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1.
Knowledge of the cause and source of Pb pollution is important to abate environmental Pb pollution by taking source-related actions. Lead isotope analysis is a potentially powerful tool to identify anthropogenic Pb and its sources in the environment. Spatial information on the variation of anthropogenic Pb content and anthropogenic Pb sources in rural topsoils is remarkably limited. This study presents results of a survey of approximately 350 topsoil samples from rural locations covering the entire Netherlands, for which the bulk geochemical and Pb isotope compositions were determined. The specific aim of this study is to determine the anthropogenic Pb sources in the topsoils from rural areas in The Netherlands. The spatial distribution of anthropogenic Pb in soils in The Netherlands will be explained in terms of land use and pollution sources.Nearly all studied topsoils display Pb contents that exceed the amount expected based on the soil lithology. The range in Pb isotope ratios of the additional Pb fraction in rural Dutch topsoils is established at 1.056–1.199, 2.336–2.486 and 0.452–0.490 for 206Pb/207Pb, 207Pb/208Pb and 206Pb/208Pb, respectively. Five land use types are distinguished (forest, open nature, moor, arable land and grassland) with distinct isotopic compositions for added Pb. Additional Pb in soils of natural areas (forest, open nature and moor) has on average lower 206Pb/207Pb, 208Pb/207Pb and 206Pb/208Pb ratios than the agricultural soils (arable land and grassland). Additional Pb in both natural area soils and agricultural soils is interpreted to be of anthropogenic origin: most likely a mixture of coal/galena, incinerator ashes and gasoline Pb. The dominant sources of additional Pb in the topsoil of open nature areas are most likely incinerator ash and gasoline Pb. In contrast, the on average higher 206Pb/207Pb, 208Pb/207Pb and 206Pb/208Pb ratios of additional Pb in agricultural soils are most likely caused by the presence of animal manure and N–P fertilizers.Several areas are observed with notably high additional Pb contents (26–211 mg/kg on an organic matter-free basis) in the topsoil. The largest area is the Randstad area, which has the highest population and traffic density, and hosts a considerable fraction of the Dutch chemical industry. Two other areas with high additional Pb contents in the topsoil are located near the Dutch borders and are most likely influenced by German and Belgian chemical industries. The topsoils in the coastal dunes and southern, central and northern forests are characterized by relatively low additional Pb contents (<10 mg/kg on an organic matter-free basis). The population, traffic and chemical industry density is low in these areas and no fertilizers are applied.  相似文献   

2.
The depth-distribution of lead and its stable isotope ratios were determined in a dated sediment core from a Canadian Shield lake receiving anthropogenic Pb inputs exclusively from atmospheric deposition. The results demonstrate that anthropogenic Pb deposited to the sediments of this lake since the preindustrial period can be modeled successfully using as little as two isotopically distinct Pb types. The first, whose flux was not detectable before 1850, reached a maximum value around 1950, and then decreased significantly thereafter; it was characterized by 206Pb/207Pb and 206Pb/208Pb ratios of 1.222 and 0.495, respectively, and was derived mainly from coal combustion. The second, whose flux was not detectable before 1880, increased sharply to exceed that of the Pb type derived from coal combustion around 1930, and reached a maximum in the mid 1970s; it is characterized by 206Pb/207Pb and 206Pb/208Pb ratios of 1.179 and 0.482, respectively, and was derived mainly from leaded gasoline combustion and industrial sources. The chronology of deposition of these two anthropogenic lead types agrees well with the historical records of fossil fuel uses in Canada and the USA, and also with the history of sediment-deposited polycyclic aromatic hydrocarbons (PAHs) originating from coal combustion. The inventory of Pb derived from coal combustion (0.09 μmol cm−2) is ∼30% of that derived mainly, but not exclusively, from leaded gasoline (0.31 μmol cm−2). Apportionment among source regions of lead deposited to the sediments during the period when leaded gasoline dominated Pb atmospheric emissions indicates that ∼50% of this lead originated in the USA.  相似文献   

