Remediation Of Contaminated Sites Research Articles

Estimating Tetrachloroethene Sorption Coefficients Based on Soil Properties in Organic-Poor Soils

In the context of contaminated site remediation, the fate of chlorinated solvents in the subsurface and subsequent groundwater contamination is influenced by soil properties governing sorption. The solid–water distribution coefficient (Kd) is a key parameter for modeling contaminant distribution and transport, essential for risk assessment and remediation planning. This study evaluated tetrachloroethene sorption isotherms in 34 low-organic-carbon soils from the Czech Republic, assessing the influence of soil properties on Kd. Soil samples exhibited variability in organic carbon content (˂0.05–0.81%), with clay ranging from 0% to 64.9%, silt 5.1% to 71.2%, and sand 5.2% to 88.9%, specific surface area (0.41–64.39 m2 g−1), particle density (2.05–4.09 g cm−3), and porosity (43.5–67.3%). Batch experiments were conducted using standard procedures, with Kd values ranging from 0.379 to 2.272 L kg−1. Statistical analysis grouped the soils into three textural classes: sandy, clayey fine, and silty loam. The findings reveal that organic carbon content and specific surface area are the primary predictors of Kd, while clay and sand also play a significant role in shaping sorption behavior. Multivariate regression models explained 63.6% to 98.5% of Kd variability with high accuracy, as indicated by low root means square error (0.070–0.329) and mean absolute percentage error (3.8–28.8%) values. These models offer reliable predictions of sorption behavior, providing valuable tools for risk assessment and remediation strategies.

Developing an institutional control framework for contaminated sites in China: An analytical case study

Institutional controls, as an important measure for risk management of contaminated sites, is widely used in site management by the United States, Canada and European countries. At present, some regions in China have also begun to explore the implementation of institutional controls, but its path, safeguard mechanism, and tracking evaluation are still unclear. Based on China's unique contaminated site remediation control system and land management system, this paper proposes a framework for the whole life cycle institutional controls of China's contaminated sites: (1) evaluate the need for institutional controls; (2) establish the objectives of institutional controls; (3) identify the restrictive requirements of institutional controls; (4) establish the implementation form of institutional controls; and (5) regularly review the effectiveness of institutional controls. To demonstrate the applicability of the institutional control framework, a case demonstration study was conducted at a petrochemical contaminated site in China. By analyzing the information on residual pollutants after the implementation of risk management measures at the site, the exposure pathways and hazards in case of re-release, and the engineering facilities, we proposed eight restrictive requirements, including the prohibition of disturbing and damaging the clean and planted soil layers of the site and the protection of long-term monitoring wells. At the same time, we constructed a multi-departmental pathway to implement institutional controls in conjunction with ecological environment, natural resources and housing departments to ensure effective implementation of institutional controls. Eventually, we summarized a set of replicable and generalizable institutional controls application models, which provide valuable theoretical and practical support for China and other local governments in the implementation of institutional controls at contaminated sites.

Assessing and mitigating health risks of workers exposed to volatile organic compounds in contaminated soils during active pit excavation: Accounting for exposure variability and uncertainty

Health risks to workers involved in the active pit excavation of volatile organic compound (VOC)-contaminated soils have been overlooked, despite the prevalence of ex-situ remediation practices in China. This study developed a new VOC exposure in pit excavation (VEPE) model that comprehensively accounts for the release of gas-phase VOCs in soil pores, surface volatilization of newly exposed agglomerates, and volatilization of newly exposed excavation pit bottom surfaces. Additionally, the model incorporates the concentration variation of soil contaminants, spatial heterogeneity of soil properties, and the variability and uncertainty of worker exposure using two-dimensional Monte Carlo simulation (2D MCS), highlighting the importance of controlling area of new exposure surfaces, soil saturation, and air exchange during the pit excavation to mitigate risks. The study evaluated worker-health-based risks during the excavation of a VOC-contaminated site in Beijing and revealed that the inhalation cancer risk for trichloroethylene (2.35 × 10−6) and its hazard quotient (143.92) exceed the acceptable levels (10−6 and 1.0, respectively). The comparison of models demonstrated the theoretical advancements of the VEPE model over existing pit excavation models, while the field test comparison showed a significant improvement in the predication accuracy. This study addresses the under-researched area of worker safety in contaminated excavation sites. The findings have the potential to promote cleaner and more sustainable practices in ex-situ contaminated site remediation by providing valuable insights for implementing effective control measures to mitigate the emission of toxic VOCs, thereby reducing adverse social and environmental impacts.

