Leachability Of Lead Research Articles

Leachability of lead, cadmium, and antimony in cement solidified waste in a silo-type radioactive waste disposal facility environment

The waste acceptance criteria for heavy metals in mixed waste should be developed by reflecting the leaching behaviors that could highly depend on the repository design and environment surrounding the waste. The current standards widely used to evaluate the leaching characteristics of heavy metals would not be appropriate for the silo-type repository since they are developed for landfills, which are more common than a silo-type repository. This research aimed to explore the leaching behaviors of cementitious waste with Pb, Cd, and Sb metallic and oxide powders in an environment simulating a silo-type radioactive waste repository. The Toxicity Characteristic Leaching Procedure (TCLP) and the ANS 16.1 standard were employed with standard and two modified solutions: concrete-saturated deionized and underground water. The compositions and elemental distribution of leachates and specimens were analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES) and energy-dispersive X-ray spectroscopy combined with scanning electron microscopy (SEM-EDS). Lead and antimony demonstrated high leaching levels in the modified leaching solutions, while cadmium exhibited minimal leaching behavior and remained mainly within the cement matrix. The results emphasize the significance of understanding heavy metals' leaching behavior in the repository's geochemical environment, which could accelerate or mitigate the reaction.

Effectiveness of Calcined Calcium Carbide Waste (CCCW) in Mitigating the Leachability of Lead and Cadmium from Contaminated Soil from Evbareke Spare Parts Market Benin City Edo State Nigeria

Heavy metal contamination of soil can present dangers besides threats to humans as well as the ecosystem via uninterrupted intake or interaction with contaminated soil and the food chain. The purpose of this research is to examine the effectiveness of calcined calcium carbide waste (CCCW) in mitigating the leachability of lead and cadmium ions in contaminated soil from Evbareke spare parts market Benin City, Edo State Nigeria. Contaminated soil samples were collected using quadrant sampling method at the depth of 0-15cm with soil auger. The calcium carbide waste was obtained from a panel beating workshop dumpsite. The calcium carbide waste was dried to constant weight in an oven at 105oC. 50g of the dried calcium carbide waste (CCW) was crushed in a mortar to obtain a powdered form. The X-ray diffraction analysis for the CCCW revealed that it was made up of predominantly portlandite (47%), calcite fraction (23.0%), dolomite (12.7%), coesite (8.6%), muscovite (4.5%) and lime (4.0%), this was corroborated by FTIR analysis. SEM analysis revealed that CCCW possess a rough surface with pore of varied size and irregular shape. The contaminated soil from the Evbareke spare parts market was contaminated with petroleum hydrocarbons, the soil was saline with low C.E.C. The soil texture was loamy-sand. As the amount of CCCW amended increase in the soil, the amount of cadmium and lead ions that was releasable in the soil reduced. The cadmium and lead ions in contaminated soil was stabilized hence reducing the cadmium and lead availability in the soil. The optimum amender amount in the contaminated soil to immobilize lead ion was 4% w/w and ≥2% w/w for cadmium ion. The CCCW effectively mitigated the leachability of lead and cadmium

Assessing the possibility of solidification and stabilization of pyrite cinder by using quicklime and fly ash

The aim of this study was to determine the possibility of using two low-cost binders,quicklime and fly ash for the solidification/stabilization (S/S) of pyrite cinder.Pyrite cinder, used in this study, represents a remnant from sulfuric acid productionin fertilizer factory IHP “Prahovo” A.D. (Serbia), and has a very high toxicmetal content. High contents and leachability of copper, lead and zinc make thiswaste material hazardous, representing an extraordinary risk to the environment.In order to determine the leaching behavior of the S/S mixtures, four single-stepleaching tests were performed, each one having a different sort of leaching fluid(deionized water, inorganic and organic acidic solutions). X-ray diffraction (XRD),scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDS)were implemented to elucidate the mechanisms responsible for immobilization ofCu, Pb and Zn. Overall, the test results indicated that S/S treatment using bothquicklime and fly ash was effective in immobilizing these metals, especially whenthere is a higher share of binder present. Treated waste can be safe for disposal andeven considered for “controlled utilization”. Furthermore, the use of fly ash for S/Streatment of pyrite cinder solves the disposal problems of two waste types, as it alsorepresents a secondary industrial product.

