Heavy metals and Pb isotopic composition of aerosols in urban and suburban areas of Hong Kong and Guangzhou,South China—Evidence of the long-range transport of air contaminants

Rapid urbanization and industrialization in South China has placed great strain on the environment and on human health. In the present study, the total suspended particulate matter (TSP) in the urban and suburban areas of Hong Kong and Guangzhou, the two largest urban centres in South China, was sampled from December 2003 to January 2005. The samples were analysed for the concentrations of major elements (Al, Fe, Mg and Mn) and trace metals (Cd, Cr, Cu, Pb, V and Zn), and for Pb isotopic composition. Elevated concentrations of metals, especially Cd, Pb, V and Zn, were observed in the urban and suburban areas of Guangzhou, showing significant atmospheric trace element pollution. Distinct seasonal patterns were observed in the heavy metal concentrations of aerosols in Hong Kong, with higher metal concentrations during the winter monsoon period, and lower concentrations during summertime. The seasonal variations in the metal concentrations of the aerosols in Guangzhou were less distinct, suggesting the dominance of local sources of pollution around the city. The Pb isotopic composition in the aerosols of Hong Kong had higher ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios in winter, showing the influence of Pb from the northern inland areas of China and the Pearl River Delta (PRD) region, and lower ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios in summer, indicating the influence of Pb from the South Asian region and from marine sources. The back trajectory analysis showed that the enrichment of heavy metals in Hong Kong and Guangzhou was closely associated with the air mass from the north and northeast that originated from northern China, reflecting the long-range transport of heavy metal contaminants from the northern inland areas of China to the South China coast.     

Historical reconstruction of atmospheric lead pollution in central Yunnan province, southwest China: an analysis based on lacustrine sedimentary records

Atmospheric lead (Pb) pollution during the last century in central Yunnan province, one of the largest non-ferrous metal production centers in China, was reconstructed using sediment cores collected from Fuxian and Qingshui Lakes. Lead concentrations and isotopic ratios (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) were measured in sediment cores from both lakes. The operationally defined chemical fractions of Pb in sediment core from Fuxian Lake were determined by the optimized BCR procedure. The chronology of the cores was reconstructed using ²¹⁰Pb and ¹³⁷Cs dating methods. Similar three-phase variations in isotopic ratios and enrichment factors of Pb were observed in the sediment cores from both lakes. Before the 1950s, the sediment data showed low ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios and enrichment factors (EFs?=?~1), indicating that the sedimentary Pb was predominantly of lithogenic origin. However, these indices were increased gradually between the 1950s and the mid-1980s, implying an atmospheric Pb deposition. The EFs and isotopic ratios of Pb reached their peak during recent years, indicating aggravating atmospheric Pb pollution. The average anthropogenic Pb fluxes since the mid-1980s were estimated to be 0.032 and 0.053 g m^?2 year^?1 recorded in Fuxian and Qingshui cores, respectively. The anthropogenic Pb was primarily concentrated in the reducible fraction. Combining the results of Pb isotopic compositions and chemical speciations in the sediment cores and in potential sources, we deduced that recent aggravating atmospheric Pb pollution in central Yunnan province should primarily be attributed to regional emissions from non-ferrous metal production industries.     

A European lead isotope signal recorded from 6000 to 300 years BP in coastal marshes (SW France)

Cores covering the last 6000 years were recovered from two marshes from south-western France. They were studied in an attempt to build a reliable regional record of heavy metal pollution. The cores were dated using ¹⁴C and historical data. Both Pb concentrations and Pb isotopic composition (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb) were measured in bulk sediment samples using the inductively coupled plasma-mass spectrometer technique. The evolution of the ²⁰⁶Pb/²⁰⁷Pb ratio recorded in both marshes reveals a good correlation with the worldwide Pb production during the last 5000 years. The lead isotopic records reveal some general trends, along with a few typical events such as the imprints of the pre-anthropogenic background between 6000 and 2300 years BP, the mining activity during the Roman and Greek periods from 2300 to 1700 years BP, the fall of the Roman Empire and the mining activity in Central Europe since the 11th century AD. These results are also consistent with records obtained in other European environments. Consequently, the European atmospheric signal is recorded in these marshes, hiding expected local riverine contributions. Thus, such records may contribute to the construction of a chronological standard curve for continental environments. However, it will be necessary to study other records more accurately dated to obtain an adequate precision before such a reference curve can be set-up.     

