Remediation of Soils Contaminated with Molybdenum using Soil Amendments and Phytoremediation

For ruminants, there is a narrow span betweennutritional deficiency of Molybdenum and its potential toxicity. Molybdenosis occurs among cattlefeeding on forage with Mo concentrations above10 μg g^-1 or a Cu:Mo ratio <2. In the areaunder investigation forage Mo contents in the valleyare as high as 180 μg g^-1 due to industrialpollution, while the alpine pastures, where cattlegraze during summer, are nutrient (e.g. Cu) deficient.When driven to the valley pastures in fall, animalsoften fell ill with molybdenosis, and several died.The aim of the study was to remediate this 300 ha area. Two approaches were attempted: (1) to reduce theMo contents of the forage by immobilizing soil Mo, and(2) to increase plant Mo contents by mobilizing soilMo to increase plant Mo which may then be removed fromthe system (phytoremediation).In a soil extraction experiment we demonstrated thatphosphate fertilization, ammonium sulfate amendment,vermiculite, humic acid and sewage sludge increased Moleaching by 30 to 110%. Fe-humate and Mn-humateapplication decreased Mo in the leachate from96 μg L^-1 to 55 and 7 μg L^-1,respectively. Plant Mo contents were increased up to170% by P-fertilizer and up to 150% by vermiculite.Conversely, sewage sludge, Fe- and Mn-humate decreasedplant Mo contents by 60, 40 and 75% in thegreenhouse. In the field study, the effects weresmaller, but Mo export through plant harvest increasedby 88% after P-fertilization and 84% aftervermiculite amendment. Mn-humate and sewage sludgedecreased plant Mo content by 25 and 40%,respectively, rendering the forage suitable forfeeding of ruminants. P-fertilization and vermiculitemay thus be recommended for the severely contaminatedsites to enhance phytoremediation through Mo export,and Mn-humate and sewage sludge application appearsuited to remediate the less severely contaminated sites.     

Zn/Cd污染土壤的化学钝化修复

本文研究了天然凹凸棒石和改性凹凸棒石(凹 Fe、凹 Mn、凹 P)对Zn/Cd模拟污染土壤的修复效果.在土壤中添加改良剂20 g/kg土,进行黑麦草盆栽试验.采用植物吸收和化学提取来评价修复效果.植物吸收结果表明凹 P处理效果最好,其原因可能是形成氢氧化物或磷酸盐沉淀;化学提取实验结果表明凹凸棒石可在一定程度上降低弱交换态Zn的含量.     

In-Situ Immobilization of Cadmium and Lead by Different Amendments in Two Contaminated Soils

Different soil amendments, including 1% zeolite, 1% bentonite,5% Penghu soil (PHS), 5% Penghu soil + 1% manganese oxide (PHS + MO), 1% MO, and 1.5% silicate slag (SS), were used to immobilize Cd and Pb in two contaminated soils evaluated by single and sequential extractions and by uptake of Chinese cabbage (Brassica Chinensis L.). Results indicated that the PHS and MO significantly (p < 0.05) reduced the 0.1 M HCl extractable Cd and Pb in the two contaminated soils. Allamendment treatments did not change the organic and residual amounts of Cd and Pb in soils A and B, but the PHS andPHS + MOtreatments significantly reduced the exchangeable amounts of Cdand Pb in the two soils as measured by sequential extraction. Thecombination of PHS and MO amendments was associated with ahigh pH value and negative soil surface charge showed the best immobilizing efficiency of Cd and Pb in this study. All soil amendments investigated did not increase the dry matter weight of the plant, and most of them decreased the uptake of Cd and Pb, especially for the PHS and MO. The PHS and MO treatments reduced the extractability of Cd and Pb in two soils and theiruptake by the plant, but only the Pb content in Chinese cabbagefrom the amended soils was less than the background levels of heavy metals in leaf vegetables of Taiwan.     