3.
The magnitude and sources of lead (Pb) pollution in the Gulf of California Ecoregion (GCE) in northwest Mexico were evaluated using various samples collected from urban and rural areas around two typical subtropical coastal ecosystems. Lead concentrations and isotopic compositions (206Pb/207Pb, 208Pb/207Pb, 206Pb/204Pb and 208Pb/204Pb) were measured using high resolution inductively-coupled plasma mass spectrometry (HR-ICP-MS) and thermal ionization mass spectrometry (TIMS). Urban street dust (157 ± 10.1 μg g− 1) was heavily enriched with Pb, compared to the Pb enrichment of agricultural soils (29.0 ± 16.0 μg g− 1) and surface estuary sediments (35.6 ± 15.4 μg g− 1), all of which contained higher Pb concentrations than found in the natural bedrock (16.0 ± 5.0 μg g− 1). Pb concentrations in SPM (> 95% of total Pb) were significantly higher in sewage effluent (132 ± 49.9 μg g− 1) than in agricultural effluents (29.3 ± 5.9 μg g− 1), and river runoff (7.3 ± 4.2 μg g− 1). SPM in estuary water column averaged 68.3 ± 48.0 μg g−1. The isotopic composition of Pb (206Pb/207Pb, 208Pb/207Pb) in rural samples of aerosols (1.181 ± 0.001, 2.444 ± 0.003) and soil runoff (1.181 ± 0.003, 2.441 ± 0.004) was comparable to that of natural Pb-bearing bedrock (1.188 ± 0.005, 2.455 ± 0.008); while urban samples of aerosols, street dust, and sewage (1.190–1.207, 2.452–2.467) showed a significant contribution from automotive emissions from past leaded gasoline combustion (1.201 ± 0.006, 2.475 ± 0.005). The absence of lead from fertilizer (1.387 ± 0.008, 2.892 ± 0.005) suggests that this mixture is not representative of the GCE. A mixing model revealed that the Pb content in the environmental samples is predominantly derived from natural weathering and the past leaded gasoline combustion with the later influence of inputs from a more radiogenic source related with anthropogenic lead of North American origin (1.21 ± 0.02; 2.455 ± 0.02).  相似文献   

4.
Isotopic evidence for the source of lead in the North Pacific abyssal water   总被引：1，自引：0，他引：1  
The absence of accurate measurements of lead (Pb) isotopic composition in the North Pacific abyssal water has made it difficult to assess the relative importance of what are believed to be the two major Pb sources: the natural Pb introduced during preindustrial time and recent anthropogenic Pb resulting from leaded gasoline combustion and high temperature industrial activities. Here we report a vertical profile of seawater 206Pb/207Pb ratio and a meridional section of Pb concentration in the North Pacific Ocean. We observe 2-3-fold increases in Pb concentration along the deep-water flow path and a deep-water 206Pb/207Pb ratio (∼1.188) substantially lower than the pre-industrial value (∼1.210). These data suggest that anthropogenic Pb has invaded the North Pacific abyssal water and become the predominant Pb source there. A simple model calculation based on these data indicates that the anthropogenic Pb is transported to the deep ocean by sinking particles and that this Pb vertical flux has a 206Pb/207Pb ratio that decreased during the past two centuries.  相似文献   

5.
Lead concentrations and stable lead isotopes (204Pb, 206Pb, 207Pb, 208Pb) were measured in forest moss samples (Pleurozium schreberi or Scleropodium purum) collected at 273 sites across the Czech Republic during 2010. Continuously decreasing median Pb concentrations in moss were documented over the last two decades: 1995: 11 mg/kg, 2000: 5.66 mg/kg, 2005: 4.94 mg/kg and 2010: 2.85 mg/kg. Several local anomalies have decreased in scale, the overall regional distribution patterns remained, however, the same. The regional Pb isotope ratio distributions show that the ratios show little variation for a large central part of the country and provide the large-scale background isotope ratios for the Czech Republic of about 204Pb/206Pb = 0.0550, 206Pb/207Pb = 1.167, 206Pb/208Pb = 0.478 and 207Pb/208Pb = 0.409 for 2010. This background Pb isotope ratio signal in moss has been locally (900–7500 km2) modified by specific Pb isotopic ratio signals caused by deposition of Pb emissions from known local anthropogenic Pb emission sources, such as industrial combustion of local coal, and a variety of industrial enterprises (metallurgical, engineering and glass works). At some sites where mining of uranium and polymetallic ores took place the moss samples show also a locally specific Pb isotope signal. The in terms of area affected largest deviations in the Pb-isotope ratios, e.g., in the Bohemian Massif, may be due to the input of geogenic dust.  相似文献   