Field evaluation of a new hydroxyapatite based binder for ex-situ solidification/stabilization of a heavy metal contaminated site soil around a Pb-Zn smelter

Abstract This study presents a field trial of ex-situ solidification/stabilization of heavy metal contaminated soils using a new hydroxyapatite based binder SPC (superphosphate and calcium oxide). The field performance including electrical conductivity (EC), heavy metal and chemical oxygen demand (COD) leachability, and penetration resistance of stabilized soils up to 256 days after treatment is investigated. Moreover, acid neutralization capacity (ANC), metal speciation, and soil mineralogy analyses are performed to elucidate the heavy metal immobilization mechanisms. The results indicate that the stabilized soils have lower EC values than untreated soils, indicating the lower soluble salt contents in stabilized soils. Ex-situ treatment can significantly reduce acid soluble fraction contents and leachability of lead, zinc and cadmium in soils as a consequence. Decrease in COD leachability is observed during the curing period up to 256 days. Additionally, SPC stabilized soils give superior mechanical properties as indicated by their higher penetration resistance values as compared to the untreated soils. The improvement in ANC and reduction in acid soluble fraction resulting from the formation of phosphate-based precipitates are mainly responsible for the reduced heavy metal leachability of stabilized soils. Additionally, ex-situ SPC treatment is found to be effective in improving soil spatial homogeneity.

In-situ solidification/stabilization of heavy metals contaminated site soil using a dry jet mixing method and new hydroxyapatite based binder.

In this study, in-situ treatment using dry jet mixing construction method and SPC (single superphosphate and calcium oxide) new binder are used to solidify/stabilize a heavy metal contaminated site soil with relatively high content of organic matters. Time-dependent field performance of the soils at 41 and 326 days after treatment is evaluated, which includes electrical conductivity (EC), leachability of heavy metals and chemical oxygen demand (COD), soil penetration resistance, acid neutralization capacity (ANC), and chemical speciation of heavy metals. The results indicate that the stabilized soils exhibit satisfactory performance which is comparable with the laboratory study. In-situ SPC treatment significantly decreases EC values and increases penetration resistance values of the soils. Leachability of lead, zinc, cadmium and COD decreases with increasing SPC content or curing time. Large percentages of heave metals in the soils are transformed from exchangeable fractions to residual fractions after treatment. These, coupled with the improved ANC, result in low heavy metal leachability in stabilized soils.

Assessment of the content, occurrence, and leachability of arsenic, lead, and thallium in wastes from coal cleaning processes

The aim of the study was to evaluate the content, occurrence, and leachability of arsenic (As), lead (Pb), and thallium (Tl) in wastes from coal cleaning processes with respect to the safe management of this waste. The study focused on wastes resulting from the wet gravitation and flotation processes employed for the purposes of coking coal cleaning in four coal mines situated in the Upper Silesian Coal Basin (Poland). The scope of the study included (i) determination of the content of these elements in the investigated wastes using atomic absorption spectrometry, (ii) evaluation of their mode of occurrence using electron microprobe analysis, and (iii) preliminary assessment of their leachability in deionized water. The content of the analyzed elements in the examined samples of coal waste was twice as high as the average content of these elements in the Earth’s crust. The contents of As and Pb, however, did not exceed their permissible contents in inert waste in accordance with Polish legal regulations based on EU directives. The limit on the content of Tl is not specified by these regulations, but its amount in the examined samples was similar to that occurring in the soils. Moreover, leaching tests have shown that these elements are hardly eluted from the analyzed material. Their content in the water leachates was generally lower than the detection limit of the analytical method, complying with the standards for good and very good water quality. Low leachability of these elements most probably results from their mode of occurrence in the investigated wastes. The chemical analysis using an electron microprobe and the analysis of the correlation between these elements, e.g., total and pyritic sulfur, have shown that Pb, As, and Tl are mainly found in sulfide minerals which are characterized by negligible solubility. In conclusion, the investigated hard coal processing waste does not constitute a threat to the environment and can be commercially used or safely neutralized, e.g., by landfilling.

