Remediation Of Contaminated Soils Research Articles

Enhanced remediation of Cr(VI)-contaminated soil by incorporating a calcined-hydrotalcite-based permeable reactive barrier with electrokinetics

This paper describes the enhanced Cr(VI)-contaminated soil remediation via a combination of electrokinetics (EK) with a calcined-hydrotalcite-based permeable reactive barrier (PRB). First, this combination proved to be feasible, and remarkably facilitated Cr(VI) remediation in a column test. Then, lightly-to-severely (0.16–1.65mg/g) Cr(VI)-contaminated soil was remediated in a simulated test with the calcined hydrotalcite as the PRB under an voltage of 10–30V (i.e. an electric field intensity of 0.7–2.0V/cm). The observations demonstrated that both PRB and EK are critical to efficient remediation and the high de-contamination efficiency is supposedly attributed to the synergistic effect, for which EK concentrates anionic chromate to the anode region and PRB media (calcined hydrotalcite) absorbs and immobilizes it. Thus we have shown that the combined PRB–EK system is highly adaptive and effective in remediation of a larger area contaminated with chromate and various anionic pollutants.

Enhanced bioremediation of PAH-contaminated soil by immobilized bacteria with plant residue and biochar as carriers

Purpose Polycyclic aromatic hydrocarbons (PAHs) are largely accumulated in soils in China. The immobilized-microorganism technique (IMT) is a potential approach for abating soil contamination with PAHs. However, few studies about the application of IMT to contaminated soil remediation were reported. Due to recalcitrance to decomposition, biochar application to soil may enhance soil carbon sequestration, but few studies on the application of biochars to remediation of contaminated soil were reported. In this study, we illustrated enhanced bioremediation of soil having a long history of PAH contamination by IMT using plant residues and biochars as carriers.

Evaluation of solubility of polycyclic aromatic hydrocarbons in ethyl lactate/water versus ethanol/water mixtures for contaminated soil remediation applications

Solubility data of recalcitrant contaminants in cosolvents is essential to determine their potential applications in enhanced soil remediation. The solubilities of phenanthrene, anthracene, fluoranthene and benzo[a]pyrene in ethyl lactate/water and ethanol/water mixtures were measured using equilibrium techniques. The cosolvency powers derived from solubility data were then applied to the model developed from the solvophobic approach to predict the capability of ethyl lactate and ethanol in enhancing the desorption of contaminants from soils. Both ethyl lactate and ethanol cosolvents were shown to be able to enhance the solubilisation of the tested four polycyclic aromatic hydrocarbons by > 4 orders of magnitude above the levels obtained with water alone. However, ethyl lactate demonstrated a greater capacity to enhance PAH solubility than ethanol. The cosolvency powers of ethyl lactate/water system obtained from the end-to-end slope (σ) and the end-to-half slope (σ0.5) of the solubilisation curve were 1.0–1.5 and 2.0–2.9 higher than ethanol/water system respectively. In line with this, ethyl lactate/water was demonstrated to enhance the desorption of contaminants from soil by 20%–37% and 18%–61% higher compared to ethanol/water system in low organic content and high organic content soils respectively, with a 2:1 (V/W) ratio of solution: soil and with cosolvent fraction as low as 0.4. With the exception of benzo[a]pyrene, the experimental desorption results agreed fairly with the predicted values, under an applied solution: soil ratio that was enough to hold the capacity of released contaminants.

State of the art of contaminated site management in The Netherlands: Policy framework and risk assessment tools

This paper presents the policy framework of contaminated site management in The Netherlands and the corresponding risk assessment tools, including innovations that have taken place since an overview was published in 1999.According to the Dutch Soil Protection Act assessment framework, soils are subdivided into three quality classes: clean, slightly contaminated and seriously contaminated. Historic cases of slightly contaminated soils are managed in a sustainable way by re-use of soil material within a region on the basis of risk-based and land use specific Maximal Values and Background Values. In case of serious soil contamination remediation is in principle necessary and the urgency of remediation has to be determined based on site-specific risks for human health, the ecosystem and groundwater.The major risk assessment tools in The Netherlands are the CSOIL exposure model (human health risks and food safety), Species Sensitivity Distributions and the Soil Quality Triad (ecological risks), along with a procedure to assess the risks due to contaminant spreading to and in the groundwater.Following the principle ‘simple if possible, complex when necessary’, tiered approaches are used. Contaminated site practices are supported with web-based decision support systems.

