Lead Aerosols Research Articles

Gas-to-particle conversion of mercury, arsenic and selenium through reactions with traffic-related compounds? Indications from lead isotopes

Relationships between metal (Cu, Zn, Pb, Cd, Hg, As, Se) concentrations and lead isotope compositions of Geneva aerosols for the period October 1996–September 1997 are investigated. Lead in Geneva is contributed by petrol, waste incineration and, only in winter, coal. Lead and copper during summer and copper and zinc during winter correlate positively with the lead isotope signature of the incinerator suggesting derivation of relevant amounts of these metals from such source. On the contrary, three volatile metals (Hg, As, Se), which can be present in the atmosphere as gaseous compounds at significant levels, display an anomalous strong correlation with the isotope signature of traffic-lead in summer. These metals are unlikely to be contributed by automotive combustion and their most probable summer source is also represented by waste incineration. We suggest that the correlation of Hg, As and Se with automotive lead could unveil conversion of these volatile metals from the gaseous to the particulate phase in concomitance with increasing concentration of traffic-related compounds of which lead isotopes are a valid tracer. Hg, As and Se do not correlate directly with traffic-related gases (e.g. CO, NO x , O 3, THC) while they do correlate only with automotive lead. This is probably due to an atmospheric residence time more similar to traffic-generated lead aerosols than to automotive gases. It has been suggested elsewhere that gaseous mercury can be transformed to the particulate phase through atmospheric reactions with traffic-related oxidants like ozone. Our data might indicate that similar processes are responsible for the gas-to-particle conversion not only of gaseous Hg, but also of As and Se in the atmosphere of Geneva.

Assessment of pollution aerosols sources above the Straits of Dover using lead isotope geochemistry

We assess the capability of lead isotopes to study the transport of pollution aerosols above the Straits of Dover by collecting atmospheric aerosols above the Eastern Channel and the Southern Bight of the North Sea. During the same period, we characterized the lead isotopic signature of the main industrial sources on the French coast near the Straits of Dover. Urban and automobile-derived aerosols were also collected. Due to the phasing out of lead in gasoline, the urban isotopic composition ( 206Pb/ 207Pb=1.158±0.003) has become more radiogenic, although it is highly variable. On a regional scale, major industrial emissions have a well-defined isotopic composition (1.13< 206Pb/ 207Pb<1.22), more radiogenic than the petrol-lead signature (1.06< 206Pb/ 207Pb<1.12). These results together with those measured near the main coastal highway show that the automobile source has become a minor component of particulate lead in air. On a local scale, Dunkerque, the most urbanized and industrialized area along the Straits of Dover, may transiently control elevated lead concentrations. Except for the occurrence of local and regional range transport episodes, lead concentrations in the Straits of Dover can be related to remote or semi-remote pollution source emissions. Combining air mass retrospective trajectories and related lead abundances and isotopic compositions, it can be shown that lead aerosols originating from eastern Europe have an isotopic signature (1.145< 206Pb/ 207Pb<1.169) different from the isotopic composition of west-European lead aerosols (1.111< 206Pb/ 207Pb<1.142). The influence of remote North American sources is suggested, with caution, due to uncertainties in meteorological calculations.

Isotopic evidence of pollutant lead sources in Northwestern France

Ratios of stable lead isotopes ( 204Pb, 206Pb, 207Pb, 208Pb) are used to characterize both spatial and temporal variations in anthropogenic emissions of industrial lead aerosols to the atmosphere of northwestern France. Differences in isotopic compositions of aerosols collected from a rural area (Wimereux) in the Nord-Pas de Calais region along the English Channel in 1982–1983 ( 206Pb/ 207Pb=1.108±0.005) and 1994 ( 206Pb/ 207Pb=1.148±0.003) are paralleled by similar variations in urban aerosols within France during the same period (e.g., 206Pb/ 207Pb=1.115±0.008 from 1981–1989 and 1.143±0.006 from 1992–1995). These results correlate well with recent findings in the Mediterranean basin (Alleman, 1997) where this radiogenicity increase is clearly associated with industrial sources other than leaded gasoline that has remained relatively constant during its phasing out ( 206Pb/ 207Pb=1.08–1.11). Here we used archived data, air mass trajectories and aerosol diameters combined with isotopic signatures to confirm this trend at a regional scale. Indeed, the main industrial signatures from lead smelting ( 206Pb/ 207Pb=1.133±0.001) and steel metallurgy ( 206Pb/ 207Pb=1.196±0.015) in northwestern France appear more radiogenic than that of leaded gasoline. The shift in isotopic compositions also conform with the systematic change in the mean size (diameter) of aerosols at Wimereux, which ranged from 0.30 to 0.61 μm in 1982–1984 and from 0.70 to 0.89 μm in 1994.

