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.

Effects of Using Softwood Pellet Biochar Prepared at Different Temperatures with Grass Chippings on Retention of Heavy Metals in Contaminated Soils

Heavy metals have been viewed as hazardous environmental pollutants, and anthropogenic activities due to their high toxicity and persistent nature in the environment. Anthropogenic activities such as artisanal mining, industrial activities, improper usage of fertilizers and pesticides, and indiscriminate open waste disposal bring about an increase in the presence of heavy metals in the environment. In the Keffi Metropolis, different elements lead to land contamination which debilitates soil quality, plant survival, human well-being, and the environment as a result of extensive dispersion or quantity of heavy metals in the soil and water. In recent years, biochar has emerged as a promising soil amendment for mitigating heavy metal pollution due to its unique physicochemical properties. This paper provides the effects of softwood pellet biochar on the retention of heavy metals in contaminated soils. A microcosm experiment was carried out to investigate the effects of biochar on the retention of heavy metals in contaminated soils. This research aimed to give an overview of the effects of softwood biochar at different temperatures (550˚C and 700˚C) on the retention of heavy metals and metalloids released from the soil during water inundation. The results show that the addition of organic matter (grass chippings) minimizes heavy metal mobilization. Also, biochar at high temperatures is more effective than those at low temperatures. The expected outcome of the research analysis includes providing insights into the role of biochar in retaining heavy metal contamination and further understanding the use of biochar as a sorbent for the management of contaminated soil.

Potential of weed species applied to remediation of soils contaminated with heavy metals

To screen out a series of ideal plants that can effectively remedy contaminated soils by heavy metals is the main groundwork of phytoremediation engineering and the first step of its commercial application on a large scale. In this study, accumulation and endurance of 45 weed species in 16 families from an agricultural site were in situ examined by using the pot-culture field experiment, and the remediation potential of some weed species with high accumulation of heavy metals was assayed. The results showed that Solanum nigrum and Conyza canadensis can not only accumulate high concentration of Cd, but also strongly endure to single Cd and Cd-Pb-Cu-Zn combined pollution. Thus 2 weed species can be regarded as good hyperaccumulators for the remediation of Cd-contaminated soils. Although there were high Cd-accumulation in Artemigia selengensis, Znula britannica and Cephalanoplos setosum, their biomass was adversely affected due to action of heavy metals in the soils. If the problem of low endurance to heavy metals can be solved by a reinforcer, 3 weed species can be perhaps applied commercially.

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.

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.

Influence factors analysis of removing heavy metals from multiple metal-contaminated soils with different extractants

Some key factors on the heavy metals removal efficiencies were studied when soil washing technology was used in the remediation of soils contaminated by multiple heavy metals. The results show that the dissolubilities of Cu and Zn are promoted by humic acids, but Pb and Cd are inhibited by humic acids; heavy metals in the clay are more difficult to be extracted than silt; the strong acidic soils can cause the protonation of EDTA and weaken its extracting ability; EDTA is effective for extracting Pb and Cd, while oxalate (OX) is effective for extracting Cu and Zn; and biosurfactant can be used as additive to improve the removal of some particular heavy metals.

Remediation of Steel Slag on Acidic Soil Contaminated by Heavy Metal

The technology of in situ immobilization with amendments is an important measure that remediates the soil contaminated by heavy metals, and selecting economical and effective amendments is the key. The effects and mechanism of steel slag, the silicon-rich alkaline byproduct which can remediate acidic soil contaminated by heavy metal, are mainly introduced in this paper to provide theory reference for future research. Firstly, the paper analyzes current research situation of in situ immobilization with amendments. Then, it introduces the main physicochemical properties of steel slag, and the effect on soil pH value as well as heavy metal activity. Besides, the paper elaborates the promoting effect on silicon-requiring plant and the strengthening mechanism for its resistant capability of heavy metal. According to the analysis, the application of steel slag could be a potential valuable strategy to remediate acidic soil contaminated by heavy metal by modifying the transformation of heavy metals in both soil and plant, so that the translocation of heavy metal in food chain is reduced.

