Publications by authors named "Deyi Hou"

94 Publications

Effect of production temperature and particle size of rice husk biochar on mercury immobilization and erosion prevention of a mercury contaminated soil.

J Hazard Mater 2021 Jul 14;420:126646. Epub 2021 Jul 14.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Mercury (Hg) contaminated soil is a potential hazardous material especially under soil erosion and surface runoff. This work aims to use rice husk biochar to immobilize Hg and prevent erosion, and find the optimal production temperature and particle size of the biochar. The biochars were produced at 300, 500, and 700 °C and sieved to three particle sizes ~20, < 2, and < 0.15 mm. They were applied to a Hg contaminated loamy sand (20.2 mg/kg) and undergone simulated rainfall erosion representing 7 years of heavy rain events in Beijing. All biochar amendments reduced the runoff volume by 5.1-15.4%. Hg amount in runoff were significantly reduced by 36.7-48.8% after the amendments of biochar. The Hg concentration of infiltration was reduced by biochar treatments except that produced at 300 °C, while its amount was increased due to larger infiltration volume. All biochar amendments significantly reduced soil loss in runoff by 43.5-77.2%. Hg was enriched in the sediments (39.7-46.8 mg/kg) compared with the parent soil (20.2 mg/kg) regardless of biochar treatment, but its bioavailability was low. Higher pyrolysis temperature of the rice husk biochars resulted in less runoff, more infiltration, and better erosion prevention, while the effect of biochar particle size is less significant.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126646DOI Listing
July 2021

Vertical migration of microplastics in porous media: Multiple controlling factors under wet-dry cycling.

J Hazard Mater 2021 Jun 17;419:126413. Epub 2021 Jun 17.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Terrestrial soils are not only a large reservoir for Microplastics (MPs), but also a possible entrance to the subsurface environment, posing potential risks to the subterranean habitats and groundwater. In this study, we examined the vertical transport of MPs of four polymers, i.e., polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polyamide (PA), in porous sand media driven by wet-dry cycling. The effects of polymer properties, MP size, sand particle size, wet-dry cycles, and dissolved organic matter (DOM) on their migration behavior were investigated. Surface hydrophobicity showed a strong positive correlation with MP mobility, with PA exhibiting the greatest movement potential, followed by PE, PET, and PP. The penetration depth of MP particles increased with decreasing MP particle size (d) and increasing sand diameter (d). MP particles migrated deeper in sand media when d/d < 0.11. Furthermore, frequent wet-dry cycles and the presence of DOM promoted the vertical migration of MPs in the sand. The results revealed multiple factors influencing the vertical migration of MPs in sand, which is instructive for understanding the ecological risk of MPs in potentially contaminated soil (e.g., farmland with long-term mulching) to the subsurface environment and potential negative impact to public health.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126413DOI Listing
June 2021

Simultaneous reduction and immobilization of Cr(VI) in seasonally frozen areas: Remediation mechanisms and the role of ageing.

J Hazard Mater 2021 08 17;415:125650. Epub 2021 Mar 17.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Among the toxic metals, hexavalent chromium [Cr(VI)] has attracted much attention due to its high mobility and toxicity, rendering considerable challenges for long-term remediation. In this study, the soil was collected from a dichromate contaminated industrial site in Liaoning Province, a seasonally frozen area in northern China, and subjected to frequent freeze-thaw cycles. Three additives, including (i) ferrous sulfate; (ii) calcium polysulfide; and (iii) combined biochar and calcium polysulfide were applied to reduce and immobilize Cr(VI) in the soils. The samples underwent 28 days of incubation followed by 16 freeze-thaw cycles. The toxicity characteristic leaching procedure (TCLP) and simulated acid rain leaching were adopted to test the remediation performances. It was observed that all three treatments can significantly reduce and immobilize Cr(VI) after short-term incubation, while biochar with abundant functional groups could adsorb and reduce Cr(VI) effectively. Notably, the concentration of Cr(VI) in TCLP leachates after incubation in combined treatment decreased by 67.87% and 37.27%, respectively, compared with the application of ferrous sulfate or calcium polysulfide alone. Freeze-thaw cycles induced the disintegration of soil particles and increased the risk of contaminant mobilization. Conversely, biochar particles has become finer and even produced nanoparticles with ageing, accompanied by the increase in oxygen-containing surface functional groups. Additionally, the specific surface area increased with the pyrolysis of biochar, which further enhanced the retention of soil colloidal particles and suppressed the migration of contaminants. Therefore, the cumulative release of Cr(VI) in the combined treatment (i.e., 10.97 ~ 32.97 mg/kg) was much lower than that of the other two treatments after freeze-thaw ageing. Overall, the combination of biochar and calcium polysulfide displayed advantages in the reduction and immobilization of Cr(VI), and offered a long-term, effective strategy for the remediation of Cr(VI) contaminated soils in cold regions.
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http://dx.doi.org/10.1016/j.jhazmat.2021.125650DOI Listing
August 2021

The term "heavy metal(s)": History, current debate, and future use.

Sci Total Environ 2021 Oct 24;789:147951. Epub 2021 May 24.

Ghent University, Gent, Belgium. Electronic address:

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http://dx.doi.org/10.1016/j.scitotenv.2021.147951DOI Listing
October 2021

(Im)mobilization of arsenic, chromium, and nickel in soils via biochar: A meta-analysis.

Environ Pollut 2021 May 1;286:117199. Epub 2021 May 1.

Department of Agricultural and Food Chemistry, Universidad Autónoma de Madrid, 28049, Madrid, Spain.