REMEDIATION OF DIESEL CONTAMINATED SOILS USING SURFACTANTS: COULUMN STUDY

This study presents the experimental remediation studies of diesel contaminated soil with Sodium Deducible Sulfate (SDS) as surfactants using column tests. Sandy selected soil had the grain size distribution of # 40 meshes to the # 200 mesh range. The soil columns were contaminated with adequate diesel amount to achieve the concentration of 10000 and 20000 ppm in soil. 0.1, 0.2, 0.3, 0.4 percent of surfactants and pH values of 4, 7, 9 and 11, were examined. After 72 h, washing began and all tests were continued up to 10 pore volume and the trend of remediation and permeability of soil during the test was investigated. pH and TPH of outlet solution measured during 2, 4, 6 and 10 pore volumes. Times were recorded during 0.67, 1, 1.33, 2, 3.33, 4, 5.67, 6, 7.33, 8, 8.67, 9.33 and 10 pore volumes, in order to calculate permeability values.Results showed that in all states the quantity of remediation for acidic states was very low and efficiency of remediation when using only water was about (1:3) of maximum amount. For soil with initial contaminant concentration of 10000 ppm the maximum efficiency is for surfactant in the concentration of 0.3 and pH = 11 and for soil with initial contamination amount of 20000 ppm the maximum efficiency is for surfactant in the concentration of 0.1 and pH = 11. By increasing the amount of surfactant concentration, the permeability of soil decreased and in pH = 11 the amount of permeability is maximum. With increasing initial contamination quantity rate of increasing of remediation and permeability decreased. Consequently in the low level of contamination the effect of washing solution pH value in soil remediation and permeability is more in comparing with high level of contamination. For initial contamination of 10000 ppm optimum removal efficiency obtained 35% for surfactant of 0.3% and pH = 11. For initial contamination of 20000 ppm, optimum removal efficiency is obtained as 45% for 0.1% of surfactant and pH = 11. Using of higher soil column, sampling from different elevation for investigating remediation trend in height and surveying temperature effect on diesel contaminated soil remediation can help to modification procedure and improvement of efficiency.

Effect of soil composition on electrokinetically enhanced persulfate oxidation of polychlorobiphenyls

In situ oxidation processes for the remediation of organic contaminants in soils have gained much interest in last decade. They are rapid, aggressive and easy to apply, but their application in low permeability soils is limited due to the ineffective delivery of oxidants in such soils. In this study, electrokinetically enhanced persulfate delivery and oxidation is investigated in two diverse low permeability soils: artificially contaminated kaolin and glacial till soil. These two soils were used to investigate the effects of soil type on persulfate oxidation of tetrachlorobiphenyl (PCB 44), a representative polychlorobiphenyl (PCB). Laboratory batch tests were conducted using the soils spiked with PCB 44 at an initial concentration of 50mg/kg to determine the optimal conditions for effective oxidation. This study also investigated the activation of persulfate by elevated temperature (45°C) and high pH (at anode) as a means to maximize PCB degradation. The activation of persulfate improved the oxidation of PCB in kaolin, but the effect in the glacial till was insignificant. The final pH values of the kaolin were around 1, while they were around 7 for glacial till because of the high buffering capacity of glacial till. Low pH conditions are also shown to activate persulfate, leading to higher PCB oxidation. The degradation of PCB 44 was significantly higher for the kaolin than the glacial till. In kaolin, the highest level of PCB oxidation, 77.9%, was achieved with temperature activated persulfate in 7 days. However, in the glacial till the highest PCB oxidation was 14.4% with 30% Na-persulfate concentration without any activation. The high buffering capacity, non-homogeneous mineral content and high organic content of glacial till may have contributed to the low persulfate oxidation of PCB.