Study on the overall performance of e-waste dismantling industry polluted cultivated land utilization from a holistic view

The utilization of heavy metal-organic polluted cultivated land caused by the e-waste dismantling industry was affected by multi-dimensional factors. Thus a comprehensive evaluation of these multi-dimensional impacts was necessary for the technical selection and solution of cultivated land utilization. This study attempted to conduct a total benefit simulation analysis on the redevelopment of polluted cultivated land, which was of great significance to decision-making. With a systematic framework designed including the casual relations between components, a system dynamics model was constructed to simulate the technological, economic, and ecological benefits of different polluted cultivated land-used modes, along with which a questionnaire was designed to investigate and analyze the associated social effects. Based on these, the total benefits of the land-use mode were evaluated and optimized within the framework of the “technological-economic-ecological-social” evaluation system. This study included microscale, mesoscale, and macroscale, with multi-dimensional and complex influencing factors, and had advanced research value. The results of the system dynamics model simulation showed that remediation plants played a decisive role in pollutants removal. The flower industry had the highest net present value, but its ecological performance was poor. The overall analysis showed that the scenario of utilization after remediation had the highest performance score, which was attributed to high pollutant removal, low cost, and high carbon sink. This study was meaningful for providing research ideas of comprehensive benefits of polluted cultivated land utilization and also helpful for decision-making. This paper also provided research ideas for other industries such as contaminated site remediation and sewage sludge treatment.

Enhanced migration and degradation of nitrobenzene in heterogeneous porous media using pulsed direct current electrical resistance heating with hydraulic circulation

Electrical resistance heating (ERH) is a promising in-situ technology for heterogeneous organic contaminated site remediation, yet may have low efficiency when treating semi-volatile organic contaminant (SVOC) of relatively high boiling point. Herein, we chose nitrobenzene as a representative SVOC, and proposed an ERH system powered by pulsed direct current (PDC) with simple hydraulic circulation for improved remediation efficiency in heterogeneous media. The proposed PDC-ERH with hydraulic circulation showed overall improvement in heating performance and energy efficiency, as well as migration and removal of nitrobenzene. This new system improved the uniformity of PDC heating and achieved a temperature increase of ~15°C compared to that using conventional alternating current (AC) of same voltage. Nitrobenzene migration out of the low permeability zone (LPZ) was intensified by the dual effects of heat-induced diffusion enhancement and electric field-induced electroosmotic flow, while subsequent removal was enhanced by electrochemical degradation and volatilization. After 96h, the proposed system has a higher nitrobenzene removal from LPZ (> 97.1%) compared to that using AC (84.0%–95.9%). These results suggest PDC heating coupled with hydraulic circulation was a promising approach for heterogeneous site remediation.

Are contaminated soil and groundwater remediation with nanoscale zero-valent iron sustainable? An analysis of case studies

Nanoscale zero valent iron (nZVI) is globally the main nanomaterial used in contaminated site remediation. This study aims to evaluate the sustainability of using nZVI in the nanoremediation of contaminated sites and to determine the factors that affect the sustainability of the use of nZVI in remediation. Five case studies of nZVI use on a pilot scale were selected. Life cycle analysis tools were used to evaluate environmental, economic, social impacts, and sustainability. The functional unit of the life cycle analyses was 1.00 m3 of remediated soil and groundwater. Case study of Brazil was the least sustainable, while case study of United States was the most sustainable. Only the modification of the functional unit results in variations in the sustainability index. Different factors influence the sustainability of nZVI in remediation, the main factor being the amount of nZVI used in the processes. Finally, this work contributes significantly to the state-of-the-art sustainable use of nZVI in remediation. This is a pioneering study in the detailed and comprehensive assessment of the sustainability of the use of nZVI in remediation. Through the analysis of case studies, it is possible to determine the main factors that influence the sustainability of the nZVI remediation life cycle.

