Soluble Lead Research Articles

Switchable hydrophilicity solvent based and solidification-assisted liquid-phase microextraction combined with GFAAS for quantification of trace soluble lead in raw bovine and derivative milk products

ABSTRACTA novel microextraction method was developed by combining CO2-controlled switchable hydrophilicity solvent (SHS) with solidification of the aqueous phase (SAP), referred to as CSHS-SAP. It was applied for pre-concentration/extraction of the complexes of Pb-ammonium pyrrolidine dithiocarbamate (APDC) prior to GFAAS detection in raw bovine milk and milk products (whole-fat, half-skimmed and skimmed milks). In the CSHS-SAP microextraction, a clear interface was easily formed, and convenient and complete collection was achieved by directly transferring the SHS phase into a vial, which overcame the shortcomings of blurred interface and difficult collection of SHS phase using CSHS-based microextraction. SAP led to the increase of extraction recoveries for Pb2+ by 8–11%. Some important factors were optimised using a one-factor-at-a-time approach: 800 µL of N,N-dimethylbutylamine and water at a ratio of 1:1 as SHS, 1.0 g L−1 APDC as chelating agent, sample pH = 6.0, 0.6 mL of 1.0 mol L−1 NaOH, solidification time of 70 min and 300 µL of 0.5 mol L−1 HNO3 for back extraction. Under optimised conditions, limits of detection were as low as 0.01–0.02 µg kg−1 and enrichment factors reached more than 23-fold. Inter- and intra-day precisions had relative standard deviations of 3.6–6.4%. With the CSHS-SAP/GFAAS method Pb2+ was detected at 0.5–1.8 µg kg−1 in four bovine raw milk samples, which were collected from Hubei and Henan Provincial oil-producing area, China. However, Pb2+ was below the LOD in all of the local milk products. Overall, the newly developed CSHS-SAP/GFAAS method is convenient, efficient and robust, giving it great potential for rapid and accurate analysis of trace Pb2+ in liquid milks.

Survey of lead concentration in tap water on a university campus.

In this study, a sampling campaign was conducted for 29 buildings on the National Taiwan University (NTU) campus where lead pipes were present in 4 buildings. Total lead, soluble lead, and water quality parameters including pH, temperature, residual free chlorine, and total organic carbon were measured. Results from the first-round sequential sampling (10×100mL) showed that the presence of lead pipe did not necessarily cause elevated lead levels. However, the highest lead concentration and the highest frequency of exceeding 10μg/L were detected in a building with lead pipe. Faucet was identified to be a major lead source in at least 8 buildings. No significant correlations between lead levels and water parameters were found. The building showing the highest lead level in the first round was sampled for a second round using four different methods, namely, first draw sampling, random daytime sampling, sequential sampling (5×1L), and flushing sampling. Lead levels in samples collected using the four sampling methods all exceeded 10μg/L. The first draw sampling showed the highest lead level, followed by comparable levels for random daytime sampling and sequential sampling. Flush sampling yielded the lowest lead concentration. Particles collected from the faucet aerators in 14 buildings were also characterized for their compositions and lead contents.

Effect of Sodium Fluoride and Sodium Lignosulphonate Additives on Performance of the Soluble Lead Redox Flow Battery

Soluble lead redox flow battery (SLRFB) is a flow battery with a common electrolyte and can be developed in undivided, divided and semi-divided configurations [1]. At present, the development of SLRFB is hindered mainly due to (i) the formation of lead dendrites at anode, (ii) oxygen evolution reaction (OER) at cathode and (iii) accumulation of PbO2 due to poor electrode kinetics [2]. In an earlier study, we have reported a study on extending the cycle-life of SLRFB using an auxiliary electrode concept [3]. In the present study, we report the independent and combined effects of adding sodium lignosulfonate (SLS) and sodium fluoride (NaF) to the electrolyte as anode and cathode benefitting additives, respectively. The study reveals that adding 4.2 gm/L NaF alone improves the kinetics of both electrode reactions as compared to that with no additive but fails to prevent dendrite formation. Adding 1 gm/L SLS alone has beneficial effect on anode by preventing dendrite formation but the concentration of SLS gradually decreases with the cycling of the battery. The combined effect of adding SLS and NaF depends on the concentration of SLS. It is observed that adding low concentration of SLS 0.2 gm/L along with 4.2 gm/L NaF has beneficial effect on both the anode and cathode reactions and hence maintaining this concentration would help extending the cycle-life of SLRFB. The individual as well as combined effects of these additives on the reaction products is studied by quasi in situ XRD and FESEM techniques. The effect on electrode kinetics and cycle life are also reported.