不同钝化剂和培养时间对Cd污染土壤中可交换态Cd的影响

原位化学钝化技术是修复重金属污染土壤的重要途径之一,通过施入一些钝化剂以降低土壤中重金属有效态含量,从而减少其迁移及对植物的毒害。选取羟基磷灰石（HA）、磷矿粉（PRX和PRH）、沸石、赤泥、新鲜植物残体、玉米秸秆粉末以及相应的处理共21种钝化剂,在同一培养条件和添加浓度下,比较其对人工Cd污染土壤中可交换态Cd含量的影响,并分析了其在不同培养时间对钝化效果的时间效应,试验的结果对于筛选Cd污染土壤钝化剂有着重要的意义。结果表明,纳米化赤泥、羟基磷灰石和纳米化酸洗赤泥可显著降低土壤中可交换态Cd含量,钝化比例高达35%-55%;赤泥、酸洗赤泥、沸石达15%-25%;富含巯基植物蒜苗、油菜、大葱植物残体也可达20%-25%。磷矿粉、大葱粉末、玉米秸秆和巯基化玉米秸秆的钝化效果相对较差;HA、铵型沸石、纳米赤泥、酸洗纳米赤泥、干油菜粉末、酸洗赤泥对可交换态Cd的钝化效果的时间效应不明显;赤泥、大葱残体、特别是玉米秸秆和巯基玉米秸秆随时间增长钝化效果增加显著,在8周和16周时段钝化效果较好。     

Remediation of Cadmium Pollution in Soils by Different Amendments: A Column Study

Abstract

A column study was conducted to determine the effect of city compost, lime, gypsum, and phosphate on cadmium (Cd) mobility in three well‐recognized benchmark soils of India [viz., (Islamnagar) Vertisol, (Amarpur) Inceptisol, and (Khala) Alfisol]. Columns made of PVC were filled with soil treated with different treatment doses [viz., 0.5% city compost, 1% city compost, 2% city compost, 2.5 t lime/ha, 5 t lime/ha, 2.5 t lime/ha+0.5% city compost, 2.5 t gypsum/ha, 2.5 t gypsum/ha+0.5% city compost, and 100 kg P₂O₅/ha as potassium phosphate (KH₂PO₄). The columns were leached with 100 mg L^?1 Cd under saturated condition. The amount of water moving through the soils was measured as the pore volume. A delayed breakthrough curve (BTC) of Cd in the presence of lime has been observed in all the studied benchmark soil series. Among the treatments, lime application reduced the movement of Cd from surface soil to lower depth of soil to a large extent resulted in 9, 25, and 45% more retention of Cd in surface soil of the Islamnagar, Amarpur, and Khala series respectively. Explanation for reduced Cd mobility in limed soil can be derived from pH changes of soils. In comparison to control soil, phosphate application caused 6, 21, and 30% more retention of Cd in surface soil in the Islamnagar, Amarpur, and Khala series, respectively. Combined application of lime and city compost reduced the movement of Cd in the soil profile. It appears that organic matter controls the sorption of Cd in soils. The amount of Cd sorbed increased with increasing organic carbon content, but gypsum application may leach Cd beyond the root‐zone depth. A rapid breakthrough curve was observed under gypsum‐treated soils. Retardation factor revealed that a somewhat lower degree of Cd retention occurred in the Khala series, which might possibly be attributed to less clay content and low pH. Overall, the column study indicated that total Cd accumulation occurred up to depths of 5–7.5 cm, 7.5–10 cm, and 10–15 cm in soils of Islamnagar, Amarpur, and Khala series, respectively.     

不同钝化剂对Cu、Cr和Ni复合污染土壤的修复研究

利用盆栽试验研究了不同钝化剂(沸石、牡蛎壳、鸡蛋壳、硅藻土和聚丙烯酰胺(PAM))对生长在重金属污染土壤上的青菜(Brassica chinensis L.)生物量、重金属吸收以及超氧化物歧化酶的活性(SOD)和丙二醛(MDA)含量的影响,同时,通过对土壤p H和土壤重金属提取态的分析,探讨了钝化剂影响青菜生物量和重金属吸收的可能原因。结果表明:钝化剂加入可显著降低青菜地上部分Cu、Zn、Ni和Cd的含量及其氧化性损伤和脂膜损伤(SOD和MDA指标显著降低)。施入钝化剂后,土壤p H显著提高,重金属提取态Cu、Zn、Pb、Ni和Cd普遍降低(硅藻土处理除外)。相关性分析表明,土壤p H与提取态重金属Pb、Zn、Ni和Cd呈显著的负相关,而青菜中的重金属Zn、Ni和Cd的含量与土壤提取态含量呈显著正相关。综合考虑,单一钝化剂牡蛎壳和沸石+牡蛎壳+鸡蛋壳(FMJ)组合对降低青菜重金属吸收的效果尤为显著,可推荐作为重金属复合污染土壤的改良剂。本研究为重金属中轻度污染菜地的土壤修复提供了一种新方法。     

Heavy Metal Immobilization in Contaminated Soils using Phosphogypsum and Rice Straw Compost