6.
Stable Pb-isotope ratios are widely used as tracers for Pb-sources in the environment. Recently, a few publications have challenged the predominating view of environmental applications of Pb-isotopes. Present applications of Pb-isotopic tracers in soils largely represent the northern hemisphere. This study focuses on tropical soils from Paraíba, north-eastern Brazil. Lead concentrations and Pb-isotopic signatures (both 7N HNO3) were determined at 30 sites along a 327 km E–W-transect, from the Atlantic coast at João Pessoa to some kilometers west of Patos, to identify possible processes for the observed (and anticipated) distribution pattern. Thirty samples each of litter (ORG) and top mineral soil (TOP) were taken on pasture land at suitable distance from roads or other potential contamination sources. Lead-content was determined by inductively-coupled plasma atomic emission spectrometry (ICP-AES) and the ratios of 206Pb/207Pb, 206Pb/208Pb, and 208Pb/207Pb by ICP-sector field mass spectrometry (ICP-SFMS). Both sample materials show similarly low Pb-concentrations with a lower median in the ORG samples (ORG 3.4 mg kg−1 versus TOP 6.9 mg kg−1). The 206Pb/207Pb ratios revealed a large spread along the transect with median 206Pb/207Pb ratios of 1.160 (ORG) and 1.175 (TOP). The 206Pb/207Pb ratios differ noticeably between sample sites located in the Atlantic Forest biome along the coast and sample sites in the inland Caatinga biome. The “forest” sites were characterised by a significant lower median and a lower spread in the 206Pb/207Pb and 206Pb/208Pb ratios compared to the Caatinga sites. Results indicate a very restricted influence of anthropogenic activities (individual sites only). The main process influencing the spatial variability of Pb-isotope ratios is supposed to be precipitation-dependent bioproductivity and weathering.  相似文献   

7.
Todos os Santos (all Saints) Bay area on Brazil’s east coast is known for one of the most significant cases of lead contamination in the country owing to the past activities of a Pb-smelter plant. This work was carried out to assess the concentration and sources of Pb based on Pb isotopes and enrichment factor of soil profiles surrounding Todos os Santos Bay in order to understand the expansion of contamination and to help the establishment of Pb regulatory standards for the region. Forty-four samples were collected from soil genetic horizons of six pedons that represent the range of dominant soil properties and geologic materials in the region. Concentrations of Pb and the isotopes 204Pb, 206Pb, 207Pb, and 208Pb were determined on an inductively coupled plasma (quadrupole) mass spectrometry. The soil enrichment factor was calculated using Al and Fe as conservative index elements. Average Pb concentration (15.87 mg kg?1) in uppermost horizons (from all six pedons) is slightly higher than soil background concentrations commonly reported in Brazil. Samples feature a wide range of Pb isotope ratios, ranging from 36.71 to 47.38 for 208Pb/204Pb, 15.00 to 15.65 for 207Pb/204Pb, 16.86 to 20.59 for 206Pb/204Pb, and 1.10 to 1.31 for 206Pb/207Pb. For the enrichment factor calculations, only Fe demonstrated a good agreement with Pb isotopic ratios. Both Pb isotopic composition and enrichment factor were useful tools to distinguishing natural and anthropogenic influence on the Pb soil concentrations.  相似文献   

8.
Concentrations of total lead as high as 1,600 g/L were detected in gasoline-contaminated and uncontaminated groundwater at three gasoline-release sites in South Carolina. Total lead concentrations were highest in turbid groundwater samples from gasoline-contaminated and uncontaminated wells, whereas lower turbidity groundwater samples (collected using low-flow methods) had lower total lead concentrations. Dissolved lead concentrations in all wells sampled, however, were less than 15 g total lead/L, the current United States Environmental Protection Agency (US EPA) maximum contaminant level (MCL). Because many total lead concentrations exceeded the MCL, the source of lead to the groundwater system at two of the three sites was investigated using a stable lead isotope ratio approach. Plots of the stable isotope ratios of lead (Pb) in groundwater as 207Pb/206Pb versus 208Pb/206Pb, and 208Pb/204Pb versus 206Pb/204Pb were similar to ratios characteristic of lead-based minerals in local rocks of the southeastern US, and were not similar to the stable lead isotopes ratios characteristic of distant lead ore deposits such as Broken Hill, Australia, used to produce tetraethyl lead in gasoline products prior to its phase-out and ban in the United States. Moreover, the isotopic composition of dissolved lead was equivalent to the isotopic composition of total lead in turbid samples collected from the same well, suggesting that the majority of the lead detected in the groundwater samples was associated with sediment particulates of indigenous aquifer material, rather than lead associated with spilled leaded gasoline. The results of this investigation indicate that (1) lead detected at some gasoline-release sites may be derived from the local aquifer material, rather than the gasoline release, and consequently may affect site-specific remediation goals; (2) non-low flow groundwater sampling methods, such as a disposable bailer, may result in turbid groundwater samples and high total lead concentrations, and; (3) stable lead isotopes can be used to clarify the source of lead detected above permissible levels in gasoline-contaminated groundwater systems.  相似文献   

