Effectiveness of leaded petrol phase-out in Tianjin, China based on the aerosol lead concentration and isotope abundance ratio

The phase-out of leaded petrol has been a measure widely used to reduce atmospheric lead pollution. Since the 1980s, China began to promote unleaded petrol. In order to assess the effectiveness of the measure an isotope fingerprint technique was applied for aerosol samples in the city of Tianjin. After dilute acid leaching, the lead concentration and isotope abundance ratios were determined for 123 samples collected in Tianjin during eight years (1994-2001). The 206Pb/207Pb ratio was lower in summer, when coal combustion emission was low and vehicle exhaust became more important, indicating that the 206Pb/207Pb ratio of leaded petrol in Tianjin is lower than that of aerosol samples. The 206Pb/207Pb ratio gradually increased from 1994 to 2001, a trend that suggests that the contribution from vehicle exhaust was diminishing. Overall, the measurements matched well with national statistical data of leaded and unleaded petrol production. After the nationwide switch to unleaded gasoline, comprehensive control measures are urgently needed to reduce air lead pollution in China, as aerosol lead reduced slightly but remains at a relatively high level.     

Lead isotope ratios in tree bark pockets: an indicator of past air pollution in the Czech Republic

Tree bark pockets were collected at four sites in the Czech Republic with differing levels of lead (Pb) pollution. The samples, spanning 1923-2005, were separated from beech (Fagus sylvatica) and spruce (Picea abies). Elevated Pb content (0.1-42.4 microg g(-1)) reflected air pollution in the city of Prague. The lowest Pb content (0.3-2.6 microg g(-1)) was found at the Kosetice EMEP "background pollution" site. Changes in (206)Pb/(207)Pb and (208)Pb/(206)Pb isotope ratios were in agreement with operation times of the Czech main anthropogenic Pb sources. Shortly after the Second World War, the (206)Pb/(207)Pb isotope ratio in bark pockets decreased from 1.17 to 1.14 and the (208)Pb/(206)Pb isotope ratio increased from 2.12 to 2.16. Two dominant emission sources responsible for these changes, lignite and leaded petrol combustion, contributed to the shifts in Pb isotope ratios. Low-radiogenic petrol Pb ((206)Pb/(207)Pb of 1.11) lead to lower (206)Pb/(207)Pb in bark pockets over time. High-radiogenic lignite-derived Pb ((206)Pb/(207)Pb of 1.18 to 1.19) was detected in areas affected by coal combustion rather than by traffic.     

A comparison of lead isotope ratios in the bark pockets and annual rings of two beech trees collected in Derbyshire and South Yorkshire, UK

ICP-MS analysis of the bark pockets and annual rings of two beech (Fagus sylvatica L.) trees collected from Longshaw, Derbyshire and Swinton, South Yorkshire in the UK recorded differences in the (206)Pb/(207)Pb isotope ratio. In the Longshaw sample, the (206)Pb/(207)Pb isotope ratio of the bark pockets ( approximately 1914-1998, 78-260 microg g(-1) Pb) declined from approximately 1.16 to 1.12, whilst the annual rings (1899-1998, 0.2-2.5 microg g(-1) Pb) had a (206)Pb/(207)Pb ratio of approximately 1.18. In the Swinton sample, the bark pockets (approximately 1919-1998, 7-78 microg g(-1) Pb) declined from 1.15 to 1.11 and the annual rings (1899-1998, 0.2-0.5 microg g(-1) Pb) from 1.18 to 1.15. The data implied that the bark pockets accumulated lead directly from the atmosphere through wet and dry deposition, whilst the annual rings accumulated lead from the soil via the roots. The bark pockets recorded a relative decline in the accumulation of lead from indigenous sources, such as lead smelting and coal combustion (1.17-1.19), and increase in imported sources such as the smelting of Australian ores (1.04) and leaded petrol usage (1.06-1.09). In contrast, the annual rings at Longshaw recorded ratios typical of indigenous lead, whilst the annual rings in Swinton recorded a relatively small decrease in (206)Pb/(207)Pb reflecting leaded petrol usage. The decline in (206)Pb/(207)Pb of the bark pockets was consistent with the historical decline in (206)Pb/(207)Pb of atmospheric lead recorded in peat, lake sediments and archival herbage at other UK locations.     

