Total Soil Pb Research Articles

Concentration of Lead in Soils and Some Vegetable Plants in North Nile Delta as affected by Soil Type and Irrigation Water

Soil pollution by lead (Pb) is of great concern because of its adverse effect to human health. This study was conducted in the north Nile Delta, Egypt, to investigate the influence of soil type and irrigation water on the total and ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB‐DTPA)–extractable Pb content of soils and growing vegetable plants. Eight soil profiles were selected from the three representative deposits existing in the area (i.e., fluvial, lacustrine, and marine). Three of them represent the three deposits, which were irrigated with fresh Nile water, whereas the other five represent those irrigated with mixed wastewater. Samples of soils, waters, and vegetable plants growing in the area were selected from the studied locations and analyzed for total [nitric acid (HNO3)–hydrochloric acid (HCl)–hydrogen peroxide (H2O2)–extractable] and available (AB‐DTPA‐extractable) Pb (soil samples), Pb concentration (water samples), and total Pb after digestion by using perchloric (HClO4)–sulfuric (H2SO4)–nitric (HNO3) acids (plant samples), respectively.The results of this study showed that the mean values of the total and available Pb differed significantly between the studied soils, the higher being in the lacustrine and lower in the marine soils. However, marine soils showed the highest values of Pb availability index. Irrigation with wastewater significantly increased the concentration of the total Pb in fluvial soils compared to those irrigated with Nile water. Total and available Pb concentrations were significantly correlated with clay, silt, organic matter, and equivalent calcium carbonate content, cation exchange capacity, and CBD‐extractable iron (Fe), aluminum (Al), and manganese (Mn) (positively) as well as with sand content and soil pH (negatively). Metal content in leaves was found to be higher than in fruits for the different plant species but lower than the upper permissible limits. Values of bioconcentration ratio and accumulation factor of Pb of the growing plants in marine soils were higher than those grown in fluvial and lacustrine soils.

Assessing Lead Thresholds for Phytotoxicity and Potential Dietary Toxicity in Selected Vegetable Crops

Lead tolerance and accumulation in shoots and edible parts varied with crop species and soil type. The critical Pb concentrations at 10% yield reduction were 24.71, 28.25, and 0.567 mg kg(-1) for pakchoi, celery, and hot pepper, respectively under hydroponic conditions, whereas were 13.1, 3.83, 0.734 mg kg(-1) grown in the Inceptisol and 31.7, 30.0, 0.854 mg kg(-1) in the Alluvial soil, respectively. Based on the threshold of human dietary toxicity for Pb, the critical levels of soil available Pb for pakchoi, celery, and hot pepper were 5.07, 8.06, and 0.48 mg kg(-1) for the Inceptisol, and 1.38, 1.47, and 0.162 mg kg(-1) for the Alluvial soil, respectively. Similarly, the total soil Pb thresholds were different from vegetable species and soil types.

Accumulation of Pb, Cu, and Zn in native plants growing on contaminated sites and their potential accumulation capacity in Heqing, Yunnan

Phytoremediation is one of the cost-effective and environmental friendly technologies used to remove contaminants from contaminated soils, which has been intensively studied during the last decade. Presently, few economical and effective remediation methods are available for the remediation of Pb contaminated sites. This study was conducted to assess the potential of 19 plants growing on contaminated sites in Pb mine area. Plants and associated soil samples were collected and analyzed for total metal concentrations. While total soil Pb, Cu and Zn concentrations varied from 1,239 to 4,311, 36 to 1,020 and 240 to 2,380 mg/kg, those in the plant shoots ranged from 6.3 to 2,029, 20 to 570, and 36 to 690 mg/kg, respectively. Among the plants, we found that one cultivated crop (Ricinus communis L.) and two native species (Tephrosia candida and Debregeasia orientalis) have a great potential for phytoremediation of Pb contaminated soils, the Pb hyperaccumulation capacity of the 3 plants was found as the order: R. communis > D. orientalis > T. candida in the investigated area.

