Μg Pb Research Articles

Spatial and chemical patterns of PM 10 in road dust deposited in urban environment

Recent research interest has been focused on road dust resuspension as one of the major sources of atmospheric particulate matter in an urban environment. Given the dearth of studies on the variability of the PM 10 fraction of road deposited sediments, our understanding of the main factors controlling this pollutant is incomplete. In the present study a new sampling methodology was devised and applied to collect PM 10 deposited mass from 1 m 2 of road pavement. PM 10 road dust fraction was sampled directly from active traffic lanes at 23 sampling sites during a campaign in Barcelona (Spain) in June 2007. The aim of the study was to gain more insight into the variability of mass and chemistry of road dust in different urban environments, such as the city centre, ring roads, and locations nearby demolition/construction sites. The city centre showed values of PM 10 road dust within a range of 3–23 mg m −2, whereas levels reached 24–80 mg m −2 in locations affected by transport of uncovered heavy trucks. The largest dust loads were measured in the proximity of demolition/construction sites and the harbor entry with values up to 328 mg m −2. The city centre road dust profiles (%) were enriched in OC, EC, Fe, S, Cu, Zn, Mn, Cr, Sb, Sn, Mo, Zr, Hf, Ge, Ba, Pb, Bi, SO 4 2−, NO 3 −, Cl − and NH 4 +, but several crustal components such as Ca, Ti, Na, and Mg were also considerably concentrated. Locations affected by construction and demolition activities had high levels of crustal components such as Ca, Li, Sc, Sr, Rb and also As whereas ring roads, characterized by a higher load of uncovered heavy trucks showed an intermediate composition. Levels of PM 10 components per area were also evaluated to quantify the resuspendable amount of each element from 1 m 2. In the inner city environment mean values of 1363 μg Ca m −2, 816 μg OC m −2, 239 μg EC m −2, 13 μg Cu m −2, 12 μg Zn m −2, 1.9 μg Sb m −2 and 2.0 μg Pb m −2, in PM 10 in all cases, were registered. Moreover the deposited PM load at demolition/construction sites acts as a reservoir or trap for traffic-related particles, which gives rise to large amounts of hazardous pollutants, available for resuspension.

Toxicokinetic models as predictive tools in biomonitoring metals in zooplankton: a synthesis of ideas

The objective of the present study was to evaluate previously reported compartment models as a predictive tool, in particular, to investigate the potential of nonlinear predictions in case of saturation of the uptake process. Examples supporting this idea are presented for the amphipods Gammarus oceanicus from northern Norway and Themisto abyssorum from the Greenland Sea as well as for the copepod Calanoides acutus from the Weddell Sea. A further objective was to investigate verification of model parameters with independent experimental observations, aided by the statistical analysis of the results. This can be regarded as a first step toward a meta-analysis. While modeling results obtained for T. abyssorum in 1993 underestimated observed uptake of Pb and Cu in independent experiments (1999) in the same species, a good agreement was encountered between models obtained for T. abyssorum in 1993 and experimental data obtained for Themisto libellula (1999). Furthermore, a fairly good agreement was found between modeling results obtained for Pb in Calanus hyperboreus from the Greenland Sea (1993) and experimental data obtained for C. acutus (1999). Therefore, the biological species cannot be regarded as a “natural” unit in biomonitoring studies without further evaluation (viz. calibration as biomonitor), while even samples of animals belonging to different species may serve as such a unit, allowing for a comparison of bioaccumulation on large temporal and spatial scales. Finally, the concept of the sensitivity of zooplankton organisms for biomonitoring was elaborated in detail. These procedures involve analytical and experimental variability and model simulations based on previously derived parameters of compartment models. The minimal increments in exposure concentrations estimated in this way were 0.4–1.2 μg Pb l−1 for T. abyssorum, T. libellula, C. hyperboreus, and C. acutus. Corresponding results for Cu varied to a greater extent: 4–9 μg l−1 for the amphipods and 1–5 μg l−1 for the copepods. A correction of these values is proposed, taking into account the ratios of experimental (kinetic) and field bioconcentration factors; this yields exposure concentrations close to those reported for natural seawater.

