。污染物去除效率间存在明显的相互作用,同时受酶活性和不同功能微生物丰度的动态影响,反之土壤微生物群落结构和功能也在土壤污染物种类、浓度及理化性质等综合作用下发生改变。

氧化钙活化过硫酸盐修复重金属-有机物复合污染土壤

采用氧化钙活化过硫酸盐氧化法修复重金属-有机物复合污染土壤,考察了过硫酸钠投加量、过硫酸钠与氧化钙投加比、水土比等对修复效果的影响,探讨了机理。结果表明,在过硫酸钠投加量2.5 mmol/g,氧化钙与过硫酸钠投加比2∶5,水土比3∶1的条件下,汞、砷的钝化率分别为81%和83%,存在形态由弱酸提取态转化为更为稳定的残渣态,氯仿、苯、总石油烃和1,2,3-三氯丙烷的去除率分别为99%,98%,82%,80%。氧化钙一方面,催化过硫酸盐,产生硫酸根自由基和羟基自由基氧化重金属、降解有机污染物。另一方面,通过物理固封和吸附、络合、沉淀作用钝化汞、砷。研究为重金属-有机物复合污染土壤修复技术的实际应用奠定基础。

煤矿矿区土壤重金属及多环芳烃污染治理修复技术综述

土壤重金属和有机物污染是当前许多煤矿矿区及周边地区面临的严重问题,威胁居民健康,要采取有效措施予以解决。在对煤矿矿区周边土壤重金属和多环芳烃(PAHs)来源及危害分析的基础上,发现重金属元素在自然条件下难以降解,导致其在生物体中累积,并且PAHs具有致癌性、致畸性和诱变性。通过比较物理化学修复、植物修复和生物修复等方法在治理重金属及PAHs污染土壤的优缺点,发现植物修复和生物修复对气候和环境的依赖程度高,物理修复成本和能耗较高,因此提出矿区周边土壤污染的修复技术需要进一步创新,实现多领域、多学科协作发展的观点。通过持续的技术创新和多种修复方法的联合应用,达到有效治理煤矿矿区及周边重金属和PAHs污染的目的,实现土壤的重新利用,进而实现环境保护与经济可持续发展的良性互动。

菊芋(Helianthus tuberosus)对镉、铅、锌复合污染土壤的修复潜力

菊芋是一种生物量大、生长旺盛、易于栽培的能源作物。为探究菊芋对镉(Cd)、铅(Pb)、锌(Zn)复合污染土壤的修复潜力,利用土培盆栽和原位大田试验,研究菊芋对Cd、Pb、Zn复合胁迫的生长特性、富集特征、去除率及修复潜力。结果表明:随着盆栽土壤中Cd、Pb、Zn含量的增加,菊芋的株高、生物量先降低再升高再降低,SOD酶活性先升高再降低再升高,CAT酶活性先升高再降低,POD酶活性总体表现为逐渐升高。菊芋对Cd的富集系数范围为1.08~1.79,转运系数范围为2.05~6.27,地上部Cd最大积累量达到98.25 mg/kg;Pb富集系数范围为0.77~1.31,转运系数范围为3.41~5.67,地上部Pb最大累积量为585.81 mg/kg;Zn富集系数范围为0.44~0.79,转运系数范围为1.69~3.33,地上部Zn最大累积量为2668.04 mg/kg。原位大田试验中,菊芋地上部Cd、Pb、Zn含量范围分别为125.79~201.08 mg/kg、1075.99~1525.46 mg/kg、6896.21~7443.66 mg/kg,每亩受污染土壤种植2茬菊芋对Cd、Pb、Zn的年去除率分别为5.16%~9.04%、10.84%~16.90%、4.60%~5.46%。菊芋具有较好的Cd、Pb、Zn复合胁迫耐受性和修复潜力,可作为Cd、Pb、Zn复合污染土壤修复的潜在超富集植物种质资源,具有较好的应用前景。