Bioreactive Organoclay: A New Technology for Environmental Remediation

Organoclays, which are synthesized by introducing organic molecules into the clay structure, have been proven effective for remediation of many contaminants in soil and water. The underlying principle for this is sorption. However, a new remediation approach that combines sorption and biodegradation/biotransformation has evolved in recent years. Contaminants sorbed on organoclays can be successfully degraded or transformed into less toxic forms by specific microorganisms, provided the participating microbes thrive well on the organoclays. Thus, bioreactive organoclays are prepared. The authors present a critical review of the scientific principles and scope of integrating microorganisms with organoclays to develop a new environmental friendly, risk–based, and cost-effective remediation technology. Furthermore, they propose new research directions in the field.

Life cycle assessment of polychlorinated biphenyl contaminated soil remediation processes

A life-cycle assessment (LCA) was performed to evaluate the environmental impacts of the remediation of industrial soils contaminated by polychlorobiphenyl (PCB). Two new bioremediation treatment options were compared with the usual incineration process. In this attributional LCA, only secondary impacts were considered. The contaminated soil used for the experiments contained 200 mg of PCB per kilogram. Three off-site treatment scenarios were studied: 1) bioremediation with mechanical aeration, 2) bioremediation with electric aeration and 3) incineration with natural gas. Bioremediation processes were designed from lab-scale, scale-up and pilot experiments. The incineration technique was inspired by a French plant. A semi-quantitative uncertainty analysis was performed on the data. Environmental impacts were evaluated with the CML 2001 method using the SimaPro software. In most compared categories, the bioremediation processes are favorable. Of the bioremediation options, the lowest environmental footprint was observed for electric aeration. The uncertainty analysis supported the results that compared incineration and bioremediation but decreased the difference between the options of aeration. The distance of transportation was one of the most sensitive parameters, especially for bioremediation. At equal distances between the polluted sites and the treatment plant, bioremediation had fewer impacts than incineration in eight out of 13 categories. The use of natural gas for the incineration process generated the most impacts. Irrespective of the aeration option, bioremediation was better than incineration. The time of treatment should be taken into account. More precise and detailed data are required for the incineration scenario. More parameters of biological treatments should be measured. LCA results should be completed using ecological and health risk assessment and an acceptability evaluation.

Nanoenhanced Materials for Reclamation of Mine Lands and Other Degraded Soils: A Review

Successful mine soil reclamation facilitates ecosystem recovery, minimizes adverse environmental impacts, creates additional lands for agricultural or forestry uses, and enhances the carbon (C) sequestration. Nanoparticles with extremely high reactivity and deliverability can be applied as amendments to improve soil quality, mitigate soil contaminations, ensure safe land–application of the conventional amendment materials (e.g., manures and biosolids), and enhance soil erosion control. However, there is no report on using nanoenhanced materials for mine soil reclamation. Through reviewing the up-to-date research results on using environment-friendly nanoparticles for agricultural soil quality improvement and for contaminated soil remediation, this paper synthesizes that these nanomaterials with high potentials for mine soil reclamation include zeolites, zero-valent iron nanoparticles, iron oxide nanoparticles, phosphate-based nanoparticles, iron sulfide nanoparticles and C nanotubes. Transport of these particles in the environment and their possible ecotoxicological effects are also discussed. Additionally, this article proposes a practical and economical approach to applying nanotechnology for mine soil reclamation: adding small amounts of nanoparticles to the conventional soil amendment materials and then applying the mixtures for soil quality improvements. Hence the cost of using nanoparticles is reduced and the benefits of both nanoparticles and the conventional amendment materials are harnessed.

DDT-Contaminated Soil Treatment with Persulfate and Hydrogen Peroxide Utilizing Different Activation Aids and the Chemicals Combination with Biosurfactant

AbstractThe efficacy of DDT-contaminated soil treatment with hydrogen peroxide and persulfate utilizing different activation aids and the chemicals combination with biosurfactant was evaluated. The addition of a supplementary activator was able to improve the degradation of total DDT with both the hydrogen peroxide and persulfate oxidation processes indicating a lack of available activator. Ferrous iron added gradually was effectively utilized in the oxidation system with gradual addition of hydrogen peroxide, while chelated metal iron addition promoted the oxidation with more stable persulfate. The treatment with solid carriers of hydrogen peroxide, either calcium peroxide or magnesium peroxide, can be an effective alternative to the liquid one resulting in a higher degradation level of the contaminant. Strong alkalization with elevated dosages of NaOH sustained the persulfate oxidation of DDT. The addition of biosurfactant, rhamnolipid-alginate complex obtained by biosynthesis of strain Pseudomonas sp. PS-17, and EDTA improved the degradation of DDT by both persulfate and hydrogen peroxide oxidation processes indicating that the combined application of chemical oxidants and biosurfactant at natural soil pH has prospects as an effective option for contaminated soil remediation.