Regional lead isotope study of a polluted river catchment: River Wear, Northern England, UK

High precision, lead isotope analyses of archived stream sediments from the River Wear catchment, northeast England (1986-88), provide evidence for three main sources of anthropogenic lead pollution; lead mining, industrial lead emissions and leaded petrol. In the upper catchment, pollution is totally controlled and dominated by large lead discharges from historic mining centres in the North Pennine Orefield (²⁰⁸Pb/²⁰⁶Pb, ²⁰⁷Pb/²⁰⁶Pb ratios range from 2.0744-2.0954 and 0.8413-0.8554 respectively). In the lower catchment, co-extensive with the Durham Coalfield and areas of high population density, pollution levels are lower and regionally more uniform. Isotope ratios are systematically higher than in the upper catchment (²⁰⁸Pb/²⁰⁶Pb, ²⁰⁷Pb/²⁰⁶Pb ratios range from 2.0856-2.1397 and 0.8554-0.8896 respectively) and far exceed values determined for the geogenic regional background. Here, the pollution is characterised by the atmospheric deposition of industrial lead and petrol lead. Lead derived from the combustion of coal, although present, is masked by the other two sources. Recent sediments from the main channel of the River Wear are isotopically indistinguishable from older, low order stream sediments of the North Pennine Orefield, indicating that contamination of the river by lead mining waste (up to several 1000 mg/kg Pb at some locations) continues to pose an environmental problem; a pattern that can be traced all the way to the tidal reach. Using within-catchment isotope variation and sediment lead concentrations, estimates can be made of the discharges from discrete mines or groups of mines to the overall level of lead pollution in the River Wear. As well as providing information pertinent to source apportionment and on-going catchment remediation measures, the database is a valuable resource for epidemiologists concerned with the health risks posed by environmental lead.     

Comparative study of the temporal evolution of atmospheric lead deposition in Scotland and eastern Canada using blanket peat bogs

The temporal evolution of atmospheric lead deposition and its possible sources were assessed in eastern Canada and in western Scotland, using blanket peat bogs as geochemical archives. Short cores were taken from two remote sites located close to the sea. Significant lead enrichments in the upper layers at both sites reflect the increasing emission of lead into the atmosphere due to anthropogenic activities during the last century. At the Scottish site, a region under aeolian influence from Europe, anthropogenic derived lead could be recognized by the distinctive unradiogenic composition (206Pb/207Pb ratios down to approximately 1.115), being clearly different from the pre-industrial values (206Pb/207Pb approximately 1.166). In contrast, the lead pollution in eastern Canada (influenced by North American sources) is identified by a more radiogenic lead isotope composition (206Pb/207Pb ratios up to approximately 1.199) compared to preindustrial values (206Pb/207Pb approximately 1.161). Emission inventories and isotope characteristics suggest that industrial (coal burning, mining) and traffic (leaded gasoline) outputs are the most likely sources during the first and the second half of the 20th century, respectively, in both, western Scotland and eastern Canada alike. The Scottish record is in line with previous studies of past atmospheric lead deposition. However, the Canadian deposit suggests that the wind derived, pre-industrial lead, is less radiogenic as previously implied using sediment archives. These results are thus the first to report pre-industrial lead isotope ratios and concentrations of atmospheric derived aerosols in North America.     

Pb and 206Pb/207Pb isotopic analysis of a tree bark pocket near Sheffield,UK recording historical change in airborne pollution during the 20th century