Air lead pollution and lead exposure of experimental animals and children in Stara Zagora town (Bulgaria)

The air pollution with lead aerosols in Stara Zagora town was investigated at four sampling sites over a period of 6 years. Transport is the main source of air lead pollution in the town. The mean annual air lead concentrations varied from 0.06 to 0.6 μg/m3. The highest air lead levels were measured in the area of a big crossroads during the whole period. An experimental group of mice were exposed near to the crossroads and a control group was exposed in a relatively cleaner residential district for 6 months. The lead concentrations in blood, urine, bones, kidney, liver and lung investigated by atomic absorption spectrometry were significantly higher in the animals from the experimental group in comparison with the control. The lead levels in blood, urine and nails were investigated in children living and going to school in the area with high transport traffic and in a control group of children from the residential district where the control mice were exposed. The mean blood lead level estimated in the group of children exposed at the higher air lead pollution (10.28 μg/dl) slightly exceeded this estimated in the control group (9.47 μg/dl) and the standard for childhood of the Center for Disease Control and Prevention, US (10 μg/dl). It was found that 60% of children from the 'experimental' and 50% from the control group had PbB concentrations equal to or higher than the lowest limit action level. Lead levels in urine were significantly higher in the 'experimental' group as a whole, and in the 'female experimental' group of children also.

Assessment of particle size distributions of healthrelevant aerosol exposures of primary lead smelter workers

Experiments were conducted at a primary lead smelter to investigate the particle size distributions of lead-containing aerosol to which workers were exposed, using personal inhalable dust spectrometers (PIDS) in specific smelter process areas. A total of 46 PIDS samples were evaluated, taken from the ore storage/mill, sinter plant, blast furnace and dross furnace process areas. Continuous particle size distributions were derived from the raw PIDS data employing a recentlydeveloped optimisation routine, enabling determination of the percentages of inhalable, thoracic and respirable aerosol (in terms of lead content) as fractions of total lead aerosol. In addition, the mass ratios thoracic/inhalable and respirable/inhalable were also determined. Although the parameters of the measured particle size distributions ranged widely, some clear trends emerged. Firstly, the aerosols were coarser than had been expected based on measurements of previously reported workplace particle size distributions. This is thought to be due to the fact that the PIDS collects larger particles more efficiently than other instruments which have been used for such measurements. Secondly, there were significant differences in particle size distribution between process areas, in particular that the aerosol in the blast furnace area was generally finer than in the sinter plant. Such results may be used to support the results of workplace studies (reported elsewhere) into the differences between exposures to inhalable and ‘total’ aerosol as measured using different sampling instruments, especially when they are used together with knowledge of the physical processes governing the performances of such instruments.

Concentrations, phase partitioning and deposition of specific alkyl-lead compounds in the atmosphere

Measurements of alkyl-lead compounds in air and rain at rural and urban sites in central England during 1996 are reported. Vapour, aerosol and rain concentrations of individual tetra-, tri- and di-alkyl-lead species have been determined simultaneously at both sites, along with inorganic lead aerosol. The results show the predominance of vapour-phase over particle-associated species, with tetramethyl-lead being the most prevalent vapour-phase compound, with concentrations of up to 5.8 ng Pb m−3. Theoretical phase-partitioning coefficients for individual alkyl-lead compounds have been calculated and compared with measured values. Washout ratios for alkyl-lead compunds were found to be smaller than for inorganic lead. Atmospheric concentrations of both organic and inorganic lead appear to be falling, broadly in line with recent reductions in the use of alkyl-lead in gasoline. © 1997 John Wiley & Sons, Ltd.

