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.

LED3A强化紫花苜蓿修复Cd污染土壤的效果研究

研究可生物降解螯合剂N-十二酰基乙二胺三乙酸盐(LED3A)诱导强化紫花苜蓿修复Cd污染土壤的效果,采用盆栽方法,考察LED3A对紫花苜蓿生理指标、Cd亚细胞分布和化学形态以及增效提取土壤中Cd的影响.结果表明,Cd胁迫显著抑制紫花苜蓿的生长及光合作用,增加丙二醛(MDA)的积累.而在土培体系中施用LED3A,可以提高植株生物量、光合色素含量、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性,缓解细胞膜脂过氧化损伤和Cd诱导产生的氧化应激.LED3A的螯合强化作用能够增大紫花苜蓿细胞质中Cd的分布比例,促使植株中的Cd由高活性形态向低活性形态转化,通过细胞壁固持和液泡区隔化提高耐Cd性能,进而减轻毒害.与不添加LED3A组相比,最佳LED3A添加量(321.3 mg·kg^(-1))组紫花苜蓿植株中的总Cd含量和积累量分别提高了29.4%和69.1%,地下/地上富集系数及转运系数分别增加了28.6%,36.4%和10.5%.说明添加适量LED3A可有效提高紫花苜蓿对Cd的耐受性与修复Cd污染土壤的效果.

Study on the Remediation of Cd-contaminated Soil

[Objective] The remediation effect of the plant to Cd-contaminated soil was studied. [Method] By taking simulation test and field test, the ryegrass （Lolium perenne L.） was planted, and the remediation effect of the plant to contaminated sites was studied. [Result] The ryegrass was planted in the eluotropic soil for 0-60 d, Cd content in the soil showed a rapid decreasing trend; after 60 d, the enrich- ment ability of the plant to Cd gradually weakened over time; after 75 d of phytore- mediation, the Cd content in the soil decreased greatly, and the remediation effi- ciency was 90.66%. [Conclusion] Ryegrass remediation technology had good reme- diation effect to Cd-contaminated soil.

Cadmium Release in Contaminated Soils due to Organic Acids

There is limited information on the release behavior of heavy metals fromnatural soils by organic acids. Thus, cadmium release, due to two organic acids (tartrate andcitrate) that are common in the rhizosphere, from soils polluted by metal smeltersor tailings andsoils artificially contaminated by adding Cd were analyzed. The presence of tartrate or citrate at alow concentration (<= 6 mmol L^(-1) for tartrate and <= 0.5 mmol L^(-1) for citrate) inhibited Cdrelease, whereas the presence of organic acids in high concentrations (>= 2 mmol L^(-1) for citrateand >= 15 mmol L^(-1) for tartrate) apparently promoted Cd release. Under the same conditions, theCd release in naturally polluted soils was less than that of artificially contaminatedsoils.Additionally, as the initial pH rose from 2 to 8 in the presence of citrate, a sequentialvalley and then peak appeared in the Cd release curve, while in the presence of tartrate the Cdrelease steadily decreased. In addition, Cd release was clearly enhanced as the electrolyteconcentration of KNO_3 or KC1 increased in the presence of 2 mmol L^(-1) tartrate. Moreover, ahigher desorption of Cd was shown with the KCl electrolyte compared to KNO_3 for the sameconcentration levels. This implied that the bioavailability of heavy metals could be promoted withthe addition of suitable types and concentrations of organic acids as well as reasonable fieldconditions.

典型矿区周边水田土壤Cd生物有效性研究

为遴选可有效表征农田土壤Cd生物有效性的指标,文章采集浙江某地20组稻米及其协同土壤,分析稻米Cd质量比、土壤的基本理化性质、Cd总质量比、不同浸提态Cd质量比及欧共体标准物质局(European Community Bureau of Reference,BCR)形态。结果表明:稻米Cd质量比为0.01~0.51 mg/kg,土壤Cd质量比为0.17~3.15 mg/kg,稻米Cd富集系数为0.04~1.42;土壤Cd主要以弱酸态(40.5%)和还原态(37.1%)存在,二乙烯三胺五乙酸(diethylenetriaminepentaacetic acid,DTPA)浸提土壤Cd能力最强(15.6%);基于w(CaCl_(2)-Cd)构建的三次函数建立的回归模型可解释稻米Cd 57.4%方差,w(CaCl_(2)-Cd)可以作为表征水稻土壤Cd生物有效性的指标,基于水稻土壤Cd生物有效性可提高污染风险评价的科学性。