In situ heavy metals (copper, lead and cadmium) in different plankton compartments and suspended particulate matter in two coupled Mediterranean coastal ecosystems (Toulon Bay, France)

We monitored the concentrations of copper, lead and cadmium in seawater, in suspended particulate matter (SPM) and in bacteria, phyto- and zooplankton communities separated from abiogenic particles, over a one year cycle in two coupled Mediterranean coastal ecosystems (Little Bay (LiB) and Large Bay (LaB)). Metals were present in seawater in the order Cu > Pb > Cd in both bays and showed important variations within the same month than among months. In LiB, their concentrations were between 0.62 and 2.82 μg Cu l −1, 0.16 and 19 μg Pb l −1 and 0.007 and 0.14 μg Cd l −1, respectively, whereas in LaB, they were between 0.23 and 2.11 μg Cu l −1, 0.09 and 0.76 μg Pb l −1 and not detected and 0.65 μg Cd l −1. SPM play an important role on metal adsorption, especially for copper. Bioaccumulation factors showed that bacteria and phytoplankton accumulate metals whereas zooplankton tends to biodiminish them in the plankton food web.

Bioaccumulation of trace metals in the brown shrimp Crangon crangon (Linnaeus, 1758) from the German Wadden Sea

The objective of the present study is to evaluate the suitability of the brown shrimp Crangon crangon (Linnaeus, 1758) from the German Wadden Sea as a biomonitor for the trace metals Cd, Pb, Cu, and Zn and to analyse whether the two-compartment model sensu OECD could be used as a predictive tool to assess environmental quality. The tested decapods accumulated Cd and Pb upon exposure and it was possible to estimate significant model parameters of two-compartment models, while they did not respond to waterborn Cu and Zn. Kinetic BCFs at theoretical equilibrium were 860 for Cd and 750 for Pb. A tentative estimation showed the following sensitivity of C. crangon to an increase of soluble metal exposure: 0.4 μg Cd l −1 and 0.9 μg Pb l −1. Available information can be used to quantify a measure of agreement or disagreement between bioaccumulation in various decapods. This can be regarded as an important step in the calibration of biomonitors, which is necessary to assess the potential for bioaccumulation on different temporal and geographical scales.

Toxic heavy metal biosorption by some marine bacteria isolated from the sediments of industrial effluents of Iligan Bay

Heavy metal-resistant marine bacteria were isolated from the sediments of Iligan Bay near the effluents outlets of certain factories. Isolation was done using marine agar fortified with corresponding different heavy metal concentrations. Isolates were grouped using their morphological and colonial growth characteristics. Among the purified isolates(61), 19 were cadmium-resistant, 29 were lead-resistant and 13 were mercury-resistant. These isolates were tested for their absorptive capability using marine broth added with metal ions: 23.20 µg of Cd, 250.24 µg of Pb and 495.66 µg of Hg, and consequently analyzed using Atomic Absorption Spectrophotometric(AAS) method. From these isolates, 10 heavy metal-resistant species with relatively high absorptive efficiency were identified using conventional method and API 20E Test Kit. Out of ten isolates, 3 were Gram-positive and 7 were Gram-negative rods. All Gram-positive bacteria belong to the genus Bacillus and were found to absorb lead metals at 94% absorptive efficiency. However, Enterobacter sp. 2 had the highest absorptive efficiency for Cd at 99% among Gram negative bacteria followed by Chryseomonas sp. 2 with 96% biosorption. Furthermore, among the mercury resistant isolates, Pseudomonas sp. had the highest absorptive efficiency at 79%. Only those heavy metal-resistant isolates which exhibited the highest absorptive efficiency were able to form a zone of growth promotion around a heavy metal-containing filter paper disk which suggests that these bacteria have accumulated heavy metals in their cells. The presence of heavy metal-resistant bacteria is helpful in cleaning up or remediating metal contaminated environments released from industrial effluents.

