Speciation and Vertical Distribution of Lead and Lead Shot in Soil at a Recreational Firing Range

In this study, the speciation, vertical distribution and soil particle size fractions of lead in soil samples at a recreational firing range was determined. This study was performed to gain a better understanding of how lead shot breaks down at ranges. Both the chemical form of lead and the types of soil particles with which lead is associated are important for understanding not only the mobility and persistence, but also the human and ecological impact of lead at these ranges. Lead as shot gun pellets was found to be the dominant form of lead in soil samples. The highest levels were measured in surface samples located in the “fall zone” of the range. Results indicate shot to be relatively absent below surficial samples. Lead concentrations in soil decreased markedly across a 0–6″ depth profile. Lead carbonates were the dominant non-shot form of lead present at all depths. Water-soluble lead species made up a minor fraction of the non-shot lead present in the samples. Based on soil particle sizes measured, highest concentrations of lead were measured in soil particles passing a 0.075 mm sieve.     

石灰对铅污染土壤修复效果评价

为了研究铅污染菜地土壤施用石灰对小白菜-土壤生态系统的影响及持续效果,探讨石灰修复铅污染菜地土壤的可行性,采集铅污染菜地土壤开展连续盆栽试验,设置5个石灰用量处理（0、1.5 g/kg、3.0 g/kg、4.5 g/kg、6.0 g/kg）。石灰施入土壤中平衡2周后移栽小白菜,连续种植3茬。同时采集小白菜样本和土壤样本,测定土壤pH、土壤Pb有效态含量和微生物活性等指标,并分别测定小白菜地上和地下部的生物量和铅含量。结果显示：石灰对降低土壤铅有效态和小白菜中铅含量的持效性较差,但施用石灰可增加土壤中的微生物活性,特别是种植小白菜后对增加土壤中微生物活性效果更明显,研究发现对羧酸类和胺类等碳源利用能力强的微生物可增加土壤中铅有效态的含量,对聚合物类、糖类、氨基酸类和其他类碳源利用能力强的微生物可以降低小白菜中的铅含量。研究结果为石灰修复重金属污染土壤的使用提供了更合理的理论支撑。     

Lead Distribution and Mobility in a Soil Embankment Used as a Bullet Stop at a Shooting Range

The distribution of lead in and below a soil embankment used as a stop butt for lead bullets at a sport shooting range for more than 30 years was investigated. A vertical profile, just behind the shooting target, was mapped by 54 soil samples characterized by contents of lead bullets, soil lead, and easily leachable lead as measured in a leaching test (L/S 2). At the target, the soil contained up to 40% metallic lead and 5 to 10% lead associated with the soil particles (<2?mm). The leaching test showed concentrations of dissolved lead in the range 5 to 20?mg/l. However, in the bottom of the stop butt (about 1?m lower than the target) soil lead was only slightly elevated, and no increase in lead was found below the stop butt in the original soil profile. In the lower part of the stop butt, pH was around 5, which is considered to favor lead migration, but in the soil samples with lead bullets present pH was between 6 and 7. The elevated pH values, probably caused by the corrosion of lead bullets, may have been a significant factor in limiting the migration of lead in the stop butt. The investigation showed that the lead in the stop butt did not affect the surroundings, but that the high lead content of the soil would require that this be treated as waste if the facility was abandoned.     

模拟氮沉降对典型阔叶红松林土壤有机碳和养分的影响简

为探讨氮沉降对典型阔叶红松（Pinus koraiensis）林的影响,从2008年6月~2010年8月进行了人工模拟氮沉降实验,实验分为对照、低N、中N、高N4个处理,每个处理3个重复。所施氮肥为CO(NH₂)₂,以溶液的形式喷施,4个处理浓度分别为0、30、60、120 kg·hm^-2·a^-1。在氮沉降进行1年后,采集各处理0～20、20～40和40～60 cm的土壤样品,测定其土壤有机C、全N、碱解N和速效P、速效K。结果表明：相同处理下,有机C和全N含量随土层的加深均逐渐减少。总体上低、中N处理显著增加了土壤有机C、碱解N和速效K含量,中、高N处理显著降低了土壤速效P含量（P<0.05）,而对全N含量影响不显著（P>0.05）。土壤有机C与土壤全N、碱解N、速效P、速效K之间存在极显著正相关关系（P<0.001）。有机C和土壤养分对氮沉降的响应说明氮沉降在短期内可能影响阔叶红松林土壤碳库积累和土壤肥力水平。     