Biogas purification with biomass ash

The aim of the study was to investigate the option to purify biogas from small-scale biogas plants by entrapping CO2 and H2S with regionally available biomass ash. Connected to the existing biogas plant Neustift (Tyrol) wood ash placed in a 1 m3 container was used as a trap for CO2 and H2S in the biogas. With the process conditions chosen, for a period of a few hours CO2 was trapped resulting in pure methane. The removal of H2S was much longer-lasting (up to 34 d). The cumulative H2S uptake by the biomass ash ranged from 0.56 to 1.25 kg H2S per ton of ash. The pH of the ash and the leachability of Lead and Barium were reduced by the flushing with biogas, however toxicity towards plants was increased thus reducing the potential of ash use in agriculture. It can be concluded that biomass ash may be used for removal of hydrogen sulphide from biogas in small and medium biogas plants. The economic evaluation, however, indicated that the application of this system is limited by transport distances for the ash and its potential use afterwards.

Treatment of Lead Contaminated Soil using Solidification/Stabilization Method Incorporated with Sugarcane Bagasse

In recent years, tremendous researches have been carried out for solid waste treatment using the solidification/stabilization (S/S) method incorporated with agricultural wastes after the incineration process. These researches, although they showed efficient results, but they may be expensive due to the incineration procedure cost. In the current research, the treatment of lead (Pb) contaminated soil was studied by the incorporation of sugarcane bagasse in its fibrous state into the S/S method. Chemical properties of the materials used were determined by X-Ray Fluorescence (XRF) test. Some mechanical tests like density, water absorption and compressive strength were conducted in order to meet the regulatory limits for disposing the treated waste. Some leaching tests were also conducted, to measure the leachability of lead (Pb) from the matrices. Solidification/stabilization was found as an effective method that was able to reduce more than 99% of leachability of Pb from polluted soil. Moreover, this method can incorporate until 10% of sugarcane bagasse into the matrices. Although incorporation of sugarcane bagasse up to 10% decreases the strength of the samples and increase the leachability of Pb, but they still fit to the standard. Incorporation of sugarcane bagasse waste in its fibrous state into the solidification/stabilization method may provide an alternative low cost treatment method for Pb polluted soils and may eliminate huge amounts of this waste from the environment.

Toxicity characteristic leaching procedure over- or under-estimates leachability of lead in phosphate-amended contaminated soils

In this study, Pb(NO3)2-, PbSO4-, or PbCO3-contaminated soils were treated with triple super phosphate (TSP) or phosphate rock (PR) and then subjected to the toxicity characteristic leaching procedure (TCLP) to assess Pb leachability. Soluble TSP resulted in the transformation of Pb into insoluble Pb phosphate precipitates in all contaminated soils, and the transformation increased with extended leaching times. Consequently, Pb concentrations in the TCLP leachates treated with TSP were reduced by 97.3–99.7% compared with the untreated soils, and Pb leaching decreased over the extraction time and did not reach equilibrium even after 96h of extraction. Precipitation of Pb phosphate minerals in the less soluble PR-treated soil was limited, and Pb leaching was controlled by the dissolution of the Pb compounds, resulting in elevation of Pb in the TCLP leachate. Pb leaching continued to increase with time due to continuous dissolution of PbSO4 and PbCO3. The results indicated that Pb leaching is kinetically controlled by either Pb compound dissolution or phosphate mineral formation. The standard TCLP test using a designated 18h incubation time can overestimate the leachability of Pb in soils contaminated with lead and amended with soluble TSP and underestimate the leachability of Pb in soils contaminated with Pb and amended with less soluble PR. Therefore, wide use of TCLP for assessing Pb leachability in all contaminated soils is insufficient, and development of a site-specific evaluation method is urgently needed.

Solidification/stabilization of lead‐contaminated soil using cement and waste phosphorus slag

Solidification/stabilization (S/S) is an effective technique for reducing the leachability of contaminants in soils. Very few studies have investigated the use of waste phosphorus slag (WPS) for S/S treatment of contaminated soils. Partial replacement of ordinary Portland cement (OPC) with WPS in the binder system is used to S/S of lead‐contaminated soil. Batch tests were conducted to study the physical properties of solidified forms with different concentrations of lead and WPS, namely unconfined compressive strength (UCS), setting times of early mixtures and changes in crystalline phases as well as chemical properties such as the leachability of lead and pH of the leachate. Results indicated that partial replacement of OPC with WPS could reduce the Pb leaching concentration of solidified samples effectively. XRD results indicated that the formation of fluoropyromorphite was strongly associated with the immobilization of lead. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 957–963, 2015

