Combining magnet-assisted soil washing and soil amendment with zero-valent iron to restore safe rice cultivation in real cadmium-contaminated paddy fields.

Local villagers in Mae Sot District, Tak Province, Thailand are at risk of diseases related to cadmium (Cd) due to excessive consumption of rice contaminated with Cd due to zinc mining. This study verifies the hypothesis that to achieve safe rice cultivation, magnet-assisted soil washing followed by soil amendment using zero-valent iron (ZVI) is required not only for rapid remediation of the existing Cd contamination but also for the prevention of Cd recontamination caused by contaminated run-off from an upgradient contaminated paddy. Accordingly, this study conducted a pilot-scale demonstration of the combined technique to restore a real Cd-contaminated paddy (41.02 ± 5.47 mg/kg-1) and compared it with remediation using only soil amendment with ZVI or only magnet-assisted soil washing. The Cd concentration in rice grains from the contaminated rice field without treatment was 0.86 ± 0.01 mg/kg-1, and thus higher than the acceptable level of 0.4 mg/kg-1. Even though the use of magnet-assisted soil washing without amendment initially removed all the bioavailable Cd from the soil, it failed to reduce Cd uptake by the rice plants. This failure was caused by heavy off-season rain, which flooded and re-contaminated the experimental fields with Cd-contaminated run-off from an upgradient contaminated field, leading to a Cd concentration in rice grains of 1.21 ± 0.01 mg/kg-1. Similarly, the use of ZVI as a soil amendment without magnet-assisted soil washing could not ensure safe rice cultivation during the off-season flood, as Cd concentration in the rice grains was still 0.60 mg/kg-1. However, magnet-assisted soil washing followed by soil amendment using ZVI successfully removed Cd from soil and sequestered Cd from Cd-contaminated run-off, resulting in protection against Cd re-contamination in soil and the reduction of Cd content in rice grains to 0.33 mg/kg-1, representing a 60% removal efficacy. Also, this combined technique remained positive for rice growth compared to non-treatment.

Potential use of engineered nanoparticles in ocean fertilization for large-scale atmospheric carbon dioxide removal.

Artificial ocean fertilization (AOF) aims to safely stimulate phytoplankton growth in the ocean and enhance carbon sequestration. AOF carbon sequestration efficiency appears lower than natural ocean fertilization processes due mainly to the low bioavailability of added nutrients, along with low export rates of AOF-produced biomass to the deep ocean. Here we explore the potential application of engineered nanoparticles (ENPs) to overcome these issues. Data from 123 studies show that some ENPs may enhance phytoplankton growth at concentrations below those likely to be toxic in marine ecosystems. ENPs may also increase bloom lifetime, boost phytoplankton aggregation and carbon export, and address secondary limiting factors in AOF. Life-cycle assessment and cost analyses suggest that net CO2 capture is possible for iron, SiO2 and Al2O3 ENPs with costs of 2-5 times that of conventional AOF, whereas boosting AOF efficiency by ENPs should substantially enhance net CO2 capture and reduce these costs. Therefore, ENP-based AOF can be an important component of the mitigation strategy to limit global warming.

Using sequential H2O2 addition to sustain 1,2-dichloroethane detoxification by a nanoscale zerovalent iron-induced Fenton's system at a natural pH.