The Study of Remediation Standards of Heavy Metal-Cu Contaminated Soil Based on Risk Assessment

This paper describes the model of heavy metal-Cu contaminated soil remediation standard value based on risk assessment. In the Cu contamination risk assessment model, the main exposure methods are oral ingestion and inhalation through breathing, which not only simplifies the calculation but also make people get a clearer understanding of the way of Cu contamination. We get the simplified formula, calculate and discuss Cu contaminated soil remediation target value in specific parameters to provide reference and basis for the remediation of Cu contaminated soil.

Health Risk Assessment and Quantitative Calculation of Typical Cr Contaminated Sites

Select the former site of a chemical factory in Chongqing, China as the typical Cr contaminated site. According to “Technical guidelines for risk assessment of contaminated sites” and “Standard of Soil Quality Assessment for Exhibition Sites (Interim)” (HJ-350-2007), this paper conducts health risk assessment for the site, and provide a basis for contaminated soil remediation. At the same time, according to the contaminated condition, used the Golden Software Surfer 8 to draw the boundary of contaminated soils and thus calculate the volume of contaminated soil. By estimation the volume is about 3122.3 m3, which provide detailed data for the later remediation engineering.

The Remediation Standards and Evaluation Methods for Remediation Effectiveness of Contaminated Soil

The contaminated soil remediation standard formulation's aim is under the premise of ensuring the reuse of contaminated land, to reduce or cut the contaminants which cause to receive in the more serious contaminated soil environment is insufficient to lead to greater ecological damage and health risks. In this paper, some suggestions on the establishment of remediation standards for contaminated soils such as clean technology factors, factors of soil background values, standards and regulations to control pollution of ecological factors and assessment of toxicological risks were put forward, based on the analysis of the disadvantages of soil environmental quality standard research on evaluation methods for remediation effectiveness of contaminated soil, commonly used evaluation methods, such as phytotoxicity testing, terrestrial invertebrate toxicity testing, soil microorganism toxicity testing and biomarker assessment methods were described. Furthermore, future research directions were also discussed.

Effects of Chemical, Biological, and Physical Aging As Well As Soil Addition on the Sorption of Pyrene to Activated Carbon and Biochar

In this study, the suitability of biochar and activated carbon (AC) for contaminated soil remediation is investigated by determining the sorption of pyrene to both materials in the presence and absence of soil and before as well as after aging. Biochar and AC were aged either alone or mixed with soil via exposure to (a) nutrients and microorganisms (biological), (b) 60 and 110 °C (chemical), and (c) freeze-thaw cycles (physical). Before and after aging, the pH, elemental composition, cation exchange capacity (CEC), microporous SA, and sorption isotherms of pyrene were quantified. Aging at 110 °C altered the physicochemical properties of all materials to the greatest extent (for example, pH increased by up to three units and CEC by up to 50% for biochar). Logarithmic K(Fr) values ranged from 7.80 to 8.21 (ng kg(-1))(ng L(-1))(-nF) for AC and 5.22 to 6.21 (ng kg(-1))(ng L(-1))(-nF) for biochar after the various aging regimes. Grinding biochar to a smaller particle size did not significantly affect the sorption of d(10) pyrene, implying that sorption processes operate on the subparticle scale. Chemical aging decreased the sorption of pyrene to the greatest extent (up to 1.8 log unit for the biochar+soil). The sorption to AC was affected more by the presence of soil than the sorption to biochar was. Our results suggest that AC and biochar have a high sorption capacity for pyrene that is maintained both in the presence of soil and during harsh aging. Both materials could therefore be considered in contaminated land remediation.