Characterization of Lead in Soils of a Rifle/Pistol Shooting Range in Central Florida,USA

The distribution of lead in soil samples collected from both surface (0 to 10?cm) and profile (O 0 to 10?cm, E 11 to 30?cm, Eb 31 to 50?cm, Bw 51 to 100?cm, and C 181 to 200?cm) at a 14-year-old rifle/pistol shooting range located in central Florida were determined using EPA Method 3051a (microwave, HNO₃/HCl=3:1, v/v). In addition to total lead analysis, Toxicity Characteristic Leaching Procedure (TCLP) analysis was performed on corresponding samples to determine whether the soils would require special handling as hazardous waste if the soils were to be removed from the range. Total lead in surface soils varied from 330 to 17 850?mg Pb kg^?1, with the greatest concentration in the middle of the backstop berm. The TCLP tests indicated that lead in all surface soils exceeded the 5?mg Pb L^?1 critical level of federal regulation for solid wastes and hazardous wastes provided by the Resource Conservation and Recovery Act (RCRA) and would be characterized as hazardous waste. Sequential fractionation and X-ray diffraction (XRD) analyses revealed that lead carbonate existed predominantly (91.3%) in the berm soil. The weathering of lead bullets in the soil environments formed primarily as hydrocerussite (Pb₃(CO₃)₂(OH)₂), with small amounts of massicot (PbO) and cerussite (PbCO₃). However, the elevated soil pH, caused by the oxidization and transformation process of elemental lead in lead bullets, could be a significant factor in limiting the migration of lead in the soil.     

Using Lanthanum,Neodymium, and Thorium as Conservative Indexing Elements to Indicate Soil Lead Deposition

A critical need exists for data evaluation protocols to determine if heavy metal deposition has impacted soil or sediment. For routine reconnaissance these protocols need to be analytically precise and affordable, two issues lacking in many regions. We employed a low-cost, commercially available aqua regia digestion procedure and developed a simple protocol for isolating pristine soil horizons and conservative indexing elements to compare to more Pb impacted soil horizons. Strongly Pb impacted soil horizons are easy to ascertain; however, moderately to slightly Pb impacted soils are more problematic to identify because of the natural Pb variation in soils. Using the harmonic mean of the soil concentrations of Lanthanum (La) and Neodymium (Nd) and also the soil concentrations of Thorium (Th) as conservative indexing elements, we were able to discriminate pristine soils from slightly to moderately Pb impacted soils. Ro values are estimators of elemental gain and loss, with Ro values greater than unity implying Pb addition, providing the comparative loss of other elements or biocycling are substantial contributing factors. All pedons known to have received Pb from atmospheric addition exhibited Ro values appreciably greater than unity, whereas soils known to be not impact or at most minimally impacted showed Ro values near unity. Commercially available and relative low cost aqua regia digestion analysis provided the analytical data for Pb, Fe, La, Nd and Th.     

Factors Controlling the Bioaccessibility of Arsenic(V) and Lead(II) in Soil

The relative oral bioaccessibility of labile Pb(II) and As(V) added to soils was investigated in a well-characterized soil using a physiologically based extraction test (PBET) to simulate metal solubility in a child's digestive system. The effect of soil and PBET (i.e., simulated stomach and small intestine) pH, soil metal concentration, soil to solution ratio, and soil-metal aging time were investigated. Arsenic bioaccessibility was relatively unaffected by a variation in simulated stomach and small intestine pH over the range 2 to 7 and soil pH over the range 4.5 to 9.4. In contrast, Pb(II) bioaccessibility was strongly dependent on both the simulated stomach, small intestine, and soil pH, showing enhanced sequestration and decreased bioaccessibility at higher pH values in all cases. Although the bioaccessibility of Pb(II) was constant over the concentration range of approximately 10 to 10,000?mg/kg, the As(V) bioaccessibility significantly increased over this concentration range. The bioaccessibility of both arsenic and lead increased as the soil-to-solution ratio decreased from 1:40 to 1:100. Additional lead sequestration was not observed during 6 months of soil aging, but As(V) bioaccessibility decreased significantly during this period.     