A section of tree trunk (beech, Fagus sylvatica) containing a bark pocket progressively enclosed at the junction of two branches was collected from a semi-rural location near Sheffield, UK. According to the annual growth rings, the bark pocket formed between ca. 1919 and 1998 (the date of felling). The bark pocket was divided into consecutive samples of differing radial depth (and thus age), that were analysed by ICP mass spectrometry. The Pb concentration varied from 7 to 78 mg kg (-1) and the 206Pb/207Pb isotope ratio from 1.11 to 1.15. In contrast, the current surface bark contained 46 mg kg(-1) Pb and recorded a 206Pb/207Pb ratio of 1.11. The changing elemental and isotopic composition of the bark pocket recorded historical change in the level and sources of airborne Pb pollution. An overall increase in Pb concentration with time was accompanied by a progressive reduction in 206Pb/207Pb from ca. 1935 to 1943. Mass balance calculations indicated that Pb additives in petrol contributed significantly to the rise in concentration, accounting for a maximum of 50% of the total Pb for ca. 1986-1998, but that other sources were generally dominant. The highest Pb concentrations were recorded from ca. 1951 to 1973, suggesting a high level of industrial pollution. A reduction in Pb concentration and reversal of the trend in 206Pb/207Pb was observed in the current bark.     

Pb contamination and isotopic composition of urban soils in Hong Kong

In the urban environment, intense human activities can lead to degradation of environmental quality and have potential long-term effects on human health. In the present study, Pb contamination of urban soil cores in Hong Kong was investigated using a combination of the 'total' concentration, chemical partitioning and isotopic composition of Pb in the soils. The analytical results showed that urban soil cores in close vicinity to high traffic volumes (> 40000 vehicles per day) were usually contaminated with Pb, suggesting atmospheric deposition of Pb as a consequence of vehicular emissions arising from the combustion of leaded gasoline in the past. Increasing Pb concentrations were generally associated with decreasing 206Pb/207Pb ratios of the contaminated soil cores, offering strong evidence of accumulation of Pb derived from anthropogenic sources. In selected contaminated soil cores, the 206Pb/207Pb ratios tended to increase in the order: carbonate < exchangeable < Fe-Mn oxide < organic < residual fractions. The distribution of the 206Pb/207Pb ratios in the five operationally defined chemical fractions showed that the 206Pb/207Pb ratios generally increased with increasing stability, demonstrating preferential association of anthropogenic Pb with the carbonate, exchangeable, Fe-Mn oxide and organic fractions in the soils.     

Isotopic characterisation of the historical lead deposition record at Glensaugh, an organic-rich, upland catchment in rural N.E. Scotland

As part of a wider investigation of the biogeochemistry and fate of Pb deposited from the atmosphere at Glensaugh, a rural upland catchment in N.E. Scotland, the concentration and isotopic composition of Pb were determined in four thinly sectioned monolith cores (25 cm) of peat collected at altitudes of 426--434 m from different faces of Thorter Hill and in a series of 21 10-cm unsectioned cores of peat and organic-rich soil along a transect from near the top (434 m) to the bottom (224 m) of the catchment. Depth profiles of Pb concentration and (206)Pb/(207)Pb ratio were similar for the longer cores. Subsurface Pb maxima (238--489 mg kg(-1)) typically occurred below (206)Pb/(207)Pb minima (1.123-1.134). One core was (210)Pb-dated and had a fairly constant (206)Pb/(207)Pb value of 1.170 from mid-19th century to ca. 1930, followed by a decline (attributable to the increasing influence of Australian Pb of much lower (206)Pb/(207)Pb ratio) to 1.134 by the early 1990s, and then a rapid increase to 1.160 by 2002, after the phased withdrawal of leaded petrol. The fluxes of Pb increased from 15 mg m(-2) year(-1) in the late 19th century to a peak of 60 mg m(-2) year(-1) ca. 1960, before declining steadily to 3.6 mg m(-2) year(-1) by the beginning of the 21st century. Some 40% of the anthropogenic Pb in the core had been deposited prior to 1900. The mean anthropogenic Pb inventory of the four longer cores was 7.4+/-1.5 g m(-2), of which approximately 70% occurred in the top 10 cm, in good agreement with the inventories of the shorter cores collected above 400 m. These inventories are higher than those of the industrial central belt of Scotland, probably because of enhanced deposition at altitude. This is consistent with the derived average (210)Pb flux of 198+/-11 Bq m(-2) year(-1), which is twice that of typical UK (210)Pb deposition and the rainfall for the site. The past deposition of Pb at Glensaugh, including that from sources (e.g., smelting, coal combustion) other than leaded petrol, has clearly been considerable. Even since the introduction of leaded petrol ca. 1930, car-exhaust emissions may have accounted for no more than 35% of the Pb deposited.     