Speciation analysis of mercury and lead in fish samples using liquid chromatography–inductively coupled plasma mass spectrometry

A liquid chromatography–inductively coupled plasma mass spectrometric (LC–ICP-MS) method for lead and mercury speciation analysis was described. Sample containing ionic lead and mercury compounds was subjected to liquid chromatographic separation before injection into the direct injection high efficiency nebulizer (DIHEN, 170-AA). The species studied include inorganic lead (Pb(II)), trimethyl lead (trimethyl-Pb), triethyl lead (triethyl-Pb), inorganic mercury (Hg(II)), methyl mercury (methyl-Hg) and ethyl mercury (ethyl-Hg), which were well separated by reversed-phase liquid chromatography with a C18 column as the stationary phase and a pH 2.8 solution of 0.2% (v/v) 2-mercaptoethanol, 1 mg L −1 ETDA, 174.2 mg L −1 sodium 1-pentanesulfonate and 12% (v/v) methanol as the mobile phase. The lead and mercury species in biological tissues were quantitatively extracted, into 10 g L −1 EDTA and 0.2% (v/v) 2-mercaptoethanol solution taken in a closed centrifuge tube and kept on water bath, using microwaves at 65 °C for 2 min. The spike recovery of individual lead and mercury species determined by spiking the samples with suitable concentration of lead and mercury mixture standard were between 93% and 99%. The detection limits of the species studied were in the range 0.1–0.3 μg Pb L −1 and 0.2–0.3 μg Hg L −1. The procedure has been applied for the speciation analysis of two reference samples namely NRCC DOLT-3 Dogfish Liver and DORM-2 Dogfish Muscle and a swordfish sample obtained locally. The sum of the concentrations of individual species has been compared with the certified values for total lead and mercury to verify the accuracy of the method. The precision between sample replicates was better than 10% with LC–DIHEN-ICP-MS method.

A liquid-scintillation-based primary standardization of 210Pb

A new radioactivity solution standard of 210Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new 210Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133±0.002) g of a nominal 1 mol L −1 nitric acid solution, has a density of (1.028±0.002) g mL −1 at 20 °C, has carrier ion concentrations of about 11 μg Pb 2+ and 21 μg Bi 3+ per gram of solution, and is certified to contain a massic activity (9.037±0.22) kBq g −1 as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the 210Pb content of the solution was based on 4 παβ liquid scintillation (LS) measurements using CIEMAT/NIST 3H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe γ-ray spectrometry, by 2 πα spectrometry with a Si surface barrier detector of separated 210Po, and by 4 πβ(LS)– γ(NaI) anticoincidence counting.

Contaminants in organically and conventionally produced winter wheat ( Triticum aestivum ) in Belgium

A database has been compiled with the levels of important contaminants (mycotoxins, heavy metals and pesticides) measured from 2002 to 2005 in winter wheat (Triticum aestivum) grown in Belgium according to the organic and conventional farming systems. Assuming no further change in contaminant levels during cereal processing and during the preparation of foodstuffs, conservative intakes are estimated for the consumers of cereal-based products such as flour, bread, breakfast cereals, dough and pastry. The results show that for the consumer of organic foodstuffs, estimated daily intakes are 0.56 µg deoxynivalenol (DON), 0.03 µg zearalenone (ZEA), 0.19 µg Cd, 0.28 µg Pb and 0.0006 µg Hg kg−1 body weight, taking into account the average contaminant levels in unprocessed grains and the average cereal products consumptions in Belgium. For the consumers of conventional foodstuffs, the corresponding estimated daily intakes are 0.99 µg DON, 0.06 µg ZEA, 0.17 µg Cd, 0.12 µg Pb and 0.0007 µg Hg kg−1 body weight. In addition, it appears that for the consumers of conventional products, intakes of some post-harvest insecticides have to be taken into account (0.11 µg chlorpyriphos-methyl, 0.2 µg dichlorvos and 0.24 µg pirimiphos-methyl kg−1 bw). When expressed as a percentage of the tolerable/acceptable daily intake (TDI/ADI), it seems that the corresponding estimated (conservative) intakes are the highest for DON (56% for organic and 99% for conventional cereal products), ZEA (16% for organic and 32% for conventional cereal products), and Cd (19% for organic and 17% for conventional cereal products), all other estimated intakes of contaminants (including pesticides) being lower than 10% of the TDI/ADI.