POU water filters effectively reduce lead in drinking water: a demonstration field study in flint, Michigan

A field study was conducted to test the effectiveness of faucet-mounted point of use (POU) water filters for removing high concentrations of lead in drinking water from premise plumbing sources and lead service lines (LSL). These filters were concurrently certified for total lead removal under NSF/ANSI Standard 53 (NSF/ANSI-53) and for fine particulate (Class I) reduction under NSF/ANSI Standard 42 (NSF/ANSI-42). In 2016, filtered and unfiltered drinking water samples were collected at over 345 locations in Flint, Michigan. Over 97% of filtered water samples contained lead below 0.5 µg/L. The maximum lead concentration in filtered water was 2.9 µg/L, well below the bottled water standard. The effectiveness of the POU activated carbon block filters in reducing lead concentrations, even above the 150 µg/L NSF/ANSI-53 challenge standard, is likely related to trapping particles due to the small effective pore size of the filters, in addition to ion-exchange or sorption removal of soluble lead. Properly installed and maintained POU filters, certified under both NSF/ANSI-53 (for total lead) and NSF/ANSI-42 (for fine particulate), can protect all populations, including pregnant women and children, by reducing lead in drinking water to levels that would not result in a significant increase in overall lead exposure.

Verification of Pharmacokinetic Approaches in Prior Drug Development

In this review, 9 compounds with insufficient absorption characteristics, safety or efficacy were selected from among the compounds for which the author was in charge of development between 2000 and 2005, in order to evaluate the pharmacokinetic (PK) approaches used to develop these compounds. Optimization of the PK characteristics of a compound at the early stage of chemical design was found to be the most important factor for successful development. For example, (i) selecting class I or II drugs in the biopharmaceutical classification system, while avoiding efflux transporters, and introducing an appropriate dissociation moiety into a compound to make it soluble lead to sufficient drug absorption; (ii) designing compounds whose production of reactive metabolites, such as acyl glucuronide, does not largely affect total metabolism, yet helps to prevent abnormal PK caused by reactive metabolites. Other factors include (i) selection of a drug efficacy evaluation system based on the correct understanding of the relationship between PK and pharmacodynamics (PD) helps to solve species differences in PD; (ii) the establishment of a nonclinical study based on the identification of the involvement of specific cytochrome P450 molecules in the total metabolic clearance of a drug (fm,CYPs) helps to solve species differences in PK; and (iii) PK analysis using the tube model for hepatic extraction kinetics, and knowledge of the fm,CYPs of the victim drug, lead to successful drug-drug interaction (DDI) prediction. I hope that this review aids in future drug discovery or development.

Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive.

In this report, we present a method for the construction of a soluble lead flow battery (SLFB) with an extended cycle life. By supplying an adequate amount of sodium acetate (NaOAc) to the electrolyte, a cycle life extension of over 50% is demonstrated for SLFBs via long-term galvanostatic charge/discharge experiments. A higher quality of the PbO2 electrodeposit at the positive electrode is quantitatively validated for NaOAc-added electrolyte by throwing index (TI) measurements. Images acquired by scanning electron microscopy (SEM) also exhibit more integrated PbO2 surface morphology when the SLFB is operated with the NaOAc-added electrolyte. This work indicates that electrolyte modification can be a plausible route to economically enable SLFBs for large-scale energy storage.

A modelling and simulation study of soluble lead redox flow battery: Effect of presence of free convection on the battery characteristics

In this paper, we develop a mathematical model for soluble lead redox flow battery. The model accounts for simultaneous effect of forced convection and induced free convection in electrolyte domain of the battery. It predicts existence of dominant free convection over the forced convection in vicinity of the electrodes. The predictions suggests that both, electrode kinetics and ion transfer assisted by free convection alone, controls charge-discharge characteristics of the battery. The free convection augments ion transfer rate to the electrodes. By virtue of this, limiting current density at the electrodes increases to twice the theoretical limit under forced convection. The predictions coherently explains Collins et al. [1]‘s observations of high charge efficiencies when charging currents are higher than the theoretical limit. Also, the model consistently explains Pletcher et al. [2]‘s observation of insensitivity of the battery characteristics to the electrolyte flow rate. The model predicts satisfactory battery performance even at microscopic (μL s−1) flow rates which opens up the possibility for significant reduction in electrolyte pumping cost.