1,2-dichloroethane (1,2-DCA) is a chlorinated hydrocarbon used for polyvinyl chloride plastic production. As such, 1,2-DCA is a common persistent contaminant in saturated zones. While nanoscale zerovalent iron (NZVI) is considered an effective reductant for removing a wide range of chlorinated hydrocarbons, 1,2-DCA is resistant to reduction by NZVI as well as by modified forms of NZVI (e.g., sulfidated-NZVI). Hydroxyl radicals produced in Fenton's reaction can effectively degrade 1,2-DCA, but Fenton's reaction requires the acidification of saturated zones to achieve a groundwater pH of 3 to facilitate the catalytic reaction. To overcome this problem, this study has developed a sequential treatment process using an NZVI-induced Fenton-like reaction that can effectively degrade 1,2-DCA at an initially neutral pH range. The experiments were conducted using a high 1,2-DCA concentration (2000 mg/L) to evaluate the feasibility of using the treatment process at source zones. The process degraded 99% of 1,2-DCA with a pseudo-first-order rate constant of 0.49 h-1. Unlike the single-stage treatment process, the sequential treatment can control the used H2O2 concentration in the system, thus sustaining the reaction and resulting in more efficient 1,2-DCA degradation. To mimic subsurface conditions, batch experiments were conducted to remove 1,2-DCA sorbed in contaminated soil. The results show that 99% removal of 1,2-DCA was obtained within 16 h. Additionally, this study suggests that the NZVI can be used for at least three consecutive 1,2-DCA degradation cycles while maintaining high removal efficiency.

Constructed sediment microbial fuel cell for treatment of fat, oil, grease (FOG) trap effluent: Role of anode and cathode chamber amendment, electrode selection, and scalability.

For wastewater treatment, sediment microbial fuel cells (SMFCs) have advantages over traditional microbial fuel cells in cost (due to their membrane-less structure) and operation (less intensive maintenance). Nevertheless, the technical obstacles of SMFCs include their high internal electrical resistance due to sediment in the anode chamber and slow oxygen reduction reaction (ORR) in the cathode chamber, which is responsible for their low power density (PD) (0.2-50 mW/m2). This study evaluated several SMFC improvements, including anode and cathode chamber amendment, electrode selection, and scaling the chamber size up to obtain optimally constructed single-chamber SMFCs to treat fat, oil, and grease (FOG) trap effluent. The chemical oxygen demand (COD) removal efficiency, PD, and electrical energy conversion efficiency concerning theoretically available chemical energy from FOG trap effluent treatment (%ECWW) were examined. Packing biochar in the anode chamber reduced its electrical resistance by 5.76 times, but the improvement in PD was trivial. Substantial improvement occurred when packing the cathode chamber with activated carbon (AC), which presumably catalyzed the ORR, yielding a maximum PD of 109.39 mW/m2, 959 times greater than without AC in the cathode chamber. This SMFC configuration resulted in a COD removal efficiency of 85.80 % and a %ECWW of 99.74 % in 30 days. Furthermore, using the most appropriate electrode pair and chamber volume increased the maximum PD to 1787.26 mW/m2, around 1.7 times greater than the maximum PD by SMFCs reported thus far. This optimally constructed SMFC is low cost and applicable for household wastewater treatment.

Assessment of Lead (Pb) Leakage From Abandoned Mine Tailing Ponds to Klity Creek, Kanchanaburi Province, Thailand.

In 2013, Klity Creek became the site of Thailand's first legally required remediation, 15 years after the spill of lead (Pb)-contaminated mine tailings into the creek. Even today, nature cannot attenuate Pb-contaminated sediment, arguably due to either high geological background Pb or continuous leakage of Pb from the unlined tailing ponds, upstream of the creek. In this study, four lines of evidence were used to reveal that the leakage from tailing ponds is primarily responsible for the long-term Pb contamination. First, stable Pb isotope ratios (206Pb/207Pb and 208Pb/207Pb) were used to apportion sources between the tailings and geological background. The analysis of samples from the tailing ponds, geological background, and local zinc (Zn)-Pb deposit revealed five different Pb sources (i.e., two distinct mine tailings, two different backgrounds, and a local Zn-Pb deposit) in the area based on five unique isotope ratios. Using source apportionment analysis, Pb-contaminated sediments in Klity Creek were consistent with tailings being the dominant source (30%-100%). Likewise, an analysis of Pb radionuclide (210Pb) revealed the Pb in the contaminated sediment was relatively new, 0-6.7 years old, suggesting that the Pb source was recent leakage from the tailing ponds rather than the 15-year-old tailing spill. Isotope evidence was supported by the elevated Pb-contaminated seepage (0.30 ± 0.22 mg/L) from the tailing ponds and groundwater samples (up to 0.225 mg/L) collected from monitoring wells surrounding the tailing ponds. Consequently, proper management of Pb leakage from the tailing ponds is critical for successful Klity Creek remediation.