Investigation of Pb(ii) binding to pectin in Arabidopsis thaliana

Phytochelatins and glutathione are known as the most common peptides responsible for binding with toxic metals in plants, but recently the role of other bioligands, such as proteins, organic acids, flavonoids and oligosaccharides, has received renewed attention. Size-exclusion chromatography (SEC) coupled to ICP-MS and electrospray MS were applied for the analysis of lead species synthesised by Arabidopsis thaliana, a model genetic plant. Lead was found to be accumulated mainly in roots (9.6 ± 0.1 μg of Pb per g of the dry mass) and showed good affinity to galacturonic acid, the main component of two pectin domains homogalacturonan and rhamnogalacturonan I. The results demonstrate the potential application of SEC-ICP-MS and SEC-ESI-MS as a complementary and efficient approach to study toxic heavy metals in biological systems.

Minimally-invasive filter paper test in combination with solid sampling-graphite furnace atomic absorption spectrometry for Pb determination in whole blood

This work describes a simple procedure for the determination of blood lead levels in dried-spot filter paper specimens. The method permits the minimally-invasive collection of blood on filter paper and the subsequent direct analysis of discs punched from these filters by solid sampling-graphite furnace atomic absorption spectrometry (SS-GFAAS). A systematic study on the possible effects of different factors (total volume of blood deposited onto the filter paper, potential chromatographic effects affecting the distribution of Pb over the surface, potential differences in the amount of blood deposited per surface area for samples with different hematocrit values) was carried out, leading to the conclusion that the variation of these parameters within the usual clinical range does not result in any significant effect on the amount of Pb deposited in each disc. Thus, a simple methodology was developed based on (i) the performance of Pt as a chemical modifier and (ii) the use of matrix-matched standards for calibration (Pb-free blood samples spiked with known amounts of Pb) treated in the same way as the samples. The method was validated by analysis of a reference material, as well as by comparison of the results obtained for 18 patients from which blood was also taken and analyzed following the standard procedure (venous sampling, blood dilution and GFAAS monitoring). The main analytical features of the method proposed are: a detection limit of 2.5 μg Pb L−1, a working range up to 840 μg Pb L−1, a sample throughput of approximately 10 min per sample (5 replicates) and precision values below 10% RSD. The ease of sample collection, transporting and storing, in combination with the expeditiousness and relative inexpensiveness of the analytical technique used, make the procedure investigated very attractive for the screening of children in order to detect those with blood lead levels above the present threshold of concern (100 μg L−1), particularly in countries/areas were collecting sites might be far away from central laboratories.

Enzymatic inhibition and morphological changes in Hoplias malabaricus from dietary exposure to lead(II) or methylmercury

Neotropical fish traíra ( Hoplias malabaricus) were used to investigate the effects of dietary doses of metals through individual exposures to either inorganic lead(II) or methylmercury, respectively, 21 μg Pb 2+ g −1 w.w. and 75 ng H 3C-Hg + g −1 w.w., every 5 days, for 70 days (14 doses). The erythrocyte δ-aminolevulinic acid dehydratase (ALAd) activity was inhibited after 14 doses of Pb 2+and H 3C–Hg +. The muscle cholinesterase (ChE) activity was inhibited after 14 doses of H 3C-Hg +. Damage in cytoskeleton and nuclei were observed after exposure to inorganic lead. Individuals exposed to H 3C-Hg + showed the presence of atypical granules and vesicles, cytoplasm disorganization, and mitochondria damages in hepatocytes also after 14 doses. The present results demonstrate that erythrocyte ALAd and muscle ChE activities can be used as long-term biomarkers of sublethal, subchronic, and trophic exposures to Pb 2+, and H 3C-Hg + in fish. Also the morphological aspects described in the present work confirm the toxicity of both studied metals.