Characteristics of lead aerosols in different work environments.

Air samples were collected to examine physical and chemical characteristics of lead aerosols in different work environments in the airborne lead concentration range from 28-783 micrograms/m3. Size distribution of aerosols was measured using a Marple personal cascade impactor, and lead analysis was conducted using graphite atomic absorption spectrometry. Lead aerosol size distribution was found to be different from that of total particles. Such differences are not negligible and must be taken into account when estimating aerosol deposition within the human respiratory tract. Variation of MMAD (mass median aerodynamic diameter) and GSD (geometric standard deviation) of lead aerosols in the coarse mode wit total airborne concentration was found to be small, and the assumption that lead aerosol distribution is constant is reasonable for establishing the relationship between airborne lead concentration in all work areas of the three plants except the charging area of the capacitor plant. Therefore, it is expected that either total airborne lead or respirable airborne lead concentration can be used to correlate blood lead concentration.

Characteristics of Lead Aerosols in Different Work Environments

Characteristics of Lead Aerosols in Different Work Environments

On-line and in-situ detection of lead aerosols by plasma-spectroscopy and laser-excited atomic fluorescence spectroscopy

A set-up for on-line and size-segregated detection of lead in ultrafine aerosols was developed. Lead nitrate aerosols with particle diameters between 10 and 300 nm were generated by ultrasonic nebulization of aqueous Pb(NO 3) 2-solutions. A differential mobility particle sizer (DMPS) was used for size-resolved mass calibration. Either a miniaturized acetylene-air-flame or a laser-induced plasma (LIP) was employed for atomization. Lead was detected with a spectrograph and a gateable, intensified CCD-camera by atomic emission spectroscopy (AES) and laser excited atomic fluorescence (LEAF). Due to the lower sensitivity, for LIP-AES no size-resolved calibration was possible and for calibration with polydisperse aerosols a detection limit of 155 μg m −3 was found for lead. With LEAF and flame atomization, a linear calibration curve was obtained with on-line detection limits of 47 ng m −3 for lead. No dependence of the detection limit on the particle diameter was observed. For LEAF with a laser-induced plasma as atom source, a correlation between the detection limit and the particle diameter was found. The detection limit increased from 55 ng m −3 for a particle diameter of 48 nm to 130 ng m −3 for a particle diameter of 300 nm. The increasing detection limit with increasing particle diameter was probably due to the incomplete atomization of larger particles in the colder periphery of the plasma.

Semen analysis of military personnel associated with military duty assignments

A collaborative study between the U.S. Army Biomedical Research and Development Laboratory (USABRDL) and the National Institute for Occupational Safety and Health (NIOSH) was designed to assess fecundity of male artillery soldiers with potential exposures to airborne lead aerosols. Potential exposure assessment was based upon information provided in an interactive questionnaire. It became apparent from extensive questionnaire data that many soldiers in the initial control population had potentially experienced microwave exposure as radar equipment operators. As a result, a third group of soldiers without potential for lead or microwave exposures, but with similar environmental conditions, was selected as a comparison population. Blood hormone levels and semen analyses were conducted on artillerymen (n = 30), radar equipment operators (n = 20), and the comparison group (n = 31). Analysis of the questionnaire information revealed that concern about fertility problems motivated participation of some soldiers with potential artillery or microwave exposures. Although small study population size and the confounding variable of perceived infertility limit the reliability of the study, several statistically significant findings were identified. Artillerymen who perceived a possible fertility concern demonstrated lower sperm counts/ejaculate (P = 0.067) and lower sperm/mL (P = 0.014) than the comparison group. The group of men with potential microwave exposures demonstrated lower sperm counts/mL (P = 0.009) and sperm/ejaculate (P = 0.027) than the comparison group. Variables used to assess endocrine, accessory sex gland, and sperm cell function were not different than the comparison group. Additional studies, incorporating larger numbers of individuals, should be performed in order to more optimally characterize potential lead and microwave exposure effects on male fecundity.