Effects of Exogenous 5-Aminolevulinic Acid and 24-Epibrassinolide on Cd Accumulation in Rice from Cd-Contaminated Soil

High grain-Cd-accumulating rice variety Yongyou 9 was planted in Cd-contaminated farmland in Taizhou City, Zhejiang Province, China to study the effects of 5-aminolevulinic acid(ALA) and24-epibrassinolide(EBR) on Cd accumulation in brown rice. Results showed that the exogenous ALA and EBR had no significant effects on agronomic traits, soil pH and total Cd content in soil, but had some effects on the available Cd content in soil, and significantly influenced the Cd accumulation in the different parts of rice. Results also showed that 100 mg/L exogenous ALA significantly reduced the Cd accumulation in brown rice to blow the food safety standard(0.2 mg/kg), and also significantly reduced the Cd contents in the roots and culm of rice. However, 200 mg/L exogenous ALA treatment increased the Cd content in brown rice remarkably. In addition, 0.15 mg/L EBR treatment increased Cd accumulation in roots, culm, leaves and brown rice notably, whereas 0.30 mg/L exogenous EBR treatment reduced the Cd accumulation in brown rice properly, but it was not significant. Therefore,proper concentration of ALA can effectively reduce the Cd accumulation in brown rice, which can be used as an effective technical method for the safe production of rice in Cd polluted farmland.

纳米材料修复Cd污染土壤的人体健康风险研究

为评估纳米材料修复Cd污染土壤因偶然摄入导致的健康风险,该研究加入1.0%、1.5%、2.0%的纳米羟基磷灰石(n-HAP)、纳米四氧化三铁、改性纳米碳黑修复Cd污染棕壤,通过体外胃肠模拟法评估其对人体健康的影响。结果表明,3种纳米材料可有效降低土壤中DTPA提取态Cd含量,其中n-HAP效果最好;同时Cd的胃肠相生物可给性显著降低,并且随纳米材料添加量而降低,经口摄入的Cd胃相生物可给性均大于肠相。3种材料的添加量与胃肠相中Cd的生物可给性呈线性负相关,且对肠相生物可给性影响更大。纳米材料修复土壤显著降低了Cd污染土壤的非致癌健康风险和致癌健康风险,修复后土壤不存在显著的非致癌健康风险(HQ<1)和致癌风险(CR<1×10^(-6)),且对儿童的健康风险高于成人。因此,纳米材料能有效降低棕壤颗粒中Cd的生物可给性,从而缓解因偶然摄入导致的健康风险,为纳米材料修复Cd污染土壤的健康风险评估提供科学依据。

两种Cd积累型番茄品种联合土著微生物对土壤有效态Cd的影响

镉(Cd)在作物体内的累积能力主要受土壤Cd有效性决定,为降低Cd积累和保障作物安全,本研究以低Cd积累型‘普罗旺斯’和高Cd积累型‘合作908’番茄品种为研究对象,结合Illumina MiSeq测序,探讨番茄和土著微生物共同作用对土壤中有效态Cd及微生物多样性的影响。试验设置背景土壤(Cd含量0.24 mg·kg^(-1))和Cd污染土壤(Cd含量0.60 mg·kg^(-1))的灭菌(无土著微生物)与不灭菌(有土著微生物)处理,在此基础上,分别设置不种植番茄、种植‘合作908’和‘普罗旺斯’处理。结果表明:在背景土壤和Cd污染土壤中,‘合作908’吸收积累土壤Cd的能力均显著高于‘普罗旺斯’。与不种植(CK)相比,在灭菌土壤种植‘普罗旺斯’和‘合作908’的单一作用使污染土壤有效态Cd含量分别增加3.16%和5.26%;不灭菌土壤的土著微生物单一作用使污染土壤有效态Cd增加27.37%;不灭菌土壤种植‘普罗旺斯’和‘合作908’(与土著微生物联合)比在灭菌土壤中作物单一种植使土壤有效态Cd含量分别增加29.59%和28.00%,比不灭菌土壤(土著微生物单一作用)分别提高4.96%和5.79%。与CK处理相比,不灭菌污染土壤种植‘普罗旺斯’和‘合作908’使土壤鞘氨醇单胞菌属(Sphingomonas)、微鞘藻属(Microcoleus)、Haliangium和爬管菌属(Herpetosiphon)相对丰度均明显增加。同时,在不灭菌污染土壤种植‘普罗旺斯’处理中游动放线菌属(Actinoplanes)和硝化螺菌属(Nitrospira)相对丰度增加,而在不灭菌污染土壤种植‘合作908’处理中噬氢菌属(Hydrogenophaga)和溶杆菌属(Lysobacter)相对丰度增加,两处理间存在着明显的差异菌属。这些优势菌属可能与两种积累型番茄品种种植下的土壤有效态Cd含量差异有关。综上,两种积累型番茄品种-土著微生物的联合作用提高了土壤微生物的多样性,改变了土壤细菌群落结构,显著提升了土壤中有效态Cd的含量。