The contribution of glomalin-related soil protein to Pb and Zn sequestration in polluted soil

The distribution of lead and zinc in glomalin-related soil protein (GRSP), a widespread glycoprotein presumably produced by arbuscular mycorrhizal fungi (AMF) in soil, and in some other soil fractions (soil organic matter — [SOM], carbonates, phosphates, etc.) was studied in soils from an area near a lead smelter that differed in SOM, carbonates and heavy metal (HM) content. Total GRSP represented 5.4–21.2% of the SOM and was positively correlated with the soil Pb and Zn concentrations ( r = 0.57 and 0.66, p = 0.007 and p = 0.001 for Pb and Zn, respectively). Pb and Zn were predominantly bound to carbonates and organic matter. The amount of lead bound to GRSP varied between 0.69 and 23.4 mg g − 1 DW GRSP which is 0.8–15.5% of the total soil Pb. The amount of GRSP-bound metal was positively correlated with the total concentration in the case of Pb ( r = 0.90, p = 0.000) but the opposite was found for Zn ( r = − 0.41, p = 0.048), indicating that GRSP predominantly binds Pb. The percentages of HM-GRSP in HM-SOM were variable and were not correlated with SOM content.

Bioaccessibility of lead in high carbonate soils

Metal bioaccessibility is not currently considered in the French human health risk assessment procedure. For contaminants such as Pb this parameter could have a significant effect on the risk calculation. From the literature, it seems that Pb bioaccessibility is strongly controlled by the occurrence of cerrussite in soils: with a high cerussite content showing a positive correlation with high Pb bioaccessibility. Assuming this hypothesis, Pb contained in carbonated soils could show strong human bioaccessibility. This study aims to examine the link between high carbonate soil minerals, focussing particularly on cerrussite and the Pb bioaccessibility. Four soils were sampled in a high carbonate area in France contaminated with Pb due to mining activities. Pb bioaccessibility was measured using the in vitro RIVM protocol. In parallel, the solid phase Pb distribution was determined using chemical sequential extraction for each sample and physical analysis on the more contaminated sample. Results showed that Pb bioaccessibility was significantly different among soil samples. As shown in literature, cerussite (PbCO3) was a highly bioaccessible phase and 40% of Pb in the waste material was present in this form. However, cerussite alone did not account for all of the Pb which was also present in highly stable minerals containing sulphur. Pb associated to these minerals is also likely to be significantly bioaccessible. Indeed, sequential extraction showed that most of the Pb was associated with the sulphur-compartment. This study shows that Pb bioaccessibility in high carbonate soils can be low (down to 20% of the total soil Pb content) and is not correlated with cerussite soil contents even if the concentration of this mineral is relatively high. Consequently, risk management of Pb contamination should not focus only on high carbonate soils but also on Pb contained in other minerals which is also likely to be significantly bioaccessible.

Relationship of soil properties to fractionation, bioavailability and mobility of lead and zinc in soil

Sequential extractions, metal uptake by <i>Taraxacum officinale</i>, Ruby’s physiologically based extraction test (PBET) and toxicity characteristic leaching procedure (TCLP), were used to assess the risk of Pb and Zn in contaminated soils, and to determine relationships among soil characteristics, heavy metals soil fractionation, bioavailability and leachability. Regression analysis using linear and 2nd order polynomial models indicated relationships between Pb and Zn contamination and soil properties, although of small significance (<i>P</i> < 0.05). Statistically highly significant correlations (<i>P</i> < 0.001) were obtained using multiple regression analysis. A correlation between soil cation exchange capacity (CEC) and soil organic matter and clay content was expected. The proportion of Pb in the PBET intestinal phase correlated with total soil Pb and Pb bound to soil oxides and the organic matter fraction. The leachable Pb, extracted with TCLP, correlated with the Pb bound to carbonates and soil organic matter content (<i>R</i><sup>2</sup> = 69%). No highly significant correlations (<i>P</i> < 0.001) for Zn with soil properties or Zn fractionation were obtained using multiple regression.