Biochar is a promising immobilizing agent of trace elements (TEs) in contaminated soils. However, several contradictory results have been reported regarding the potential of biochar to immobilize arsenic (As), chromium (Cr), and nickel (Ni) in contaminated soils. We conducted a meta-analysis on the published papers since 2006 until 2019 to examine the effects of biochar on the chemical (im)mobilization of As, Cr, and Ni in contaminated soils and to elucidate the major factors that control their interactions with biochar in soil. We synthesized 48 individual papers comprised of a total of 9351 pairwise comparisons and used the statistical tool of Cohen's d as an appropriate effect size for the comparison between means. We found that the application of biochar often increased the As mobilization in soils. Important variables that modulated the biochar effects on As mobilization in soil were pyrolysis temperature and time (ranging between 8 and 16 times when T > 450 °C and t > 1hr), organic matter (7-16 times when SOM<3%) and further site conditions. In contrast to As, biochar efficiently immobilized Cr and Ni in contaminated soils. The extent of the Cr and Ni immobilization was determined by the feedstock (Cr: 7-18 times for agricultural residue-derived biochar; Ni: 13-32 times for woody biomass-derived biochar). Our meta-analysis provides a compilation on the potential of different types of biochar to reduce/increase the mobilization of As, Cr, and Ni in various soils and under different experimental conditions. This study provides important insights on factors that affect biochar's efficiency for the (im)mobilization of As, Cr, and Ni in contaminated soils. While biochar effectively immobilizes Cr and Ni, a proper management of As-polluted soils with pristine biochar is still challenging. This limitation might be overcome by modification of biochar surfaces to exhibit higher surface area and functionality and active sites for surface complexation with TEs.
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http://dx.doi.org/10.1016/j.envpol.2021.117199DOI Listing
May 2021

Comparison of the Hydraulic Fracturing Water Cycle in China and North America: A Critical Review.

Environ Sci Technol 2021 06 10;55(11):7167-7185. Epub 2021 May 10.

Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada.

There is considerable debate about the sustainability of the hydraulic fracturing (HF) water cycle in North America. Recently, this debate has expanded to China, where HF activities continue to grow. Here, we provide a critical review of the HF water cycle in China, including water withdrawal practices and flowback and produced water (FPW) management and their environmental impacts, with a comprehensive comparison to the U.S. and Canada (North America). Water stress in arid regions, as well as water management challenges, FPW contamination of aquatic and soil systems, and induced seismicity are all impacts of the HF water cycle in China, the U.S., and Canada. In light of experience gained in North America, standardized practices for analyzing and reporting FPW chemistry and microbiology in China are needed to inform its efficient and safe treatment, discharge and reuse, and identification of potential contaminants. Additionally, conducting ecotoxicological studies is an essential next step to fully reveal the impacts of accidental FPW releases into aquatic and soil ecosystems in China. From a policy perspective, the development of China's unconventional resources lags behind North America's in terms of overall regulation, especially with regard to water withdrawal, FPW management, and routine monitoring. Our study suggests that common environmental risks exist within the world's two largest HF regions, and practices used in North America may help prevent or mitigate adverse effects in China.
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http://dx.doi.org/10.1021/acs.est.0c06119DOI Listing
June 2021

Critical Impact of Nitrogen Vacancies in Nonradical Carbocatalysis on Nitrogen-Doped Graphitic Biochar.

Environ Sci Technol 2021 05 29;55(10):7004-7014. Epub 2021 Apr 29.

Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon 852, Hong Kong, China.

Nitrogen-doped graphitic biochar (NBC) has boosted the development of nonradical peroxymonosulfate (PMS) activation in environmental remediation. However, the specific role of nitrogen species played in NBC-based nonradical carbocatalysis remains vaguely interpreted. To pinpoint the critical nitrogen speciation, a sophisticated thermo-mechanochemical manipulation was exploited to prepare a series of NBCs with similar dimensional structures and oxygen levels but different nitrogen species (.., dopants and vacancies). Different from conventional perspectives, nonradical NBC-based carbocatalysis was found to be preferably determined by the nitrogen vacancies more than their parent nitrogen dopants. Raman depth analysis evidenced that a complete transformation of nitrogen dopants into nitrogen vacancies could be achieved at 800 °C, where an excellent nonradical abatement of 4-chlorophenol (4-CH, 90.9% removal) was found for the NBC800 with a low PMS consumption (1.24 mM). According to PMS adsorption experiments, nitrogen vacancies exhibited the highest affinity toward the PMS molecules compared to nitrogen dopants, which accounted for the superior carbocatalysis. Electron paramagnetic resonance and Raman spectroscopic analyses indicated that the original PMS molecules were bound to positively charged nitrogen vacancies, and a robust metastable complex (*HSO) evolved subsequently hydrogen abstraction by adjacent persistent free radicals. Raman techniques could be adopted to estimate the level of nitrogen vacancies associated with the polarization of electron distribution. The flexible feature and practical prospects of nitrogen vacancy-based carbocatalysis were also observed in the remediation of simulated phenolic industrial wastewater. Overall, this study unravels the dilemma in the current NBC-based nonradical carbocatalysis and advances our understanding of nitrogen doping technology for next-generation biochar design.
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http://dx.doi.org/10.1021/acs.est.0c08531DOI Listing
May 2021

An integrated assessment methodology for management of potentially contaminated sites based on public data.

Sci Total Environ 2021 Aug 6;783:146913. Epub 2021 Apr 6.

Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China. Electronic address:

Ranking assessment of potentially contaminated sites (PCS) provides a great quantity of information (namely the risk screening list) that is usually examined by environmental managers, and therefore reduces the cost of risk management in terms of site investigation. Here we propose an integrated assessment methodology to establish a risk screening list of PCS in China using the Choquet integral correlation coefficient (ICC), which takes the uncertainty and interaction of PCS attributes into explicit account. The proposed method globally considers the importance and ordered positions of PCS attributes while reflecting their overall ranking. The model evaluation and actual validation results demonstrate the success in PCS ranking by the proposed method, which is superior to other methods such as the intuitionistic fuzzy multiple attribute decision-making, the technique for order preference by similarity to an ideal solution, and the weighted average. The resulting spatial distribution of Choquet ICC indicates that high-attention PCS in China are mainly located in Guangdong, Jiangsu, Zhejiang, and Shandong Provinces. This study is the first attempt to conduct a ranking assessment of PCS across China. The proposed assessment method based on Choquet ICC offers a step towards establishing a risk screening list of PCS globally.
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http://dx.doi.org/10.1016/j.scitotenv.2021.146913DOI Listing
August 2021

Modeling the Conditional Fragmentation-Induced Microplastic Distribution.

Environ Sci Technol 2021 05 11;55(9):6012-6021. Epub 2021 Apr 11.

School of Environment, Tsinghua University, Beijing 100084, China.

Microplastics (MPs) are drawing increasing attention from the international community due to their potential threats to the ecosystem and human health. Although their occurrence and spatial distribution have been extensively studied in recent years, the relationship between their abundance and sizes remains unclear. Moreover, the underlying mechanisms dominating their size distribution have rarely been explored. In the present study, we developed a novel conditional fragmentation model to describe MP size distribution in the soil environment. It is proposed that the distribution of MPs is not a coincidence but controlled by conditional aging. The applicability of this model was tested using data collected from different land use settings in Beijing, China. A distinct downsizing phenomenon from fibers, films, and fragments to granules is observed. Undisturbed land use types accumulated larger sized MPs with higher stability, while human interference accelerated the fragmentation of MPs. Both morphological analysis and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) observations provided direct evidence for the conditional fragmentation process. Furthermore, the model has proven to be suitable for describing the size distribution of MPs from various sources (including atmospheric deposition, transportation, and agriculture) and aging processes (such as mechanical abrasion, chemical oxidation, and photochemical transformation). It is proposed that this model can be used for various purposes in MP-related studies, especially source identification, transport modeling, and risk assessment.
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http://dx.doi.org/10.1021/acs.est.1c01042DOI Listing
May 2021

A critical review on performance indicators for evaluating soil biota and soil health of biochar-amended soils.

J Hazard Mater 2021 07 17;414:125378. Epub 2021 Feb 17.

Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China. Electronic address:

Amendment of soil with biochar has been widely investigated for soil quality improvement in terms of biotic and abiotic functionalities. The performance of biochar-based amendment varies according to the site characteristics, biochar properties, and soil management targets. There is no existing review that summarizes a broad range of performance indicators to evaluate the health of biochar-amended soil. Based on the latest studies on soil amendment with biochar, this review critically analyzes the soil health indicators that reveal the potential impact of biochar amendment with respect to physicochemical properties, biological properties, and overall soil quality. It is found that soil pH, soil aggregate stability, and soil organic matter are the basic indicators that could influence most of the soil functions, which should be prioritized for measurement. Relevant functional indicators (e.g., erosion rate, crop productivity, and ecotoxicity) should be selected based on the soil management targets of biochar application in agricultural soils. With this review, it is expected that target-oriented performance indicators can be selected in future studies for field-relevant evaluation of soil amendment by biochar under different situations. Therefore, a more cost-effective and purpose-driven assessment protocol for biochar-amended soils can be devised by using relevant measurable attributes suggested in this review.
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http://dx.doi.org/10.1016/j.jhazmat.2021.125378DOI Listing
July 2021

Mapping soil pollution by using drone image recognition and machine learning at an arsenic-contaminated agricultural field.

Environ Pollut 2021 Feb 14;270:116281. Epub 2020 Dec 14.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Mapping soil contamination enables the delineation of areas where protection measures are needed. Traditional soil sampling on a grid pattern followed by chemical analysis and geostatistical interpolation methods (GIMs), such as Kriging interpolation, can be costly, slow and not well-suited to highly heterogeneous soil environments. Here we propose a novel method to map soil contamination by combining high-resolution aerial imaging (HRAI) with machine learning algorithms. To support model establishment and validation, 1068 soil samples were collected from an arsenic (As) contaminated area in Zhongxiang, Hubei province, China. The average arsenic concentration was 39.88 mg/kg (SD = 213.70 mg/kg), with individual sample points determined as low risk (66.9%), medium risk (29.4%), or high risk (3.7%), respectively. Then, identified features were extracted from a HRAI image of the study area. Four machine learning algorithms were developed to predict As risk levels, including (i) support vector machine (SVM), (ii) multi-layer perceptron (MLP), (iii) random forest (RF), and (iii) extreme random forest (ERF). Among these, we found that the ERF algorithm performed best overall and that its prediction performance was generally better than that of traditional Kriging interpolation. The accuracy of ERF in test area 1 reached 0.87, performing better than RF (0.81), MLP (0.78) and SVM (0.77). The F1-score of ERF for discerning high-risk points in test area 1 was as high as 0.8. The complexity of the distribution of points with different risk levels was a decisive factor in model prediction ability. Identified features in the study area associated with fertilizer factories had the most important contribution to the ERF model. This study demonstrates that HRAI combined with machine learning has good potential to predict As soil risk levels.
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http://dx.doi.org/10.1016/j.envpol.2020.116281DOI Listing
February 2021

Possible application of stable isotope compositions for the identification of metal sources in soil.