Community Citizen Science for Risk Management of a Spontaneously Combusting Coal-Mine Waste Heap in Ban Chaung, Dawei District, Myanmar.

Since 2015, a large heap of improperly disposed coal-mine waste in Ban Chaung, Dawei district, Myanmar, has repeatedly spontaneously combusted, affecting an indigenous community. Recently, the regional Myanmar government has compelled the mine to properly manage the mine waste heap, but there is no opportunity for affected villagers to participate. This study empowers the affected villagers to make risk management decisions via a community citizen science approach. First, field investigations were performed with the affected community to identify hot spots at the waste heap releasing gaseous pollutants that may exceed acceptable levels. Next, existing monitoring data previously collected by the community were interpreted as clear evidence of past poor waste management. Information about suppression of existing fire and mine waste storage options was presented to the community for them to make an informed decision about the most appropriate corrective action that should be taken by the mine. The mining company chose to use surface sealing for both suppression of existing fire and on-site storage of the mine waste but did not install any long-term monitoring system. Nevertheless, the community's choice was surface sealing with preventive monitoring together with emergency response, which is the more scientifically appropriate option. This outcome of a science-based risk management decision by the community will be forwarded to the regional government for enforcement. This process of community citizen science is in line with the normative rationale of public participation, which is meant to influence decisions, elevate democratic capacity, and empower marginalized individuals and communities.

Human continuous hydrogen cyanide inhalation predictor with a physiologically based pharmacokinetic (PBPK) model.

Hydrogen cyanide (HCN) is volatile and highly toxic with acute and chronic effects on humans. Gaseous HCN enters the atmosphere from natural processes or industrial activities, which lead to human exposure. Effective intervention in cases of HCN inhalation requires an efficient diagnostic tool. The existing physiologically based pharmacokinetic (PBPK) model for HCN cannot clearly simulate continuous HCN inhalation or predict HCN levels in inhaled air. The current study presents a PBPK model for continuous inhalation of HCN, called Human Continuous Cyanide Inhalation Predictor (HCCIP). Since existing data on pharmacokinetics of HCN inhalation are limited, HCCIP utilizes extensive data from the current authors' PBPK model on cyanide ingestion. The structure of HCCIP comprises the lungs, kidneys, liver, and slowly perfused tissue. In both the human body and in exhaled air, HCCIP features the ability to predict concentration-time courses of cyanide. Moreover, HCCIP can predict HCN concentration in inhaled air from known blood cyanide levels. After completion, the results of HCCIP were validated against preexisting published datasets. The simulation results agreed with these datasets, validating the model. The HCCIP model is an effective tool for assessing risk from continuous HCN inhalation, and HCCIP extends the capabilities of air dispersion modeling, such as AERMOD or CALPUFF, to assess HCN risk from specific release sources.

Assessing potential hydrogen cyanide exposure from cyanide-contaminated mine tailing management practices in Thailand's gold mining.