Spatiotemporal dynamic temperature variation dominated by ion behaviors during groundwater remediation using direct current

Direct current (DC) electric field has shown promising performance in contaminated site remediation, in which the Joule heating effect plays an important role but has been previously underappreciated. This study focuses on the spatiotemporal characteristics and mechanism of temperature change in heterogeneous porous media with applied DC. The heating process can be divided into four phases: preferential heating of the low permeability zone (LPZ), rapid heating in the middle region, temperature drop and hot zone shift, and reheating. The dynamic ion behaviors with complex interplays among reactions, electrokinetic-driven migration, and mixed convection induced an uneven redistribution of ions and dominated the heating rate and temperature distribution. The concentration of major ions near the pH jump decreased to 1% of the initial value, even though ions were continuously pumped into the heating zone. This ion depletion caused a drop in current, heating rate, and temperature. Here ions cannot be delivered rapidly into the ion-depleted zone by electromigration due to the potential flattening in the surrounding region. The presence of LPZ intensified the nonuniformity of ion redistribution, where a regional focusing of water-soluble ions was observed, and weakened the temperature rebound compared with that using homogeneous sand. These results provide a new perspective on the regulation of DC heating in site remediation.

Visual analysis of contaminated site studies in recent 30 years based on bibliometrics and knowledge graph

AbstractThe problem of contaminated sites is a hot and difficult issue in global environmental sustainable development. Because the contaminated site carries a large number of harmful substances (heavy metal ions, organic polycyclic aromatic hydrocarbons, toxic gases, etc.), it brings great security risks to the environmental ecological security and people's health. Effective identification of the characteristics of contaminated sites and understanding of the research status and development trend of contaminated sites are of great significance to environmental sustainable development and environmental governance and restoration. Based on Web of Science database, this study systematically, quantitatively and visually analyzes the research status of contaminated sites by bibliometrics and knowledge graph technology. The results show that bibliometrics and knowledge graph are effective in information retrieval and visualization. It can display the information of different scales and different times in the study of contaminated sites, and find the distribution characteristics of popular keywords. The cluster cases of this study show that the problems of contaminated site research mainly focus on suspended particulate matter pollution, water pollution, heavy metal pollution, organic pollution, pollution reduction and bioremediation technology research. In the future, the hot issues of contaminated site remediation and environmental sustainable development will focus on strengthening the research of microbial remediation technology, nanomaterial technology, composite material adsorption technology and so on.

The Role of Procedure Duration in the Sustainability Assessment of Contaminated Site Management in Italy

The European Union (EU) has placed a strong focus on soil contamination and remediation in its Thematic Strategy for Soil Protection, emphasizing the critical need for comprehensive soil data at the EU level. To effectively support EU soil management strategies, it is necessary to develop soil-related indicators and standardized datasets across all EU member states. However, the lack of standardized methodologies for estimating the time required for contaminated site remediation is a dilemma in Italy and throughout Europe. This study examines statistical data on the time-consuming nature of the contaminated site remediation process in Italy. In fact, early intervention not only simplifies site remediation but also reduces long-term financial obligations such as monitoring costs and potential legal implications. This study categorized data according to remedial procedures, explored different management phases, and revealed different timescales for completing the procedure. The findings show that processes completed after preliminary investigations are often shorter in time than those completed following conceptual model assessments. In contrast, processes that require corrective measures typically take a longer period of time to complete. Notably, remedial interventions tend to have a shorter duration compared to risk management interventions. Furthermore, procedures that address both soil and groundwater contamination generally require more time compared to those that focus only on soil remediation. This study provides valuable insight into the time-consuming aspects of remediation procedures, recommending potential changes to regulatory frameworks to accelerate site remediation activities.

Nature-based solutions for contaminated site remediation: Key principles and a practical case

The article considers opportunities applying nature-based solutions to remediate oil-contaminated sites. It is suggested using such industrial wastes as brewer’s spent grain, beet pulp, and lignin as structurers. It is demonstrated that structurers bearing such genes as Bacillus, Arthrobacter, etc. perform as active petroleum degraders. It was found out that the hydrocarbon removal rate ranged from 90 to 99% for all structurers studied. It is recommended using 1% of the lignin-based degrader to reduce hydrocarbon content in soils preparing them to the future phytoremediation.