土壤铅和锌对植物根际丛枝菌根真菌分布的影响

从秦岭凤县铅锌污染区4种植物根际共鉴定出球囊霉属(Glomus)丛枝菌根真菌(Arbuscular mycorrhizal ungi,AMF)12种,其中缩球囊霉(G.constrictum)是该区域的优势种;缩球囊霉、副冠球囊霉(G.coronatum)、苏格兰球囊霉(G.caledonium)和聚丛球囊霉(G.aggregatum)对铅锌污染具有较强的耐性,而地球囊霉(G.geospo-rum)、台湾球囊霉(G.formosanum)、地表球囊霉(G.versiforme)和两型球囊霉(G.dimorphicum)对铅锌污染的耐性较弱.相关分析表明,土壤Pb、Zn、速效P浓度和pH较低时,对AMF丰度有一定的促进作用,当Pb、Zn、速效P浓度和pH较高时,对AMF丰度为抑制作用,AMF丰度与高浓度Pb呈极显著负相关,与高浓度速效P呈显著负相关.通径分析表明,Pb是影响秦岭重金属污染区AMF丰度的主要因素,其直接和间接作用都较大,而pH、速效P和Zn主要通过Pb的间接作用来影响AMF丰度.     

Effect of Soil Chemical and Physical Properties on Sorption and Desorption Behavior of Lead in Different Soils of India

Lead (Pb) is a non-biodegradable contaminant, present in the environment, especially near lead-based industrial sites, agricultural lands, and roadside soils. Bioavailability of Pb in the soil is controlled by the sorption and desorption behavior of Pb, which are further controlled by the soil chemical and physical properties. In this study, sorption and desorption amounts of Pb in soil were compared with soil physical (sand, silt, clay content) and chemical (pH; electrical conductivity, EC; percent organic carbon, (%OC); cation exchange capacity, CEC) properties. Twenty-six surface soils (0–5cm), expected to vary in physical and chemical properties, were collected from different parts of India and were treated with known concentration of Pb solution (40 μg/L). The amount of Pb sorbed and desorbed were measured and correlated with soil properties using simple linear regressions. Sorption was significantly (p ≤ 0.05) and positively correlated with pH, and %OC; desorption was significantly (p ≤ 0.05) negatively correlated with the same two factors. Stepwise multiple regressions were performed for better correlations. Predicted sorption and desorption amounts, based on multiple regression equations, showed reasonably good fit (R² = 0.79 and 0.83, respectively) with observed values. This regression model can be used for estimation of sorption and desorption amounts at contaminated sites.     

Impacts of Vehicle Emissions and Ambient Atmospheric Deposition in Nigeria on the Pb,Cd, and Ni Content of Fermented Cassava Flour Processed by Sun-Drying

A study of air pollution in Nigeria due to Pb, Cd, and Ni contamination of fermented cassava meant for flour production was carried out by AAS. Fermented cassava samples were purchased from farmers in the study area and one-third of each was oven-dried (OD) while the rest were sun-dried either along roadside (RS-SD) or under ambient atmosphere conditions (AA-SD). Mean concentrations (μg/g) for OD samples in year 2008 were: Pb (0.17 ± 0.04); Cd (0.04 ± 0.01); and Ni (0.27 ± 0.05) while RS-SD samples gave Pb (0.24 ± 0.08), Cd (0.04 ± 0.01), and Ni (0.48 ± 0.17). Mean values (μg/g) in 2009 for OD, AA-SD, and RS-SD, respectively, were Pb (0.03 ± 0.01, 0.05 ± 0.02, 0.15 ± 0.08), Cd (0.18 ± 0.01, 0.04 ± 0.02, 0.05 ± 0.02), and Ni (0.09 ± 0.06, 0.21 ± 0.10, 0.57 ± 0.12). Mean concentrations in sun-dried samples were greater (p < .01), while RS-SD samples were 185% in Pb, 53% in Cd, and 176% in Ni greater (p < .01) than AA-SD samples. With an estimated country-wide annual Pb emissions from petrol and diesel ranging from 616,241 to 968,086 kg, and dust, considered the major source of Cd and Ni, and other extraneous factors including metals adsorbed on pavement surfaces, sun-drying of wet foodstuff on the bare surface of roadside pavements could lead to high levels of Pb, Cd, and Ni in such food compared to drying under factory conditions or oven-drying.     