The application of soil amendments to immobilize heavy metals is a promising technology to meet the requirements for environmentally sound and cost‐effective remediation. The present study was carried out to evaluate the result of phosphogypsum (PG) used alone and in combination with compost (CP) at a mix ratio of 1:1 wet weight ratio (PG + CP) at 10 and 20 g dry weight kg⁻¹ dry soil, on heavy metal immobilization in contaminated soil and on canola growth. The results revealed that the Pb, Cd and Zn uptake of canola plants was reduced by the application of PG alone and when it was mixed with CP as compared with untreated soil. At an application rate of 10 g dry weight kg⁻¹ dry soil of (PG + CP) the dry weight of canola plants increased by 66·8% was increased in comparison with its weight in the untreated soil. The addition of PG alone resulted in more pronounced immobilization of heavy metal as compared with PG mixed with CP. Plant growth was improved with CP addition, but heavy metals immobilization was the greatest in PG alone treatments. Results suggest that PG may be useful for the immobilization of heavy metals in contaminated soils. Copyright © 2014 John Wiley & Sons, Ltd.     

Remediation of Pesticide Contaminated Soil by Planting and Compost Addition

Pesticide contaminated material was obtained from an agrichemical retail facility in Illinois. In an effort to improve physical properties and increase microbial activity and plant growth in the contaminated matrix, the material was mixed with uncontaminated soil or with mature yard waste compost to determine the impact of compost compared to soil on plant establishment and growth, development of soil microbial activity, and herbicide inactivation. Plant growth, particularly weed growth, was significantly greater in compost containing mixes than it was in soil mixes. Microbial activity, as measured by dehydrogenase activity, was significantly higher in compost-containing mixes than in soil mixes. The combination of planting and compost addition resulted in significant increases in herbicide inactivation in the contaminated materials. The results strongly suggest that remediation of herbicide contamination at agrichemical retail facilities can be achieved quite rapidly and at moderate cost and also demonstrate that the combination of compost addition and planting can accelerate xenobiotic degradation in contaminated soils.     

Organic and Inorganic Amendments Affect Soil Concentration and Accumulation of Cadmium and Lead in Wheat in Calcareous Alkaline Soils

Irrigation with untreated effluent in periurban agriculture could result in accumulation and bioconcentrations of cadmium (Cd) and lead (Pb). Different amendments were used to investigate their effect on availability, concentration, and uptake of metals by wheat in texturally different soils. Crop was irrigated with water containing Cd and Pb at 20 mg L^?1, thereby adding 260 mg pot^?1 of each metal. Amendments included calcium carbonate at 6 or 12%, gypsum at 50 or 100% of the soil gypsum requirement, farm manure at 7.50 or 15.00 g kg^?1 soil, and a control. Amendments decreased ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA)–extractable Cd and Pb concentrations and uptake by wheat. Dry matter, concentration, uptake, and extractability of Cd and Pb were greater in sandy loam soil compared with those in sandy clay loam soil irrespective of amendments. Sequential extraction showed that more metals were extracted from the control in all fractions and that predominantly metals were found in the carbonate fraction.     

壳聚糖修复重金属污染土壤的研究进展

壳聚糖是一种来源广泛、具有良好的生物相容性、生物降解性的高分子材料,其含有大量氨基、羟基等活性基团,能与重金属离子进行螯合,发生吸附作用。壳聚糖还具有改良土壤、促进植物生长,诱导植物抗逆的作用,在重金属污染农田土壤修复中具有独特的应用优势。综述了近年来国内外有关壳聚糖修复重金属污染土壤的研究进展,探讨了壳聚糖对土壤重金属污染修复的潜力,阐述了壳聚糖在重金属原位钝化修复、土壤淋洗修复、强化植物提取修复三个方面的应用,并指出壳聚糖在重金属污染土壤修复中存在的问题以及对其在未来修复重金属污染土壤的发展进行了展望,以期为壳聚糖重金属修复技术的推广和应用提供参考。     

4种生物炭对镉污染潮土钝化修复效果研究

以甘蔗叶、木薯秆、水稻秸秆和蚕沙为原材料,采用限氧热解法在500℃下制备生物炭,通过室内培养实验,研究在不同培养时间(0,15,30,45d)条件下,生物炭施入潮土(Cd浓度5mg/kg)后对土壤基本性质及土壤中镉(Cd)化学形态的影响,探讨了生物炭修复镉污染土壤的可行性。结果表明:添加生物炭后,土壤pH值和阳离子交换量(CEC)随着培养时间的增加而逐渐增加,而土壤有机碳(SOC)含量则呈先增加至最大值而后缓慢降低的趋势,但仍高于对照。同时,生物炭的施入显著降低了土壤中弱酸可提取态Cd和可还原态Cd含量,提高了可氧化态Cd和残渣态Cd含量,且随着培养时间的延长这种转化趋势更为明显。4种生物炭对潮土中Cd钝化效果表现为蚕沙生物炭水稻秸秆生物炭木薯秆生物炭甘蔗叶生物炭。培养结束(45d)时,与对照相比,添加蚕沙生物炭的土壤中弱酸可提取态Cd含量降低了42.07%,可还原态Cd含量降低了35.19%,可氧化态Cd和残渣态Cd含量分别增加了292.59%和339.29%,从而大大降低了Cd的生物有效性,由此可见,生物炭对镉污染土壤的修复是切实可行的。     