Dispersion of Heavy Metals (Metalloids) in Soils from 800-Year-Old Pollution (Mont-Lozère, France)

Numerous palaeo metallurgical sites (n = 70) characterized by slag presenting a homogeneous typology have been reported on the Mont-Lozère Massif (Southern France). These activities took place in the medieval period. The silicated slag matrix comprises mainly Pb (25%), Sb (0.4%), and several thousand parts per million of As, Cu, and Zn. Soil samples were collected in and around two sites, to understand the dispersion mechanism affecting the slag tailings through use of metal concentrations and lead isotopic compositions. The majority of polluted soil samples show high enrichment factors (EF) for Pb and Sb, slightly lower EFs for Cu, and much lower EFs for As and Zn. We show that this "old" metal pollution was physically dispersed, through erosion of workshop soils and slag tailings, in a restricted area (ca. 200 m down slope form the site). There is no evidence for massive leaching of slag metals by soil waters, except for Zn. Thus, the pollution is mainly due to the metal-making process, i.e., smoke-fallout, pieces of ore, the crackling of smelting ore outside the oven during reduction, and charcoal, etc. The lead isotopic compositions of the soils define a binary mixing trend between local granite or background soil and slag (which represent the workshop soil). Simple mass balance equations using either Pb isotopes or Pb concentrations suggest that between 40 and 100% of the total Pb in soils comes from the Medieval workshop pollution, leaving any later pollution negligible. The large number of sites on the Mont-Lozère means this medieval pollution is significant and poses a real environmental risk.

Accumulation of Pb, Cu, and Zn in native plants growing on a contaminated Florida site

Contamination of heavy metals represents one of the most pressing threats to water and soil resources as well as human health. Phytoremediation can be potentially used to remediate metal-contaminated sites. This study evaluated the potential of 36plants (17species) growing on a contaminated site in North Florida. Plants and the associated soil samples were collected and analyzed for total metal concentrations. While total soil Pb, Cu, and Zn concentrations varied from 90 to 4100, 20 to 990, and 195 to 2200mg kg−1, those in the plants ranged from 2.0 to 1183, 6.0 to 460, and 17 to 598mg kg−1, respectively. None of the plants were suitable for phytoextraction because no hyperaccumulator was identified. However, plants with a high bioconcentration factor (BCF, metal concentration ratio of plant roots to soil) and low translocation factor (TF, metal concentration ratio of plant shoots to roots) have the potential for phytostabilization. Among the plants, Phyla nodiflora was the most efficient in accumulating Cu and Zn in its shoots (TF=12 and 6.3) while Gentiana pennelliana was most suitable for phytostabilization of sites contaminated with Pb, Cu and Zn (BCF=11, 22 and 2.6). Plant uptake of the three metals was highly correlated, whereas translocation of Pb was negatively correlated with Cu and Zn though translocation of Cu and Zn were correlated. Our study showed that native plant species growing on contaminated sites may have the potential for phytoremediation.

Nondestructive pollution exposure assessment in the european hedgehog (Erinaceus europaeus): I. Relationships between concentrations of metals and arsenic in hair, spines, and soil