Effect of acid rain pH on leaching behavior of cement stabilized lead-contaminated soil

Cement stabilization is a practical approach to remediate soils contaminated with high levels of lead. However, the potential for leaching of lead out of these stabilized soils under variable acid rain pH conditions is a major environmental concern. This study investigates the effects of acid rain on the leaching characteristics of cement stabilized lead contaminated soil under different pH conditions. Clean kaolin clay and the same soil spiked with 2% lead contamination are stabilized with cement contents of 12 and 18% and then cured for 28 days. The soil samples are then subjected to a series of accelerated leaching tests (or semi-dynamic leaching tests) using a simulated acid rain leachant prepared at pH 2.0, 4.0 or 7.0. The results show that the strongly acidic leachant (pH ∼2.0) significantly altered the leaching behavior of lead as well as calcium present in the soil. However, the differences in the leaching behavior of the soil when the leachant was mildly acidic (pH ∼4.0) and neutral (pH ∼7.0) prove to be minor. In addition, it is observed that the lead contamination and cement content levels can have a considerable impact on the leaching behavior of the soils. Overall, the leachability of lead and calcium is attributed to the stability of the hydration products and their consequent influence on the soil buffering capacity and structure.

Effect of ash circulation in gasification melting system on concentration and leachability of lead in melting furnace fly ash

In some gasification-melting plants, generated melting furnace fly ash is returned back to the melting furnace for converting the ash to slag. This study investigated the effect of such ash circulation in the gasification-melting system on the concentration and leachability of lead in the melting furnace fly ash. The ash circulation in the melting process was simulated by a thermodynamic calculation, and an elemental analysis and leaching tests were performed on a melting furnace fly ash sample collected from the gasification-melting plant with the ash circulation. It was found that by the ash circulation in the gasification-melting, lead was highly concentrated in the melting furnace fly ash to the level equal to the fly ash from the ash-melting process. The thermodynamic calculation predicted that the lead volatilization by the chlorination is promoted by the ash circulation resulting in the high lead concentration. In addition, the lead extraction from the melting furnace fly ash into a NaOH solution was also enhanced by the ash circulation, and over 90% of lead in the fly ash was extracted in 5 min when using 0.5 mol l−1 NaOH solution with L/S ratio of 10 at 100 °C. Based on the results, a combination of the gasification-melting with the ash circulation and the NaOH leaching method is proposed for the high efficient lead recovery.

Determining the experimental leachability of copper, lead, and zinc in a harbor sediment and modeling

The potential leaching of pollutants present in harbor sediments has to be evaluated in order to choose the best practices for managing them. Little is known about the speciation and mobility of heavy metals in these specific solid materials. The objective of this paper is to determine and model the leachability of copper, lead, and zinc present in harbor sediments in order to obtain essential new data. The mobility of inorganic contaminants in a polluted harbor sediment collected in France was investigated as a function of physicochemical conditions. The investigation relied mainly on the use of leaching tests performed in combination with mineralogical analysis and thermodynamic modeling using PHREEQC. The modeling phase was dedicated to both confirm the hypothesis formulated to explain the experimental results and improve the determination of the main physico-chemical parameters governing mobility. The experimental results and modeling showed that the release of copper, lead, and zinc is very low with deionized water which is due to the stability of the associated solid phases (organic matter, carbonate minerals, and/or iron sulfides) at natural slightly basic conditions. However, increased mobilization is observed under pH values below 6.0 and above 10.0. This methodology helped to consistently obtain the geochemical parameters governing the mobility of the contaminants studied.