This study assessed the effectiveness of the current cyanide management practice of a large gold mine as a case study of Thailand's cyanide-contaminated mine waste management policy. Most gold mines worldwide use cyanide to extract gold from ore, and various cyanide compounds, including hydrogen cyanide (HCN), are then discharged into a tailing storage facility (TSF). From there, HCN volatizes into the air, and people inhaling HCN can experience chronic, acute, or even fatal effects. Although recently only two gold mines operated in Thailand, many new gold mines are under consideration for future. Unfortunately, no specific government regulations for cyanide-contaminated mine waste management exist besides guidelines from environmental impact assessments prepared by the gold mines themselves. This raises concerns that cyanide volatilization may threaten public health. The current study addresses the need for vital scientific analysis by applying AERMOD modeling to simulate HCN dispersion from the gold mine studied, under 20 scenarios of various pH levels and cyanide concentrations. The results show that the HCN emissions cause acute effects to the public under most scenarios. Chronic effects also occur in scenarios of low pH or high cyanide concentration; however, no simulation showed fatalities. This study determined an acceptable cyanide concentration in TSF that is low enough to theoretically avoid dangerous public exposure. Results show that the mine's recent cyanide discharge limit of 20 mg/l, set by the mine itself, is not safe. To limit dangers from the mine's HCN emissions, cyanide levels in tailings must be carefully calculated and regulated using the HCN dispersion model, being sure to account for pH.

Enhanced degradation of methylene blue by a solution plasma process catalyzed by incidentally co-generated copper nanoparticles.

This study presents a catalytic organic pollution treatment using the solution plasma process (SPP) with incidentally co-generated copper (Cu) nanoparticles via Cu electrode erosion. Methylene blue (MB) was used as a model organic contaminant. The treatment time was from 0 to 60 minutes at the plasma frequencies of 15 and 30 kHz. The treatment efficacy using the Cu electrode was compared with that of the tungsten (W) electrode. The high erosion-resistant W electrode provided no W nanoparticles, while the low erosion-resistant Cu electrode yielded incidental nanoparticles (10-20 nm), hypothesized to catalyze the MB degradation during the SPP. The percentage of MB degradation and the hydrogen peroxide (H2O2) generation were determined by an ultraviolet-visible spectrophotometer. The results showed that, after the SPP by the Cu electrode for 60 minutes, the MB was degraded up to 96%. Using the Cu electrode at a high plasma frequency strongly accelerated the Cu nanoparticle generation and MB treatment, although the amount of H2O2 generated during the SPP using the Cu electrode was less than that of the W electrode. The Cu nanoparticles were hypothesized to enhance MB degradation via both homogeneous (release of dissolved Cu ions) and heterogeneous (on the surface of the particles) catalytic processes.

Investigation of magnetic silica with thermoresponsive chitosan coating for drug controlled release and magnetic hyperthermia application.

In this study, a drug delivery system for chemo-hyperthermia applications is proposed and fabricated. The delivery system consists of magnetic-silica (MagSi) particles being encapsulated within a pH/thermo-responsive chitosan­g­N­isopropylacrylamide (Chi-g-NIPAAm) polymer matrix. The as-prepared MagSi@Chi-g-NIPAAm particles exhibit superparamagnetic behavior with a saturation magnetization (Ms) of 20.14 emu/g. In addition, the MagSi@Chi-g-NIPAAm particles can act as a heat source when subject to an alternating magnetic field (AMF) and have a specific absorptions rate (SAR) of 8.36 Wg-1. The release of the drug DOX from the synthesized particles is sensitive to both the pH and temperature of its environment. We have compared the drug release when the solution is externally heated up and when it is heated up by the AMF (internal heating). For external heating (when the pH/temperature is 4.0/45 °C), 83.30 ±â€¯2.92% of the DOX were released within the first 5 h. The release of the DOX by the particles in pH 7.4 (temperature of 37 °C) was much slower (around 25.87 ±â€¯1.30% after 25 h). The release of the DOX was much higher (under an acidic condition pH = 4.0) around 57.13 ±â€¯2.36% within 1 h in the presence of AMF heating. The in vitro cytotoxicity tests of the of DOX-loaded MagSi@Chi-g-NIPAAm particles towards HeLa cancer cells. In general, the toxicities of the drug DOX as part of a MagSi@Chi-g-NIPAAm particles were less than those of the standalone DOX until the concentration of DOX-loaded particles reached 250 µg/mL, after which the toxicity of DOX in both forms were the same.