Conventional metal exposure assessment in terrestrial mammals is generally based on organ analyses of sacrificed animals. Few studies on mammals use nondestructive methodologies despite the growing ethical concern over the use of destructive sampling. Nondestructive methods involve minimal stress to populations and permit successive biomonitoring of the same populations and individuals. In the present study we assessed metal exposure of hedgehogs (Erinaceus europaeus) by investigating relationships between concentrations of metals (Ag, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) and As in soil samples and in hair and spines of hedgehogs. Samples were collected in seven study sites along a metal pollution gradient, characterized by decreasing total soil Ag, As, Cd, Cu, Ni, and Pb concentrations with increasing distance from a nonferrous metallurgic factory. For a number of elements, soil contamination was related both to distance to the smelter and to habitat. Soil concentrations were positively related to levels in hair and spines for Ag, As, Cd, and Pb and thus to hedgehog exposure. Metal concentrations in soil did not relate to metal concentrations in hair and spines for essential elements (e.g., Cu, Fe, Mn, Ni, and Zn), except Co in hair and soil. Our results demonstrate that, at least for nonessential elements, concentrations in soils can be used to predict contamination of these elements in hedgehogs or vice versa. Furthermore, hedgehog exposure increased toward the smelter and was higher for hedgehogs foraging in grasslands than for animals foraging in the forest. Moreover, we believe that hair and spines are promising tools in terrestrial wildlife exposure assessment studies of metals and As.

Colonisation of a Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen with indigenous arbuscular mycorrhizal fungal mixture induces changes in heavy metal and nutrient uptake

Plants of the Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen (Brassicaceae) inoculated or not with indigenous arbuscular mycorrhizal (AM) fungal mixture were grown in a highly Cd, Zn and Pb contaminated substrate in order to evaluate the functionality of symbiosis and assess the possible impact of AM colonisation on heavy metal uptake and tolerance. The results suggest AM development in the metal hyperaccumulating T. praecox is favoured at elevated nutrient demands, e.g. during the reproductive period. AM colonisation parameters positively correlated with total soil Cd and Pb. Colonised plants showed significantly improved nutrient and a decreased Cd and Zn uptake as revealed by TRXRF, thus confirming the functionality of the symbiosis. Reduced heavy metal uptake, especially at higher soil metal contents, indicates a changed metal tolerance strategy in colonised T. praecox plants. This is to our knowledge the first report on AM colonisation of the Zn, Cd and Pb hyperaccumulator T. praecox in a greenhouse experiment.

Assessment of lead availability in contaminated soil using isotope dilution techniques

Isotope dilution methods using a stable isotope tracer ( 207Pb) were developed for the determination of Pb availability in contaminated soils. The methods included determination of E values (isotopically exchangeable pool), L values (plant labile pool) and isotopic exchange kinetics (IEK). Isotopically exchangeable Pb was monitored at different exchange times based on measurement of the 207Pb/ 208Pb ratio in soil solution following addition of the tracer. The rate of decrease in the 207Pb/ 208Pb ratio in solution could be described by using the same IEK equation as used previously with radioisotope tracers. The amounts of isotopically exchangeable Pb in Pb-contaminated soils estimated from long-term IEK parameters were in good agreement with directly determined E values up to 15 days. However, values of some of the fitted IEK parameters cast doubts on the validity of using the IEK approach with 207Pb, most probably as a result of irreversible fixation of some of the spike by reactive surfaces in the soils. Estimation of isotopically exchangeable Pb using short-term kinetics data was unsuccessful, substantially underestimating E values. Results for the control (uncontaminated) soil were highly variable, most probably as a result of fixation of tracer by the soil and poor analytical precision due to low solution Pb concentrations. A compartmental analysis of the variation in E values with time indicates a good potential for estimating bioavailable Pb in contaminated soils. The amounts of available Pb obtained from summation of the E 1 min and E 1 min–24 h pools ( E (available)), accounting for an average of 57.62% of total soil Pb, were significantly correlated with both the L values and with Pb extracted from soil with EDTA.