Lead detoxification by coontail ( Ceratophyllum demersum L.) involves induction of phytochelatins and antioxidant system in response to its accumulation

Coontail ( Ceratophyllum demersum L.) plants when exposed to various concentrations of Pb (1–100 μM) for 1–7 days, exhibited both phytotoxic and tolerance responses. The specific responses were function of concentration and duration. Plants accumulated 1748 μg Pb g −1 dw after 7 d which reflected its metal accumulation ability, however most of the metal (1222 μg g −1 dw, 70%) was accumulated after 1 d exposure only. The toxic effect and oxidative stress caused by Pb were evident by the reduction in biomass and photosynthetic pigments and increase in malondialddehyde (MDA) content and electrical conductivity with increase in metal concentration and exposure duration. Morphological symptoms of senescence phenomena such as chlorosis and fragmentation of leaves were observed after 7 d. The metal tolerance and detoxification strategy adopted by the plant was investigated with reference to antioxidant system and synthesis of phytochelatins. Protein and antioxidant enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) showed induction at lower concentration and duration followed by decline. All enzymes except GPX showed maximum activity after 1 d. An increase in cysteine, non-protein thiols (NP-SH) and glutathione (GSH) content was observed at moderate exposure conditions followed by decline. Phytochelatins (PC 2 and PC 3) were synthesized to significant levels at 10 and 50 μM Pb with concomitant decrease in GSH levels. Thus production of PCs seems important for the detoxification of metal, however it may lead to depletion of GSH and consequently oxidative stress. Results suggest that plants responded positively to moderate Pb concentrations and accumulated high amount of metal. Due to metal accumulation coupled with detoxification potential, the plant appears to have potential for its use as phytoremediator species in aquatic environments having moderate pollution of Pb.

Effects of overlying soft tissue on X-ray fluorescence bone lead measurement uncertainty

The effects of overlying soft tissue on the measurement uncertainty of the in vivo 109Cd K-shell X-ray fluorescence (XRF) technique were investigated, as applied to the tibia bone site. Experimental measurements were performed on a set of nine leg phantoms of different soft tissue thickness, intended to model the lower leg at mid-tibia. A standard bone phantom made from plaster-of-Paris and having a nominal lead concentration of 25.6 μg Pb per gram was used in all trials. Monte Carlo simulations of the experimental set-up were also performed. Results indicate a strong relation between measurement uncertainty and overlying tissue thickness (OTT) for the XRF bone lead method. In increasing the OTT from 3.2 to 14.6 mm, an increase in average measurement uncertainty by a factor of 2.40 was observed experimentally. Monte Carlo simulations indicated an increase in minimum detectable limit (MDL) by a factor of 2.46 over the same interval. Experimental and Monte Carlo results were generally in strong agreement. For subject screening purposes, direct measurement of soft tissue overlying the tibia is recommended whenever practical.

Acute toxicities of four metals on the early life stages of the crab Chasmagnathus granulata from Bahía Blanca estuary, Argentina

Acute semistatic toxicity tests were carried out for 96 h with first zoeae and young crabs of Chasmagnathus granulata. Survival curves and LC 50 (lethal concentration 50, the concentration which produces the death of 50% of the exposed population) indices for copper, zinc, cadmium, and lead were determined. Furthermore, mixture toxicity tests (Cd/Cu and Cd/Zn) with first-stage larvae were also carried out. The LC 50-96 h values determined in this study were 1093.4 (881–1319) μg Pb 2+ L −1, 219.2 (188.9–248.9) μg Cu 2+ L −1, 172.1 (141.3–203.6) μg Zn 2+ L −1, and 47.8 (37.9–58.0) μg Cd 2+ L −1 for zoeae I and 130.1 (121.7–139.0) mg Cu 2+ L −1, 51.0 (41.9–61.6) mg Zn 2+ L −1, and 35.7 (30.1–41.9) mg Cd 2+ L −1 for young crabs. The LC 50-96 h indices for mixture tests with zoeae I were 260.6 (227.3–286.3) μg Cd 2+/Zn 2+ L −1 and 41.3 (37.4–60.7) μg Cd 2+/Cu 2+ L −1. Cadmium presented the highest acute toxicity for both stages of the life cycle examined. The toxicity of the metals analyzed followed the order cadmium >zinc>copper>lead. First zoeae were more sensitive than young crabs to acute exposure to all metals analyzed. The young crabs were considered potentially dangerous agents of transference to the associated trophic chain because of their relatively elevated resistance and their capacity to bioaccumulate heavy metals in their tissues. Mixed toxicity tests carried out on first-stage larvae showed different kinds of interactions. Cadmium/copper presented an additive interaction trend while the mixture cadmium/zinc showed an antagonistic interaction.