Adsorbed poly(aspartate) coating limits the adverse effects of dissolved groundwater solutes on Fe0 nanoparticle reactivity with trichloroethylene.

For in situ groundwater remediation, polyelectrolyte-modified nanoscale zerovalent iron particles (NZVIs) have to be delivered into the subsurface, where they degrade pollutants such as trichloroethylene (TCE). The effect of groundwater organic and ionic solutes on TCE dechlorination using polyelectrolyte-modified NZVIs is unexplored, but is required for an effective remediation design. This study evaluates the TCE dechlorination rate and reaction by-products using poly(aspartate) (PAP)-modified and bare NZVIs in groundwater samples from actual TCE-contaminated sites in Florida, South Carolina, and Michigan. The effects of groundwater solutes on short- and intermediate-term dechlorination rates were evaluated. An adsorbed PAP layer on the NZVIs appeared to limit the adverse effect of groundwater solutes on the TCE dechlorination rate in the first TCE dechlorination cycle (short-term effect). Presumably, the pre-adsorption of PAP "trains" and the Donnan potential in the adsorbed PAP layer prevented groundwater solutes from further blocking NZVI reactive sites, which appeared to substantially decrease the TCE dechlorination rate of bare NZVIs. In the second and third TCE dechlorination cycles (intermediate-term effect), TCE dechlorination rates using PAP-modified NZVIs increased substantially (~100 and 200%, respectively, from the rate of the first spike). The desorption of PAP from the surface of NZVIs over time due to salt-induced desorption is hypothesized to restore NZVI reactivity with TCE. This study suggests that NZVI surface modification with small, charged macromolecules, such as PAP, helps to restore NZVI reactivity due to gradual PAP desorption in groundwater.

Modified MODFLOW-based model for simulating the agglomeration and transport of polymer-modified Fe0 nanoparticles in saturated porous media.

The solute transport model MODFLOW has become a standard tool in risk assessment and remediation design. However, particle transport models that take into account both particle agglomeration and deposition phenomena are far less developed. The main objective of the present study was to evaluate the feasibility of adapting the standard code MODFLOW/MT3D to simulate the agglomeration and transport of three different types of polymer-modified nanoscale zerovalent iron (NZVI) in one-dimensional (1-D) and two-dimensional (2-D) saturated porous media. A first-order decay of the particle population was used to account for the agglomeration of particles. An iterative technique was used to optimize the model parameters. The model provided good matches to 1-D NZVI-breakthrough data sets, with R 2 values ranging from 0.96 to 0.99, and mass recovery differences between the experimental results and simulations ranged from 0.1 to 1.8 %. Similarly, simulations of NZVI transport in the heterogeneous 2-D model demonstrated that the model can be applied to more complicated heterogeneous domains. However, the fits were less good, with the R 2 values in the 2-D modeling cases ranging from 0.75 to 0.95, while the mass recovery differences ranged from 0.7 to 6.5 %. Nevertheless, the predicted NZVI concentration contours during transport were in good agreement with the 2-D experimental observations. The model provides insights into NZVI transport in porous media by mathematically decoupling agglomeration, attachment, and detachment, and it illustrates the importance of each phenomenon in various situations. Graphical Abstract ᅟ.

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review.