Lead and Copper Research

The Lead and Copper Rule (LCR) was enacted in the United States more than 25 years ago, and the water industry is now anticipating a proposal from the US Environmental Protection Agency (USEPA) to update those regulations in early 2019. The anticipated LCR revisions, along with recent and highly publicized drinking water lead events, have resulted in renewed interest in drinking water lead levels. In response, this special focus issue of Journal AWWA is dedicated to presenting current information on lead and copper in drinking water. Much has been learned about lead and copper corrosion control over the past two decades or so, thanks to research by academic and governmental investigators (especially at USEPA itself) and the practical experiences of water professionals at countless drinking water utilities. For example, little was known about the importance of particulate lead relative to soluble lead 25 years ago. Drinking water sampling strategies focused on first draw according to the LCR, yet now we understand the value of alternative sampling approaches to address different lead and copper objectives. Parameters such as the Langelier saturation index and calcium carbonate precipitation potential were previously considered viable lead corrosion control assessment options in the original guidance, yet their value is now questioned as they may actually prove misleading for lead control. The role that orthophosphates play in lead corrosion control compared with polyphosphates is better appreciated even if it is still not well understood. The role of pipe age in copper mineralogy and solubility has been explored, as has the connection between pipe scale analysis findings and metal release to drinking water, and corrosion mechanisms and making corrosion treatment changes are better understood. Despite recent progress, there is still much to learn. Research on lead and copper in water systems and their effects on human health is ongoing. As demonstrated by the original research published in this special issue of Journal AWWA, the drinking water industry seeks to further reduce lead and copper in drinking water. Special thanks goes to all of the authors who contributed to this issue of the Journal. Feature articles begin with a review by Cornwell (page 30) on how well the water industry has reduced lead levels since the LCR with a focus on current national levels. McTigue et al. (page 38) review AWWA's new standard on lead service line replacement. And Burlingame et al. (page 44) focus on utility efforts to help reduce lead in schools. There are several peer-reviewed research articles in this issue, as well, including the article by Roth et al. (page 15) on how blending source waters affects lead corrosion—an often-forgotten issue. The article by Deshommes et al. (page 28) discusses lead service line management and public perception. Lytle et al. (page 26) describe a model they developed based on laboratory and field data for estimating the impact of orthophosphate dose on copper reduction. Williams et al. (page 27) present details on what they have learned in designing a pipe rig system to evaluate corrosion control on harvested lead pipes. Finally, Bradley and Horscroft (page 29) describe their approach to using historical LCR and water quality data to evaluate corrosion control effectiveness.

Performance of recovered and reagent grade electrolyte in a soluble lead redox cell

Abstract This paper presents the performance of ‘recovered’ electrolyte for the soluble lead flow battery, made by recycling conventional lead-acid battery electrodes, and compares it to reagent grade electrolyte for the same system. The two electrolyte compositions were cycled in static and flow cells and their charge, energy, and voltage efficiencies compared. The average charge, energy, and voltage efficiencies of static cells using 1.0 mol·dm¯³ Pb²+ recovered electrolyte were 89%, 86%, and 96%, while cells using reagent grade electrolyte averaged 63%, 49%, and 78%, respectively. The average charge efficiency of flow cells with recovered electrolyte was consistently above 80% and within 10% of the average for cells with reagent grade electrolyte. The average energy and voltage efficiencies were 62% and 73%, respectively, diverting from averages for the reagent grade electrolyte cells by less than 15%. The highest average cycle life was for cells with recovered electrolyte at 187 cycles, while that of cells with reagent grade electrolyte peaked at 102. Trace elements in both electrolyte compositions were analysed and their presence in the recovered electrolyte appears to enhance performance of the soluble lead cells. The recovered electrolyte is an electrochemically viable substitute for the reagent grade electrolyte.