J Hazard Mater 2021 04 10;407:124812. Epub 2020 Dec 10.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Metals in soil are potentially harmful to humans and ecosystems. Stable isotope measurement may provide "fingerprint" information on the sources of metals. In light of the rapid progress in this emerging field, we present a state-of-the-art overview of how useful stable isotopes are in soil metal source identification. Distinct isotope signals in different sources are the key prerequisites for source apportionment. In this context, Zn and Cd isotopes are particularly helpful for the identification of combustion-related industrial sources, since high-temperature evaporation-condensation would largely fractionate the isotopes of both elements. The mass-independent fractionation of Hg isotopes during photochemical reactions allows for the identification of atmospheric sources. However, compared with traditionally used Sr and Pb isotopes for source tracking whose variations are due to the radiogenic processes, the biogeochemical low-temperature fractionation of Cr, Cu, Zn, Cd, Hg and Tl isotopes renders much uncertainty, since large intra-source variations may overlap the distinct signatures of inter-source variations (i.e., blur the source signals). Stable isotope signatures of non-metallic elements can also aid in source identification in an indirect way. In fact, the soils are often contaminated with different elements. In this case, a combination of stable isotope analysis with mineralogical or statistical approaches would provide more accurate results. Furthermore, isotope-based source identification will also be helpful for comprehending the temporal changes of metal accumulation in soil systems.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124812DOI Listing
April 2021

Iron-modified biochar and water management regime-induced changes in plant growth, enzyme activities, and phytoavailability of arsenic, cadmium and lead in a paddy soil.

J Hazard Mater 2021 04 22;407:124344. Epub 2020 Oct 22.

Biochar Engineering Technology Research Center of Guangdong Province, School of Environmental and Chemical Engineering, Foshan University, Guangdong, Foshan 528000, China; Key Laboratory of Soil Contamination Bioremediation of Zhejiang Province, Zhejiang A&F University, Zhejiang, Hangzhou 311300, China. Electronic address:

The aim of this study was to evaluate the effect of raw (RawBC) and iron (Fe)-modified biochar (FeBC) derived from Platanus orientalis Linn branches on the plant growth, enzyme activity, and bioavailability and uptake of As, Cd, and Pb by rice in a paddy soil with continuously flooded (CF) or alternately wet and dry (AWD) irrigation in a pot experiment. Application of RawBC (3%, w/w) significantly increased soil pH, while FeBC decreased it. The FeBC was more effective in reducing As and Pb bioavailability, particularly under the AWD water regime, while RawBC was more conducive in reducing Cd bioavailability under the CF water regime. The FeBC decreased As concentration, but increased concentrations of Cd and Pb in the straw and brown rice, as compared to the untreated soil. Soil catalase and urease activities were enhanced by RawBC, but decreased by FeBC treatment. The FeBC increased the grain yield by 60% and 32% in CF and AWD treatments, respectively. The FeBC can be recommended for immobilization of As in paddy soils, but a potential human health risk from Cd and Pb in FeBC-treated soils should be considered due to increased uptake and translocation of the metals to brown rice.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124344DOI Listing
April 2021

Biochar Aging: Mechanisms, Physicochemical Changes, Assessment, And Implications for Field Applications.

Environ Sci Technol 2020 12 2;54(23):14797-14814. Epub 2020 Nov 2.

School of Environment, Tsinghua University, Beijing 100084, China.

Biochar has triggered a black gold rush in environmental studies as a carbon-rich material with well-developed porous structure and tunable functionality. While much attention has been placed on its apparent ability to store carbon in the ground, immobilize soil pollutants, and improve soil fertility, its temporally evolving in situ performance in these roles must not be overlooked. After field application, various environmental factors, such as temperature variations, precipitation events and microbial activities, can lead to its fragmentation, dissolution, and oxidation, thus causing drastic changes to the physicochemical properties. Direct monitoring of biochar-amended soils can provide good evidence of its temporal evolution, but this requires long-term field trials. Various artificial aging methods, such as chemical oxidation, wet-dry cycling and mineral modification, have therefore been designed to mimic natural aging mechanisms. Here we evaluate the science of biochar aging, critically summarize aging-induced changes to biochar properties, and offer a state-of-the-art for artificial aging simulation approaches. In addition, the implications of biochar aging are also considered regarding its potential development and deployment as a soil amendment. We suggest that for improved simulation and prediction, artificial aging methods must shift from qualitative to quantitative approaches. Furthermore, artificial preaging may serve to synthesize engineered biochars for green and sustainable environmental applications.
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http://dx.doi.org/10.1021/acs.est.0c04033DOI Listing
December 2020

VIRS based detection in combination with machine learning for mapping soil pollution.

Environ Pollut 2021 Jan 13;268(Pt A):115845. Epub 2020 Oct 13.

School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address:

Widespread soil contamination threatens living standards and weakens global efforts towards the Sustainable Development Goals (SDGs). Detailed soil mapping is needed to guide effective countermeasures and sustainable remediation operations. Here, we review visible and infrared reflectance spectroscopy (VIRS) based detection methods in combination with machine learning. To date, proximal, airborne and spaceborne carrier devices have been employed for soil contamination detection, allowing large areas to be covered at low cost and with minimal secondary environmental impact. In this way, soil contaminants can be monitored remotely, either directly or through correlation with soil components (e.g. Fe-oxides, soil organic matter, clay minerals). Observed vegetation reflectance spectra has also been proven an effective indicator for mapping soil pollution. Calibration models based on machine learning are used to interpret spectral data and predict soil contamination levels. The algorithms used for this include partial least squares regression, neural networks, and random forest. The processes underlying each of these approaches are outlined in this review. Finally, current challenges and future research directions are explored and discussed.
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http://dx.doi.org/10.1016/j.envpol.2020.115845DOI Listing
January 2021

Remediation of poly- and perfluoroalkyl substances (PFAS) contaminated soils - To mobilize or to immobilize or to degrade?

J Hazard Mater 2021 01 9;401:123892. Epub 2020 Sep 9.

Soil- and Groundwater-Management, Institute of Soil Engineering, Waste- and Water-Management, Faculty of Architecture und Civil Engineering, University of Wuppertal, Germany; Department of Environment, Energy and Geoinformatics, Sejong University, Seoul 05006, South Korea.