Lead (Pb) is Now a Non-Threshold Substance: How Does this Affect Soil Quality Guidelines?

Risk-based concentrations (RBCs) for lead (Pb) in soil were estimated using equations for development of Canadian soil quality guidelines. Based on the latest toxicological assessments by various health agencies, risk specific doses for Pb were defined for children (for impacts on intelligence quotient [IQ]) and adults (for impacts on systolic blood pressure [SBP] as well as protection of fetal effects in the case of pregnant women). The analysis suggests that a RBC in soil of 180 μg/g (dry weight) for residential and other areas where children routinely play is protective of a 1 IQ point decrement on a population basis and may actually be associated with decrements of less than 0.2 to 0.35 IQ points when the weight of evidence is considered. For soils that children do not contact on a frequent basis, RBCs as great as 8800 μg/g are considered to be protective of a 1 mmHg SBP increase in adults (as well as IQ effects to the fetus). It is stressed that non-soil sources of Pb may be even more important than soil. The approach may also be useful in jurisdictions outside of Canada as the importance of considering IQ decrements on a population basis rather than an individual basis and uncertainties in soil ingestion rates are considered.     

Short-Term Response of Soil Enzyme Activity and Soil Respiration to Repeated Carbon Nanotubes Exposure

Nanomaterials such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) may repeatedly enter the soil environment with unknown adverse consequences. To provide the information on the effects of repeated exposure of CNTs, we determined the response of soil enzyme activity and soil basal respiration (SBR) through a two-week incubation of farmland soil repeatedly treated with different concentrations of CNTs (100, 200, 500 mg kg^?1 for SWCNTs and 100, 500, 1000 mg Kg^?1 for MWCNTs). The activities of catalase, alkaline phosphatase, and invertase and SBR were measured after one- and two-time treatments. The repeated contamination of SWCNTs and MWCNTs repressed the activity of alkaline phosphatase and invertase in the 14-day incubation. Alkaline phosphatase and invertase were more sensitive indicators of CNTs’ contamination than catalase and soil basal respiration. High concentration of the SWCNTs stimulated SBR while the lower concentration suppressed SBR. The recurred exposure of SWCNTs and MWCNTs repressed the activity of catalase and invertase. The obtained results indicated that the soil microorganisms were suppressed under repeated pollution, as suggested by the same suppressed response of SBR between SWCNTs and MWCNTs treatment, except for the concentration of 500 mg kg^?1.     

Complex Interaction and Adsorption of Glyphosate and Lead in Soil

Glyphosate [N-(phosphonomethyl)-glycine] is a herbicide widely used in large quantities in agricultural applications. It is also known to form complexes with metal ions, although its influence on metal behavior, such as lead (Pb) in soil, is not well understood. In this study, the adsorption and co-adsorption of Pb and glyphosate were determined on two soils [a red (RS) soil, Udic Ferrisol, and a yellow-brown (YB) soil, Udic Luvisol] of distinctly different chemical characteristics at varying pH conditions. Results indicate that the adsorption of lead and glyphosate strongly depends on soil types: the RS soil, characterized by a relatively high iron/aluminum content but a low pH and organic matter content, shows a much lower adsorption capacity for Pb but a higher sorption for glyphosate than the YB soil. The co-existence of Pb and glyphosate in soils resulted in complex interactions among Pb, glyphosate, Pb-glyphosate complexes, and soil minerals. The presence of glyphosate decreased Pb adsorption on the two soils, which was attributed primarily to the formation of soluble Pb-glyphosate complexes having relatively low affinities to soil surfaces. On the other hand, addition of Pb increased the adsorption of glyphosate on both soils, which was attributed to: (1) a decreased solution pH due to the ion exchange between Pb²⁺ and H⁺ on soil surfaces; and (2) increased sorption sites where Pb was adsorbed and acted as a bridge between glyphosate and the soil. The present study illustrates that the complex interactions among glyphosate, Pb, and soil may have important implications for the mobility and bioavailability of Pb in soil and should thus be considered in future environmental risk assessments.     