土壤重金属复合污染的化学固定修复研究

本文研究糠醛渣、磷矿粉、风化煤3 种修复剂对重金属复合污染土壤的化学固定修复效果.结果表明:糠醛渣、磷矿粉、风化煤3 种修复剂都可一定程度地降低复合污染土壤中的Cu、Zn、Pb、Cd含量,其中以风化煤降低土壤有效态Zn、Cu的效果较好,在风化煤添加量为80 g/kg时土壤有效态Zn的含量降低了37.22%,土壤有效态Cu的含量降低了31.22%;磷矿粉处理修复Pb的效果比糠醛渣、风化煤好,在磷矿粉添加量为80 g/kg时,土壤有效态Pb的含量降低了23.79%;3 种修复剂都能显著降低土壤有效态Cd,在磷矿粉添加量为40 g/kg时,土壤有效态Cd的含量降低最显著,较对照降低了83.09%.在本试验条件下,3 种修复剂对4 种重金属复合污染土壤的修复效果,以Cd 较好,其次是Zn,对Pb的修复效果较差.     

土壤有机污染物电化学修复技术研究进展

综述了有机污染土壤的电动力修复和微生物电化学修复的最新研究进展.分析了电动力修复中电极材料、运行条件等因素对污染物去除效果的影响,总结了添加表面活性剂、引入具有降解能力的基质、与化学或生物联合等方式对土壤修复效果的强化作用,阐述了微生物电化学修复的效果、影响因素和微生物群落演变的规律.电化学技术能够有效去除土壤中的有机...     

Rhamnolipid Foam Enhanced Remediation of Cadmium and Nickel Contaminated Soil

Column experiments were conducted to evaluate the feasibility of using a rhamnolipid foam to remove heavy metals (Cd and Ni) from a sandy soil contaminated with Cd (1706 ppm) and Ni (2010 ppm). Best results were obtained from the foam generated by a 0.5% rhamnolipid solution with an initial pH value of 10.0 after flushing with 20-pore-volume of solution. These conditions removed 73.2% of the Cd and 68.1% of the Ni. Removal efficiencies by foam generated by a chemical surfactant, Triton X-100, were investigated as a comparison. It removed 65.5% of the Cd and 57.3% of the Ni under the same conditions. After a 20-pore-volume liquid solution flushing, 0.5% rhamnolipid (initial pH 10.0) without foam generation removed 61.7% of the Cd and 51.0% of the Ni, whereas 0.5% Triton X-100 (initial pH 10.0) removed 52.8% of the Cd and 45.2% of the Ni. Distilled water with adjusted pH only was also used to flush through the contaminated soil column as a control. It removed 17.8% of the Cd and 18.7% of the Ni. This study shows that rhamnolipid foam technology can be an effective means for the remediation of cadmium and nickel contaminated soil.     

Amelioration of Cadmium Contaminated Soils Using Cation Exchangers

ABSTRACT

The contamination of soil and water with cadmium (Cd) is an environmental issue worldwide. Using lettuce (Lactuca sativa cv. ‘Cos’) in a glasshouse-based growth trial, two cation exchange materials [a zeolite and a kaolin amorphous derivate (KAD)] were examined for their ability to remove Cd from the soil solution and hence decrease the uptake of Cd by plants. Zeolite (applied at a rate of 2.5 t ha^{? 1}) was ineffective at reducing Cd uptake and accumulation in lettuce. When applied at a rate of 2.5 t ha^{? 1}, the KAD significantly reduced Cd uptake in all soils examined (ranging from a 26 to 64% reduction). Thus, KAD is considered to be potentially beneficial for the growth of plants in Cd-contaminated soils, although care must be taken to ensure that growth is not limited by deficiencies of the other nutrients for which KAD has a high affinity.     