Aging effects on the mobility of Pb in soil: Influence on the energy requirements in electroremediation

This paper studies the possible differences in the behavior of lead as a contaminant in soil samples when it is present as “naturally-aged” for decades after the contamination, and when it has been spiked in the laboratory. This behavior differences are stablished mainly in two ways: as changes in the fractionation analysis obtained after a sequential extraction procedure (SEP) and as changes in the efficiency of the acid-enhanced electroremediation (EKR) technique. Additionally, aging effects have been studied for almost five years. In the case of the lead-spiked soil the influence of storage conditions on contaminant behavior have also been explored: 1) samples stored in capped containers at constant moisture conditions, and 2) samples in containers open to the atmosphere, with periods of water flooding and drying.Lab-spiked and the “naturally-aged” contaminants show very different behavior with respect not only to SEP analysis but also to EKR experiments. The soil spiked with a soluble lead salt presents a higher percent in the more mobile fractions. Regarding storage conditions, some changes were observed in the lead distribution along the vertical soil profile for samples stored in uncapped containers. The EKR results were also in agreement with those from fractionation analysis. Energy requirements for the remediation were estimated by a mathematical model with important differences obtained for the different soil samples. Results are indicating that it will be very unreliable to draw estimations for the “naturally-aged” soils from contaminant-spiked samples.

The separator-divided soluble lead flow battery

The soluble lead flow battery (SLFB) is conventionally configured with an undivided cell chamber. This is possible, unlike other flow batteries, because both electrode active materials are electroplated as solids from a common species, Pb2+, on the electrode surfaces during charging. Physically separating the active materials has the advantage that a single electrolyte and pump circuit can be used; however, failure mechanisms such as electrical shorting may be observed. In addition, a common electrolyte requires that any electrolyte additives are compatible with both half-cell reactions. This paper introduces two new configurations; semi- and fully divided for the SLFB. Cationic, anionic, and microporous separators are assessed for ionic conductivity in SLFB electrolytes, showing that their incorporation adds as little as a 20 mV to the cell voltage. Voltammetry shows the effect of additives on the equilibrium potential and stripping overpotential of PbO2. It is then demonstrated that the incorporation of a separator into the SLFB can reduce failure due to electrical shorting and permit electrode-specific additives to be used. A unit flow cell with electrode area of 100 cm2 is shown to operate for over 300 Ah in the semi-divided configuration, more than doubling the previously reported cycle life for cells of similar size.Graphical

Lead-based paint in children's toys sold on China's major online shopping platforms

Lead in paint is a major public health concern and has drawn much attention from international organizations such as the World Health Organization (WHO) and the United Nations Environmental Programme (UNEP). However, there is limited research on lead-based paint, especially its use in toys, which poses an explicit health risk to vulnerable children. The present study sampled 100 different toys purchased from the three largest online shopping platforms in China: JD, Taobao (TB) and Tmall (TM). These selected toys have been sold nearly 3 million times in total, suggesting that they may have reached the dwellings of millions of children. It was found that the toys sold by JD and TM, which are considered organized sellers, had average lead concentrations of 25 mg/kg and 32 mg/kg, respectively, much lower than that of toys sold by unorganized sellers on the TB platform, at 219 mg/kg. Approximately 12% of the toys purchased from TB contained paint with total lead concentrations exceeding China's regulatory standard for paints in toy manufacturing, and nearly 36% of the toys purchased from TB exceeded the equivalent US regulatory standard and EU standard. These results suggest that further action is needed to verify the health and safety standards of toys sold by such unorganized sellers. Moreover, this study found that China's regulatory standard (90 mg/kg) based on soluble lead may underestimate the risk posed by lead in paints, and it is suggested that future regulatory thresholds for lead levels in paints for toy manufacture be based on total rather than soluble lead concentrations. The present study also explored various influencing factors on lead concentration, and found that lead concentrations were related to toy price, age group, color, and sales volume.

Lead as a legendary pollutant with emerging concern: Survey of lead in tap water in an old campus building using four sampling methods

In this study, a sampling campaign with a total of nine sampling events investigating lead in drinking water was conducted at 7 sampling locations in an old building with lead pipes in service in part of the building on the National Taiwan University campus. This study aims to assess the effectiveness of four different sampling methods, namely first draw sampling, sequential sampling, random daytime sampling and flush sampling, in lead contamination detection. In 3 out of the 7 sampling locations without lead pipe, lead could not be detected (<1.1 μg/L) in most samples regardless of the sampling methods. On the other hand, in the 4 sampling locations where lead pipes still existed, total lead concentrations >10 μg/L were consistently observed in 3 locations using any of the four sampling methods while the remaining location was identified to be contaminated using sequential sampling. High lead levels were consistently measured by the four sampling methods in the 3 locations in which particulate lead was either predominant or comparable to soluble lead. Compared to first draw and random daytime samplings, although flush sampling had a high tendency to reduce total lead in samples in lead-contaminated sites, the extent of lead reduction was location-dependent and not dependent on flush durations between 5 and 10 min. Overall, first draw sampling and random daytime sampling were reliable and effective in determining lead contamination in this study. Flush sampling could reveal the contamination if the extent is severe but tends to underestimate lead exposure risk.