Biosolids compost amendment for reducing soil lead hazards: a pilot study of Orgro® amendment and grass seeding in urban yards

In situ inactivation of soil Pb is an alternative to soil removal and replacement that has been demonstrated in recent years at industrial sites with hazardous soil Pb concentrations. Most children exposed to elevated soil Pb, however, reside in urban areas, and no government programs exist to remediate such soils unless an industrial source caused the contamination. Modern regulated biosolids composts have low Pb concentrations and low bioaccessible Pb fractions and can improve grass growth on urban soils. High Fe and P biosolids composts can reduce the bioavailability and bioaccessibility of soil Pb and can aid in establishing vegetation that would reduce soil transfer into homes. For these reasons, we conducted a field test of their use to reduce Pb bioaccessibility in urban soils in Baltimore, MD USA. We chose biosolids compost for its expected reduction in the bioaccessible Pb fraction of urban soils, ease of use by urban residents, and ability to beautify urban areas. Nine urban yards with mean soil Pb concentrations >800 mg Pb kg −1 were selected and sampled at several distances from the house foundation before soil treatment. The soils were rototilled to 20 cm depth to prepare the sites, and resampled. The yards were then amended with 6–8 cm depth of Orgro® biosolids compost (110–180 dry t/ha) rich in Fe and P, mixed well by rototilling, and resampled. Kentucky bluegrass ( Poa pratensis) was seeded and became well established. Soils were resampled 1 year later. At each sampling time, total soil Pb was measured using a modified U.S. EPA nitric acid hotplate digestion method (SW 846 Method 3050) and bioaccessible Pb fraction was measured using the Solubility/Bioaccesibility Research Consortium standard operating procedure with modifications, including the use of glycine-buffered HCl at pH 2.2. Samples of untreated soils were collected from each yard and mixed well to serve as controls for the Pb bioaccessibility of field treated soils over time independent of positional variance within yards. At 1-year post-treatment, grass cover was healthy and reductions in bioaccessible Pb concentrations compared to pre-tillage were 64% (from 1655 to 595 mg kg −1) and 67% (from 1381 to 453 mg kg −1) at the sampling lines closest to the houses. Little or no reduction in bioaccessible Pb concentration was observed at sampling lines more remote from the house that also had the lowest bioaccessible Pb concentrations at pre-tillage (620 and 436 mg kg −1, respectively). For the control soils, changes over time in total Pb and bioaccessible Pb concentrations and the bioaccessible Pb fraction were insignificant. This study confirms the viability of in situ remediation of soils in urban areas where children are at risk of high Pb exposure from lead in paint, dust and soil.

Factors affecting the concentrations of lead in British wheat and barley grain

The entry of Pb into the food chain is of concern as it can cause chronic health problems. The concentration of Pb was determined in cereal grain samples collected representatively from British Cereal Quality Surveys in 1982 and 1998 ( n=176, 250 and 233 for wheat collected in 1982 and 1998, and barley in 1998, respectively). In addition, paired soil and grain samples were collected from 377 sites harvested across Britain in 1998–2000. Wheat grain Pb ranged from below the analytical detection limit (0.02 mg kg −1 dry weight, DW) to 1.63 mg kg −1 DW, and barley grain Pb from <0.02 to 0.48 mg kg −1 DW. The vast majority of samples (>99% for both wheat and barley, excluding Scottish barley samples collected in 2000) were well below the newly introduced EU limit for the maximum permissible concentration of Pb in cereals (0.2 mg kg −1 fresh weight, equivalent to 0.235 mg kg −1 DW). There was a significant reduction in wheat grain Pb in the 1998 survey compared with the 1982 survey. However, 40 barley samples collected from Scotland in 2000 in the paired soil and crop survey showed anomalously high concentrations of Pb, with 10 samples exceeding the EU limit. Washing experiments demonstrated that surface contamination, introduced during grain harvest and/or storage, was the main reason for the high concentrations in these samples. In the paired soil and crop surveys, there were no significant correlations between grain Pb concentrations with total soil Pb and other soil properties, indicating low bioavailability of Pb in the soils and limited uptake and transport of Pb to grain. The Pb in cereal grain is likely to originate mainly from atmospheric deposition and other routes of surface contamination during harvest and storage.