Phytoremediation Mechanisms of Heavy Metal Contaminated Soils: A Review

Phytoremediation is a green emerging technology used to remove pollutants from environment components. Mechanisms used to remediate soils contaminated by heavy metal are: phytoextraction, phytostabilisation, phytovolatilization and rhizofiltration. The two first mechanisms are the most reliable. Many factors influence the choice of the suitable phytoremediation strategy for soil decontamination. It depends on soil properties, heavy metal levels and characteristics, plant species and climatic conditions. The present review discusses factors affecting heavy metals uptake by plant species, the different phytoremediation strategies of heavy metal contaminated soils and the advantages and disadvantages of phytoremediation and each of its mechanisms.

Phytoremediation Potential of Sorghum as a Biofuel Crop and the Enhancement Effects with Microbe Inoculation in Heavy Metal Contaminated Soil

Phytoremediation is an eco-friendly and low-cost biotechnology using plants to extract, contain, degrade, or immobilize pollutants from the contaminated environment. Selection of the ideal plant species and suitable enhancing measures to obtain high remediation efficiency and large valuable biomass are essential requirement for a successful phytoremdaition. Sorghum (Sorghum bicolor L.) is one of the most attractive bioenergy crops for producing biofuels with high biomass production. In this study, the phytoremediation potential of sorghum to heavy metals and the promotion effects by a lead-tolerant fungus (LTF) were investigated using a multiple heavy metal contaminated soil with Pb, Ni, and Cu. The results showed that the sorghum survived the heavy contamination, and LTF inoculation promoted the plant growth and increased the phytoextraction yields of Pb, Ni, and Cu. The phytoextraction potential (μg/plant) of the whole sorghum for Sorghum were 410 (Pb), 74 (Ni), and 73 (Cu), and for Sorghum with LTF inoculation were 590 (Pb), 120 (Ni), and 93 (Cu), respectively. The results suggested that sorghum would be one of the ideal candidates for phytoremediation of contaminated soil because of its high phytoremediation potential, large biomass production, and utilization in biofuel production.

Feasibility of Isolation Remediation Technology for Heavy Metal Contaminated Soil

This paper discussed current situations of researches about the isolation remediation technology " soil barrier and landfill technology" and " physical isolation remediation technology" for heavy metal contaminated soil in mining areas.In view of defects of current technologies,it introduced a new isolation remediation technology,of which the new isolation materials were mixed by slaked lime,soil,find sand,and clay mineral in certain proportion.The new isolation remediation technology is expected to realize isolation remediation of heavy metal combined pollution of soil through chemical passivation of slaked lime and physical adsorption function of clay minerals or activated carbons.

Study of Remediation of Soil Contamined with Heavy Metals by Coal Fly Ash

The labile fraction of heavy metals in soils is the most important for toxicity for plants. Thus it is crucial to reduce this fraction in contamined soils to decrease the negative effect of heavy metals. In an experiment, the effects of two additives on the labile fractions of Cu, Mn and Zn were investigated in a soil contamined during long-term application. The additive used was the coal fly ash. The treated soil was further enriched with heavy metals and allowed to age at room temperature for 30 days. After this period, they were extracted plant-available (EDTA;HNO3;CH3COOH) metal species. The addition of fly ash strongly reduced the plant-available of Mn for plants but to a lesser extent this applies to the plant-available of Cu and Zn for plants. By addition of 1% of fly ash as well as 2% of fly ash, the labile fraction of Cu, Mn and Zn were lowered by 6.3, 145.0 and 29.7 mg?kg-1, respectively. Moreover essential correlation between total Cu and Zn contents was stated in the soil with plant-available content of metals, with reference to both metals. Value of coefficients of correlation is attesting to it between the total and plant-available Cu and Zn contents which are respectively equal: R(Cu) = 0.845, R(Mn) = 0.864 and R(Zn) = 0.872 for p = 99.5%. The results suggested that leading into the soil of the additional amount of fly ash can be an effective way of chemical remediation with reference to soils contaminated by Cu or Mn or Zn. Because he causes immobilization of examined heavy metals in the soil and in the process in the arrangement a—soil is limiting the availability of these metals plant and more distant bonds of the food chain.

Contamination and Remediation of Heavy Metals in Soils near E-waste Recycling Area

In order to assess heavy metals pollution in agricultural soil after renovation in typical e-waste recycling areas, 212 soil samples were col- lected and the mass fractions of 7 kinds of heavy metals （Cd, Cr, Cu, Hg, Ni, Pb and Zn） were analyzed. The results indicated that heavy metals pollution in agricultural soil was commonly existed in the study areas, and the soil was slightly contaminated by Pb but was moderately or critically polluted by Cd and Cu. However, the carcinogenic risk and non-carcinogenic risk status by heavy metals pollution were beyond acceptable levels, and soil remediation was quite necessary. After some investigations of bioremediation, we found that saponin as washing agent could highly strenqthen the behavior of heavy metals desorption from soil ,which had a good prospect of engineering practice.