Spatial and temporal variations in Pb concentrations and isotopic composition in road dust, farmland soil and vegetation in proximity to roads since cessation of use of leaded petrol in the UK

Results are presented for a study of spatial distributions and temporal trends in concentrations of lead (Pb) from different sources in soil and vegetation of an arable farm in central Scotland in the decade since the use of leaded petrol was terminated. Isotopic analyses revealed that in all of the samples analysed, the Pb conformed to a binary mixture of petrol Pb and Pb from industrial or indigenous geological sources and that locally enhanced levels of petrol Pb were restricted to within 10 m of a motorway and 3 m of a minor road. Overall, the dominant source of Pb was historical emissions from nearby industrial areas. There was no discernible change in concentration or isotopic composition of Pb in surface soil or vegetation over the decade since the ban on the sale of leaded petrol. There was an order of magnitude decrease in Pb concentrations in road dust over the study period, but petrol Pb persisted at up to 43% of the total Pb concentration in 2010. Similar concentrations and spatial distributions of petrol Pb and non petrol Pb in vegetation in both 2001 and 2010, with enhanced concentrations near roads, suggested that redistribution of previously deposited material has operated continuously over that period, maintaining a transfer pathway of Pb into the biosphere. The results for vegetation and soil transects near minor roads provided evidence of a non petrol Pb source associated with roads/traffic, but surface soil samples from the vicinity of a motorway failed to show evidence of such a source.     

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.     

Childhood lead exposure and uptake in teeth in the Cleveland area during the era of leaded gasoline

Childhood uptake of lead from exposure to atmospheric leaded gasoline in the United States has been studied using mainly blood lead levels. Since reliable blood lead techniques were used only after the peak use of leaded gasoline, the prior exposure history is unclear. The well-documented decline in blood lead levels after the mid-1970s could represent the continuation of a historic steady decline in exposure from many sources. Alternatively, the post-1970s decline might represent the declining phase of a unimodal rise and fall corresponding closely to usage of leaded gasoline. To assess these possibilities, lead concentration and 207Pb/206Pb isotope ratios were measured in the enamel of permanent molar teeth formed between 1936 and 1993 in mainly African-American donors who grew up in the Cleveland area. Tooth enamel preserves the lead concentration and isotope ratio that prevails during tooth formation. Historical trends in enamel lead concentration were significantly correlated with surrogates of atmospheric lead exposure: lead in sediments of two dated Lake Erie cores, and lead consumed in gasoline. About two-thirds of the total lead uptake into enamel in this period was attributable to leaded gasoline, and the remainder to other sources (e.g. paint). Enamel 207Pb/206Pb isotope ratios were similar to those of one lake sediment. Multivariate analysis revealed significant correlation in neighborhoods with higher levels of traffic, and including lake sediment data, accounted for 53% of the variation in enamel lead levels. Enamel lead concentration was highly correlated with reported African-American childhood blood levels. The extrapolated peak level of 48 μg/dL (range 40 to 63) is associated with clinical and behavioral impairments, which may have implications for adults who were children during the peak gasoline lead exposure. In sum, leaded gasoline emission was the predominant source of lead exposure of African-American Cleveland children during the latter two-thirds of the 20th century.     

Anthropogenic impacts in North Poland over the last 1300 years — A record of Pb, Zn, Cu, Ni and S in an ombrotrophic peat bog

Lead pollution history over Northern Poland was reconstructed for the last ca. 1300 years using the elemental and Pb isotope geochemistry of a dated Polish peat bog. The data show that Polish Pb-Zn ores and coal were the main sources of Pb, other heavy metals and S over Northern Poland up until the industrial revolution. After review of the potential mobility of each element, most of the historical interpretation was based on Pb and Pb isotopes, the other chemical elements (Zn, Cu, Ni, S) being considered secondary indicators of pollution. During the last century, leaded gasoline also contributed to anthropogenic Pb pollution over Poland. Coal and Pb-Zn ores, however, remained important sources of pollution in Eastern European countries during the last 50 years, as demonstrated by a high ²⁰⁶Pb/²⁰⁷Pb ratio (1.153) relative to that of Western Europe (ca. 1.10). The Pb data for the last century were also in good agreement with modelled Pb inventories over Poland and the Baltic region.     