淹水灌溉协同钝化剂对水稻Cd吸收和积累的影响

在严格管控区Cd污染稻田开展田间试验,探讨淹水灌溉协同石灰和土壤调理剂对土壤Cd的有效性,以及水稻Cd吸收和累积的影响。结果表明:淹水灌溉协同钝化修复技术可有效降低土壤Cd的有效性和水稻Cd的吸收和积累。淹水灌溉协同石灰和调理剂处理下,土壤pH值较对照显著(P<0.05)提高0.97个单位,且土壤有效态Cd含量以及水稻根、茎和叶片Cd含量较对照分别显著(P<0.05)降低36.4%、63.0%、80.3%和42.4%,糙米Cd含量降至0.15 mg·kg^(-1)。淹水灌溉协同石灰和调理剂处理还显著抑制Cd向糙米部位的累积。糙米Cd的富集系数和Cd累积量较对照分别显著(P<0.05)降低67.8%和62.8%。因此,淹水灌溉协同土壤钝化修复技术是一种有效实现Cd污染稻田水稻安全生产的措施。

Monitoring of Cadmium Contaminated Soil in Kvemo Kartli Region (Republic of Georgia)

Environmental pollution increases from year to year and concentrations of pollutants reach a colossal point, which ultimately affects the health of the living organisms. Industrial pollution and old mining methods are one of the sources of harmful agents in the environment. It is important to study and monitor environmental pollution in dynamics. During several years we have been researching heavy metals distribution in soils in the South East part of Georgia. “RMG Gold and Copper” mine in Kazreti is one of the biggest enterprises in Georgia. As a result of open-cast mining aerosols containing heavy metals are ejected which causes harmful effects of the environment. Within this research 21 villages in Bolnisi and Dmanisi municipalities were investigated;analysis of agricultural soils showed that the concentration of cadmium in the vicinity of the enterprise was significantly increased and exceeded maximum allowed concentrations. Through the wind, cadmium-containing dust spreads out to the 22

Influence of Lherzolite on the Growth of Chinese Spinach and Soil Respiration in Cadmium Contaminated Soil

A glasshouse pot experiment was conducted to investigate cadmium (Cd) tolerance on the growth of Chinese spinach (Spinacia Oleracea L.) grown in sandy loam soil and microbial respiration after application of lherzolite (0%, 2.5% and 5%) with added Cd (0, 2.5 and 5 mg·kg-1). Soil pH tended to increase with increasing application rate of lherzolite about 1.5 units after plant harvest. Plant growth and microbial respiration in one hand decreased with the rates of Cd application in soil but on the other hand lherzolite application in soil reduced Cd toxicity and enhanced plant growth and microbial respiration. Microbial respiration of soil showed significant positive relationship with shoot and root dry weight of spinach but negative relationship of Cd concentration in plant tissue. This result indicated that application of lherzolite detoxified Cd toxicity in plant resulted in an increase plant growth and microbial respiration in Cd contaminated soil.