Remediation of lead and cadmium-contaminated soils

The research was designated to study the ability of plants to bio-accumulate, translocate and remove the heavy metals, lead and cadmium from contaminated soil. The herbal plant ryegrass, Lolium multiflorum was investigated as a bio-accumulator plant for these metals. The translocation of these heavy metals in the herbal plant was compared considering root to shoot transport and redistribution of metals in the root and shoot system. The trace metal contents from root and shoot parts were determined using atomic absorption spectrometer. The results showed that the percent of lead and cadmium transferred to ryegrass plant were averaged as 51.39, and 74.57%, respectively, while those remained in the soil were averaged as 48.61 and 25.43% following 60 days of treatment. The soil-plant transfer index in root and shoot system of ryegrass was found to be 0.32 and 0.20 for lead, and 0.50 and 0.25 for cadmium. These findings indicated that the herbal plant ryegrass, Lolium multiflorum is a good accumulator for cadmium than lead. The soil-plant transfer factor (the conc. of heavy metal in plant to the conc. in soil) indicated that the mechanism of soil remedy using the investigated plant is phytoextraction where the amounts of heavy metals transferred by plant roots into the above ground portions were higher than that remained in the soil. The method offers green technology solution for the contamination problem since it is effective technology with minimal impact on the environment and can be easily used for soil remedy.     

Lead fractionation and bioaccessibility in contaminated soils with variable chemical properties

Abstract

The hazard imposed by trace elements within soils is dependent on soil properties and the relative distribution of metal species. Hence, a greenhouse column study was conducted to investigate the geochemical speciation and bioaccessibility of lead (Pb) as a function of soil properties. Four different soil types (Immokalee, Belle Glade, Tobosa and Millhopper series) varying in physico-chemical properties were selected and amended with Pb as Pb(NO₃) at 400, 800, and 1,200 mg kg^?1. A sequential extraction was employed to define the reactive metal pool, which was correlated with Pb bio-accessibility as determined by the physiologically based extraction test. Results show that Pb was mainly distributed in soluble+exchangeable phase in Immokallee (82%) and Millhopper (45%) series, and carbonate and Fe+Mn oxide fractions in Belle Glade (14–74%) and Tobosa (31–64%) series at time zero. With soil aging, Pb underwent chemical transformations in the soils and the majority of added Pb was associated with Fe+Mn oxide fraction (64–81%). Also, Pb bioaccessibility varied widely as a function of soil type and soil aging. Gastric phase (IVG-S) extracted 34–81% and 29–75% and the absorbed intestinal phase (IVG-AI) extracted 12–79% and 12–45% of amended Pb in all the soils at time zero and 6 months, respectively. Among soil types, Tobosa and Belle Glade showed reduced bioaccessibility relative to Immokalee and Millhopper. Statistical analysis revealed that the IVG-S Pb decreases as soil organic matter and cation exchange capacity (CEC) increases and total P decreases. While the Mehlich extractable P and Ca+Mg, total Fe+Al and organic matter predicted the Pb in an intestinal system.     

上海地区大气氮湿沉降及其对湿地水环境的影响

根据1998～2003年上海地区雨水中NO₃^--N、NH₄⁺-N浓度,采用单因子评估模式评价了降雨对湿地水环境的影响,并结合降雨量数据,研究了大气湿沉降氮通量.结果表明,上海地区雨水中氮浓度较高,6年雨水平均硝态氮浓度为259 mg·L^-1,铵态氮浓度为2.16 mg·L^-1,总无机氮（TIN）浓度474 mg·L^-1,远大于水体富营养水中氮浓度阀值（0.2 mg·L^-1）,依据降水中的氮浓度,降水已达到地表水V类、劣V类水平.6年湿沉降氮通量平均值为58.1 kg·hm^-2·yr^-1,其中NO₃^--N占54%.大气氮沉降对湿地水体富营养化影响值得关注.     