Point of zero charge: Role in pyromorphite formation and bioaccessibility of lead and arsenic in phosphate amended soils.

Soluble lead (Pb) can be immobilized in pure systems as pyromorphite by adding sources of phosphorus (P), but uncertainties still remain in natural systems. Knowledge of PZC is important to predict the ionization of functional groups and their interaction with metal species in solution. This study utilized the Pb- and As-contaminated soils to determine the combined effect of pH with respect to PZC and different rates of P-application on pyromorphite formation, and Pb and arsenic (As) bioaccessibility as impacted by speciation changes. Solution chemistry analysis along with synchrotron-based Pb- and As-speciation, and bioaccessibility treatment effect ratios (TERs) were conducted. Results indicated no significant effect of PZC on pyromorphite formation in P-amended soils; however, the TERPb appeared significantly lower at pH>pHPZC and higher at pH<pHPZC (α = 0.05). In contrast, the TERAs was significantly higher at pH>pHPZC, compared to the other two treatments, for the tested soils. The lack of conversion of soil Pb to pyromorphite may be attributed to presence of stable minerals limiting soluble-Pb availability and high organic matter content of the tested soils.

Stabilization of Electrodeposit in Soluble Lead Flow Batteries with Acetate Additive

The emerging of renewable energy demands energy storage. Redox flow batteries are inherently suited for large-scale applications, but their market penetration is thwarted by the high materials cost. In contrast, membrane-less and single-flow soluble lead flow batteries (SLFBs) are more economical to scale up and free of expensive noble metals. However, lifespan of SLFBs reported so far is limited to approximately 200 cycles under normal flow conditions, which is insufficient for long-term operation in utility applications. Failures of SLFBs are believed to be associated with PbO2 deposition/dissolution at the positive electrode. Although failure mechanisms are not well understood, passivation and shedding of PbO2 are suggested to decrease efficiency of SLFBs. Formation of a passivation layer of non-stoichiometric PbOx is found to be correlated to proton activities. PbO2 deposits of poor adherence and low quality are also observed to occur when the electrolyte is high in acidity. We therefore employ sodium acetate (NaOAc) as electrolyte additive, and successfully extend the cycle life of SLFBs by over 50%. In this study, effects of acetate additive on electroplating of PbO2 are investigated. Surface morphology and mechanical strength of electroplated PbO2 via electrolyte with and without NaOAc are examined by scanning electron microscopy (SEM) and nano-indentation, respectively. Acetate-assisted electrolyte is found to substantially enhance deposited film strength and leads to a more integrated and smoother surface. Crystal structures, grain sizes, and grain orientations of plated PbO2 are analyzed via x-ray diffraction (XRD) and electron back scatter diffraction (EBSD), and very different phase distributions and grain orientations are observed for electrolyte with and without NaOAc. Electroplating and oxygen evolution kinetics are further investigated by rotating disk electrode (RDE) experiments. Our findings elucidate acetate additive effects on electroplating of PbO2 in SLFB systems and shed lights on battery life extension.

On Extending Cycle-Life of the Soluble Lead Redox Flow Battery

Cycle-life of the soluble lead redox flow battery (SLRFB) is limited due to the oxygen evolution reaction taking place at its cathode. This parasitic reaction leads to imbalanced deposition of lead metal at anode and PbO2 particles at cathode. As a result, the concentration of Pb2+ ions decreases in the electrolyte during repeated charge and discharge cycles leading to formation of sludge containing Pb and PbO2. In this study, we have developed and demonstrated a method of using a bi-functional auxiliary gas-diffusion electrode to mitigate these problems that consequently helps extending cycle life of the SLRFB. The auxiliary gas-diffusion electrode is operated either as an (a) air electrode or (b) a hydrogen electrode. When the auxiliary gas-diffusion electrode is an air electrode, it is used as positive electrode and on coupling with anode of the SLRFB, it forms a galvanic Pb – air cell that on discharge results in dissolving Pb particles. When auxiliary gas-diffusion electrode is a hydrogen electrode, it acts as negative electrode and on coupling with the cathode of the SLRFB forms a galvanic PbO2-H2 cell which on discharge dissolves the PbO2 particles. A novel insight on extending the performance of the SLRFB will be discussed.