不同修复剂对Cd污染土壤的修复效果研究

针对Cd污染土壤,本文对比分析海泡石、沸石和凹凸棒石三种修复剂的修复效果。试验结果显示,3种修复剂均能有效降低Cd含量,根据修复效果,排序为海泡石>凹凸棒石>沸石,海泡石表现最佳,平均降低率达46.98%。研究发现,随着修复剂加入量的增加,修复效果逐渐提高,土壤初始镉含量越高,修复效果越明显。此外,所有修复剂均能提高土壤pH,减少镉的生物有效性。本研究为Cd污染土壤修复提供新方法。

Research Progress on Remediation Technology Suitable for Farmland Soil Contaminated by Cd

Cd contamination range of farmland soil in China is wide,which has constituted a major threat for food safety and residents＇ health. Via multi-year development,there are more remediation methods suitable for soil contaminated by Cd among the world,but some methods are only suitable for the contaminated sites and indoor research,and can not be applied in large-range contaminated farmland. We analyze the source of Cd in farmland soil. By combining farmland＇s characteristics,three remediation techniques（ low-absorption crops plantation,soil solidification and phytoremediation） and their effects are analyzed,and the existing problems and research prospects of the above techniques are explored. The research could provide reference for restoring farmland soil contaminated by Cd in China,recovering its production function and enhancing food safety standards.

铁锰改性生物炭对土壤中Cd的吸附稳定性的影响

本文以水稻秸秆为原料,制备了生物炭(BC)及铁锰改性生物炭(FMBC),对Cd^(2+)溶液进行了吸附-解析实验,对吸附前后生物炭的傅里叶红外光谱(FT-IR)和X射线衍射(XRD)结果进行分析,探究了生物炭对土壤中Cd^(2+)的吸附稳定性和土壤理化性质的影响。结果表明:1)改性后,生物炭FMBC的碳化程度相比生物炭BC有一定的提高,表面的活性官能团种类和数量也有一定增加,为Cd^(2+)提供了更多的吸附位点,提升了生物炭对Cd的吸附性能;2)FMBC对Cd的吸附过程更符合Langmuir等温线方程,说明其吸附行为可能是单分子层的化学吸附,吸附机理可能更倾向于离子交换作用和共沉淀。FMBC对Cd的吸附效果和固定性能优于BC,Cd^(2+)溶液浓度为40~80mg·L^(-1)时,FMBC对Cd的吸附率达到92%以上,解析率则低于11.2%。

Effects of Farm Yard Manure and Lime on Cadmium Uptake by Rice Grown in Two Contaminated Soils of Chittagong

A pot experiment was conducted to evaluate the efficiency of farm yard manure （FYM） and lime （calcium carbonate） on reducing the uptake of Cd by rice in two Cd contaminated soils of Chittagong. The effects of farm yard manure, lime and farm yard manure mixed with lime （FYM ＋ Lime） on rice （Oryza sativa L.） growth, Cd uptake by rice and 0.1 N HC1 extractable Cd in soil were investigated. Results showed that addition of lime and farm yard manure mixed with lime significantly decreased 0.1 N HCl extractable Cd in the city sewage soil. Application of farm yard manure significantly decreased Cd concentration in rice in the city sewage soil. Lime and farm yard manure mixed with lime significantly reduced Cd concentration in rice m both the contaminated soils. Lime was more efficient than farm yard manure in reducing the uptake of Cd by rice.

Status of Heavy Metal Contamination in Paddy Soil of Guangxi Province and Effect of Silicon Fertilization on Cd Content in Brown Rice

[Objective] To provide a scientific basis for the management of Cd contamination, the status of Cd contamination in paddy soil of Guangxi Province, as well as the effect of silicon fertilization on Cd content in brown rice, was investigated. [Method] A total of 157 topsoil（0-20 cm） samples were collected from the major rice-growing paddy fields in Guangxi Province. The Cd contents in the topsoil samples were determined. The paddy soil environment quality and potential ecological risk were evaluated by single factor index and potential ecological index methods. In addition, in the Cd-contaminated paddy fields, the effects of different silicon fertilization treatments（no application（CK）, soil application of 750 kg/hm^2 silicon fertilizer（S）, leaf application of 1 500 L/hm^2 0.2% nanometer silicon（L）, soil application of 750 kg/hm^2 silicon fertilizer ＋ leaf application of 1 500 L/hm^2 0.2% nanometer silicon（SL）） on Cd content in brown rice were investigated. [Result] The total Cd contents in the 157 topsoil samples from paddy fields of Guangxi Province ranged from 0.02 to 7.33 mg/kg with an average content of 0.53 mg/kg. The Cd contents in 35.03% of the topsoil samples exceeded the grade II of national soil environment quality standards, and the topsoil samples were dominated by moderate and mild Cd contamination. Different silicon fertilization treatment all significantly reduced the Cd content in brown rice（P〈0.05）. In the treatment III, the Cd content in brown rice was lowest. Compared with that in the CK group, the Cd content in brown rice in the treatment III was reduced by 73.45%, in the treatment II was reduced by 62.07%, and in the treatment I was reduced by 34.48%. [Conclusion] The Cd in paddy fields of Guangxi Province showed a moderate to high ecological risk,and rational application of silicon fertilizer could effectively reduce the Cd content in brown rice.