Leachability of cadmium, lead, and zinc in a long-term spontaneously revegetated slag heap: implications for phytostabilization

Purpose: For abandoned slag heaps, the spontaneous establishment of a vegetation cover is usually considered beneficial as it represents a means of phytostabilization. However, for slag containing heavy metals, such a vegetation cover has a potential long-term effect on the fate of the metals. The objective of this study was to investigate how the long-term spontaneous revegetation of a slag heap can affect the fractionation and the leachability of Cd, Zn, and Pb. Materials and methods: Soils from two plots covered by either Armeria maritima or Agrostis tenuis and a bare plot soil were sampled from a slag heap from a zinc smelting plant and characterized. The BCR sequential extraction scheme was adopted to determine the metal pools. The leachability of Cd, Pb and Zn was assessed by means of a leaching column experiment. Results and discussion: Long-term presence of a plant cover increased the proportion of Zn in the most mobile fraction and Pb in the fraction bound to organic matter. Cd distribution was relatively unaffected. Overall, the metal leachability was enhanced in the revegetated soils, notably due to higher organic anion release. However, responses of metal behavior to revegetation depended on the established plant species. The highest leachability of Cd was found in the soil covered by A. tenuis while the highest leachability of both Zn and Pb was observed in the soil below A. maritima. Conclusions: Any remediation strategy for metal-rich waste dumps by phytostabilization should take into careful consideration the potential long-term mobilization effect of plant establishment on heavy metals. We conclude that when using pioneer plants for phytostabilization purposes, preference should be given to pseudo-metallophyte over hyperaccumulator species.

Incubation of air-pollution-control residues from secondary Pb smelter in deciduous and coniferous organic soil horizons: Leachability of lead, cadmium and zinc

The leachability of air-pollution-control (APC) residues from a secondary lead smelter in organic soil horizons (F and H) from a deciduous and a coniferous forest during incubation periods of 0, 3 and 6 months were compared in this work. While the concentration of Pb, Zn and Cd associated with the exchangeable/acid extractable fraction in the horizon F from the coniferous forest was higher compared to the deciduous, significantly lower concentrations in the humified horizon H was found. It is suggested that lower pH and a higher share of fulvic acids fraction (FAs) of solid phase soil organic matter (SOM) in the humified soil horizon H from the coniferous compared to the deciduous forest is responsible for a higher metal association with solid phase SOM and therefore a lower metal leaching in a soil system. From this point of view, the humified soil horizon H from the deciduous forest represents a soil system more vulnerable to Pb, Zn and Cd leaching from APC residues.

Utilization of recycled glass derived from cathode ray tube glass as fine aggregate in cement mortar

Rapid advances in the electronic industry led to an excessive amount of early disposal of older electronic devices such as computer monitors and old televisions (TV) before the end of their useful life. The management of cathode ray tubes (CRT), which have been a key component in computer monitors and TV sets, has become a major environmental problem worldwide. Therefore, there is a pressing need to develop sustainable alternative methods to manage hazardous CRT glass waste. This study assesses the feasibility of utilizing CRT glass as a substitute for natural aggregates in cement mortar. The CRT glass investigated was an acid-washed funnel glass of dismantled CRT from computer monitors and old TV sets. The mechanical properties of mortar mixes containing 0%, 25%, 50%, 75% and 100% of CRT glass were investigated. The potential of the alkali-silica reaction (ASR) and leachability of lead were also evaluated. The results confirmed that the properties of the mortar mixes prepared with CRT glass was similar to that of the control mortar using sand as fine aggregate, and displayed innocuous behaviour in the ASR expansion test. Incorporating CRT glass in cement mortar successfully prevented the leaching of lead. We conclude that it is feasible to utilize CRT glass in cement mortar production.

Sequential digestion for measuring leachable and total lead in the same sample of dust or paint chips by ICP-MS

House lead exposure is generally assessed using total lead, except in France, where acid-leachable lead is used for routine regulatory purposes. In order to allow an international comparison of French lead dust contamination, a sequential digestion protocol is developed to determine both leachable and total lead on the same sample with a two-step digestion stage: firstly, hydrochloric acid is added to the sample at 37°C to solubilize leachable lead; then nitric acid is added to an aliquot at 95°C to solubilize residual (i.e., non-leachable) lead. Both sample fractions are analyzed with inductively coupled plasma mass spectrometry (ICP-MS). The sum of the two fractions allows to determine total lead. This new protocol has been tested with wiped dust (n = 111) and paint chip (n = 46) samples collected in houses (n = 16). The leachability of lead ranged from 63 to 100% in dust and from 4 to 100% in paint. These findings confirm the strong variability of lead leachability in houses samples and thus the importance of considering it for lead poisoning prevention. This double determination of leachable and total lead for each wiped dust or paint sample appears to be a reproducible, simple, low-cost protocol and thus a useful tool for international comparison of house dust lead contamination.