Lead contamination of the Seine River, France: geochemical implications of a historical perspective

Four sediment cores collected in the Seine River basin and dated between 1916 and 2003 were analyzed for lead concentrations and isotopic composition. In all four cores, the measured Pb concentration (up to 460 mg kg⁻¹) lies significantly above the natural background (27-40 mg kg⁻¹), although a significant decrease (down to 75 mg kg⁻¹) was observed during the second half of the 20th century which can be explained by the reduction of lead emissions. The ²⁰⁶Pb/²⁰⁷Pb ratio measured in these samples indicates that the main source of Pb used in the Paris conurbation is characterized by a “Rio Tinto” signature (defined as ²⁰⁶Pb/²⁰⁷Pb = 1.1634 ± 0.0001). A high contribution, up to 25%, from the leaded gasoline (characterized by ²⁰⁶Pb/²⁰⁷Pb = 1.08 ± 0.02) is revealed in the Seine River downstream Paris, indicating that lead from the leaded gasoline is preferentially released to the river.The dominating Pb signature in the Paris conurbation that is currently sampled through incinerators fumes (²⁰⁶Pb/²⁰⁷Pb = 1.1550 ± 0.0005) and waste water treatment plant (²⁰⁶Pb/²⁰⁷Pb = 1.154 ± 0.002), represents a mixture of highly recycled lead from the Rio Tinto mine and lead from leaded gasoline (imprinted by the low ²⁰⁶Pb/²⁰⁷Pb of the Broken Hill mine). This signature is called “urban” rather than “industrial”, because it is clearly distinct from the Pb that is found in areas contaminated by heavy industry, i.e. the heavy industries located on the Oise River which used lead from European ores characterized by high ²⁰⁶Pb/²⁰⁷Pb ratios (∼1.18-1.19) and possibly a minor amount of North American lead (²⁰⁶Pb/²⁰⁷Pb ratios > 1.20). The “urban” signature is also found in a rural area upstream of Paris in the 1970’s. At the Seine River mouth in 2003, Pb with an urban signature represents 70% of the total Pb sediment content, with the 30% remaining corresponding to natural Pb.     

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.     

Pb isotope ratios of lake sediments in West Greenland: inferences on pollution sources

Lead (Pb), like many other pollutants, is carried into the Arctic by long-range atmospheric transport from industrial centers at lower latitudes. Unlike other pollutants, Pb can be used to assess emission source regions through the use of stable Pb isotope analyses. Using sediment cores from 17 lakes (three profiles and 14 top/bottom sample pairs) in the Søndre Strømfjord (Kangerlussuaq) region, West Greenland (67°N), this study assesses the extent and origin of Pb pollution along a 150 km transect between the Inland Ice and Davis Strait. Like ice core analyses from the interior of Greenland, the isotope analyses suggest pre-industrial contamination, although significant concentration changes in the lake sediments do not occur until the 18th/19th centuries, with the maximum concentrations occurring about 1970. Compared to the background, the Pb concentrations in recent sediments have increased about 2.5-fold, with slightly higher enrichments towards the coast, where annual precipitation is highest. For all of the lakes, there is a major decline in the ²⁰⁶Pb/²⁰⁷Pb ratio in the recent sediments (mean 1.218±0.030) as compared to deeper sediments (mean 1.365±0.084). Using a Pb isotope mixing model, we calculated an excess Pb isotope ratio, i.e. the isotope ratio necessary to produce the observed declines in recent sediments. While studies of atmospheric aerosols in the high Arctic (²⁰⁶Pb/²⁰⁷Pb ratio ∼1.16) have indicated that Russian emissions (²⁰⁶Pb/²⁰⁷Pb ratio ∼1.15–1.16) are a dominant source of arctic pollution, the excess Pb ratios of the lake sediments in the Søndre Strømfjord region (²⁰⁶Pb/²⁰⁷Pb ratio ∼1.14–1.15), in the low Arctic, suggest that W Europe (²⁰⁶Pb/²⁰⁷Pb ratio ∼1.14) is also a major emission source for this region.     