Machine learning methods to predict cadmium(Cd)concentration in rice grain and support soil management at a regional scale

Rice is a major dietary source of the toxic metal cadmium(Cd).Concentration of Cd in rice grain varies widely at the regional scale,and it is challenging to predict grain Cd concentration using soil properties.The lack of reliable predictive models hampers management of contaminated soils.Here,we conducted a three-year survey of 601 pairs of soil and rice samples at a regional scale.Approximately 78.3%of the soil samples exceeded the soil screening values for Cd in China,and 53.9%of rice grain samples exceeded the Chinese maximum permissible limit for Cd.Predictive models were developed using multiple linear regression and machine learning methods.The correlations between rice grain Cd and soil total Cd concentrations were poor(R^(2)<0.17).Both linear regression and machine learning methods identified four key factors that significantly affect grain Cd concentrations,including Fe-Mn oxide bound Cd,soil pH,field soil moisture content,and the concentration of soil reducible Mn.The machine learning-based support vector machine model showed the best performance(R2=0.87)in predicting grain Cd concentrations at a regional scale,followed by machine learning-based random forest model(R^(2)=0.67),and back propagation neural network model(R^(2)=0.64).Scenario simulations revealed that liming soil to a target pH of 6.5 could be one of the most cost-effective approaches to reduce the exceedance of Cd in rice grain.Taken together,these results show that machine learning methods can be used to predict Cd concentration in rice grain reliably at a regional scale and to support soil management and safe rice production.

Compound contamination and secondary ecological effects of Cd and As in soil－alfalfa ecosystems

d and As both have harmful effects on the growth,development and seed germination of alfalfa, especially in such a condition as the coexistence of Cd and As in soil environment The research using the pot-culture imitative method first found that if soil was simultaneously polluted by Cd and As,function of alfalfa absorbing Cd from soil may be promoted because of the existence of As,in conversely,Cd may inhibit alfalfa plant from absorbing As It was also found that secon- dary ecological effects were most likely to be brought out due to the coexistence of Cd and As. For example,alfalfa is passive to excessively absorb Cu and Pb .The harmful effects undoubtedly intensi- fy the contamination of alfalfa, The results showed that the mechanism of the interaction among Cd,As,Pb and Cu in soil-alfalfa ecosystems is very complicated.

Temporal-spatial distribution and variability of cadmium contamination in soils in Shenyang Zhangshi irrigation area,China

Heavy metal contamination in soils has been of wide concern in China in the last several decades. The heavy metal contamination was caused by sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides and so on. The Shenyang Zhangshi irrigation area （SZIA） in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years duration. This study investigated the spatial distribution and temporal variation of soil cadmium contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd of soils was analyzed and then the spatial distribution and temporal variation of Cd in soils was modelled using kriging methods. The kriging map showed that long-term sewage irrigation had caused serious Cd contamination in topsoil and subsoil. In 2004, the Cd mean concentrations were 1.698 and 0.741 mg/kg, and the maxima 10.150 and 7.567 mg/kg in topsoils （0-20 cm） and subsoils （20-40 cm） respectively. These values are markedly more than the Cd levels in the second grade soil standard in China. In 1990, the Cd means were 1.023 and 0.331 mg/kg, and the maxima 9.400 and 3.156 mg/kg, in topsoils and subsoils respectively. The soil area in 1990 with Cd more than 1.5 mg/kg was 2701 and 206.4 hnl2 in topsoils and subsoils respectively; and in 2004, it was 7592 and 1583 hm^2, respectively. Compared with that in 1990, the mean and maximum concentration of Cd, as well as the soil area with Cd more than 1.5 mg/kg had all increased in 2004, both in topsoils and subsoils.