In Situ Monitoring of Pb2+ Leaching from the Galvanic Joint Surface in a Prepared Chlorinated Drinking Water.

A novel method using a micro-ion-selective electrode (micro-ISE) technique was developed for in situ lead monitoring at the water-metal interface of a brass-leaded solder galvanic joint in a prepared chlorinated drinking water environment. The developed lead micro-ISE (100 μm tip diameter) showed excellent performance toward soluble lead (Pb2+) with sensitivity of 22.2 ± 0.5 mV decade-1 and limit of detection (LOD) of 1.22 × 10-6 M (0.25 mg L-1). The response time was less than 10 s with a working pH range of 2.0-7.0. Using the lead micro-ISE, lead concentration microprofiles were measured from the bulk to the metal surface (within 50 μm) over time. Combined with two-dimensional (2D) pH mapping, this work clearly demonstrated that Pb2+ ions build-up across the lead anode surface was substantial, nonuniform, and dependent on local surface pH. A large pH gradient (ΔpH = 6.0) developed across the brass and leaded-tin solder joint coupon. Local pH decreases were observed above the leaded solder to a pH as low as 4.0, indicating it was anodic relative to the brass. The low pH above the leaded solder supported elevated lead levels where even small local pH differences of 0.6 units (ΔpH = 0.6) resulted in about four times higher surface lead concentrations (42.9 vs 11.6 mg L-1) and 5 times higher fluxes (18.5 × 10-6 vs 3.5 × 10-6 mg cm-2 s-1). Continuous surface lead leaching monitoring was also conducted for 16 h.

Stabilizing the electrodeposit-electrolyte interphase in soluble lead flow batteries with ethanoate additive

The soluble lead flow battery (SLFB) is a promising energy storage system. In comparison to conventional flow batteries, the membrane-less and single-flow design of SLFBs is potentially much more economical to scale up for utility-scale applications. However, SLFB lifespan reported so far is less than 200 cycles under normal flow conditions. This study reports a method for significantly extending the cycle life and expanding capacity of SLFBs. By adding an adequate amount of sodium ethanoate to the electrolyte, lead dioxide (PbO2) deposition stability is materially improved and shed PbO2 particles are substantially reduced. Lifespan of ethanoate-added SLFBs is shown to extend by over 50%, and under optimal condition exceeds 500 cycles at over 65% energy efficiency. This improvement in SLFB performance is primarily attributed to the stabilization of both the electroplated PbO2 layers and proton activity at the electrodeposit-electrolyte interphase. We demonstrate a novel and economical approach for advancing performance of membrane-less flow batteries that involve redox reactions associated with acidity variation and operate through electrodeposition.

Formation of a lead-insoluble phase, pyromorphite, by hydroxyapatite during lead migration through the water-unsaturated soils of different lead mobilities.

This study combined the original unsaturated-column-percolation test with X-ray diffraction (XRD) analysis to understand how lead is transformed into lead-insoluble phase and immobilized by hydroxyapatite during lead migration in the water-unsaturated soil of different lead mobilities. The amounts of lead migrated from the soils without hydroxyapatite ranged from 4 to 46%, depending on the lead mobilities of soils. On the other hand, those of soils with hydroxyapatite were greatly suppressed by > 95% as compared with those without hydroxyapatite. The XRD analysis showed that the amounts of lead transformed into pyromorphite were compatible with those of lead migrated from the soil irrespective of the different lead mobilities. To the best of our knowledge, this study provides the first experimental evidence that lead migration can induce lead to transform into pyromorphite in the water-unsaturated soil. In addition, this study quantitatively demonstrates that the amount of lead migrated is almost equal to that of lead formed into pyromorphite. Thus, it was found that even if soluble lead remains after the application of immobilization material, it would be immobilized by the material during the lead migration as long as adequate material is applied to the soil.