Bioaccumulation kinetics of sediment-associated DE-83 in benthic invertebrates (Nereis succinea, polychaete)

Polychaetes (Nereis succinea) were exposed to DE-83 contaminated sediments to investigate the bioaccumulation and bioavailability of nona- and deca-BDEs in sediment. All the major congeners in DE-83 were bioavailable to the lugworms. The uptake coefficients (K_s) of nona- and deca-BDE congeners in lugworms were in the range of 0.18-0.65 (d⁻¹), with the values of BDE-207 and -208 slightly higher than those of BDE-206 and -209. Elimination of nona- and deca-BDE congeners from lugworms was very fast. The estimated half-lives of nona- and deca-BDE congeners in the lugworms were at 0.7 d. The bioavailability of nona- and deca-BDE congeners was very low, with BSAF of 0.017 for BDE-206 and -209 and 0.054 for BDE-207 and -208. These may be due to the large molecular size and high affinity of PBDEs to sediment particles. The contribution of BDE-206 in the profile of nona-BDEs in lugworm tissue decreased with exposure time while those of BDE-207 and -208 increased, which could be the result of the biotransformation of BDE-209 to BDE-207 and -208.     

Contamination and source differentiation of Pb in park soils along an urban-rural gradient in Shanghai

Urban soil Pb contamination is a great human health risk. Lead distribution and source in topsoils from 14 parks in Shanghai, China were investigated along an urban-rural gradient. Topsoils were contaminated averagely with 65 mg Pb kg⁻¹, 2.5 times higher than local soil background concentrations. HCl-extracts contained more anthropogenic Pb signatures than total sample digests as revealed by the higher ^207/206Pb and ^208/206Pb ratios in extracts (0.8613 ± 0.0094 and 2.1085 ± 0.0121 versus total digests 0.8575 ± 0.0098 and 2.0959 ± 0.0116). This suggests a higher sensitivity of HCl-extraction than total digestion in identifying anthropogenic Pb sources. Coal combustion emission was identified as the major anthropogenic Pb source (averagely 47%) while leaded gasoline emission contributed 12% overall. Urbanization effects were observed by total Pb content and anthropogenic Pb contribution. This study suggests that to reduce Pb contamination, Shanghai might have to change its energy composition to clean energy.     

Isotope ratios of lead in Japanese women’s hair of the twentieth century

Introduction  

Isotope ratios of lead (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) in Japanese women’s hair of the twentieth century were measured to evaluate lead contamination of human proximate environment of those days.     

Characteristics of lead geochemistry and the mobility of Pb isotopes in the system of pedogenic rock–pedosphere–irrigated riverwater–cereal–atmosphere from the Yangtze River delta region,China

Knowledge of the characteristics of Pb and its isotopic transfer in different compartments is scant, especially for the mobility of Pb isotopes in the geochemical cycle. The present study characterizes differential Pb transport mechanism and the mobility of Pb isotopes in the pedogenic parent rock–pedosphere–irrigated riverwater–cereal–atmosphere system in the Yangtze River delta region, by determining Pb concentration and Pb isotopic ratios of pedogenic parent rocks, fluvial suspended particle matter, tillage soils, soil profiles, irrigated riverwater, fertilizer, Pb ore, cereal roots and grains. The results show that Pb isotopes in the geochemical cycle generally follow the equation of ²⁰⁸Pb/²⁰⁶Pb = −1.157 × ²⁰⁶Pb/²⁰⁷Pb + 3.46 (r² = 0.941). However, Pb isotopes have different mobility in different environmental matrixes. Whereas in the pedosphere, the heavier Pb (²⁰⁸Pb) usually shows stronger mobility relative to the lighter Pb, and is more likely to transfer into soil exchangeable Pb fraction and carbonates phase. The lighter Pb shows stronger transfer ability from soil to cereal grain via root compared to the heavier Pb. However, the cereal grains have lower ²⁰⁶Pb/²⁰⁷Pb and higher ²⁰⁸Pb/²⁰⁶Pb ratios than root and tillage soil, similar to the airborne Pb and anthropogenic Pb, implying that a considerable amount of Pb in cereal grains comes from the atmosphere. The estimate model shows that 16.7–52.6% (average: 33.5%) of Pb in rice grain is the airborne Pb.     