氮沉降及菌根真菌对长白落叶松苗木根系构型及根际酶活性的影响

为探究氮沉降和接种菌根真菌对长白落叶松苗木根系构型和根际土壤酶活性的影响,以1年生长白落叶松(Larix olgensis)的盆栽菌根苗(简称+M,混合接种8种外生菌根真菌)和非菌根苗(简称-M,未接种处理)为研究对象,设置4个氮沉降处理(不施氮(0N,0 kg·N·hm^-1·yr^-1)、低氮(LN,15 kg·N·hm^-1·yr^-1)、中氮(MN,30 kg·N·hm^-1·a^-1)和高氮(HN,60 kg·N·hm^-1·a^-1)),测定直径0~0.5 mm根系的总根长、总表面积、总体积和根尖数等根系形态指标,对比分析氮沉降和接种菌根真菌处理对苗木根际土壤酶(β-1,4葡萄糖苷酶(BG)、亮氨酸氨基肽酶(LAP)、β-1,4-N-乙酰-氨基葡糖氨糖苷酶(NAG)、酸性磷酸酶(ACP)和碱性磷酸酶(ALP))活性的影响。结果表明:①长白落叶松苗木直径0~0.5 mm根系的总根长、总表面积、总体积和根尖数均随氮浓度的递增呈下降的趋势;在0N、LN和MN处理下,-M处理的根系形态指标均高于+M处理。②随氮浓度增加,+M和-M处理苗木根际土壤中BG、LAP、ACP和ALP活性均呈先增加后下降的趋势,而NAG活性呈下降的趋势。③+M和-M处理下,长白落叶松直径0~0.5 mm根系的形态指标与根际土壤BG活性均呈显著负相关关系(P<0.05);除根尖数外,其它根系形态指标与NAG活性相关性均为正相关(P<0.05)。综上所述,苗木菌根化处理削弱了氮沉降对落叶松苗木根系构型的影响;而低氮处理下,+M处理对苗木根际土壤酶的活化程度高于-M处理。     

Lead Accumulation Ability of Selected Plants of Noccaea spp.

Several species of the Noccaea genus are known for their hyperaccumulation ability especially in the case of Cd, Ni, and Zn. However, ambiguous observations were previously published concerning their accumulation properties for Pb. The Pb accumulation properties of Noccaea rotundifolia, Noccaea montana, and Noccaea jankae hungarica plants were tested in field and pot experiments in soils differing in the mobile pool of Pb, as well as in soilless hydroponic culture. The Pb content in the dry biomass of plant shoots reached up to 54 mg/kg in field conditions and 84 mg/kg in pots regardless of the bioavailable pool of Pb in the pots. The hydroponic experiment showed a stepwise increase in Pb content in plant biomass with increasing Pb concentration in the solution, but the predominant proportion of plant Pb was retained in the roots. Although the hyperaccumulation ability of some of the Noccaea species is widely discussed in the literature, our results are in agreement with those suggesting no Pb hyperaccumulation potential in these plants.     

Employment of Rhizobacteria for the Inoculation of Barley Plants Cultivated in Soil Contaminated with Lead and Cadmium

In laboratory experiments, the rhizobacteria Azospirillum lipoferum 137, Arthrobacter mysorens7, Agrobacterium radiobacter 10, and Flavobacterium sp. L30 were found to have a relatively high resistance to the toxic heavy metals lead and cadmium (except that strain L30 was found to be sensitive to Cd). When introduced by means of seed bacterization, the heavy metal–resistant strains actively colonized the rhizosphere of barley plants cultivated in uncontaminated and contaminated soils. In both pot and field experiments, seed bacterization improved the growth of barley plants and the uptake of nutrient elements from soil contaminated with Pb and Cd. The bacterization also prevented the accumulation of Pb and Cd in barley plants, thereby mitigating the toxic effect of these heavy metals on the plants.     

Removal of Lead from a Calcareous Soil by Chloride Complexation

Remediation of a lead-contaminated calcareous soil using NaCl solutions was examined. The removal of Pb from a coarser fraction of the soil was found to be 83% after three successive extractions at a NaCl concentration of 8?M, whereas an average of 9% of the calcium was removed. Multibatch extractions of Pb from finer soil containing a higher level of Pb were also performed. The removal of Pb from this soil after six successive extractions with 8?M NaCl was found to be 93%. The removal of Pb increased with time in a batch test and approached 80% after 90?h. It was found that the data were adequately described by a first-order rate, and hence it is believed that a single reaction mechanism controlled the release of Pb (i.e., from carbonate bound or exchangeable Pb fractions in the soil). Increasing removal of Pb was found as the volume of water added was increased as the mass of NaCl in solution remained constant. The removal of Pb from the leachate was found to be 90%, 99.7%, and 35% with lime (25.20?g/L), sodium carbonate (4.48?g/L), and calcium carbonate (82.0?g/L) addition, respectively. In the case of sodium carbonate, the removal of Pb was further improved when the pH was adjusted to 8.2. The recycling of free chloride that was generated from leachate resulted in 91% removal of Pb from the soil (particle size < 4.75?mm) after six recycles.