Ecological Remediation of Hydrocarbon Contaminated Soils with Weed Plant

Considerable efforts have been undertaken to accelerate the breakdown of existing anthropogenic petroleum hydrocarbons (PHCs) by appropriate in situ remediation technologies. In situ phytoremediation, using higher plants to remove, stabilize, degrade, and/or metabolize hazardous contaminants, has emerged as a promising green technology for cleaning up environments contaminated with PHCs. Weed plants are generally considered to have great potential for use in phytoremediation due to their extensive fibrous root systems and relatively robust characteristics, thus helping establish a strong rhizosphere through contaminated soils. In this review, some important mechanisms involved in phytoremedation of PHC contaminated soils, including phytoaccumulation, phytostabilization, phytodegradation, phytovolatilization, and rhizodegradation, were summarized and discussed. In recent years, a large number of laboratory approaches have been developed to further enhance the phytoremediation efficiency of PHC contaminated soils. The success of these laboratory studies has encouraged researchers to attempt phytoremediation of PHC contaminated soils in the field. However, many limitations still exist in order to successfully apply laboratory experiments to trials in the field.

Environmental life-cycle comparisons of two polychlorinated biphenyl remediation technologies: Incineration and base catalyzed decomposition

Remediation action is critical for the management of polychlorinated biphenyl (PCB) contaminated sites. Dozens of remediation technologies developed internationally could be divided in two general categories incineration and non-incineration. In this paper, life cycle assessment (LCA) was carried out to study the environmental impacts of these two kinds of remediation technologies in selected PCB contaminated sites, where Infrared High Temperature Incineration (IHTI) and Base Catalyzed Decomposition (BCD) were selected as representatives of incineration and non-incineration. A combined midpoint/damage approach was adopted by using SimaPro 7.2 and IMPACTA2002+ to assess the human toxicity, ecotoxicity, climate change impact, and resource consumption from the five subsystems of IHTI and BCD technologies, respectively. It was found that the major environmental impacts through the whole lifecycle arose from energy consumption in both IHTI and BCD processes. For IHTI, primary and secondary combustion subsystem contributes more than 50% of midpoint impacts concerning with carcinogens, respiratory inorganics, respiratory organics, terrestrial ecotoxity, terrestrial acidification/eutrophication and global warming. In BCD process, the rotary kiln reactor subsystem presents the highest contribution to almost all the midpoint impacts including global warming, non-renewable energy, non-carcinogens, terrestrial ecotoxity and respiratory inorganics. In the view of midpoint impacts, the characterization values for global warming from IHTI and BCD were about 432.35 and 38.5 kg CO 2-eq per ton PCB-containing soils, respectively. LCA results showed that the single score of BCD environmental impact was 1468.97 Pt while IHTI's score is 2785.15 Pt, which indicates BCD potentially has a lower environmental impact than IHTI technology in the PCB contaminated soil remediation process.

Heavy metal tolerance of weed species and their accumulations by phytoextraction

>The ability of the invasive weed species Parthenium hysterophorus L. for the accumulation of the heavy metal Cd was studied in a greenhouse experiment. This study aimed at identifying a metal tolerant species from natural vegetation and to assess the phytoextraction potential of the plant. To compare metal concentration in the aboveground biomass to those in roots and in soils,To study their effect on growth and comparison with metal amended soils treated with EDTA. The Cd accumulated by test species was increased significantly after 0.1g / Kg of EDTA was added to the medium. An increase in metal uptake with increase in test concentrations during the early stages and developmental stages was observed which indicates the plant's tolerance to the heavy metal. But a decrease in metal uptake with the maturity of the plant was observed. This indicates that the plant's ability for the metal uptake reduces with time i.e. with maturity. The BCF's of the shoots and roots and TF's being >1 shows the validity of the weeds species for hyperaccumulation of the metal Cd. This is due to the plant's capability to uptake the metal and its tolerance capacity for the heavy metal Cd. Hence, it can be a promising species for phytoextracton of heavy metals and remediation of contaminated soils which is economical and ecofriendly.