天然矿物修复剂筛选及其对镉固持性能研究

对湖南省14个产地、4类矿物材料的镉固持性能进行对比,优选出4种天然高效镉修复材料(宁乡县喻家坳的石灰石、湘潭县楠木冲的低品位锰矿石、桃源县马宗岭的膨润土和石门县新岗的海泡石)。4种天然矿物材料对镉的固持动力学速率从快到慢排序为:膨润土>石灰石>海泡石>锰矿石。各矿物材料对镉的吸附量随着镉初始质量浓度增大而增大,镉质量浓度不高于10.0 mg/L时,各矿物材料对镉的吸附量从大到小排序为:石灰石>膨润土>锰矿石>海泡石;镉质量浓度高于10.0 mg/L时,各矿物材料对镉的吸附量从大到小排序为:膨润土>石灰石>锰矿石>海泡石。吸附行为均符合Langmuir吸附模型,膨润土、石灰石、锰矿石、海泡石对镉的最大吸附容量分别为29.38、14.51、9.67、5.27 mg/g。溶液pH=6~9时,各矿物材料对镉的去除效率排序为:石灰石>膨润土>锰矿石>海泡石。天然矿物材料对镉的固持效果与矿物的化学组分、初始镉质量浓度、pH值有关。

重金属污染土壤修复方法及资源化利用途径分析

面对土壤重金属污染问题,迫切需要采取措施来修复重金属污染土壤并将其资源化。通过文献调研,旨在阐明我国目前土壤重金属污染的状况,阐述了重金属污染土壤常见的修复方法,包括物理修复、化学修复、生物修复和联合修复等;并在此基础上,分析了目前重金属污染土壤资源化利用主要方向为土壤化利用、建材化处理及路基填筑,针对当前研究存在的问题提出建议,并对未来研究方向进行展望。

冀北花岗岩地区坡积冲洪积型污染耕地土壤治理比较研究

土壤是农业生态系统重要的组成部分,耕地土壤重金属污染会影响农产品质量安全。本研究选取冀北花岗岩地区坡积物母质区和冲洪积物母质区的弱酸性农田土壤为研究对象,依托钝化修复和植物提取(玉米和龙葵为植物修复材料)两种修复技术,探究了不同成土母质类型和修复技术对耕地土壤重金属的修复效果影响。研究结果表明:(1)坡积物和冲洪积物母质区土壤的有机质、速效钾、有效磷和pH值存在显著差异,坡积物母质区土壤pH显著低于冲洪积物母质区土壤,两区成土母质均具有较高的Pb背景值;(2)钝化修复后,冲洪积物母质区玉米籽粒Cd和Pb含量显著降低,玉米籽粒增产19.10%~33.00%,较坡积物母质区显示出更好的修复效果;(3)坡积物母质区采用龙葵和玉米间作模式,植物修复每年每公顷中提取Cd、Pb和Cu分别为167.25、208.35和555.05 g,Cd、Pb和Cu的去除率分别为2.727%、0.043%和0.234%,较冲洪积物母质区显示出更好的修复效果;(4)龙葵和玉米的间作模式优于单一种植模式,间作可以提高土壤中重金属的生物可利用性和植物吸收效率;(5)制定土壤污染修复策略时,需考虑土壤特性、成土母质及不同农作物的影响,选用合适的修复技术和种植模式。本研究可为地质异常区域农田土壤安全利用与修复提供参考依据。