Comparison of two digestion procedures for the determination of lead in lichens by electrothermal atomic absorption spectrometry

The efficiency of two procedures for the digestion of lichen was investigated using a heating block and a microwave oven. In the open vessels, concentrated nitric acid was added to the samples, left for 1 h, and the addition of 30% (v / v) hydrogen peroxide completed the digestion. In the closed system, the complete digestion was performed using concentrated nitric acid and hydrogen peroxide, reducing the amount of chemicals, time and contamination risk. Both digestion methods gave comparable results, and recoveries were statistically not different. For a lichen sample spiked with 10 μg Pb, the recovery was 111% and 110% using microwave and heating block digestion, respectively, while it was 100% and 103% for a 100 μg Pb spike. For the determination by electrothermal atomic absorption spectrometry samples were diluted 20 times with water and a volume of 20 μL was injected into the graphite furnace without chemical modifier. Pyrolysis and atomization temperatures of 700 °C and 1500 °C, respectively, were used. The characteristic mass was 8.4 ± 0.6 pg for aqueous calibration solutions and 8.9 ± 0.8 pg for samples. Calibration was against matrix matched standards. The recovery test showed some contamination problem with the lowest concentrations in both procedures. The detection limits were 4.4 μg L − 1 with microwave oven and 5.4 μg L − 1 with the heating block in the undiluted blank.

Speciation of lead compounds in fish by capillary electrophoresis-inductively coupled plasma mass spectrometry

A capillary electrophoresis-inductively coupled plasma mass spectrometric (CE-ICP-MS) method for lead speciation application is described. Sample containing ionic lead compounds were subjected to electrophoretic separation before injection into the micro-concentric nebulizer (CEI-100). The species studied include inorganic lead (PbII), trimethyl lead (TML) and triethyl lead (TEL). The separation has been achieved on a 70 cm length × 75 μm id fused silica capillary. The electrophoretic buffer used is 15 mmol l−1 Tris (pH 8.25) containing 10 mmol l−1 SDS (sodium dodecyl sulfate), 0.2 mmol l−1 EDTA and 2% v/v methanol, while the applied voltage is set at +26 kV. The lead species in biological tissues are extracted into 1% m/v EDTA solution taken in a closed centrifuge tube and kept on a water bath, using microwaves at 70 °C for 10 min. The extraction efficiencies of individual lead species added to the sample at 2 μg Pb g−1 level are between 97% and 102%. The detection limits of the species studied are in the range 0.2–0.6 ng Pb ml−1. The procedure has been applied for the speciation analysis of two reference materials namely dogfish liver tissue (NRCC DOLT-3) and oyster tissue (NIST SRM 1566a) and two real-world samples.

Lead tolerance in Aporrectodea rosea earthworms from a clay pigeon shooting site

Lead tolerance in individuals of the earthworm species Aporrectodea rosea collected from a clay pigeon shooting site was investigated. Lead concentrations in the shooting site soil and the un-shot control site were 6410±2250 and 296±98 mg Pb kg −1 dry weight, respectively. Of these concentrations 1050±240 and 12±9 mg Pb kg −1 dry weight were suggested to be available, using ammonium acetate (1 M), respectively. With respect to earthworm body burdens of lead the shooting site earthworms had a body burden of 6.1±1.2 mg Pb g −1 dry weight while the uncontaminated site earthworms had almost a 1000-times lower body burden of 7.1±9.0 μg Pb g −1 dry weight. Lead tolerance was assessed in uncontaminated soil that had been augmented with lead, using lead nitrate solutions, to obtain lead concentrations in soil of 0.5, 5 and 50 mg Pb kg −1 dry weight. Earthworms were exposed for 28 days during which time a semi-qualitative assessment was made of their condition. Results showed no decrease in condition in the shooting site earthworms with increasing exposure time or concentration. In contrast, earthworms collected from an uncontaminated site showed a significant ( p<0.05) decrease in condition when exposed to lead concentrations above, and including, a concentration of 5 mg kg −1 dry weight soil. These results suggested lead tolerance in the shooting site earthworms.