Remediation of Lead Contaminated Soils by Stabilization/Solidification

Most available remediation technologies for treatment of heavymetal contaminated soils are very expensive and result in residues requiring further treatment. Stabilization/solidification (immobilization) techniques however, which aredesigned to decrease leaching potential of heavy metals from soil by addition of chemical additives, provide very cost-effective solutions for heavy metal contaminated soils. Thisstudy investigates the most efficient additive for immobilization of lead. To achieve this goal, several leachingexperiments were conducted for mixtures of different additives(lime, activated carbon, clay, zeolite, sand and cement) withartificially Pb contaminated (spiked) soil samples in accordancewith the Toxicity Characterization Leaching Procedure (TCLP) developed by U.S. EPA. Results showed that among the additivestried, activated carbon, clay, zeolite and sand are not very efficient for Pb immobilization. On the other hand, lime andcement are significantly effective in Pb immobilization with 88% efficiency at 1:21 lime:soil ratio and 99% efficiency at1:15 cement:soil ratio, respectively.     

Remediation of a Magnesium‐Contaminated Soil by Chemical Amendments and Leaching

The deposition of magnesium (Mg)‐rich dust from magnesite mining activities has resulted in serious land degradation. However, the main factors limiting plant growth in Mg‐contaminated soils are unclear. Moreover, little information is available on the remediation of Mg‐contaminated soils. In this study, remediation of soils contaminated with Mg‐rich dust was investigated in a pot experiment using maize as the indicator plant. There were five treatments: (i) control; (ii) leaching; (iii) application of CaCl₂; (iv) leaching + CaCl₂ application; and (v) application of Ca(H₂PO₄)₂ · H₂O. Soil properties and growth of maize (Zea mays L.) seedlings were measured. Leaching alone significantly decreased soluble Mg concentration. Leaching + CaCl₂ application greatly increased exchangeable Ca concentration and decreased soil pH by 0·3 units. Application of CaCl₂ alone increased soluble Mg concentration sharply, which directly inhibited the germination of maize seeds. Application of Ca(H₂PO₄)₂ · H₂O significantly increased the concentrations of exchangeable Ca and available phosphorus and decreased soil pH by 1·7 units. The biomass of maize seedlings increased in the order of control = leaching < leaching + CaCl₂ < < Ca(H₂PO₄)₂ · H₂O. These results suggested that the plant growth in Mg‐contaminated soils was limited primarily by Ca deficiency and secondarily by high soil pH when exchangeable Ca was sufficient. High soil pH suppressed plant growth probably mainly by inhibiting phosphate uptake from the soil. Applying acid Ca salt with low solubility is an attractive option for the remediation of Mg‐contaminated soils. Copyright © 2015 John Wiley & Sons, Ltd.     

不同钝化剂对铜污染土壤原位钝化修复

考察了磷酸二氢钾、碳酸钙、硅酸钠、自制草木灰和自制生物质炭5种钝化剂对Cu污染土壤的钝化修复效果,对修复后的土壤进行了X射线衍射(XRD)分析;同时,对欧共体标准物质局提出的三步提取法(简称BCR法)进行了适当的改进,并运用改进的BCR法对Cu在土壤中的形态进行分析,以探讨不同钝化剂的作用机理。结果表明,5种钝化剂的投加量分别为50、100、20、20和20 g/kg时,对土壤钝化修复效果最佳,投加钝化剂后,土壤中可交换态Cu含量快速减少、残渣态Cu含量快速增加。其中,自制草木灰由于提高土壤p H更易与Cu生成沉淀,对Cu的钝化效果最佳,该钝化剂使有效态Cu含量减少53%,可交换态Cu含量减少49.2%,残渣态Cu含量增加4.7倍,有效地降低了Cu的生物毒性。     

Remediation of a Sandy Soil Contaminated with Cadmium,Nickel, and Zinc using an Insoluble Polyacrylate Polymer

Abstract

This study was carried out to investigate whether an insoluble polyacrylate polymer could be used to remediate a sandy soil contaminated with cadmium (Cd) (30 and 60 mg Cd kg^?1 of soil), nickel (Ni) (50 and 100 mg Ni kg^?1 of soil), zinc (Zn) (250 and 400 mg Zn kg^?1 of soil), or the three elements together (30 mg Cd, 50 mg Ni, and 250 mg Zn kg^?1 of soil). Growth of perennial ryegrass was stimulated in the polymer‐amended soil contaminated with the greatest amounts of Ni or Zn, and when the three metals were present, compared with the unamended soil with the same levels of contamination. Shoots of plants cultivated in the amended soil had concentrations of the metals that were 24–67% of those in plants from the unamended contaminated soil. After ryegrass had been growing for 87 days, the amounts of water‐extractable metals present in the amended soil varied from 8 to 53% of those in the unamended soil. The results are consistent with soil remediation being achieved through removal of the metals from soil solution.