Metallic Particle Formation and Growth Dynamics During Incineration

Abstract A comprehensive model to predict the lead aerosol size distribution for typical incinerator operating conditions has been developed. Using the feed rate and incinerator operating conditions, the metal transfer rate to the gas phase is determined using a mass transfer calculation. A detailed, multicomponent aerosol dynamic model is developed accounting for the chemical kinetics and applied to a lead-oxygen-chlorine system. Reasonable agreement is obtained between model predictions and experimental data from controlled studies for different aspects of the model. The effect of chlorine on the resulting aerosol size distribution has been determined. The role of the transfer rates of lead to the gas phase on the resulting size distributions have also been determined. Simulations have been performed for typical conditions encountered in a waste incinerator.

Temporal variations in lead concentrations and isotopic composition in the Southern California Bight

Lead concentrations in surface waters of the Southern California Bight appear to have decreased threefold (from > 170 to <60 pM) since they were initially measured by Clair Patterson and his associates in the 1970s. The decrease parallels a threefold decline in anthropogenic inputs of industrial lead to the bight over the past two decades. Moreover, mass balance calculations indicate that the primary source of lead to the bight now is upwelling. This is evidenced by the isotopic compositions of surface waters in the bight, which are most characteristic of Asian industrial lead aerosols ( 0.4793 ≤ 206Pb 208Pb ≤ 0.4833 ) deposited in oceanic waters of the North Pacific. While the decrease in surface water lead concentrations in the bight reflects the reduction in industrial lead emissions from the United States, the isotopic compositions of surface waters in the southern reach of the bight reflect a concurrent increase in industrial lead emissions from Mexico ( 0.4852 ≤ 206Pb 208Pb ≤ 0.4877 ). The isotopic composition ( 208Pb 207Pb ≈ 2.427 ) of elevated lead concentrations of surface waters in San Diego Bay indicate that lead is being remobilized from contaminated sediments within that bay.

Distribution of lead inside the home: case studies in the North of England

Air lead concentrations, deposition on moss bags and window velocity decreased rapidly through an open window in a university room. The indoor/outdoor air lead ratio was 0.82. Other experiments took place in houses in Bradford and Manchester. Lead deposition was studied using irrigated moss bags, by cleaning surfaces with moistened tissues, by washing curtains and by vacuum cleaning floors. Within a home, air lead concentrations were approximately the same upstairs and downstairs, but there was less lead in settled floor dusts upstairs compared with downstairs. Lead and dust loading on a hall floor decreased away from the front door and a front room downstairs had more lead in floor dust than a back room. Lead loadings on other surfaces were in the order window sills > furniture > walls > ceilings. Net curtains on windows effectively trapped lead aerosols. Garden soil contained more lead near the house. More lead was tracked into a hallway in wet weather and more lead entered through windows in summer months when windows were left open more often. Overall, lead loadings were higher for houses on busy streets near city centres.

Hazardous waste incineration: The in-situ capture of lead by sorbents in a laboratory down-flow combustor

Experiments on a 17 KW downflow combustor determined how sorbent injection into the post flame influenced the particle size distribution of a lead aerosol formed from a surrogate lead containing waste. In the absence of chlorine, the lead aerosol size distribution evolved within the combustor to lie predominantly between 0.02 and 0.2 microns by the time it was sampled, at the combustor exit. When a commercial kaolinite sorbent was added, the lead sampled in that particle size range was reduced by 99%, and there is clear evidence that the heavy metal was reactively scavenged in the combustor by the larger sorbent particles. Chlorine kept the lead in the vapor form, until it was sampled, at which point it formed a fume in the probe. At large Cl/Pb ratios (greater than 10), the addition of sorbent was not effective in scavenging the lead vapor, although capture was again apparent as Cl/Pb ratios were reduced to 2. Data from experimental runs with a large excess of chlorine present, but not those where Cl/Pb ratio was equal to 2, are in sharp contrast to literature data from bench scale reactor studies.