植物-电动耦合修复重金属污染土的效能及其强化机制

重金属污染土壤的净化效果直接影响修复后土体的再利用。以Cd、Cu、Ni、Zn、Pb污染土壤为研究对象,采用改进环绕式电极布置,以植物-电动耦合修复下土壤的净化度及土壤性质为重点,厘清关键因素,揭示耦合强化修复机制。结果表明:植物-电动耦合修复下不同重金属的去除率均较单一修复有所提高,重金属赋存形态及植物对重金属的响应是影响修复效果的关键因素。改进环绕式电场的施加能积极调动更大范围土壤中的重金属向植物根系迁移聚集,解决了植物修复中重金属可及性和生物活性低的问题;植物修复的协助有利于改善电动修复对土壤性质的不利影响,解决聚焦效应和高能耗问题。植物-电动耦合修复联合了重金属的空间分布改善、重金属生物利用度提升、植物生长代谢强化及土壤微生物生命活动调节等作用机制,有效提高了重金属污染土壤的净化度,修复后土体可维持稳定的pH值(6.27~7.91)、电导率(108~159μs/cm)及低能耗(13.76~18.81 kW·h/m3),有助于推进污染土壤的可持续利用。

硅肥和磷矿粉复配对垃圾填埋场重金属污染土壤的修复

以四川省盐亭县云溪镇垃圾填埋场的紫色土为研究对象,将不同质量分数的硅肥(Si1:0.5%,Si2:1.0%)和磷矿粉(P1:0.2%,P2:0.4%,P3:1.0%)复配添加到土壤中培养90 d,研究钝化培养前后重金属Cd、Cu、Pb、Zn有效态含量的变化,并利用风险评价系数(risk assessment code,RAC)评价土壤修复效果。结果显示,高硅处理(Si2:1.0%)相比于低硅处理(Si1:0.5%)能显著降低重金属有效性,其中,Si2P3处理对Cd、Cu、Pb、Zn的钝化率最高,分别为30.79%、27.27%、27.13%、36.88%;Si2P1和Si2P2处理之间没有显著差异,而Si2P1处理可以显著降低重金属浸出毒性量和RAC。研究表明,复配钝化剂主要通过提高土壤pH和EC值,增强O-Si-O、Si-O-Si、H_(2)PO_(4)^(-)、PO4^(3-)等官能团的络合沉淀作用促使重金属由高活性的弱酸提取态、可还原态向低活性的可氧化态、残渣态转化。综合来看,Si2P1处理钝化剂施用量更低,更适合用于垃圾填埋场重金属污染土壤的修复。

生物有机肥对土壤镉形态及玉米镉积累的影响

为探究生物有机肥治理镉污染土壤的可行性及对土壤重金属污染修复的效果,采集河南省淅川县2种镉污染土壤,分别设置6种施肥处理:CK(不施用任何物料)、NPK(常规施NPK肥)、NPK+0.5%OF(常规施肥+0.5%商品有机肥)、NPK+1%OF(NPK+1%商品有机肥)、NPK+0.5%BF(NPK+0.5%生物有机肥)和NPK+1%BF(NPK+1%生物有机肥),测定种植前后土壤全镉含量、土壤各化学形态镉、玉米植株根系及籽粒镉含量。结果显示,以添加1%生物有机肥的治理效果最佳,NPK+1%BF处理下2种土壤有效态镉含量相较于NPK+1%OF降幅分别为19.74%、7.09%;施用有机物料降低土壤弱酸提取态镉含量,提高残渣态镉含量,NPK+1.0%BF弱酸提取态镉含量相比CK下降11%、残渣态镉上升16%;施用有机物料各处理玉米植株根系、籽粒镉含量显著降低,以NPK+1.0%BF处理效果最佳,相比NPK处理,土壤Ⅰ的玉米根系、籽粒镉含量降幅达34.41%、31.59%。综上,在镉污染土壤中施用生物有机肥,可显著降低土壤有效态镉含量,促进土壤弱酸提取态镉向残渣态镉转化,降低镉危害;玉米根系及籽粒镉含量均显著下降,综合治理效果表现为生物有机肥优于商品有机肥。