Atmospheric Pb isotopic composition and trace metal concentration as revealed by epiphytic lichens:: an investigation related to two altitudinal sections in Eastern France

During Fall 1996, epiphytic lichens were collected along altitudinal sections in two areas of France (the Vosges mountains in the North-East, and the Alps, in Haute-Savoie) in order to verify any geographic distribution of atmospheric metals on a small scale. These lichens have various Pb isotopic compositions (²⁰⁶Pb/²⁰⁷Pb=1.126–1.147) which are correlated with the altitude of sampling. Lichens sampled near valleys display isotopic ratios significantly less radiogenic than those sampled at several hundred to thousand meters of altitude. In the Vosges sections, Pb concentrations and isotopic compositions of lichens may be used to define three zones: (1) valley: Pb-rich and non-radiogenic ratios, (2) transition: low-Pb and intermediate isotopic compositions, (3) mountain: heterogeneous Pb concentrations but more radiogenic and homogeneous Pb isotopic composition. Other metals (Zn, Cu, Cd, As), when normalised one to another, are not fractionated between these zones and display homogeneous relative abundance along the altitudinal sections of both sites. Variation of ²⁰⁶Pb/²⁰⁷Pb ratios with altitude is interpreted in terms of mixing of at least two pollution sources: one being the petrol (leaded and/or unleaded) combustion, and the other being of industrial origin. The latter is characterised by a more radiogenic isotopic composition. The Pb isotopic composition of flue gas residues from different municipal solid waste combustors in the Rhine valley and in other areas of France would suggest that these plants might be an important source of industrial Pb in the atmosphere. If the average industrial Pb in France has a ²⁰⁶Pb/²⁰⁷Pb close to 1.15, between 60 and 80% of the total Pb in lichens from the Rhine valley would come from gasoline combustion, whereas 85–90% of the Pb would have an industrial origin in lichens from higher altitude in the Vosges mountains. Although lichens from the Alps were collected at higher altitude, the percentage of industrial Pb for these lichens would be slightly lower (65%). Major winds and convection winds in the different valleys must then play an important role in term of distribution of atmospheric Pb in function of altitude.     

Pb isotopes as tracers of mining-related Pb in lichens, seaweed and mussels near a former Pb-Zn mine in West Greenland

Identification of mining-related contaminants is important in order to assess the spreading of contaminants from mining as well as for site remediation purposes. This study focuses on lead (Pb) contamination in biota near the abandoned ‘Black Angel Mine’ in West Greenland in the period 1988-2008. Stable Pb isotope ratios and total Pb concentrations were determined in lichens, seaweed and mussels as well as in marine sediments. The results show that natural background Pb (²⁰⁷Pb/²⁰⁶Pb: 0.704-0.767) and Pb originating from the mine ore (²⁰⁷Pb/²⁰⁶Pb: 0.955) have distinct isotopic fingerprints. Total Pb in lichens, seaweed, and mussels was measured at values up to 633, 19 and 1536 mg kg⁻¹ dry weight, respectively, and is shown to be a mixture of natural Pb and ore-Pb. This enables quantification of mining-related Pb and shows that application of Pb isotope data is a valuable tool for monitoring mining pollution.     

Multivariate statistical study of heavy metal enrichment in sediments of the Pearl River Estuary

The concentrations and chemical partitioning of heavy metals in the sediment cores of the Pearl River Estuary were studied. Based on Pearson correlation coefficients and principal component analysis results, Al was selected as the concentration normalizer for Pb, while Fe was used as the normalizing element for Co, Cu, Ni and Zn. In each profile, sections with metal concentrations exceeding the upper 95% prediction interval of the linear regression model were regarded as metal enrichment layers. The heavy metal accumulation mainly occurred at sites in the western shallow water areas and east channel, which reflected the hydraulic conditions and influence from riparian anthropogenic activities. Heavy metals in the enrichment sections were evaluated by a sequential extraction method for possible chemical forms in sediments. Since the residual, Fe/Mn oxides and organic/sulfide fractions were dominant geochemical phases in the enriched sections, the bioavailability of heavy metals in sediments was generally low. The 206Pb/207Pb ratios in the metal-enriched sediment sections also revealed the influence of anthropogenic sources. The spatial distribution of cumulative heavy metals in the sediments suggested that the Zn and Cu mainly originated from point sources, while the Pb probably came from non-point sources in the estuary.     