Environmental applications of nanoparticles (NP) increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena. This review aims to describe consistently all the important NP transport mechanisms along with their representative mathematical continuum models as found in the current scientific literature. Detailed characterizations of each transport phenomenon in regards to their manifestation in the column experiment outcomes, i.e., breakthrough curve (BTC) and residual concentration profile (RCP), are presented to facilitate future interpretations of BTCs and RCPs. The review highlights two NP transport mechanisms, agglomeration and size exclusion, which are potentially of great importance in controlling the fate and transport of NP in the subsurface media yet have been widely neglected in many existing modeling studies. A critical limitation of the continuum modeling approach is the number of parameters used upon application to larger scales and when a series of transport mechanisms are involved. We investigate the use of simplifying assumptions, such as the equilibrium assumption, in modeling the attachment/detachment mechanisms within a continuum modelling framework. While acknowledging criticisms about the use of this assumption for NP deposition on a mechanistic (process) basis, we found that its use as a description of dynamic deposition behavior in a continuum model yields broadly similar results to those arising from a kinetic model. Furthermore, we show that in two dimensional (2-D) continuum models the modeling efficiency based on the Akaike information criterion (AIC) is enhanced for equilibrium vs kinetic with no significant reduction in model performance. This is because fewer parameters are needed for the equilibrium model compared to the kinetic model. Two major transport regimes are identified in the transport of NP within porous media. The first regime is characterized by higher particle-surface attachment affinity than particle-particle attachment affinity, and operative transport mechanisms of physicochemical filtration, blocking, and physical retention. The second regime is characterized by the domination of particle-particle attachment tendency over particle-surface affinity. In this regime although physicochemical filtration as well as straining may still be operative, ripening is predominant together with agglomeration and further subsequent retention. In both regimes careful assessment of NP fate and transport is necessary since certain combinations of concurrent transport phenomena leading to large migration distances are possible in either case.

Electromagnetic induction of foam-based nanoscale zerovalent iron (NZVI) particles to thermally enhance non-aqueous phase liquid (NAPL) volatilization in unsaturated porous media: Proof of concept.

Nanoscale zerovalent iron (NZVI) is a promising remediation agent for volatile organic compound (VOC) contamination in saturated sub-surfaces, but is rarely applied to the vadose zone as there are not enough water molecules in the unsaturated zone to participate in reductive dechlorination. In this study, we evaluated the possibility of using foam as a carrying vehicle to emplace NZVI in unsaturated porous media followed by the application of low frequency-electromagnetic field (LF-EMF) to enhance VOC volatilization in laboratory batch reactors. We found that the optimal condition for generating foam-based NZVI (F-NZVI) was using sodium lauryl ether sulfate (SLES) at a concentration of 3% (w/w) and a N2 flow rate of 500 mL/min. Also, F-NZVI could carry as much as 41.31 g/L of NZVI in the liquid phase of the foam and generate heat to raise ΔT to 77 °C in 15 min under an applied LF-EMF (150 kHz and 13 A). Under these conditions, F-NZVI together with LF-EMF enhanced trichloroethylene (TCE) volatilization from TCE-dense non-aqueous phase liquid (DNAPL) in unsaturated sand by 39.51 ± 6.59-fold compared to reactors without LF-EMF application. This suggested that using F-NZVI together with LF-EMF could theoretically be an alternative to radio frequency heating (RFH) as it requires a much lower irradiation frequency (336-fold lower), which should result in significantly lower capital and operational costs compared to RFH.

Vetiver plantlets in aerated system degrade phenol in illegally dumped industrial wastewater by phytochemical and rhizomicrobial degradation.

This research evaluated the feasibility of using vetiver plantlets (Vetiveria zizanioides (L.) Nash) on a floating platform with aeration to degrade phenol (500 mg/L) in illegally dumped industrial wastewater (IDIWW). The IDIWW sample was from the most infamous illegal dumping site at Nong Nae subdistrict, Phanom Sarakham district, Chachoengsao province, Thailand. Laboratory results suggested that phenol degradation by vetiver involves two phases: Phase I, phytopolymerization and phyto-oxidation assisted by root-produced peroxide (H2O2) and peroxidase (POD), followed by phase II, a combination of phase I with enhanced rhizomicrobial degradation. The first 360-400 h of phenol degradation were dominated by phytopolymerization and phyto-oxidation yielding particulate polyphenols (PPP) or particulate organic matter (POM) as by-products, while phenol decreased to around 145 mg/L. In Phase II, synergistically, rhizomicrobial growth was ∼100-folds greater on the roots of the vetiver plantlets than in the IDIWW and participated in the microbial degradation of phenol at this lower phenol concentration, increasing the phenol degradation rate by more than three folds. This combination of phytochemical and rhizomicrobiological processes eliminated phenol in IDIWW in less than 766 h (32 days), while without the vetiver plantlets, phenol degradation by aerated microbial degradation alone may require 235 days. To our knowledge, this is the first that systematically reveals the complete phenol degradation mechanism by vetiver plantlets in real aerated wastewater.