Assessment of Lead Exposure in Thohoyandou, South Africa

Lead levels in different environmental media (soil, grass leaves, water, ceramics, pencil, paint, crayons and cosmetics) were determined to assess the major sources of lead exposure in Thohoyandou, South Africa. Soil and plant leaves were used as indicators of Pb pollution from vehicle exhaust emissions. After digestion with concentrated acids (HNO3, HCl and HClO4) Pb concentrations were determined in triplicate using a flame atomic absorption spectrometer. The mean Pb concentrations at the kerb of selected busy roads were 205.5 ± 90, 273.0 ± 90 and 312.8 ± 81 μg g−1 and 154.7 ± 67, 182.9 ± 76 and 240.6 ± 66 μg g−1 for soil and plant leaves (dry weight) respectively. These concentrations were substantially higher than the values found on soils 50 m away from the roads (97.4 ± 11 μg g−1). Pb concentrations in plants collected further away from the road (50 m) were substantially lower (71.8 ± 9.0 μg g−1). The observed levels on soil are lower than the UK critical value of 500 μg g−1 for gardens and allotments; and 2000 μg g−1 for parks and open space as well as the Canadian values for agricultural (375 μg g−1), residential (500 μg g−1 and industrial (1000 μg g−1). From these data it was clear that Pb concentrations in soil samples were substantially higher than the levels obtained for plant leaves. The Pb levels in green crayons, blue crayons, pencils (from China & Germany), were 10650 ± 75.2, 8200 ± 52.4, 1160 ± 50.2, 79 ± 10.1 μg g−1 for the inner contents; and 4870 ± 58.1, 5650 ± 55.5, 1950 ± 46.6, 60 ± 12.9 μg g−1 for the outer surface paint respectively. The ceramics showed Pb levels of 630 ± 50.3 μg g−1 (saucer) and 560 ± 32.2 μg g−1 (cup), while the inner contents and outer surface paint showed 480 ± 32.4 and 318 ± 21.2 μg g−1 of Pb respectively. Early morning tap water flush gave a Pb level of 20.6 ± 5.6 μg Pb l−1. This value is higher than the WHO and FDA maximum permissible concentrations of 10 μg l−1 and 15 μg l−1 respectively.

Evidencing lead deposition at the urban scale using “short-lived” isotopic signatures of the source term (Pb–Zn refinery)

Abstract To demonstrate the ability of the lead isotope signature technique to evidence the spatial extent of an industrial Pb deposition plume at a local scale, dry deposition of lead in the urban environment of a Pb–Zn refinery was investigated, as a study case, using transient (“short-lived”) isotopic signatures of the industrial source. Sampling campaigns were achieved in representative weather conditions, on an 8-h basis. Dry deposition rates measured downwind from refinery emissions (≈102–103 μg Pb m−2 h−1), cross-sectionally in a 3–5 km radius area around the plant, represent 10–100 times the urban background dry fallout, measured upwind, as well as fallout measured near other potential sources of anthropogenic Pb. The Pb–Zn refinery isotopic signature (approx. 1.100

Monte Carlo investigations of distance-dependent effects on energy deposition in K-shell x-ray fluorescence bone lead measurement

Radiation energy deposition results are presented from a Monte Carlo code simulating the lower part of a leg during an in vivo 109Cd K-shell x-ray fluorescence (KXRF) bone lead measurement. The simulations were run for a leg phantom model representing an adult subject, assuming concentrations of 10 µg Pb per gram bone mineral and tracing 500 million photons in each simulation. Trials were performed over a range (0.5–6.0 cm) of source-to-sample (S–S) distances. Energies deposited due to Compton and photoelectric processes occurring in the bone and the soft tissue were obtained. The data show an increase in the amount of energy deposited in the bone as the sample is moved closer to the source (from 2.0 cm to 0.5 cm). However, there is a decrease in the amount of energy deposited in the soft tissue as the sample is moved closer to the source over the same distance interval. In decreasing the S–S distance from 2.0 cm to 0.5 cm, the amount of energy deposited in the sample as a whole was found to increase by 11%. By calculating the energy deposition in the bone and in the soft tissue as a fraction of the total energy deposited in the sample, the corresponding changes are quantified as a function of S–S distance. Similarly, the proportions of energy deposited via the photoelectric effect and Compton scattering are presented as a function of S–S distance.