Temporal variability of atmospheric lead concentrations and fluxes over the northwestern Mediterranean Sea

Beginning in 1985, daily 24‐hour aerosol samples were collected on 0.4‐pm pore size filters at a coastal location in northwestern Corsica. Total atmospheric deposition (wet + dry) were sampled between February 1985 and October 1987 with a collection period of about 15 days. As indicated by three‐dimentional air mass trajectories, lead aerosol particles collected at this site are primarily derived from European continental source regions. The variability of lead aerosol concentrations on both daily and seasonal time scales is primarily due to the scavenging of lead aerosol particles by rain rather than to changes in source regions. Our results suggest that the ratio between the total atmospheric deposition of Pb and the corresponding mean daily precipitation (mdp) rate is not constant. This ratio reaches a maximum during the Mediterranean summer. We attribute this difference to wet scavenging processes which wash a more loaded atmosphere during the dry season than during the wet season. The precipitation frequency (FP) is a major factor influencing seasonal variability of the total atmospheric deposition of lead over the western Mediterranean. An intermediate value of FP allows sufficient reloading of the atmosphere with long‐range transported Pb aerosol particles as well as efficient scavenging by precipitation events.

DISCUSSION1

The sequential development of trace metal clean techniques has resulted in a systematic decrease in reported lead concentrations in the ocean. Similar decreases have been observed in reports of lead concentrations in fresh water. This was illustrated by the changes in reported baseline concentrations of lead in Lake Huron. However, even the latest (1980) of those concentrations (19 ng/L) appears to be erroneously high based on recent measurements of lead concentrations in the Great Lakes. Lead concentrations in surface waters in the center of Lake Ontario are < 2 ng/L or one order of magnitude lower than the reported baseline concentration of Lake Huron in 1980. Corresponding concentrations of lead in surface waters of Lake Huron should be equal to or less than those in Lake Ontario. Anthropogenic lead fluxes to Lake Huron (621 metric tons per year) and Lake Ontario (592 metric tons per year) are comparable, while the assimilative capacity of Lake Huron is two-fold greater than that of Lake Ontario. Moreover, the atmospheric flux of industrial lead aerosols to surface waters in Lake Huron is approximately one half of the flux in Lake Ontario. Therefore, if removal rates are similar in these two lakes, the authors expectmore » the baseline concentration of lead in Lake Huron to be {le} 2 ng/L or one order of magnitude lower than the 1980 baseline concentration. Concentrations in remote fresh water systems in North America, where inputs of industrial lead aerosols are orders of magnitude lower should also be < 2 ng/L. The preceding measurements and projected concentrations of lead in fresh water systems in North America are of note in light of some recent reports on the decrease of lead in natural waters within the US. Those reports are questionable, in spite of other reports of decreasing lead concentrations in the Mississippi River and North Atlantic.« less

Isotopic tracers of lead contamination in the Great Lakes

FLUXES of lead to the Great Lakes are dominated by atmospheric depositions of industrial lead, which account for ∼ 64% of the lead inputs to Lake Ontario and >90% of the inputs to Lake Superior1. It has recently been demonstrated that lead aerosols in the Great Lakes region may be identified by the contrasting 206Pb/207Pb ratios of industrial leads from the United States (1.221 ±0.009) and Canada (1.151 ±0.010)2. Here we show that those ratios may also be used to identify and trace industrial lead inputs to the Great Lakes. These corroborate spatial gradients in lead concentrations in surface waters, which range from 290 pmol kg−1 in Hamilton Harbour to <10 pmol kg−1 in the central waters of Lake Ontario. The latter concentrations and corresponding residence-time estimates, which are both an order of magnitude lower than previously reported, indicate that lead is rapidly scavenged in the epilimnion during periods of high primary productivity. We find that industrial lead from Canada and the United States are the two principal sources of lead contamination in the Great Lakes.