Influence of synthetic chelators and LMWOAs on the yield and quality attributes of Panicum maximum Jacq. (Poales: Poaceae) in chromium phytoextraction

Phytoextraction is a cost-effective technology for contaminated site remediation. The study was carried out to investigate the potential of Panicum maximum (Jacq.) to remediate Cr-contaminated soil in tannery industries. Using chromium chelators and hyperaccumulating plants (Guinea grass), efforts have been made to decontaminate the chromium-contaminated tannery sites. To evaluate, the pot experiment was conducted, and Guinea grass’s yield and quality parameters were analyzed. The changes in root length, shoot length, and number of tillers were studied for three months, and the maximum values were 12.6 cm, 163.6 cm, and 12.6 cm, respectively, in the treatment with citric acid. The fodder quality parameters such as crude protein (9.2%), crude fibre (27.24%), and green leaf yield (370.3 g/plant) were magnificent in the treatment with citric acid as the chelator. Indeed, maximum hexavalent chromium (2.94 ± 0.06) and total chromium (17.98 ± 0.05) were observed in the citric acid treatment. Among all the treatments analyzed, the low-molecular-weight organic acids (LMWOAs), especially citric acid at 5 mmol/kg, were the best ones that could be recommended for improving the chelating process in the phytoremediation of chromium by Guinea grass. However, among the synthetic chelators, EDTA has resulted in higher chromium chelation and yield attributes such as root length (10.7 cm), shoot length (153.6 cm), number of tillers (10.3), and quality parameters like Guinea grass such as crude protein (8.1%), crude fibre (28.03%), and green leaf yield (342.6 g/plant). The study indicates that the chelators are enhancing Guinea grass growth and incorporating that may assist in the phytoremediation process.

Development and Application of an Integrated Site Remediation Technology Mix Method Based on Site Contaminant Distribution Characteristics

Millions of contaminated sites worldwide need to be remediated to protect the environment and human health. Although numerous remediation technologies have been developed, selecting optimal technologies is challenging. Several multiple criteria decision-making methods for screening the optimal remediation technology have been proposed, but they mostly focus on a specific area rather than the whole contaminated site. In recent years, the “contamination source control—process blocking—in situ remediation” technology mix model has gradually gained high appreciation. Nevertheless, the screening of technologies within each chain of this model relies heavily on arbitrary personal experience. To avoid such arbitrariness, a petroleum-contaminated site containing light non-aqueous phase liquids (LNAPLs) was used as an example, and a scientific screening and combination procedure was developed in this study by considering the distribution characteristics of contaminants. Through the procedure, a technology mix, which includes institutional control, risk monitoring, emergency response, multiphase extraction, interception ditch, monitoring of natural attenuation, hydrodynamic control, as well as some alternative technologies, was found, aiming at different locations and strata. The clear spatial relationship concept promises to enhance the effectiveness of contaminated site remediation. The proposed method only gave us a technical framework and should be tested and enriched in future studies.

Advances in Hydrocarbon Speciation for Soil Gas Analysis

In the field of contaminated site remediation, risk analyses can be carried out by the use of appropriate mathematical models, based on simplified hypotheses of real sites. The possibility to have shared and accurate analytical methods is an important challenge for both routine laboratories and supervisory institutions. Although official methods (e.g., APH2009) are already available, they are lacking in some aspects, such as applicability to all the different sampling and analysis media and ease of use in routine analysis. Here, we report our recent advances in the implementation of an empirical method for hydrocarbon speciation in an air matrix, previously developed by the authors and published in 2015. The validation results led to a coefficient of variation (CV%) between 10–15% for the hydrocarbon fractions investigated (C5-C8 aliphatic, C9-C12 aliphatic, C9-C10 aromatic and C11-C12 aromatic) and recovery of ≤20%, in agreement with the required characteristics for the analytical methods. Several real samples were analyzed by the proposed method and the results were compared to those obtained by the official approach. The comparison led to an average bias (that is, the difference between the results from the developed method and those from the conventional one) of about 10%, confirming that the innovative approach is robust, accurate and can be applied to all the analytical media used for air sampling, such as soil gas.