In-situ Elimination Effect on Heavy Metals in Contaminated Soil from the Mining Area by Ramie

[Objective] The aim was to study on in-situ elimination effect on heavy metals in soil of the mining area by ramie （Boehmeria nivea （L.） Gaud.）. [Methods] Based on Xiangzhu No.3 and Zhongzhu No.1, we conducted research on heavy metals contents of plants growing in soil of Qibao Mountain orefield in Liuyang, Hunan Province, and on characteristics of enrichment and transfer of heavy metals （Cu, Pb, Cd, Zn） under influence of the two ramie species. [Result] It was concluded that trend of Cu content in different parts of ramie was as follows： rootskinleafbone; trend of Pb was rootleafskinbone; trend of Cd was rootskinboneleaf; the trend of Zn was rootskinboneleaf. In farmland A （with low content of heavy metal）, for per square meter of plough horizon, effect of Zhong 1 on heavy metals transferring volume and the period for restoration of the soil into national standard one （Category Ⅲ of Environmental Quality Standard for Soil） have been concluded. Specifically, for Cu, the corresponding values were 3 404.44 mg and 8.59 y, respectively; for Pb, the values were 3 638.5 mg and 13.52 y; for Cd, the values were 720.48 mg and 1.49 y; for Zn, the values were 37 324.8 mg and 0.67 y. [Conclusion] Soil contaminated by Cu, Pb, Cd, and Zn in orefield can be rapidly restored by growing ramie.

Analysis of Soil Remediation Technology for Heavy Metalcontaminated Sites in Electroplating Enterprises

The advantages and disadvantages of chemical leaching,phytoremediation,in-situ/ex-situ solidification and stabilization,cement kiln co-disposal and safe landfill remediation are analyzed.In addition,the application of chemical leaching and in-situ/ex-situ solidification and stabilization technology in the treatment of heavy metal-contaminated soil in electroplating enterprises in China is introduced in detail to provide reference for the remediation of heavy metal-contaminated soil around electroplating enterprises in China.

Mechanical properties of anti-seepage grouting materials for heavy metal contaminated soil

Cement-based composite grouting materials were used to construct grouting cutoff wall for heavy metal contaminated soil in non-ferrous metal mining areas. Cement, fly ash, and slag as principal ingredients were mixed with water glass in different ways to produce three composite grouting materials. In order to investigate the effect of water glass mixing ratio, Baume degree, fly ash and slag contents on the mechanical properties of the composite grouting materials, particularly their gel time and compressive strength, the beaker-to-beaker method of gel time test and unconfined compressive strength test were conducted. In addition, the phase composition and microstructure of the composite grouting materials were analyzed by the X-ray diffraction（XRD） and scanning electron microscope（SEM） techniques. The test results show that their gel time increases when water glass mixing ratio and Baume degree increase. The gel time increases dramatically when fly ash is added, but decreases slightly if fly ash is partly replaced by slag. When the mixing ratio of water glass is below 20%, their compressive strength increases with the increases of the ratio; when the ratio is above 20%, it significantly decreases. The compressive strength also tends to increase as Baume degree increases, and improves if fly ash and slag are added.

Biodegradation Potentials of Contaminated Soil around Ministry of Works Workshop Aba,Abia State,Nigeria