Electromagnetic induction of nanoscale zerovalent iron particles accelerates the degradation of chlorinated dense non-aqueous phase liquid: Proof of concept.

In this study, a novel electromagnetically enhanced treatment concept is proposed for in situ remediation of a source zone of chlorinated dense non-aqueous phase liquid (DNAPL) that is slowly dissolved, causing contaminated groundwater for centuries. Here, we used polystyrene sulfonate (PSS)-modified nanoscale zerovalent iron (NZVI) particles (ferromagnetic) in combination with a low frequency (LF) (150 kHz) AC electromagnetic field (EMF) to accelerate the degradation of the DNAPLs via enhanced dissolution and reductive dechlorination. Trichloroethylene (TCE) and tetrachloroethylene (PCE) were used in a bench-scaled evaluation. The PSS-modified NZVI successfully targeted the DNAPL/water interface, as evidenced by the Pickering emulsion formation. Dechlorination of TCE- and PCE-DNAPL was measured by quantifying the by-product formation (acetylene, ethene, and ethane). Without magnetic induction heating (MIH) by LF EMF, PSS-modified NZVI transformed TCE- and PCE-DNAPL to ethene and ethane at the rate constants of 12.19 × 10-3 and 1.00 × 10-3 µmol/h/m2, respectively, following pseudo zero-order reactions. However, four MIH cycles of PSS-NZVI increased the temperature up to 87 °C and increased the rate constants of TCE-DNAPL and PCE-DNAPL up to 14.58 and 58.01 times, respectively, in comparison to the dechlorination rate without MIH. Theoretical analysis suggested that the MIH of the PSS-modified NZVI enhanced the dechlorination of TCE- and PCE-DNAPL via the combination of the enhanced thermal dissolution of DNAPL, the effect of increasing the temperature on the rate constant (the Arrhenius equation), and the accelerated NZVI corrosion. Nevertheless, the effect of the Arrhenius equation was dominant. For the first time, this proof-of-concept study reveals the potential for using polyelectrolyte-modified NZVI coupled with LF EMF as a combined remediation technique for increasing the rate and completeness of in situ chlorinated DNAPL source remediation.

Ten-Year Monitored Natural Recovery of Lead-Contaminated Mine Tailing in Klity Creek, Kanchanaburi Province, Thailand.

BACKGROUND: Klity Creek has become Thailand's first official remediation ordered by the court in 2013, 15 years after the spill of lead (Pb)-contaminated mine tailing into the creek. The Pollution Control Department (PCD) decided to restore the creek through monitored natural recovery (MNR) since 2006 but has not been successful. Interestingly, the most recent remediation plan in 2015 will still apply MNR to five out of the seven portions of the creek, despite no scientific feasibility evaluation of using MNR to restore the creek. OBJECTIVE: This study qualitatively and quantitatively evaluated the feasibility of using MNR to clean up the creek in order to protect the Klity children from excess Pb exposure. METHODS: We analyzed the physical and chemical transformation of Pb contaminated sediment in the creek and developed a remedial action goal and cleanup level using the Integrated Exposure Uptake Biokinetic model (IEUBK). We empirically determined the natural recovery (NR) potentials and rates using 10 years of data monitoring the water and sediment samples from eight monitoring stations (KC1 to KC8). RESULTS: Klity Creek has NR potential for water except at KC2, which is closest to the spill and the other improperly managed Pb sources. However, the creek has no NR potential for sediment except at the KC8 location (NR rate = 11.1 ± 3.0 × 10-3 month-1) farthest from the spill. CONCLUSION: The MNR method is not suitable to use as the sole remedial approach for Klity Creek (KC2 to KC7). Although MNR is applicable at KC8, it may require up to 377 ± 76 years to restore the sediment to the background Pb concentration. CITATION: Phenrat T, Otwong A, Chantharit A, Lowry GV. 2016. Ten-year monitored natural recovery of lead-contaminated mine tailing in Klity Creek, Kanchanaburi Province, Thailand. Environ Health Perspect 124:1511-1520; http://dx.doi.org/10.1289/EHP215.