Poly- and perfluoroalkyl substances (PFASs) are synthetic chemicals, which are introduced to the environment through anthropogenic activities. Aqueous film forming foam used in firefighting, wastewater effluent, landfill leachate, and biosolids are major sources of PFAS input to soil and groundwater. Remediation of PFAS contaminated solid and aqueous media is challenging, which is attributed to the chemical and thermal stability of PFAS and the complexity of PFAS mixtures. In this review, remediation of PFAS contaminated soils through manipulation of their bioavailability and destruction is presented. While the mobilizing amendments (e.g., surfactants) enhance the mobility and bioavailability of PFAS, the immobilizing amendments (e.g., activated carbon) decrease their bioavailability and mobility. Mobilizing amendments can be applied to facilitate the removal of PFAS though soil washing, phytoremediation, and complete destruction through thermal and chemical redox reactions. Immobilizing amendments are likely to reduce the transfer of PFAS to food chain through plant and biota (e.g., earthworm) uptake, and leaching to potable water sources. Future studies should focus on quantifying the potential leaching of the mobilized PFAS in the absence of removal by plant and biota uptake or soil washing, and regular monitoring of the long-term stability of the immobilized PFAS.
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http://dx.doi.org/10.1016/j.jhazmat.2020.123892DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025151PMC
January 2021

Influence of biochar and soil properties on soil and plant tissue concentrations of Cd and Pb: A meta-analysis.

Sci Total Environ 2021 Feb 30;755(Pt 2):142582. Epub 2020 Sep 30.

Biochar Engineering Technology Research Center of Guangdong Province, School of Environmental and Chemical Engineering, Foshan University, Foshan, Guangdong 528000, China; Key Laboratory of Soil Contamination Bioremediation of Zhejiang Province, Zhejiang A&F University, Hangzhou, Zhejiang 311300, China. Electronic address:

The application of biochar to soils contaminated with potentially toxic elements (PTEs) has received particular attention due to its ability to reduce PTE uptake by the plants. Therefore, we conducted a meta-analysis to identify Cd and Pb concentrations in plant shoots and roots in response to biochar application and soil properties. We collected data from 65 peer-reviewed journal articles published from 2009 to 2020 in which 66% of manuscripts were published from 2015 to 2020. The data were processed using OpenMEE software. The results pinpointed that addition of biochar to soil caused a significant decrease in shoot and root Cd and Pb concentrations as compared to untreated soils with biochar (control), and the reduction rate was affected by plant types and both biochar and soil properties. The biochar size less than 2 mm, biochar pH higher than 10, pyrolysis temperature of 401-600 °C, and the application rate higher than 2% appeared to be effective in reducing shoot and root Cd and Pb concentration. Soil properties such as pH, SOC, and texture influenced the efficiency of biochar for reducing plant Cd and Pb uptake. Biochar application increased SOC (54.3%), CEC (48.0%), pH (0.08), and EC (59.4%), and reduced soil extractable Cd (42.1%) and Pb (47.1%) concentration in comparison to control. A detailed study on the rhizosphere chemistry and uptake mechanism will help to underpin the biochar application rates and their efficiency reducing PTE mobility and plant uptake.
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http://dx.doi.org/10.1016/j.scitotenv.2020.142582DOI Listing
February 2021

Facile synthesis of polyoxometalate-modified metal organic frameworks for eliminating tetrabromobisphenol-A from water.

J Hazard Mater 2020 11 11;399:122946. Epub 2020 Jun 11.

Biochar Engineering Technology Research Center of Guangdong Province, School of Environmental and Chemical Engineering, Foshan University, Foshan, Guangdong, 528000, China; Key Laboratory of Soil Contamination Bioremediation of Zhejiang Province, Zhejiang A&F University, Hangzhou, Zhejiang, 311300, China. Electronic address:

Removal of tetrabromobisphenol-A (TBBPA) from wastewater is of significance to protect the aquatic life. The present study reports the facile preparation of polyoxometalate-modified metal-organic framework (MOFs) materials for TBBPA removal from water. The polyoxometalate-modified MOFs exhibited significantly higher affinity towards TBBPA than the control MOFs. The experimental data were fitted with the Langmuir, Freundlich and Dubinin-Radushkevich models. The TBBPA adsorption onto modified MOFs fitted the pseudo-second-order kinetic model. The equilibrium adsorption isotherms showed that the adsorption of TBBPA can be fitted by the Langmuir model. The maximum adsorption capacity of adsorbent composites reached 3.65 mg/g, with 95 % removal of TBBPA. The thermodynamic parameters indicated that adsorption was spontaneous. A blue shift of phosphorus peaks obtained from XPS spectra implied the formation of intrinsic chemical bonding between TBBPA and MOFs composites. Moreover, response surface methodology was employed to characterize the TBBPA adsorption in the co-existence of different factors. BPA had strong competition for TBBPA adsorption in a wide range of pH, but not at the middle level of Ca concentration. Polyoxometalate-modified MOFs can easily be recycled using a simple organic solvent washing. This study provides a novel strategy for developing cost effective adsorbents to remove TBBPA from contaminated water.
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http://dx.doi.org/10.1016/j.jhazmat.2020.122946DOI Listing
November 2020

Sustainable remediation and revival of brownfields.

Sci Total Environ 2020 11 25;741:140475. Epub 2020 Jun 25.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

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http://dx.doi.org/10.1016/j.scitotenv.2020.140475DOI Listing
November 2020

Advances in algal biochar: Production, characterization and applications.

Bioresour Technol 2020 Dec 7;317:123982. Epub 2020 Aug 7.

University of Edinburgh, School of GeoSciences, UK Biochar Research Centre, King's Buildings, Edinburgh, United Kingdom.