European isotopic signatures for lead in atmospheric aerosols: a source apportionment based upon 206Pb/207Pb ratios

To investigate the capability of the lead isotope signature technique to support a source apportionment study at a Continental scale, atmospheric particulate matter was collected at Cap Gris-Nez (Eastern Channel, northern France), over one year (1995-1996). Four days retrospective trajectories of air masses were available during each sampling experiment. Twenty-eight samples, for which the origin of aerosols was unambiguously determined, were selected for isotopic measurements. Considering the Enrichment Factors, EF(Crust) of lead and its size distribution, we show that lead is mostly from anthropogenic origin and mainly associated with [0.4 < diameter < 0.9 microm] particles. The extent to which various Continental sources influence the lead abundance in aerosols is exhibited by considering both the lead concentration and the origin of air masses. Lead concentration is higher by a factor of approximately seven, when air masses are derived from Continental Europe, by comparison with marine air masses. Taking into account these concentrations and the vertical movements of air masses, we compare the different isotopic compositions using a statistical non-parametric test (Kolmogorov-Smirnov). We produce evidence that, for most of the cases, air masses originating from Continental Europe exhibit a more radiogenic composition (1.134 < 206Pb/207Pb < 1.172) than air masses coming from the United Kingdom (1.106 < 206Pb/207Pb < 1.124). Generally, lead isotopic compositions in aerosols are clearly distinct from the gasoline signatures in European countries, strongly suggesting that automotive lead is no longer the major component of this metal in the air. Gasoline and industrial isotopic signatures could explain the origin of lead in our aerosol samples. A source apportionment based upon 206Pb/207Pb ratios, suggests that the difference between British (206Pb/207Pb = 1.122 +/- 0.038) and Continental (206Pb/207Pb = 1.155 +/- 0.022) signatures may be largely explained by differences in the petrol lead content of aerosols (23-62% in Great Britain vs. 10-36% in Continental Europe).     

Stable lead isotopic characterisation of the historical record of environmental lead contamination in dated freshwater lake sediment cores from northern and central Scotland

Sediment cores from three Scottish freshwater lakes, Loch Ness in the remote north and Loch Lomond and the Lake of Menteith, much closer to the heavily populated and industrialised central belt were analysed for 210Pb, 137Cs, Pb and stable Pb isotopic composition (206Pb/207Pb). The radionuclide data were used to establish chronologies for the Loch Ness and Loch Lomond cores, but a chronology could not be developed for the Lake of Menteith core, in which the surface sediment had been subject to intense mixing. Although Pb concentrations generally started increasing during the mid-17th Century, a small peak occurred for Loch Ness in the early 16th Century, perhaps attributable to the influence of medieval mining and smelting in mainland Europe. Temporal trends in the pattern of Pb accumulation were similar for Loch Ness and both sites in Loch Lomond, with 40-50% of the anthropogenic Pb deposited prior to the 20th Century. Fluxes of anthropogenic Pb to the lake sediments peaked during the 1950s at all locations where chronologies could be established. The 5-fold increase in anthropogenic Pb inventory for the southern basin of Loch Lomond relative to Loch Ness reflected geographical proximity to the main polluting sources. The 206Pb/207Pb data for anthropogenic Pb in the sediments from Loch Ness and Loch Lomond exhibited largely similar trends related to five different time periods. Pre-1820, the 206Pb/207Pb ratio was close to that for coal (1.181). From 1820 to 1900, a fairly constant 206Pb/207Pb ratio of approximately 1.17 probably resulted from a combination of emissions from the smelting of indigenous Pb ore (1.170) and coal burning (1.181) in Scotland, and industrial activity to the south in England, where Australian Pb of characteristically low 206Pb/207Pb ratio (1.04) was already in use. From 1901 to 1930, the 206Pb/207Pb ratio declined by <0.01, due to the increasing influence of Australian Pb. From 1931 to 1975/1985, the 206Pb/207Pb ratio of anthropogenic Pb declined by a further 0.03 to 0.04, to minimum values from approximately 1975 to 1985, primarily a consequence of car-exhaust emissions of Pb arising from the introduction of alkyl Pb petrol additives (206Pb/207Pb approximately 1.06-1.09). From 1975/1985 to the mid-1990s, the 206Pb/207Pb ratio of anthropogenic Pb increased by up to 0.015, a consequence of a reduction in car-exhaust emissions of Pb, resulting from reductions in the maximum permitted concentration of Pb in petrol, and the introduction and increasing uptake of unleaded petrol. Source apportionment calculations, on the basis of 206Pb/207Pb values in surface sediment, suggested that the contribution of Pb emissions from the use of leaded petrol was 27-40% of the atmospheric burden by the mid-1990s, in line with estimates from rainwater 206Pb/207Pb data.     