Electromagnetic Induction of Zerovalent Iron (ZVI) Powder and Nanoscale Zerovalent Iron (NZVI) Particles Enhances Dechlorination of Trichloroethylene in Contaminated Groundwater and Soil: Proof of Concept.

This study evaluates the concept of using zerovalent iron (ZVI) powder or nanoscale zerovalent iron (NZVI) particles in combination with a low frequency (150 kHz) AC electromagnetic field (AC EMF) to effectively remove trichloroethylene (TCE) from groundwater and saturated soils. ZVI and NZVI are ferromagnetic, which can induce heat under applied AC EMF. The heat generated by ZVI and NZVI induction can increase the rate of dechlorination, according to Arrhenius' equation, and increase the rate of TCE desorption from TCE-sorbed soil. Both dechlorination and TCE desorption enhance the overall TCE removal rate. We evaluated this novel concept in laboratory batch reactors. We found that both ZVI and NZVI can induce heat under applied AC EMF up to 120 °C in 20 min. Using ZVI and NZVI with AC EMF enhanced dechlorination of dissolved TCE (no soil) up to 4.96-fold. In addition to increasing the temperature by ZVI and NZVI induction heating, AC EMF increased intrinsic ZVI and NZVI reactivity, ostensibly due to accelerated corrosion, as demonstrated by the increased ORP. In a soil-water-TCE system, NZVI together with AC EMF thermally enhanced desorption of TCE from soil and increased the degradation of TCE up to 5.36-fold compared to the absence of AC EMF. For the first time, this study indicates the potential for ZVI and NZVI coupled with AC EMF as a combined remediation technique for increasing the rate and completeness of in situ cleanup of adsorbed phase contaminants.

Parameter identifiability in application of soft particle electrokinetic theory to determine polymer and polyelectrolyte coating thicknesses on colloids.

Soft particle electrokinetic models have been used to determine adsorbed nonionic polymer and polyelectrolyte layer properties on nanoparticles or colloids by fitting electrophoretic mobility data. Ohshima first established the formalism for these models and provided analytical approximations ( Ohshima, H. Adv. Colloid Interface Sci.1995, 62, 189 ). More recently, exact numerical solutions have been developed, which account for polarization and relaxation effects and require fewer assumptions on the particle and soft layer properties. This paper characterizes statistical uncertainty in the polyelectrolyte layer charge density, layer thickness, and permeability (Brinkman screening length) obtained from fitting data to either the analytical or numerical electrokinetic models. Various combinations of particle core and polymer layer properties are investigated to determine the range of systems for which this analysis can provide a solution with reasonably small uncertainty bounds, particularly for layer thickness. Identifiability of layer thickness in the analytical model ranges from poor confidence for cases with thick, highly charged coatings, to good confidence for cases with thin, low-charged coatings. Identifiability is similar for the numerical model, except that sensitivity is improved at very high charge and permeability, where polarization and relaxation effects are significant. For some poorly identifiable cases, parameter reduction can reduce collinearity to improve identifiability. Analysis of experimental data yielded results consistent with expectations from the simulated theoretical cases. Identifiability of layer charge density and permeability is also evaluated. Guidelines are suggested for evaluation of statistical confidence in polymer and polyelectrolyte layer parameters determined by application of the soft particle electrokinetic theory.