一种新型重度铬污染土壤修复技术

我国退役铬化工企业的土壤铬污染严重,部分土壤六价铬浓度可高达10^(3)~10^(4)mg·kg^(-1),对植物生长、人类活动产生了不良影响。常用的铬污染土壤修复方法有还原修复技术、生物修复技术、酸淋洗-还原联合修复技术,用稀酸溶液加上还原剂将土壤中的六价铬浸出、还原。但酸溶液对难提取六价铬的溶解效果有限,且易引起土壤侵蚀等次生环境问题。碱性条件下重度铬污染土壤淋洗和还原的修复工艺能有效解决酸淋洗存在的土壤溶蚀、钙流失、含盐量大幅增加以及其他重金属浸出浓度超标等次生环境问题,且该技术通过碱淋洗还原工艺显著提高难提取六价铬的提取和还原效率,该研究形成经济可行、易于推广的铬污染土壤修复技术路线。

某矿业公司周边耕地土壤环境现状调查评价

为摸底小型矿业类厂区对周边耕地的环境影响及后期对潜在污染的评价与防控,采用单项污染指数、内罗梅综合污染指数、地统计等方法,通过土壤风险程度分类、超标倍数、背景值比较等手段,评价某矿业公司周边耕地土壤污染状况。评价结果表明:厂区周边耕地土壤重金属全铬、六价铬、汞元素及氰化物对土壤环境质量风险无,耕地土壤环境质量全部为安全利用类,土壤环境质量风险可控;耕地土壤超标率:氟化物>锰>镉>砷>锌>铅。铅元素含量偏高可能受到历史或周边其他企业等因素影响。

比较三种稳定剂对FeS纳米颗粒的稳定效果及对水土中镉的固定与去除性能的影响

本研究评估了三种多糖稳定剂(羧甲基纤维素钠(CMC)、羧甲基淀粉钠(CMS)和一种水溶性淀粉)用于稳定FeS纳米颗粒的有效性,并测试了相应稳定化纳米颗粒在水和土壤中固定Cd^(2+)的性能。使用0.010 wt%CMC、0.025 wt%CMS或0.065 wt%淀粉可获得完全稳定的FeS纳米颗粒(100 mg/L FeS)。CMC-FeS表现出较高的zeta负电位,淀粉-FeS保持中性,而CMS-FeS则表现出中等负电位。CMCFeS对Cd^(2+)的吸附速率最快,吸附容量也最高。当用100 mg/L CMC-FeS或CMS-FeS处理一种含Cd土壤(58.3 mg/kg Cd)后,Cd的TCLP浸出率分别降低了88.4%和68.0%。CMC-FeS和CMS-FeS均可在模型土壤中运移,显示出其在土壤中原位固定Cd^(2+)方面的潜力。土壤穿透曲线实验表明,CMC-FeS在4.5个孔体积,CMS-FeS在约25个孔体积处几乎完全穿透。柱实验结果表明,当用55个孔体积的CMC-FeS或CMS-FeS悬浮液(100 mg/L)处理该含Cd土壤后,Cd的水浸出率分别降低了98.2%和98.0%。根据目标污染物、材料在土壤中的传输特性和材料成本,可找到这三种稳定剂在土壤修复中的最佳应用。

无患子联合EDTA-2Na协同洗脱高细粒土壤中Pb和Cd

利用振荡淋洗试验探讨不同浓度的无患子(WHZ)和EDTA-2Na用量对重金属Pb、Cd的去除效果,并选择合适的淋洗方式,探究其最佳淋洗参数,分析淋洗前后重金属形态变化。结果表明,“WHZ+EDTA-2Na”淋洗参数中固液比为1∶3,优选的用量为EDTA-2Na为1 g,无患子粗提液浓度为5 g/L,淋洗2 h对Pb和Cd的去除率分别达到76.50%和73.40%。无患子粗提液联合低浓度EDTA-2Na复合淋洗效果均优于单独淋洗,其中两者混合淋洗组合效果最好。形态分析结果表明,复配淋洗剂对土壤中重金属Cd的可交换态和Pb的铁锰氧化物态有较好的洗脱效果。