Research Status and Trend Analysis of Environmental and Health Risk and Control of Persistent, Mobile, and Toxic Chemicals

Persistent, mobile, and toxic or very persistent and very mobile (PMT/vPvM) chemicals have been widely detected in surface water, groundwater, and drinking water around the world and are important emerging contaminants that may significantly affect human health and the environment in the future. According to the identification criteria proposed by the European Union, there are thousands of PMT/vPvM substances in existing chemicals, covering a wide range of applications, including dozens of high-yield industrial chemicals such as melamine. PMT/vPvM chemicals can be discharged into the environment through farmland runoff, industrial wastewater, and domestic sewage, and sewage treatment plants are currently considered to be their main discharge route. It is difficult to effectively remove PMT/vPvM chemicals through the current conventional water treatment technology; they can exist in the water circulation system of the urban human settlement environment for a long time, endangering the safety of drinking water and the ecosystem. The European Union has taken the lead in introducing PMT/vPvM chemicals specifically into the priority areas of the current chemical risk management system. At present, there are still many potential PMT/vPvM chemicals in the environment, and their monitoring methods need to be further improved. It will take time for the identification of substances, the scope of categories, and the establishment of lists. Studies on the environmental fate and exposure of PMT/vPvM in various regions of the world are still very limited, and research on the potential, long-term ecotoxicity, and human health hazard effects remains scarce. At the same time, the research and development of substitute or alternative technologies, as well as environmental engineering treatment technologies such as sewage treatment and contaminated site remediation, will become an urgent need for future PMT/vPvM risk scientific research and management decisions.

Research status and emerging trends in remediation of contaminated sites: a bibliometric network analysis

Site contamination poses a grave danger to the environmental quality and human health, and its remediation has been a focus of worldwide concern over the last few decades. Based on 5068 bibliographic data (2001–2022) acquired from the Web of Science Core Collection, this study employed a scientometric analysis approach to analyze the present state and investigate the trends of contaminated site remediation studies. The results of this study provide an in-depth response to the following: (1) publication characteristics of polluted site restoration studies; (2) basic information on countries, institutions, journals, and disciplines engaged in remediation research in contaminated areas; and (3) a summary of development trends and hotspots in poisoned field cleanup investigations. In summary, this study assessed the results of research on contaminated site remediation. Those unfamiliar with contaminated site remediation could utilize the information in this study to rapidly merge into the field and grasp the forefront of research on this subject. This article can be regarded as a reference for scholars who desire to conduct further research on relevant subjects.

Distinctive adsorption and desorption behaviors of temporal and post-treatment heavy metals by iron nanoparticles in the presence of microplastics

There are increasing concerns about microplastic (MP) pollution in the natural environment. Consequently, numerous physicochemical and toxicological studies have been conducted on the effects of MPs. However, few studies have concerned the potential impact of MPs on contaminated site remediation. We herein investigated the influence of MPs on the temporary and post heavy metal removal by iron nanoparticles, including pristine and sulfurized nano zero-valent irons (nZVI and S-nZVI). MPs inhibited adsorption of most heavy metals during the treatment of iron nanoparticles, and facilitated their desorption, such as Pb (II) from nZVI and Zn (II) from S-nZVI. However, such effects presented by MPs was usually less than those by dissolved oxygen (DO). Most desorption cases are irrelevant to the reduced formats of heavy metals involving redox reactions, such as Cu (I) or Cr (III), suggesting that the influence of MPs on metals are limited to those binding with iron nanoparticles through surface complexation or electrostatic interaction. As another common factor, natural organic matter (NOM) had almost no influence on the heavy metal desorption. These insights shed lights for enhanced remediation of heavy metals by nZVI/S-NZVI in the presence of MPs.

Modified red mud tailored to chromium contaminated soil remediation

The modified red mud was prepared by thermal reduction with coconut shell for Cr(VI) contaminated soil remediation. Significant reduction of Cr(VI) in soil was achieved for the modified red mud with an efficiency up to 100%. The mass ratio of the modified red mud to soil presents the greatest impact on Cr(VI) reduction in soil, followed by pH, and then the soil moisture. Under the conditions of pH = 4%, and 40% water content, the reduction of Cr(VI) in soil reached 99.37%with 10 wt% of the modified red mud (RM1C-T800(1 h)). Based on the X-ray diffraction spectrum, zero valence iron (ZVI) was detected in RM1C-T800(1 h). The characterization analysis showed that the originally tight and porous surface of RM1C-T800(1 h) became loose and flocculation state after the soil remediation. It implied that internal ZVI particles had recombined with Cr and gradually separated from the parent by exposing to the external surface of RM1C-T800(1 h). The decrease of Cr(VI)in soil was probably attributed to the adsorption and reduction of the ZVI in RM1C-T800(1 h) when mixing the Cr(VI) contaminated soil with RM1C-T800(1 h). The work offers an effective strategy for the resource utilization of solid waste and contaminated site remediation.