Factors affecting the concentrations of lead in British wheat and barley grain

The entry of Pb into the food chain is of concern as it can cause chronic health problems. The concentration of Pb was determined in cereal grain samples collected representatively from British Cereal Quality Surveys in 1982 and 1998 ( n =176, 250 and 233 for wheat collected in 1982 and 1998, and barley in 1998, respectively). In addition, paired soil and grain samples were collected from 377 sites harvested across Britain in 1998–2000. Wheat grain Pb ranged from below the analytical detection limit (0.02 mg kg −1 dry weight, DW) to 1.63 mg kg −1 DW, and barley grain Pb from <0.02 to 0.48 mg kg −1 DW. The vast majority of samples (>99% for both wheat and barley, excluding Scottish barley samples collected in 2000) were well below the newly introduced EU limit for the maximum permissible concentration of Pb in cereals (0.2 mg kg −1 fresh weight, equivalent to 0.235 mg kg −1 DW). There was a significant reduction in wheat grain Pb in the 1998 survey compared with the 1982 survey. However, 40 barley samples collected from Scotland in 2000 in the paired soil and crop survey showed anomalously high concentrations of Pb, with 10 samples exceeding the EU limit. Washing experiments demonstrated that surface contamination, introduced during grain harvest and/or storage, was the main reason for the high concentrations in these samples. In the paired soil and crop surveys, there were no significant correlations between grain Pb concentrations with total soil Pb and other soil properties, indicating low bioavailability of Pb in the soils and limited uptake and transport of Pb to grain. The Pb in cereal grain is likely to originate mainly from atmospheric deposition and other routes of surface contamination during harvest and storage.

The Soil Mineralogy of Lead at Horace's Villa

Lead pipe buried by calcareous alluvium at Horace's Villa near Licenza, Italy, for more than a millennium were excavated, along with soil from around and within the lead pipe, to identify the stable corrosion products and Pb‐bearing soil minerals. The corrosion crust of the pipe, soil from inside the pipe, and soil from around the pipe were characterized by chemical means and by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X‐ray analysis (EDX). The chemical and thermal conditions necessary to produce the identified Pb mineral assemblage was investigated through the development of activity and predominance diagrams. Analysis of total soil Pb concentrations indicates that the lateral movement of Pb from the pipe in the pH &gt;8 soil has exceeded 9 cm. However, background soil Pb concentrations are observed at a lateral distance of 50 cm. The corrosion crust of the lead pipe is composed of litharge [α–PbO(s)], cerussite [PbCO3(s)], and hydrocerussite [Pb3(CO3)2(OH)2(s)]. Similarly, soil inside the pipe and in the 0‐ to 1‐cm zone around the pipe contains cerussite and hydrocerussite. A detailed thermochemical analysis indicates that the formation of hydrocerussite is favored, relative to cerussite, when the CO2 partial pressure is approximately atmospheric (10−3.5 atm or 10−4.5 MPa) or less, or when the soil temperature is approximately 25°C or greater. The formation of stable lead phosphates has not occurred in these alkaline environments, even though apatite is present and thermochemical analysis predicts the formation of chloropyromorphite [Pb5(PO4)3Cl(s)]. If chloropyromorphite is removed from consideration, hydroxypyromorphite [Pb5(PO4)3OH(s)] is not predicted to form in the presence of apatite.