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http://dx.doi.org/10.1016/j.biortech.2020.123982DOI Listing
December 2020

Effect of immobilizing reagents on soil Cd and Pb lability under freeze-thaw cycles: Implications for sustainable agricultural management in seasonally frozen land.

Environ Int 2020 11 13;144:106040. Epub 2020 Aug 13.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Agricultural soil contamination in seasonally frozen land threatens food security. It is necessary to investigate the effects of freeze-thaw cycles on heavy metal bioavailability so as to select suitable immobilization agents. In this study, the soil was collected from a mid-latitude agricultural site in Liaoning Province, China, which was spiked with cadmium (Cd) and lead (Pb). Four immobilization treatments were set up, including (i) corn stover biochar, (ii) organic fertilizer, (iii) combined biochar and organic fertilizer, and (iv) the control group. The immobilized soils were subjected to 16 freeze-thaw cycles to temperatures of -10 °C, -20 °C, and -30 °C. It was found that freeze-thaw cycling increased the labile cadmium (Cd) and lead (Pb) content in the soil (i.e., exchangeable). The organic fertilizer treatment performed best in short-term immobilization, which was demonstrated by the amount of diethylenetriaminepentaacetic acid (DTPA) extractable lead (Pb) being 17.3-53.3% lower than that of the other treatments, and 7.2-31.5% lower for cadmium (Cd). Biochar, on the other hand, displayed better long-term performance under freeze-thaw cycling. This is probably because the biochar's organic carbon content is relatively stable, and therefore, releases relatively little dissolved organic carbon (DOC) which could re-mobilize heavy metals. Furthermore, additional sorption sites are formed and the abundance of oxygen-containing functional groups increased when biochar breaks down during freeze-thaw cycles. Overall, the joint application of biochar and organic fertilizer had the greatest immobilization effect, which inhibited the cracking of soil aggregates, reduced the labile metal content, and displayed both short- and long-term immobilization effectiveness. It is suggested that combined biochar and organic fertilizer may offer an effective strategy for the sustainable agricultural management of cadmium (Cd) and lead (Pb) contaminated in seasonally frozen land.
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http://dx.doi.org/10.1016/j.envint.2020.106040DOI Listing
November 2020

Effects of aging and weathering on immobilization of trace metals/metalloids in soils amended with biochar.

Environ Sci Process Impacts 2020 Sep;22(9):1790-1808

Korea Biochar Research Center & Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Korea. and Department of Environmental Engineering, China Jiliang University, No. 258 Xueyuan Street, Hangzhou, Zhejiang 310018, P. R. China.

Biochar is an effective amendment for trace metal/metalloid (TMs) immobilization in soils. The capacity of biochar to immobilize TMs in soil can be positively or negatively altered due to the changes in the surface and structural chemistry of biochar after soil application. Biochar surfaces are oxidized in soils and induce structural changes through physical and biochemical weathering processes. These changes in the biochar surface and structural chemistry generally increase its ability to immobilize TMs, although the generation of dissolved black carbon during weathering may increase TM mobility. Moreover, biochar modification can improve its capacity to immobilize TMs in soils. Over the short-term, engineered/modified biochar exhibited increased TM immobilization capacity compared with unmodified biochar. In the long-term, no large distinctions in such capacities were seen between modified and unmodified biochars due to weathering. In addition, artificial weathering at laboratories also revealed increased TM immobilization in soils. Continued collection of mechanistic evidence will help evaluate the effect of natural and artificial weathering, and biochar modification on the long-term TM immobilization capacity of biochar with respect to feedstock and synthesis conditions in contaminated soils.
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http://dx.doi.org/10.1039/d0em00057dDOI Listing
September 2020

Environmental fate, toxicity and risk management strategies of nanoplastics in the environment: Current status and future perspectives.

J Hazard Mater 2021 01 8;401:123415. Epub 2020 Jul 8.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Tiny plastic particles considered as emerging contaminants have attracted considerable interest in the last few years. Mechanical abrasion, photochemical oxidation and biological degradation of larger plastic debris result in the formation of microplastics (MPs, 1 μm to 5 mm) and nanoplastics (NPs, 1 nm to 1000 nm). Compared with MPs, the environmental fate, ecosystem toxicity and potential risks associated with NPs have so far been less explored. This review provides a state-of-the-art overview of current research on NPs with focus on currently less-investigated fields, such as the environmental fate in agroecosystems, migration in porous media, weathering, and toxic effects on plants. The co-transport of NPs with organic contaminants and heavy metals threaten human health and ecosystems. Furthermore, NPs may serve as a novel habitat for microbial colonization, and may act as carriers for pathogens (i.e., bacteria and viruses). An integrated framework is proposed to better understand the interrelationships between NPs, ecosystems and the human society. In order to fully understand the sources and sinks of NPs, more studies should focus on the total environment, including freshwater, ocean, groundwater, soil and air, and more attempts should be made to explore the aging and aggregation of NPs in environmentally relevant conditions. Considering the fact that naturally-weathered plastic debris may have distinct physicochemical characteristics, future studies should explore the environmental behavior of naturally-aged NPs rather than synthetic polystyrene nanobeads.
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http://dx.doi.org/10.1016/j.jhazmat.2020.123415DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345412PMC
January 2021

Performance indicators for a holistic evaluation of catalyst-based degradation-A case study of selected pharmaceuticals and personal care products (PPCPs).

J Hazard Mater 2021 01 12;402:123460. Epub 2020 Jul 12.

Faculty of Engineering, Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.