High gradients of lead isotopic composition in north-east Pacific upwelling filaments

SUBSTANTIAL differences in stable lead isotopic composition in coastal waters of the north-east Pacific have been inferred from a single vertical profile taken near western Canada1. Here we present measurements of lead isotopes in two upwelling filaments off central California (39° N, 124° W) which confirm that such marked differences exist. The distinct, filamentary structures appear in association with surface jets which transport cold upwelled water hundreds of kilometres offshore2. Surface-water ratios of stable lead isotopes (204Pb,206Pb, 207Pb, 208Pb) within the core of the first filament (for example,206Pb/207Pb = 1.17) contrasted with those of surrounding coastal waters (206Pb/207Pb = 1.19) and those of industrial lead aerosols from the United States (206Pb/207Pb = 1.22). Contrasts in the isotopic composition indicated that the lead within the core was primarily derived from aeolian inputs of Asian industrial lead (206Pb/207Pb = 1.16) to remote waters, which were then upwelled near the North American coastline. High gradients of lead isotopic composition in coastal waters were confirmed by surface and sub-surface measurements surrounding a second upwelling filament. These gradients illustrate the complexity of trace-element cycles in coastal waters, and the offshore fluxes within the ephemeral filaments demonstrate significant influences of coastal dynamics on composition within the ocean gyre.

Stable lead isotope ratios in arctic aerosols: evidence for the origin of arctic air pollution

The isotopic composition of aerosol lead in the polar region potentially contains information on the origin of Arctic pollution which will complement that from meteorological and trace elemental composition studies. Weekly samples of atmospheric aerosols were collected at three locations in the Canadian Arctic from mid-1983 to mid-1984. They were analyzed for elemental composition and stable lead isotope ratios (Pb 206 207 ). High crustal enrichment factors confirmed that the majority of samples contained lead of anthropogenic origin. Pb 206 207 ratios were very uniform over time and between sites, suggesting a common origin of lead pollution in the Canadian Arctic. The mean isotope ratios at the Alert and Mould Bay stations were 1.160±0.010 and 1.161±0.006, respectively (samples from a third site at Igloolik were evidently contaminated by local sources). A small number of samples from Spitsbergen, taken during flow predominantly out of the northern U.S.S.R., were found to have a similar mean Pb 206 207 ratio of 1.154 ±0.006. From published lead isotope analyses of Soviet lead-bearing ores, we would expect a mean isotope ratio in industrial and vehicular emissions in the U.S.S.R. of around 1.158. Contributions to Arctic lead pollution from the U.S. and western Canadian sources can probably be ruled out, as they have significantly higher Pb 206 207 ratios. Similarly, emissions from northern Canadian and Kola Peninsula smelters can be disregarded, as they appear to have low isotope ratios. Eastern Canadian automotive lead aerosol contained only marginally lower Pb 206 207 ratios than in the Arctic, but meteorological studies argue against this region being a major source area for Arctic pollution. Scant European data suggest that European Pb emissions generally have lower isotope ratios than the Arctic samples. However, more data in Eurasia are needed before apportionments of Arctic Pb between sources within the region can be made.

Lead 206/207 isotope ratios in the atmosphere of North America as tracers of US and Canadian emissions

Lead emitted into the environment (primarily by gasoline combustion and industrial processes) retains the isotopic composition of the ore from which it was derived. Therefore, there is the potential to distinguish sources of lead pollution in the atmosphere by examining the lead isotope ratios1–4. Such a tracer of atmospheric lead would be valuable in air pollution transport studies, as the relatively long residence time of lead aerosols (∼5–10 days), can result in its dispersal over thousands of kilometres. In practice, the situation is complicated by the wide, and frequently changing, variety of ore types used in gasoline additives and in smelting activities5,6. This approach has generally only been successful in identifying local sources of pollution7–9, except where gasoline lead compositions have been deliberately altered10. We have discovered that the lead isotopic composition of atmospheric particu-late matter in the eastern United States is distinctly different from that in eastern Canada, and that the composition is sufficiently constant between sites in each country over periods of several months to allow characteristic isotope ratios to be defined for each. This offers a new approach to examining transboundary pollution between the United States and Canada.