The Soil Mineralogy of Lead at Horace's Villa

Lead pipe buried by calcareous alluvium at Horace's Villa near Licenza, Italy, for more than a millennium were excavated, along with soil from around and within the lead pipe, to identify the stable corrosion products and Pb-bearing soil minerals. The corrosion crust of the pipe, soil from inside the pipe, and soil from around the pipe were characterized by chemical means and by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The chemical and thermal conditions necessary to produce the identified Pb mineral assemblage was investigated through the development of activity and predominance diagrams. Analysis of total soil Pb concentrations indicates that the lateral movement of Pb from the pipe in the pH >8 soil has exceeded 9 cm. However, background soil Pb concentrations are observed at a lateral distance of 50 cm. The corrosion crust of the lead pipe is composed of litharge [α–PbO(s)], cerussite [PbCO3(s)], and hydrocerussite [Pb3(CO3)2(OH)2(s)]. Similarly, soil inside the pipe and in the 0- to 1-cm zone around the pipe contains cerussite and hydrocerussite. A detailed thermochemical analysis indicates that the formation of hydrocerussite is favored, relative to cerussite, when the CO2 partial pressure is approximately atmospheric (10−3.5 atm or 10−4.5 MPa) or less, or when the soil temperature is approximately 25°C or greater. The formation of stable lead phosphates has not occurred in these alkaline environments, even though apatite is present and thermochemical analysis predicts the formation of chloropyromorphite [Pb5(PO4)3Cl(s)]. If chloropyromorphite is removed from consideration, hydroxypyromorphite [Pb5(PO4)3OH(s)] is not predicted to form in the presence of apatite.

The effect of lead-contaminated soil from Canadian prairie skeet ranges on the neutral red retention assay and fecundity in the earthworm Eisenia fetida.

The sublethal effects of lead (Pb) on the earthworm Eisenia fetida were evaluated in the laboratory using freshly spiked soil and soil collected from Canadian prairie skeet ranges. After a four-week exposure to soil spiked with lead acetate, earthworm neutral red retention time (NRRT). soil Pb concentrations, and earthworm Pb body burdens were measured. Lysosomal NRRT was reduced in a concentration-dependent manner (p < 0.0001), and NRRT was negatively correlated with earthworm Pb body burdens (r = -0.80, p < 0.0001). To evaluate the effects of aged Pb, earthworms were exposed to soil from three skeet ranges, and responses were compared with three matched reference sites. After a four-week exposure, NRRT, growth, fecundity, soil total Pb levels, and earthworm Pb body burdens were measured. The potentially bioavailable fraction of Pb in these sites was measured using a Ca(NO3)2 extraction. Growth and fecundity did not differ significantly between any of the skeet ranges and their reference sites. However, NRRT was significantly reduced in all three ranges compared with their respective reference sites (p < 0.05), indicating that the neutral red retention assay (NRRA) may be useful for detecting toxicity and potential hazards at Pb-contaminated sites. Lysosomal NRRT was negatively correlated with soil Ca(NO3)2-extractable Pb (r = -0.80, p < 0.0001) and soil total Pb (r = -0.73, p = 0.001). Lysosomal NRRT was negatively correlated (r = -0.67, p < 0.002) with earthworm Pb tissue levels.

Using stable and radioactive isotopes to trace atmospherically deposited Pb in montane forest soils.

Atmospheric deposition of lead (Pb) throughout the 1900s resulted in elevated amounts of this toxic metal even in remote forest soils of the northeastern United States. Soils can act as a net sink for metals and thus minimize groundwater and surface water contamination. Recent studies utilizing forest floor temporal data and models of total Pb in precipitation, surface soils, and streams have estimated the time scale of Pb release from soils. However, due to the limited availability and spatial variability of forest floor survey data, other methods for quantifying anthropogenic Pb movement are needed. This study uses the isotopic composition (206Pb/207Pb) of soil Pb and measurements of 210Pb and 226Ra to directly trace the transit of atmospherically deposited Pb in the soil profile. We also report on the recovery of an enriched 207Pb dose applied in 1984 to the surface of a soil plot in the coniferous forest at Camels Hump in Vermont. The isotopic composition of soil Pb in low elevation deciduous forests suggests that approximately 65% of the original atmospheric Pb load has migrated from the forest floor to the upper 10 cm of the mineral soil. Higher elevation sites with coniferous vegetation have thicker forest floors, which have prevented significant amounts of Pb from entering the mineral soil. After 17 years, the soil organic horizon in the coniferous zone prevented any penetration of the applied Pb into the mineral soil. Using 210Pb budgets in different soil compartments, we determine forest floor response times for atmospherically delivered Pb to be approximately 60 years in the low elevation deciduous forest zone and 150 years for the high elevation spruce-fir forest zone at Camels Hump. According to its distribution in the soil profile, we conclude that a dispersed release of anthropogenic Pb to groundwater and surface water is possible this century. Our results also offer independent confirmation of Pb deposition models previously generated for the region.