Stable lead isotopes and lake sediments--a useful combination for the study of atmospheric lead pollution history

Analysis of stable lead isotopes and lead concentrations in lake-sediment deposits, not least in varved (annually-laminated) sediments, is a useful method to study lead pollution history. This paper presents details from a study of 31 lakes in Sweden. Using a strong acid digestion of sediment samples and ICP-MS analyses, we have found that Swedish lake sediments have a high natural (pre-pollution) 206[Pb]207[Pb] ratio (mean 1.52+/-0.18, range 1.28-2.01, n=31 lakes). In contrast, atmospheric lead pollution derived from metal smelting processes, coal burning and from alkyl-lead added to petrol has a lower ratio (< 1.2). Consequently, when pollution lead deposition began approximately 3500 years ago, the lead isotope ratio of the sediments started to decline, and in modern sediments it is typically < 1.2. Using the isotope and concentration values and a mixing model, the relative contribution of pollution and natural lead in sediment samples can be calculated. The pollution lead records of the Swedish lake sediments show a consistent picture of the atmospheric lead pollution history. Some noticeable features are the Roman peak (approx. 0 AD), the large and permanent Medieval increase (approx. 1000 AD), peaks at approximately 1200 and 1530 AD, the rapid increase after World War II, the peak in the 1970s, and the large modern decline.     

The isotopic composition of lead in man and the environment in Finland 1966-1987: isotope ratios of lead as indicators of pollutant source.

The isotopic composition of lead was determined in samples collected between 1966 and 1987, mainly from the Helsinki area, in emission sources (gasoline, incinerator and lead smelter emissions, coal), air, in samples representing long-term deposition (lichen, soil, lake sediments), and in human tissue. Isotope ratios were determined by thermal ionization mass spectrometry after chemical separation of lead by anion exchange and cathodic electrodeposition. The origin of lead in man and the environment in the Helsinki area was evaluated by using the differences in the measured isotope ratios as an indicator. The mean of the ratio in gasoline (206Pb/207Pb 1.124 +/- 0.026) and the ratios in other emission sources in Helsinki (1.149-1.226) were significantly different. However, the wide range of isotope ratios in gasoline (1.063-1.173) reduced the accuracy when assessing the contribution of the different sources. Lead in air samples from Helsinki (1.123 +/- 0.013) could be attributed to gasoline, as could lead in soil near a highway (1.136 +/- 0.003). By contrast, isotope ratios measured in lichen (1.148 +/- 0.006) indicated considerable amounts of lead from sources with higher 206Pb abundances, evidently industrial sources. The isotope ratios in human liver, lung, and bone from individuals dying between 1976-79 (206Pb/207Pb ratio 1.142 +/- 0.015, 1.151 +/- 0.011, and 1.156 +/- 0.013, respectively) reflect the large lead emissions from the incinerators and lead smelters in the Helsinki area in the 1960s and 1970s. In lake sediment cores a correlation was found between the isotope ratios, lead concentration, and depth. The nonanthropogenic lead of high isotope ratios from bedrock was the major component at depths dated older than 100 years. At the surface of the sediment atmospheric lead prevailed, with ratios similar to those of gasoline, air samples and lichen. In the post-1900 layers, anthropogenic lead made up about 40-95% of the total sedimentary lead.     