<Emphasis Type="Bold">Tracing lead contamination in foods in the city of Kolkata,India</Emphasis>

Lead isotopic ratios (LIR) of eight common food items, street dust, coal, diesel, sediments, lead ore and rainwater from India have been reported for the first time in this paper. This study characterized the source and extent of lead pollution in the different foodstuff consumed in Kolkata, a major metropolis of eastern India. The atmospheric lead input to the food items, sold openly in busy roadside markets of the city, has been quantified. The mean 207/206 and 208/206 LIRs of the eight food items ranged from 0.8847 to 0.8924 and 2.145 to 2.167, respectively. Diesel had the highest mean 207/206 and 208/206 values of 0.9015 and 2.1869, respectively, apart from the lead ore. The food items had a mean lead concentration between 3.78 and 43.35 mg kg^?1. The two ratio scatter plots of all the different environmental matrices were spread linearly between the uncontaminated Ichapur sediment and diesel. The 207/206 LIRs of the coal with a mean of 0.8777 did not fall in the linear trend, while the street dust and food samples overlapped strongly. The rainwater sample had a 207/206 LIR of 0.9007. Contaminated sediments in Dhapa, the repository of the city’s municipal garbage, had a mean 207/206 LIR of 0.8658. The corresponding value obtained from the sewage-fed vegetable grown there was 0.8058. The present study indicated that diesel was one of the main contributor to Pb pollution. The atmospheric lead contribution to the food items was in the range of 68.48–86.66 %.     

Trace metal contamination of sediments in an e-waste processing village in China

This study examined trace metal contamination of sediments in Guiyu, China where primitive e-waste processing activities have been carried out. It was found that some river sediments in Guiyu were contaminated with Cd (n.d.-10.3mg/kg), Cu (17.0-4540mg/kg), Ni (12.4-543mg/kg), Pb (28.6-590mg/kg), and Zn (51.3-324mg/kg). The (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios of the Pb-contaminated sediments of Lianjiang (1.1787+/-0.0057 and 2.4531+/-0.0095, respectively) were lower than those of Nanyang River (1.1996+/-0.0059 and 2.4855+/-0.0082, respectively), indicating a significant input of non-indigenous Pb with low (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios. Copper, Pb and Zn in the non-residual fractions noticeably increased in the contaminated sediments compared to those in the uncontaminated sediments. A genuine concern is associated with potential transport of the contaminated sediments downstream and enhanced solubility and mobility of trace metals in the non-residual fractions.     

Tracking historical lead pollution in the coastal area adjacent to the Yangtze River Estuary using lead isotopic compositions

The rapid economic development in the Yangtze River Delta (YRD), China in the last three decades has had a significant impact on the environment of the East China Sea (ECS). Lead isotopic compositions of a ²¹⁰Pb dated sediment core collected from the coastal ECS adjacent to the Yangtze River Estuary were analyzed to track the Pb pollution in the region. The baseline Pb concentration in the coastal ECS sediments before the industrialization in China was 32 μg g⁻¹, and the corresponding ²⁰⁶Pb/²⁰⁷Pb ratio was 1.195. The high-resolution profiles of Pb flux and ²⁰⁶Pb/²⁰⁷Pb ratios had close relationships with the economic development and the history of the use of leaded gasoline in China, and they were clearly different from those of most European countries and United States.     

Organochlorine pesticides,polybrominated biphenyl ethers and lead isotopes during the spring time at the Waliguan Baseline Observatory,northwest China: Implication for long-range atmospheric transport

Located in the center of the Asian continent, the Waliguan Baseline Observatory (WBO) is the highest and the most inland Global Atmospheric Watch (GAW) station in the world. In the present study, organochlorine pesticides (OCPs) and polybrominated biphenyl (PBDEs) were analyzed in the daily collected samples at the WBO from 2 April to 23 May 2005, in an attempt to investigate the long-range atmospheric transport (LRAT) of persistent organic pollutants (POPs) in northwest China. The mean concentrations of OCPs at WBO were slightly higher than the Arctic regions, and the concentrations of total PBDEs (8.3±4.0 pg m⁻³) was comparable with other remote areas. The low temperature dependence of the POP concentrations in the air, and the absence of local use of these compounds implied LRAT to WBO. As suggested by backward air trajectory analysis, the high concentrations of γ-HCH, DDTs and PBDEs, during the sampled spring period, were mainly related to air mass passing over the neighboring countries (e.g., Russia, Kazakhstan). Additional evidence was also obtained by the lead isotopic composition analysis, which showed similar ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios as those of ores in these countries. The present results indicate that the WBO may serve as an excellent GAW station for monitoring the LRAT of POPs in the Asian continent.     