Prevention of lead leaching from fly ashes by mechanochemical treatment

Fly ashes from a municipal solid waste incinerator were subjected to mechanochemical (MC) treatment in a planetary ball mill, and the treated fly ashes were cemented with a binder. The leachability of lead (Pb) from the treated fly ashes and from the cement product were investigated, and the speciation of lead in the treated and untreated ashes was determined by X-ray absorption fine structure (XAFS) analysis. MC treatment of the fly ashes and subsequent cementation prevented Pb leaching by 99.9%, whereas MC treatment alone prevented Pb leaching by 92.8%. Analysis of the X-ray absorption near-edge spectrum of the untreated fly ashes revealed that the predominant Pb species in the ashes was PbCl 2. In contrast, the counterpart in the treated fly ashes was Pb 3O 4 insoluble in water. The formation of a species of Pb with a lower solubility in water than that of PbCl 2 was confirmed by MC treatment of PbCl 2-spiked fly ashes for 48 h, indicating the reduction of PbCl 2 in the spiked fly ashes to Pb via Pb 3O 4 during MC treatment. Our results indicate that such reduction to an insoluble species prevented Pb from leaching and that MC treatment followed by cementation is a feasible method for the recycling of fly ashes.

English

Granular mine waste are generated from the extraction and beneficiation of lead/zinc minerals. The fine gravel waste, commonly known as chat, contains elevated levels of lead, zinc and cadmium which can result in potentially serious human health and ecological concerns. With the use of chat in a variety of applications such as road construction, there is an increased environmental concern due to the potential leachability of lead (Pb), cadmium (Cd) and zinc (Zn) at high concentrations. In this study, we examine the release of these three metals from raw chat and its reuse products, mainly cold-mix asphalt (CMA) and hot-mix asphalt (HMA), to determine the environmental stability of the materials under different environmental conditions. The leachability of metals was evaluated using extraction tests including the toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP) and deionized water extraction procedure (DWEP). In addition, the relative bioaccessability of the metals was determined by the relative bioaccessability leaching procedure (RBLP) tests. Based on the conducted leaching tests, it was observed that all the three samples failed the TCLP test. The Cd and Pb concentrations in the TCLP extracts were higher than the mandated TCLP limits for leaching from wastes. The TCLP extracts of CMA and HMA samples were found to be less than the limit for Cd, but higher for Pb. The experimental data also showed that the concentrations of Cd and Pb in the SPLP extracts were less than the National Drinking Water Primary Standards of 0.005 mg/L and 0.015 mg/L, respectively. This indicated the suitability of the mine tailing and its reuse products for beneficial applications. The percent bioaccessible metal followed the order: raw chat < HMA < CMA, probably due to its smaller particle size (< 250 µm), compared to the particle sizes of CMA and HMA tested (< 2 mm). The data indicated that while the use of chat in asphalt is environmentally safe, care should be taken as metals could leach in significant concentrations when placed in moist environments for longer duration.

Reducing leachability and bioaccessibility of lead in soils using a new class of stabilized iron phosphate nanoparticles

This study prepared and tested a new class of iron phosphate (vivianite) nanoparticles synthesized with sodium carboxymethyl cellulose (CMC) as a stabilizer for in situ immobilization of lead (Pb 2+) in soils. Batch test results showed that the CMC-stabilized nanoparticles can effectively reduce the TCLP (toxicity characteristic leaching procedure) leachability and PBET (physiologically-based extraction test) bioaccessibility of Pb 2+ in three representative soils (calcareous, neutral, and acidic). When the soils were treated for 56 days at a dosage ranging from 0.61 to 3.0 mg/g-soil as PO 4 3 - , the TCLP leachability of Pb 2+ was reduced by 85–95%, whereas the bioaccessibility was lowered by 31–47%. Results from a sequential extraction procedure showed a 33–93% decrease of exchangeable Pb 2+ and carbonate-bound fractions, and an increase in residual-Pb 2+ fraction when Pb 2+-spiked soils were amended with the nanoparticles. Addition of chloride in the treatment further decreased the TCLP-leachable Pb 2+ in soils, suggesting the formation of chloro-pyromorphite minerals. Compared to soluble phosphate used for in situ metal immobilization, application of the iron phosphate nanoparticles results in ∼50% reduction in phosphate leaching into the environment.