The identification of lead ammunition as a source of lead exposure in First Nations: the use of lead isotope ratios

The use of lead shotshell to hunt water birds has been associated with lead-contamination in game meat. However, evidence illustrating that lead shotshell is a source of lead exposure in subsistence hunting groups cannot be deemed definitive. This study seeks to determine whether lead shotshell constitutes a source of lead exposure using lead isotope ratios. We examined stable lead isotope ratios for lichens, lead shotshell and bullets, and blood from residents of Fort Albany and Kashechewan First Nations, and the City of Hamilton, Ontario, Canada. Data were analyzed using ANOVA and regression analyses. ANOVA of isotope ratios for blood revealed significant differences with respect to location, but not sex. Hamilton differed from both Kashechewan and Fort Albany; however, the First Nations did not differ from each other. ANOVA of the isotope ratios for lead ammunition and lichens revealed no significant differences between lichen groups (north and south) and for the lead ammunition sources (pellets and bullets). A plot of (206)Pb/(204)Pb and (206)Pb/(207)Pb values illustrated that lichens and lead ammunition were distinct groupings and only the 95% confidence ellipse of the First Nations group overlapped that of lead ammunition. In addition, partial correlations between blood-lead levels (adjusted for age) and isotope ratios revealed significant (p<0.05) positive correlations for (206)Pb/(204)Pb and (206)Pb/(207)Pb, and a significant negative correlation for (208)Pb/(206)Pb, as predicted if leaded ammunition were the source of lead exposure. In conclusion, lead ammunition was identified as a source of lead exposure for First Nations people; however, the isotope ratios for lead shotshell pellets and bullets were indistinguishable. Thus, lead-contaminated meat from game harvested with lead bullets may also be contributing to the lead body burden.     

Lead decline in the Indian environment resulting from the petrol-lead phase-out programme

Recently, the lead content of various environmental components has decreased in response to replacement of leaded petrol by unleaded petrol. In India, 15 research studies are here assessed with respect to lead concentrations in various environmental components during the leaded petrol phase (before 1996), the transitional phase (1996-2000) and the unleaded petrol phase (2000 onwards). The Ganga River Water exhibited a decrease in lead concentration from 18.0 microg/l in 1988 to 3.1 microg/l in 2001. In Lucknow urban centre, mean lead concentrations in the urban air decreased from 1.6 microg/m(3) in 1994 to 0.2 microg/m(3) in 2002. Lead concentrations in Dalbergia sissoo tree leaves also decreased from 18.7 microg/g dry wt. in 1994 to 8.3 microg/g dry wt. in 2004. Mean blood-lead levels of children from Mumbai, Chennai, Bangalore, Amritsar and Lucknow urban centres have fallen from 18.1 microg/dl in the leaded petrol phase to 12.1 microg/dl in the unleaded petrol phase. The petrol-lead phase-out effort in India has reduced lead concentrations in the various environmental components after 2000. It will help to reduce the exposure of millions of people to environmental lead.     

A lead isotopic assessment of tree bark as a biomonitor of contemporary atmospheric lead

