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.     

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.     

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.     

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.     

The origin of atmospheric lead in Oslo,Norway, studied with the use of isotopic ratios

Application of the lead isotope method to differentiate between the local contribution of lead and its portion from long-range transport of air pollution from sources a few thousand kilometers away to the lead pollution level measured in the Oslo area in Norway is discussed. The ²⁰⁶Pb/²⁰⁴Pb ratio is of particular interest in this respect. The results of measurements presented in the paper show that phase-out of lead additives to gasoline in Northern Europe has not phased out the Pb contamination of the environment. The lead isotope method proved very useful to present a contribution of small local sources to the Pb contamination of the air in the Oslo area during the period when the combustion of gasoline, the major source of Pb contamination has been decreasing. Wood combustion is one of these sources in Norway. Lower impact of long-range transport of air pollutants emitted from sources in Eastern and Central Europe and transported with air masses to Scandinavia, during the recent 5 years, can also be traced utilizing isotopic ratios of lead. The application of tree-rings as environmental archives contributed significantly to elucidating the historical Pb pollution.     

Atmospheric lead deposition to Okefenokee Swamp, Georgia, USA

Contamination of the environment from atmospheric deposition during the twentieth century is pervasive even in areas ostensibly considered pristine or remote from point sources. In this study, Pb concentrations in a 210Pb-dated peat core collected from the Okefenokee Swamp, GA were used to assess historical contaminant input via atmospheric deposition. Lead isotope ratios were determined by dynamic reaction cell ICP-MS (DRC-ICP-MS). Increases in Pb concentration occurred in the late nineteenth century and a marked rise in Pb concentrations pre-dated the widespread use of leaded gasoline within the US. The 206Pb/207Pb ratios of 1.19 during this period were consistent with coal combustion emissions. A later increase in Pb concentration, concurrent with a trend toward more radiogenic 206Pb/207Pb ratios in gasoline is consistent with an increased input of Pb from leaded gasoline emissions. However, it appears that coal combustion emissions remain a major source of Pb to the Okefenokee.     

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.     

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.     

Alkylphenolic compounds and bisphenol A contamination within a heavily urbanized area: case study of Paris

This study evaluates the influence of a heavily urbanized area (Paris Metropolitan area), on receiving water contamination by both bisphenol A (BPA) and alkylphenol ethoxylate (APE) biodegradation product. The study began by investigating concentrations within urban sources. In addition to the more commonly studied wastewater treatment plant effluent, wet weather urban sources (including combined sewer overflows, urban runoff, and total atmospheric fallout) were considered. The initial results highlight a significant contamination of all urban sources (from a few nanograms per liter in atmospheric fallout to several micrograms per liter in the other sources) with clearly distinguishable distribution patterns. Secondly, concentration changes along the Seine River from upstream of the Paris Metropolitan area to downstream were investigated. While the concentrations of BPA and nonylphenoxy acetic acid (NP₁EC) increase substantially due to urban sources, the 4-nonylphenol concentrations remain homogeneous along the Seine. These results suggest a broad dissemination of 4-nonylphenol at the scale of the Seine River basin. Moreover, the relationship between pollutant concentrations and Seine River flow was assessed both upstream and downstream of the Paris conurbation. Consequently, a sharp decrease in dissolved NP₁EC concentrations relative to Seine River flow underscores the influence of single-point urban pollution on Seine River contamination. Conversely, dissolved 4-nonylphenol concentrations serve to reinforce the hypothesis of its widespread presence at the Seine River basin scale.     

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.     

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.     

Using stable lead isotopes to trace heavy metal contamination sources in sediments of Xiangjiang and Lishui Rivers in China

Lead isotopes and heavy metal concentrations were measured in two sediment cores sampled in estuaries of Xiangjiang and Lishui Rivers in Hunan province, China. The presence of anthropogenic contribution was observed in both sediments, especially in Xiangjiang sediment. In the Xiangjiang sediment, the lower ²⁰⁶Pb/²⁰⁷Pb and higher ²⁰⁸Pb/²⁰⁶Pb ratio, than natural Pb isotope signature (1.198 and 2.075 for ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively), indicated a significant input of non-indigenous Pb with low ²⁰⁶Pb/²⁰⁷Pb and high ²⁰⁸Pb/²⁰⁶Pb. The corresponding concentrations of heavy metals (As, Cd, Zn, Mn and Pb) were much higher than natural values, suggesting the contaminations of heavy metals from extensive ore-mining activities in the region.     

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.     

Isotopes as tracers of sources of lead and strontium in aerosols (TSP & PM2.5) in Beijing

Even after its being phased out in gasoline in the late 90s, lead (Pb) is still present at relatively high levels in the atmosphere of Beijing, China (0.10–0.18 μg m^?3). Its origin is subject to debate as several distinct sources may contribute to the observed pollution levels. This study proposes to constrain the origin(s) of Pb and strontium (Sr) in aerosols, by coupling both Pb and Sr isotope systematics. The characterisation of the main pollution sources (road traffic, smelters, metal refining plants, coal combustion, cement factories, and soil erosion) shows that they can unambiguously be discriminated by the multi-isotope approach (²⁰⁶Pb/²⁰⁴Pb and ⁸⁷Sr/⁸⁶Sr). The study of total suspended particulates (TSP) and fine particles (PM_2.5) from Beijing and its vicinity indicates that both size fractions are controlled by the same sources. Lead isotopes indicate that metal refining plants are the major source of atmospheric lead, followed by thermal power stations and other coal combustion processes. The role of this latter source is confirmed by the study of strontium isotopes. Occasionally, emissions from cement plants and/or input from soil alteration are isotopically detectable.     

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 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.     

Lead (Pb) isotopic fingerprinting and its applications in lead pollution studies in China: A review

As the most widely scattered toxic metal in the world, the sources of lead (Pb) observed in contamination investigation are often difficult to identify. This review presents an overview of the principles, analysis, and applications of Pb isotopic fingerprinting in tracing the origins and transport pathways of Pb in the environment. It also summarizes the history and current status of lead pollution in China, and illustrates the power of Pb isotopic fingerprinting with examples of its recent applications in investigating the effectiveness of leaded gasoline phase-out on atmospheric lead pollution, and the sources of Pb found in various environmental media (plants, sediments, and aquatic organisms) in China. The limitations of Pb isotopic fingerprinting technique are discussed and a perspective on its development is also presented. Further methodological developments and more widespread instrument availability are expected to make isotopic fingerprinting one of the key tools in lead pollution investigation.     

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.     

Isotopic characterisation of lead in contaminated soils from the vicinity of a non-ferrous metal smelter near Plovdiv, Bulgaria

Soil samples from the vicinity of a non-ferrous metal smelter near Plovdiv, Bulgaria contained very high concentrations of cadmium, lead and zinc (up to 140, 4900 and 5900 mg kg(-1), respectively). A roadside soil in a relatively uncontaminated area also contained high concentrations of the same metals (24, 1550 and 1870 mg kg(-1), respectively) indicating that the transport of ores could be a source of contamination. Even though the lead isotope ratios in all the samples fell within a very narrow range (for example, 1.186-1.195 for (206)Pb/(207)Pb), the samples could be differentiated into three distinct groups: ores ((206)Pb/(207)Pb and (208)Pb/(207)Pb ratios of 1.1874-1.1884 and 2.4755-2.4807, respectively), current deposition (1.1864 and 2.4704-2.4711, respectively) and local background (1.1927-1.1951 and 2.4772-2.4809, respectively). Although most of the current deposition has its origin in the ores used at the smelter, up to 12% could be from other sources such as petrol lead.