Global industrialization over the past centuries has resulted in widespread contamination of the environment with organic and inorganic wastes and their pattern of disposal.The study aimed at isolating fungi from spent diesel contaminated soil around Ministry of Works in Aba,Abia State for biodegradation potentials on the soil properties.About four(4)fungal species were isolated from the five(5)sites using cultural and biochemical characteristics.The isolate was screened,and optical density measured using spectrophotometer.A total of 5 soil samples from each location(0-15 cm and 15-30 cm)were collected and homogenized to have composite sample.Samples were taken to the laboratory for analysis of soil physiochemical parameters,fungi count and biodegradable potential of the fungi using standard methods.Data obtained revealed that,physical property of the soil such as sand(85.20%±0.01%),silk(6.4%±0.01%)were lower than the control location except clay(17.39%±0.01%).Chemical properties revealed highest concentration of element such as pH(4.76±0.01),total nitrogen(0.18%±0.011%),total organic carbon(3.41±0.01),sodium(0.21±0.01),potassium(0.24±0.001),magnesium(4.41±0.015),calcium(5.21±0.015),organic matter(6.18±0.011),and available phosphorus(30.99±0.01).All elements in the study site were higher than the control site with an exception to sodium(Na),which was lower.Fungi isolate identified were Aspergillus niger,Trichoderma virdae,Aspergillus flavus,and Pencillum corylophlum.The degradation potential of fungi identified shows that consortium degraded 29%of diesel oil from the soil followed by A.flavus,T.virdae,A.niger and the least was T.corylophlum.The study concludes that despite indiscriminate disposal of spent diesel oil,the nutrient content was still higher than control and consortium performed well in degradation.

Spatial Patterns of Soil Heavy Metals in Urban-Rural Transition Zone of Beijing

To identify the main sources responsible for soil heavy metal contamination, 70 topsoils were sampled from the Daxing County in the urban-rural transition zone of Beijing. The concentrations of heavy metals Cu, Zn, Pb, Cr, Cd, Ni, As, Se, Hg, and Co; the soil texture; and the organic matter content were determined for each soil sample. Descriptive statistics and geostatistics were used to analyze the data, and Kriging analysis was used to estimate the unobserved points and to map the spatial patterns of soil heavy metals. The results showed that the concentrations of all the soil heavy metals exceeded their background levels with the exception of As and Se. However, only the Cd concentration in some areas exceeded the critical value of the national soil quality standard. The semivariance analysis showed that the spatial correlation distances for soil Cu, Zn, Cr, Cd, As, Ni, and Co ranged from 4.0 to 7.0 km, but soil Se, Pb, and Hg had a larger correlation distance. Soil Co, Se, Cd, Cu and Zn showed a strong spatial correlation, whereas the other soil heavy metals showed medium spatial correlation. Soil heavy metal concentrations were related to soil texture, organic matter content, and the accumulation of heavy metals in the soils, which was because of air deposition and use of water from the Liangshui, Xinfeng, and Fenghe rivers that are contaminated by wastewater and sewage for the purpose of irrigation of fields. Hence, a comprehensive treatment plan for these rivers should be formulated.

Mechanical properties of fiber and cement reinforced heavy metal-contaminated soils as roadbed filling

The treatment of contaminated soil is a crucial issue in geotechnical and environmental engineering.This study proposes to incorporate appropriate polypropylene fibers and cements as an effective method to treat heavy metal contaminated soil(HMCS).The objective of this paper is to investigate the effects of fiber content,fiber length,cement content,curing time,heavy metal types and concentration on the mechanical properties of soils.To this end,a series of direct shear test,unconfined compression strength(UCS)test,dry-wet cycle and freeze-thaw cycle test are performed.The results confirm that the appropriate reinforcement of polypropylene fibers and cement is an effective way to recycle HMCS as substitutable fillers in roadbed,which exhibits benefits in environment and economy development.

Heavy Metal Contamination in Farmland Soil and Bioremediation Measures: A Case Study of the Mining Area in Shaoguan

With the rapid development of mining,the soil heavy metal contamination is increasingly serious in Shaoguan,directly affecting the production of crops. This paper analyzes the farmland soil heavy metal contamination in the mining area of Shaoguan and the causes of heavy metal contamination in recent years,brings forward the bioremediation measures to control soil heavy metal contamination,and points out the development direction of bioremediation in farmland soil heavy metal contamination in the mining area.

Heavy metals contamination characteristics in soil of different mining activity zones

Depending upon the polluted features of various mining activities in a typical nonferrous metal mine,the contaminated soil area was divided into four zones which were polluted by tailings,mine drainage,dust deposition in wind and spreading minerals during vehicle transportation,respectively.In each zone,soil samples were collected.Total 28 soil samples were dug and analyzed by ICP-AES and other relevant methods.The results indicate that the average contents of Zn,Pb,Cd,Cu and As in soils are 508.6,384.8,7.53,356 and 44.6 mg/kg,respectively.But the contents of heavy metals in different zone have distinct differences.The proportion of oxidizing association with organic substance is small.Difference of the association of heavy metals is small in different polluted zones.