The outermost bark layer of trees, predominantly Scots pine (Pinus sylvestris), was sampled at 82 non-urban locations from six arbitrarily designated areas (Northwest, Northeast, Central Highlands, Central and East, Central and Southwest, Southeast), throughout Scotland during 2002-2003 and analysed for lead concentration and stable lead isotopes by flame atomic absorption spectrometry (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The mean lead concentration and mean (206)Pb/(207)Pb ratio (+/-1 standard deviation, SD) for bark samples from the areas were as follows: Northwest (8.0 mg kg(-1), 1.121+/-0.014, n=17), Northeast (8.9 mg kg(-1), 1.117+/-0.012, n=12), Central Highlands (11.3 mg kg(-1), 1.130+/-0.010, n=11), Central and East (35.3 mg kg(-1), 1.120+/-0.007, n=10), Central and Southwest (20.6 mg kg(-1), 1.125+/-0.018, n=22) and Southeast (34.4 mg kg(-1), 1.120+/-0.005, n=10), with an overall mean lead concentration of 18.5 mg kg(-1) (range 0.6-146 mg kg(-1), median 8.4 mg kg(-1)) and an overall mean (206)Pb/(207)Pb ratio of 1.122+/-0.014 (range 1.089-1.168, median 1.122). The overall mean (206)Pb/(207)Pb ratio for bark was therefore significantly lower (p<0.01, t test) than the mean atmospheric (206)Pb/(207)Pb ratio of 1.154+/-0.006 (range 1.144-1.167, n=50) and 1.154+/-0.010 (range 1.134-1.171, n=26) as determined in rainwater collected routinely at Glensaugh, Central Highlands, during 2002 and 2003, respectively. The bark (206)Pb/(207)Pb values, 90% of which lay between 1.10 and 1.14, were more akin to those recorded for the atmosphere (via rainwater, atmospheric particulates, moss, etc.) at various locations throughout Scotland during the 1990s, a decade over which the use of leaded petrol (mean (206)Pb/(207)Pb ratio=1.076+/-0.011) declined markedly before its complete withdrawal in 2000. This strongly suggests that the lead content and isotopic composition of tree bark from Scots pine, which reputedly sheds its outer layers every couple of years or so, reflect exposure to atmospherically deposited lead (in the atmosphere or soil) over a much longer time period than just the previous 2-3 years of exposure to contemporary atmospheric lead. The possible influence of soil lead upon tree bark through external attachment was not observed in a comparative sub-set study of 27 paired bark (mean (206)Pb/(207)Pb ratio=1.122+/-0.016) and surface (0-2 cm) soil (mean (206)Pb/(207)Pb ratio=1.145+/-0.022) samples, in only six cases (i.e. 22%) of which did the corresponding (206)Pb/(207)Pb ratios agree within +/-2 SD. Likewise, bark (206)Pb/(207)Pb values exhibited no discernible trend with distance from the nearest road, with similar average values for 0-20 m (1.123+/-0.015, n=34) and 20-700 m (1.122+/-0.012, n=48), although the corresponding mean (and median) lead concentration of 23.5 (10) mg kg(-1) vs. 14.9 (7.5) mg kg(-1) was slightly higher for the former. The influence of airborne dusts from waste deposits related to former mining/smelting of Wanlockhead/Leadhills lead ores ((206)Pb/(207)Pb=1.170+/-0.003) could be seen, however, in the sycamore bark lead concentrations of up to 3050 mg kg(-1) and (206)Pb/(207)Pb ratios (1.168-1.171) observed at a distance of 0.5 km away.     

Temporal trends of pollution Pb and other metals in east-central Baffin Island inferred from lake sediment geochemistry

Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20° latitude, showed great variability with respect to Pb concentration and stable isotopic Pb ratios, with little apparent latitudinal trend. To constrain the temporal evolution of regional Pb pollution, a well-dated core from one of the sites, Lake CF8 on east-central Baffin Island, was analyzed geochemically at high stratigraphic resolution. A pronounced decrease in the ²⁰⁶Pb/²⁰⁷Pb ratio occurs in sediments deposited between 1923 and the mid-1970s, likely reflecting alkyl-Pb additives derived from the combustion of fossil fuels at a global scale. A two-component mixing model indicates that 17-26% of the Pb in the labile fraction of sediments deposited in Lake CF8 between 2001 and 2005 is from anthropogenic input. A Pb-Pb co-isotopic plot (²⁰⁶Pb/²⁰⁷Pb vs.²⁰⁸Pb/²⁰⁶Pb ratios) of the Lake CF8 time series data indicates multiple possible sources of industrial Pb pollution. Despite widespread reductions in industrial Pb emissions since the 1970s, there is no evidence for attendant reductions of pollution Pb at Lake CF8. Enhanced scavenging from increased primary production as well as changing precipitation rates as climate warms may represent important factors that modulate Pb deposition to Lake CF8, and Arctic lakes elsewhere.