Considerable efforts have been made to develop effective and sustainable catalysts, e.g., carbon-/biochar-based catalyst, for the decontamination of organic pollutants in water/wastewater. Most of the published studies evaluated the catalytic performance mainly upon degradation efficiency of parent compounds; however, comprehensive and field-relevant performance assessment is still in need. This review critically analysed the performance indicators for carbon-/biochar-based catalytic degradation from the perspectives of: (1) degradation of parent compounds, i.e., concentrations, kinetics, reactive oxidative species (ROS) analysis, and residual oxidant concentration; (2) formation of intermediates and by-products, i.e., intermediates analysis, evolution of inorganic ions, and total organic carbon (TOC); and (3) impact assessment of treated samples, i.e., toxicity evolution, disinfection effect, and biodegradability test. Five most frequently detected pharmaceuticals and personal care products (PPCPs) (sulfamethoxazole, carbamazepine, ibuprofen, diclofenac, and acetaminophen) were selected as a case study to articulate the performance indicators for a holistic evaluation of carbon-/biochar-based catalytic degradation. This review also encourages the development of alternative performance indicators to facilitate the rational design of catalysts in future studies.
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http://dx.doi.org/10.1016/j.jhazmat.2020.123460DOI Listing
January 2021

Microplastics as pollutants in agricultural soils.

Environ Pollut 2020 Oct 9;265(Pt A):114980. Epub 2020 Jun 9.

Global Centre for Environmental Remediation, University of Newcastle, Callaghan, NSW, 2308, Australia.

Microplastics (MPs) as emerging persistent pollutants have been a growing global concern. Although MPs are extensively studied in aquatic systems, their presence and fate in agricultural systems are not fully understood. In the agricultural soils, major causes of MPs pollution include application of biosolids and compost, wastewater irrigation, mulching film, polymer-based fertilizers and pesticides, and atmospheric deposition. The fate and dispersion of MPs in the soil environment are mainly associated with the soil characteristics, cultivation practices, and diversity of soil biota. Although there is emerging pollution of MPs in the soil environment, no standardized detection and quantification techniques are available. This study comprehensively reviews the sources, fate, and dispersion of MPs in the soil environment, discusses the interactions and effects of MPs on soil biota, and highlights the recent advancements in detection and quantification methods of MPs. The prospects for future research include biomagnification potency, cytotoxic effects on human/animals, nonlinear behavior in the soil environment, standardized analytical methods, best management practices, and global policies in the agricultural industry for the sake of sustainable development.
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http://dx.doi.org/10.1016/j.envpol.2020.114980DOI Listing
October 2020

Sulfur-modified biochar as a soil amendment to stabilize mercury pollution: An accelerated simulation of long-term aging effects.

Environ Pollut 2020 Sep 29;264:114687. Epub 2020 Apr 29.

School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address:

The stability of mercury (Hg) contamination in soil environments can change over time. This has implications for agricultural sites under long-term management after in situ treatment involving soil amendments. In this study, rice husk biochar (RHB) and sulfur modified rice husk biochar (SRHB) were synthesized and applied (dosage = 5% dry wt.) to a Hg polluted agricultural soil collected from Guizhou province, Southern China (soil total Hg content = 28.3 mg/kg; C = 2%; and, S = 0.1%). The long-term stabilization effectiveness of the soil treatments was evaluated by a combined approach involving: (i) accelerated aging for 104 simulated years; (ii) soil extraction as a proxy for plant uptake; and, (iii) sequential extraction to identify Hg fractions. The SRHB amendment raised the soil's total S content by approximately an order of magnitude (to 0.9%), which remained at a generally constant level throughout the simulation. The initial pH levels for the untreated and treated soils were alkaline and remained between 7.0 and 7.5 for the first 50 years of simulated aging, before decreasing as the simulation time increased further. The pH of the SRHB treated soils did not drop below that of untreated soils during the simulation. Soil extraction tests with 0.1 M HCl solution indicated that RHB and SRHB treatments could effectively immobilize the Hg in soil for at least 50 and 75 simulated years, respectively. At simulated year 50, the amount of Hg extracted from RHB and SRHB treated soils was <200 ng/L and <100 ng/L, respectively. Thus, showing SRHB to be a particularly promising remedial option. The soil Hg was mostly associated with the stable sequential extraction fractions (F3-5). By the end of the simulation, the F5 fraction for SRHB and RHB treated soils reduced by 44.6%, and 42.0%, respectively, whereas the F4 fraction increased by >400% in both cases. In summary, SRHB may provide long-lasting Hg stabilization at contaminated sites. Therefore, further research toward the development of this stabilization technology is warranted.
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http://dx.doi.org/10.1016/j.envpol.2020.114687DOI Listing
September 2020

Sustainable soil use and management: An interdisciplinary and systematic approach.

Sci Total Environ 2020 Aug 25;729:138961. Epub 2020 Apr 25.

School of Environment, Tsinghua University, Beijing 100084, China.

Soil is a key component of Earth's critical zone. It provides essential services for agricultural production, plant growth, animal habitation, biodiversity, carbon sequestration and environmental quality, which are crucial for achieving the United Nations' Sustainable Development Goals (SDGs). However, soil degradation has occurred in many places throughout the world due to factors such as soil pollution, erosion, salinization, and acidification. In order to achieve the SDGs by the target date of 2030, soils may need to be used and managed in a manner that is more sustainable than is currently practiced. Here we show that research in the field of sustainable soil use and management should prioritize the multifunctional value of soil health and address interdisciplinary linkages with major issues such as biodiversity and climate change. As soil is the largest terrestrial carbon pool, as well as a significant contributor of greenhouse gases, much progress can be made toward curtailing the climate crisis by sustainable soil management practices. One identified option is to increase soil organic carbon levels, especially with recalcitrant forms of carbon (e.g., biochar application). In general, soil health is primarily determined by the actions of the farming community. Therefore, information management and knowledge sharing are necessary to improve the sustainable behavior of practitioners and end-users. Scientists and policy makers are important actors in this social learning process, not only to disseminate evidence-based scientific knowledge, but also in generating new knowledge in close collaboration with farmers. While governmental funding for soil data collection has been generally decreasing, newly available 5G telecommunications, big data and machine learning based data collection and analytical tools are maturing. Interdisciplinary studies that incorporate such advances may lead to the formation of innovative sustainable soil use and management strategies that are aimed toward optimizing soil health and achieving the SDGs.
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http://dx.doi.org/10.1016/j.scitotenv.2020.138961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7182530PMC
August 2020

Green immobilization of toxic metals using alkaline enhanced rice husk biochar: Effects of pyrolysis temperature and KOH concentration.