Lead isotopes in rainfall collected by a sequential sampler in suburban Tokyo

Sequential rainfall collections were obtained with a 1-mm precipitation interval at a suburban site in Tokyo. The lead–isotope composition of each fraction was precisely determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The results showed that lead isotopes clearly changed during a single rainfall event for all rainfall events investigated, and large variations were observed for three specific events. In these three events, the values of the lead isotopes in the initial stage of rainfall (wash-out stage) were similar to the so-called common lead. As precipitation proceeded, the lead isotopes tended to be more radiogenic, and in the later stage (rain-out stage) they were highly radiogenic (up to ^{206, 207, 208}Pb/²⁰⁴Pb=29.26, 26.03, and 63.64, respectively). The source of lead in the rain-out stage completely differed from that in the wash-out stage for these events. A simple mixing model with two end members (rain-out lead and wash-out lead) could explain the isotopic variations. Preliminary trajectory analysis indicated that the highly radiogenic lead was emitted and transported from South-West China. Coal combustion could be a candidate for rain-out stage lead by a selective emission of radiogenic isotopes (²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb). A selective emission mechanism is discussed. The origin of the wash-out lead may have been local and derived from a mixture of urban particulates, e.g., particles from automobile exhaust, city incinerators, roadside dust, and factory exhaust.     

The Pb pollution fingerprint at Lochnagar: the historical record and current status of Pb isotopes

Ratios of 206Pb/207Pb in a Lochnagar sediment core slowly decline from c. 1.32 at 140 cm to c. 1.23 at 9 cm, and then rapidly decline to c. 1.15 at the surface. Ninety percent of the Pb in the surface sediments can be attributed to anthropogenic sources. The 206Pb/207Pb ratio data imply that catchment peat surface contains a higher fraction of anthropogenic Pb than the sediment surface. The 206Pb/207Pb ratios in the surface of the sediment core are consistent with ratios in trapped sediments collected annually between 1998 and 2003. However, there is no significant decline in these recent samples suggesting that the reduction in atmospheric Pb emissions has not yet been recorded by the sediments due to Pb inputs from the catchment. As catchment peats store about 840 kg previously deposited anthropogenic Pb since 1860, it is likely that catchment inputs will continue to affect future 206Pb/207Pb ratios.     

Accumulation and quantitative estimates of airborne lead for a wild plant (Aster subulatus)

Foliar uptake of airborne lead is one of the pathways for Pb accumulation in plant organs. However, the approximate contributions of airborne Pb to plant organs are still unclear. In the present study, aerosols (nine-stage size-segregated aerosols and total suspended particulates), a wild plant species (Aster subulatus) and the corresponding soils were collected and Pb contents and isotopic ratios in these samples were analyzed. Average concentration of Pb was 96.5 ± 63.5 ng m⁻³ in total suspended particulates (TSP) and 20.4 ± 5.5 ng m⁻³ in the fine fractions of size-segregated aerosols (SSA) (<2.1 μm), higher than that in the coarser fractions (>2.1 μm) (6.38 ± 3.71 ng m⁻³). Enrichment factors show that aerosols and soils suffered from anthropogenic inputs and the fine fractions of the size-segregated aerosols enriched more Pb than the coarse fractions. The order of Pb contents in A. subulatus was roots > leaves > stems. The linear relationship of Pb isotope ratios (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb) among soil, plant and aerosol samples were found. Based on the simple binary Pb isotopic model using the mean ²⁰⁶Pb/²⁰⁷Pb ratios in TSP and in SSA, the approximate contributions of airborne Pb into plant leaves were 72.2% and 65.1%, respectively, suggesting that airborne Pb is the most important source for the Pb accumulation in leaves. So the combination of Pb isotope tracing and the simple binary Pb isotope model can assess the contribution of airborne Pb into plant leaves and may be of interest for risk assessment of the exposure to airborne Pb contamination.