Solubility of pyromorphite Pb 5(PO 4) 3Cl–mimetite Pb 5(AsO 4) 3Cl solid solution series

Pyromorphite Pb 5(PO 4) 3Cl and mimetite Pb 5(AsO 4) 3Cl are isostructural minerals with apatite. Due to their high environmental stability, they have gained considerable attention as metals sequestration agents in water treatment and contaminated soil remediation. Pyromorphite and mimetite can form a continuous solid solution series in near-Earth surface environments. Precipitation of the end members and intermediate members of the series is likely to occur in the areas where the cost-effective in situ immobilization reclamation method, based on phosphate amendments, is applied. In contrast to the widely studied thermodynamic parameters of pyromorphite and mimetite, knowledge of the thermodynamics of their solid solutions is sparse. To supplement the data, a number of compounds from the pyromorphite–mimetite series were synthesized at room temperature using a method to simulate the conditions in the near-Earth surface environments. Afterwards, batch dissolution and dissolution–recrystallization experiments of seven synthesized precipitates were conducted at 25 °C, pH = 2 and in a 0.05 M KNO 3 background electrolyte. The experiments were carried out for a period of 6 (dissolution) and 14 (dissolution–recrystallization) months. A plateau in the [Pb] evolution patterns was used to determine equilibrium. All seven dissolutions were congruent, and the ionic activity products (IAP) of the minerals from the pyromorphite–mimetite solid solution series were calculated based on the dissolution reaction: Pb 5 ( PO 4 ) n ( AsO 4 ) 3 - n Cl ↔ 5 Pb 2 + + n PO 4 3 - + ( 3 - n ) AsO 4 3 - + Cl - . The IAPs for pyromorphite and mimetite exhibit a significant difference in values over three orders of magnitude between approximately 10 −79 for pyromorphite and approximately 10 −76 for mimetite. The series appeared to be ideal, and Lippmann and Roozboom diagrams were used for better understanding of its thermodynamics. The results indicated a strong tendency of pyromorphite to partition into the solid phase in the series, which explains some of the naturally observed phenomena. The improvement of the lattice stability of the mimetite due to isostructural phosphate substitutions in anionic sites was observed. The thermodynamic data reported in this study supplement existing databases used in geochemical modeling.

Application of persulfate to remediate petroleum hydrocarbon-contaminated soil: Feasibility and comparison with common oxidants

In this study, batch experiments were conducted to evaluate the feasibility of petroleum-hydrocarbon contaminated soil remediation using persulfate oxidation. Various controlling factors including different persulfate and ferrous ion concentrations, different oxidants (persulfate, hydrogen peroxide, and permanganate), and different contaminants (diesel and fuel oil) were considered. Results show that persulfate oxidation is capable of treating diesel and fuel oil contaminated soil. Higher persulfate and ferrous ion concentrations resulted in higher diesel degrading rates within the applied persulfate/ferrous ion molar ratios. A two-stage diesel degradation was observed in the batch experiments. In addition, treatment of diesel-contaminated soil using in situ metal mineral activation under ambient temperature (e.g., 25°C) may be a feasible option for site remediation. Results also reveal that persulfate anions could persist in the system for more than five months. Thus, sequential injections of ferrous ion to generate sulfate free radicals might be a feasible way to enhance contaminant oxidation. Diesel oxidation efficiency and rates by the three oxidants followed the sequence of hydrogen peroxide>permanganate>persulfate in the limited timeframes. Results of this study indicate that the application of persulfate oxidation is a feasible method to treat soil contaminated by diesel and fuel oil.

PAHs contaminated soils remediation by ozone oxidation

Remediation of PAHs contaminated soils by means of chemical oxidation is considered an attractive option because of its effectiveness in the removal of PAHs from polluted environmental matrices. In recent years, the use of ozone has gained increasing interest since this technology can be successfully implemented both in situ and ex situ as well as remediation time is fast compared to other options. Moreover, the use of gaseous ozone can provide several advantages over aqueous oxidants, such as Fenton's reagent or permanganate, as a consequence of its easier spread into unsaturated porous media. In this paper, after an introduction of PAHs properties and their environmental fate, and a short overview of the remediation technologies for the treatment of PAHs contaminated soils, the use of ozonation process for the removal of PAHs from contaminated soils is reviewed. In particular, PAHs degradation kinetics by ozonation, factors effecting ozonation effi ciency, formation of oxidation intermediates and toxici...