Sci Total Environ 2020 Jun 26;720:137584. Epub 2020 Feb 26.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Biochar is a "green" material that has been widely used in environmental applications for its capability to remove or immobilize contaminants in different environmental media (i.e. soil, water and air) and mitigate climate change. In this study, the feasibility of using KOH enhanced biochar for soil Cd and Pb stabilization was investigated, and the effects of pyrolysis temperature and alkaline concentrations for modification were explored. Field-emission scanning electron microscopy (FESEM), N adsorption-desorption, and Fourier Transform Infrared Spectroscopy (FTIR) analyses were conducted to reveal the influence on biochar physiochemical properties. The immobilization performances were examined through Toxicity Characteristics Leaching Procedure (TCLP), and Response Surface Methodology (RSM) was adopted to visualize the results from leaching tests. The stabilization mechanisms of alkaline enhanced biochars were investigated using Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), Tessier sequential extraction method and X-ray diffraction (XRD) analyses. The results indicated that rice husk biochar pyrolyzed at a relatively low temperature (i.e., 300 °C) and activated by moderate alkaline concentrations (i.e., 1 M or 3 M KOH) rendered optimum stabilization performance. KOH activation was a double-edged sword, with high alkaline concentrations destroying biochar's cell structures. Moreover, the integration of TOF-SIMS, XRD and sequential leaching method shed lights on the underlying mechanisms involved in metal stabilization. Surface complexation between toxic metals and oxygen-containing functional groups rather than liming or precipitation was proven to be the fundamental stabilization mechanism.
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http://dx.doi.org/10.1016/j.scitotenv.2020.137584DOI Listing
June 2020

Quantitative source tracking of heavy metals contained in urban road deposited sediments.

J Hazard Mater 2020 07 21;393:122362. Epub 2020 Feb 21.

College of Chemistry and Environmental Engineering, Shenzhen University, 518060, Shenzhen, China. Electronic address:

Source tracking for heavy metals contained in road deposited sediments (RDS) is essential for pollution control and human health risk management. Previous studies on tracking sources for heavy metals have mostly been qualitative or semi-quantitative. This study quantitatively assessed the relative contributions of eight sources to five typical heavy metals in the urban environment using a chemical mass-balance based stochastic method. The results indicated that tire wear contributed the most masses to RDS (33 ± 26 %) while brake lining dusts contributed the least. Urban soil, tire wear, and brake lining dusts contributed the most to Pb (41 ± 32 %), Zn (28 ± 25 %), and Cu (59 ± 30 %), respectively, while gasoline engine exhaust was the main source of both Cr (29 ± 28 %) and Ni (20 ± 23 %). The outcomes also showed that tire wear and diesel engine exhaust have higher potential to threaten human health risk because they generate high amounts of heavy metals with high bioaccessibility. The research results can also provide a quantitative guidance for taking remediation actions of heavy metal control on urban road surfaces and measuring the effectiveness of those actions.
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http://dx.doi.org/10.1016/j.jhazmat.2020.122362DOI Listing
July 2020

A numerical model to optimize LNAPL remediation by multi-phase extraction.

Sci Total Environ 2020 May 14;718:137309. Epub 2020 Feb 14.

School of Environment, Tsinghua University, Beijing 100084, China. Electronic address:

Light non-aqueous phase liquid (LNAPL) contaminated sites pose a risk to human health and the natural environment. Multi-phase extraction (MPE) is one of the most widely used technologies to remediate these sites. Thus, it is important to optimize MPE systems to improve their effectiveness and cost-efficiency. In this study, we developed a numerical model to optimize LNAPL mass removal by MPE, in which the aquifer domain was simplified as a cylinder with a single MPE extraction well located at the center. A dual-pump extraction system was applied to the model, which involved vacuum enhanced recovery to remove volatilized gaseous phase contaminants and a submerged pump to remove NAPL and contaminants in groundwater. After the model was validated with field data, the results showed that the contaminant extraction rate varied with the LNAPL thickness and submerged pump position. For benzene selected as the contaminant of concern, greater LNAPL extraction rates were achieved when the initial LNAPL thickness was large (>1.5 m) or in aquifers of high permeability (>2.45 × 10 m). Importantly, it was discovered that in highly permeable coarse sand and gravel, the submerged pump ought to be placed within the LNAPL layer, whereas the pump should be placed below the water-NAPL interface in fine to medium sand aquifers. It was also found that an optimal liquid pumping rates exist, beyond which contaminant mass removal rates do not increase. Furthermore, it was found that in aquifers contaminated with thin LNAPL layers, mass transfer modelling that assumes equilibrium between the phases may greatly overestimate the accumulated mass of contaminants removed and, therefore, non-equilibrium modelling should be adopted. Finally, a cost analysis was carried out to compare the costs of remediating a contaminated site with MPE and by an alternative chemical oxidation approach. The MPE technology was found to be more cost effective when the initial thickness of LNAPL was relatively thin. In summary, the numerical model developed in this study is a useful tool for optimizing MPE system design.
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http://dx.doi.org/10.1016/j.scitotenv.2020.137309DOI Listing
May 2020
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