Microbiology in sustainable remediation of contaminated sites

The release of chemicals that have negative human or environmental health impacts has been rife around the world for a century. Approaches to contaminated site remediation have evolved over this time to address environmental contamination. Over the past 15 years there has been an increasing focus on sustainability in remediation. Bioremediation has emerged as a remediation technology of choice based on sustainability credentials. Research on pollutant biodegradation, including the discovery and characterisation of microbes responsible, underpins biological remediation applications.

Residual NAPL Morphology Effects on Electrical Resistivity: Insights From Micromodel Displacement Experiments and Pore Network Simulations

AbstractCharacterizing residual non‐aqueous phase liquids (NAPLs) in porous media is essential for designing contaminated site remediation strategies. The direct current resistivity method is increasingly being used at sites contaminated by NAPLs, which uses the Archie's second law to connect NAPL saturation with the resistivity of porous media. A power‐law relationship connecting the phase morphology measured by Euler characteristic with resistivity has also been observed at the pore‐scale. Because these relationships are limited for porous media with specific wettability, previous research works have demonstrated deviations from Archie's second law in both the laboratory and field experiments. To evaluate the effects of residual NAPL morphology with different wettability on bulk resistivity, we developed two 2D‐micromodels and measured their electrical resistivity and phase morphology during phase displacement under laboratory‐controlled conditions. Furthermore, pore network simulations of a variety of conditions were performed in absence of surface conduction. Results show that NAPL distributed in dead ends of the pore space has limited influence on bulk resistivity since they do not control the current path and voltage distribution. The correlations between resistivity index and Euler characteristic are determined by NAPL ganglia size and pore throat width. A power‐law relationship is found between the Archie's saturation exponent and the average size of the residual NAPL ganglia, indicating that this exponent can be interpreted as the rate of change of the pore water connectivity with saturation. These insights provide a physical framework connecting the morphology and wettability of the NAPL ganglia with the Archie's saturation exponent.

Surfactant-enhanced reduction of soil-adsorbed nitrobenzene by carbon-coated nZVI: Enhanced desorption and mechanism

The reduction process of pollutants by nano zero-valent iron (nZVI) is limited by mass transfer and its effective utilization, and previous studies have ignored the electron loss caused by its oxidative passivation. The carbon-coated structure can effectively inhibit the oxidation of nZVI, but the effectiveness of carbon-coated nZVI (Fe0@C) as a reducing agent in soil remediation is unclear. Therefore, in this study, the Fe0@C/surfactant system was used to remove soil-adsorbed nitrobenzene (NB) to simultaneously enhance the mass transfer process and effective utilization of nZVI. The results showed that the use of surfactants effectively promoted the desorption of NB adsorbed by the soil, and the desorption process was affected by factors such as the type and concentration of surfactants, water-soil ratio, and soil organic matter (SOM) content. The enhanced desorption of NB by the surfactant in the soil system promoted the effective contact between the composite and NB, thereby enhancing the reduction of NB by the composite. In addition, Fe0@C exhibited excellent performance for the reduction of soil-adsorbed NB compared with the conventional nZVI, and this advantage was more obvious in the potting soil system. However, the composite will be gradually passivated due to the alkaline environment during the reduction process, and this phenomenon was especially obvious in the campus soil system. When the pH value decreased from 9 to 3, the proportion of aniline (AN) generated in the campus soil system increased from 19.37 % to 69.29 %. In addition, in potting soil systems with high SOM content, the adsorption of soil particles to the composite and the high dissolved organic matter (DOM) content resulting from the high SOM content also negatively affected the reduction process. The conclusions of this study demonstrate the great potential of the Fe0@C/surfactant system for in-situ contaminated site remediation applications.