Relationship of Soil Properties to Fractionation of Pb and Zn in Soil and Their Uptake into Plantago lanceolata

Soil samples (0 to 5 cm) from 30 locations in the Celje region, Slovenia, an area that has been subjected to severe industrial emissions of Pb and Zn, were analyzed for selected soil properties and subjected to a six-step sequential extraction of Pb and Zn. Phyto-available forms of heavy metals: soluble in soil solution and exchangeable from soil colloids to soil solution together accounted for 0 to 1.68% of Pb and 0 to 40.8% of total soil Zn. Most of the Pb and Zn was found to reside in less labile forms bound to carbonate (2.04 to 43.5% Pb, 3.9 to 35.1% Zn), bound to Fe and Mn oxides (0 to 16.1% Pb, 1.4 to 25.4% Zn), bound to organic matter (35.8 to 71.1% Pb, 14.8 to 56.2% Zn), and in the residual fraction (10.4 to 53.4% Pb, 14.2 to 75.3% Zn). Factor analysis and stepwise multiple regression revealed that the concentration of Pb in the proposed indicator plant, narrow leaf plantain (Plantago lanceolata) did not correlate with the measured soil properties, Pb fractionation in soil, and total soil Pb. Plant uptake of Zn, however, significantly correlated with soil pH and with the share of phyto-available forms of Zn in the soil (R2 = 86.9). A statistically significant correlation (P<0.01) was found between the fractions of Pb and Zn carbonates and soil organic matter content (R2 = 90.6 and 90.9, respectively); the fraction of Pb bound to organic matter and soil organic matter content (R2 = 90.6); the residual fraction of Pb and total Pb content in soil (R2 = 95.7); the fraction of Zn bound to Fe an Mn oxides, the fraction of Zn bound to organic matter, the residual fraction of Zn and total Zn content in soil (R2 = 75.9, 93.2, and 87.4, respectively). Soil texture, pH, and cation exchange capacity did not affect the relative proportions of Pb and Zn forms in soil.

Lead transformation and distribution in the soils of shooting ranges in Florida, USA

The use of lead bullets and shot at shooting ranges is under increasing scrutiny as a potentially significant source of Pb pollution. This study assessed Pb contamination in the soils of two shooting ranges (TRR and MPR) in Florida. Soil samples were collected from the two ranges and analyzed for total Pb to determine Pb contamination. Selected spent bullets and berm soil samples were mineralogically characterized to identify Pb transformation. Total Pb in the range soils was significantly elevated with the highest (up to 4.84% by weight) in the berm soils. Most soils failed the synthetic precipitation leaching procedure (SPLP) test. Also, at the MPR shooting range, a substantial amount of Pb migrated down in the subsurface soil, possibly due to the enhanced solubilization of organic Pb complexes at alkaline pH, whereas high cation exchange capacity of the profile soil may be responsible for Pb retention in the subsoil. The weathering products on the surface of the spent bullets were predominantly hydrocerussite [Pb 3(CO 3) 2(OH) 2] and cerussite (PbCO 3). Hydrocerussite was mainly found in the MPR range soils, whereas Pb was transformed into hydroxypyromorphite [Pb 5(PO 4) 3OH] in the TRR range soils because of the presence of more P. Sequential extraction and lead activity ratio modeling showed that the soil Pb solubility was controlled by Pb carbonate minerals in the MPR shooting range, and by less soluble Pb phosphate minerals in the TRR shooting range. This research suggests that it is important to develop and implement efficient management practices to minimize adverse impacts of Pb at shooting ranges. Phosphate-induced Pb immobilization may be an effective alternative for reducing Pb mobility in the shooting range soils.