9.
 Heavy metal and metalloid concentrations within stream-estuary sediments (<180-μm size fraction) in north-eastern New South Wales largely represent natural background values. However, element concentrations (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn) of Hunter River sediments within the heavily industrialized and urbanized Newcastle region exceed upstream background values by up to one order of magnitude. High element concentrations have been found within sediments of the Newcastle Harbour and Throsby Creek which drains into urbanized and light industry areas. Observed Pb enrichments and low 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios are likely caused by atmospheric deposition of Pb additives from petrol and subsequent Pb transport by road run-off waters into the local drainage system. Sediments of the Richmond River and lower Manning, Macleay, Clarence, Brunswick and Tweed River generally display no evidence for anthropogenic heavy metal and metalloid contamination (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn). However, the rivers and their tributaries possess localized sedimentary traps with elevated heavy metal concentrations (Cu, Pb, Zn). Lead isotope data indicate that anthropogenic Pb provides a detectable contribution to investigated sediments. Such contributions are evident at sample sites close to sewage outlets and in the vicinity of the Pacific Highway. In addition, As concentrations of Richmond River sediments gradually increase downstream. This geochemical trend may be the result of As mobilization from numerous cattle-dip sites within the region into the drainage system and subsequent accumulation of As in downstream river and estuary sediments. Received: 5 September 1997 · Accepted: 4 November 1997  相似文献   

10.
A regional isotopic study of Pb and S in hydrothermal galenas and U–Pb and S in potential source rocks was carried out for part of Moravia, Czech Republic. Two major generations of veins, (syn-) Variscan and post-Variscan, are defined based on the Pb-isotope system together with structural constraints (local structures and regional trends). The Pb-isotopic compositions of galena plot in two distinct populations with outliers in 206Pb/204Pb–207Pb/204Pb space. Galena from veins hosted in greywackes provides a cluster with the lowest Pb–Pb ratios: 206Pb/204Pb = 18.15–18.27, 207Pb/204Pb = 15.59–15.61, 208Pb/204Pb = 38.11–38.23. Those hosted in both limestones and greywackes provide the second cluster: 206Pb/204Pb = 18.37–18.44, 207Pb/204Pb = 15.60–15.63, 208Pb/204Pb = 38.14–38.32. These clusters suggest model Pb ages as Early Carboniferous and Triassic–Jurassic, the latter associated with MVT-like deposits. Two samples from veins hosted in Proterozoic rocks lie outside the two clusters: in metagranitoid (206Pb/204Pb = 18.55, 207Pb/204Pb = 15.64, 208Pb/204Pb = 38.29) and in orthogneiss (206Pb/204Pb = 18.79, 207Pb/204Pb = 15.73, 208Pb/204Pb = 38.54). The results from these two samples suggest an interaction of mineralizing fluids with the radiogenic Pb-rich source (basement?). The values of δ34S suggest the Paleozoic host rocks (mostly ?6.7 to +5.2‰ CDT) as the source of S for hydrothermal sulfides (mostly ?4.8 to +2.5‰ CDT). U–Pb data and Pb isotope evolutionary curves indicate that Late Devonian and Early Carboniferous sediments, especially siliciclastics, are the general dominant contributor of Pb for galena mineralization developed in sedimentary rocks. Plumbotectonic mixing occurred, it is deduced, only between the lower and the upper crust (the latter involving Proterozoic basement containing heterogeneous radiogenic Pb), without any significant input from the mantle. It is concluded that in the Moravo–Silesian and Rhenohercynian zones (including proximal districts in Poland) lead and sulfur have been mobilized from the adjacent rocks during multiple hydrothermal events in processes that are remarkably comparable in timing, geochemistry of fluids and nature of sources.  相似文献   

11.
Isotope ratios of U and Pb were measured in two types of Mn nodules from the Cambrian Timna Formation, Israel. Type A nodules are mainly composed of pyrolusite and hollandite, with Mn, Ba, Pb and U concentrations of 30–60%, 0.2–2.5%, 0.2–1.0% and 500–3500 ppm, respectively, whereas type B nodules were formed by alteration of the former, and contain mainly coronadite, with Mn, Ba, Pb and U concentrations of 7–48%, 0.2–7%, 0.6–5% and 10–160 ppm, respectively. The isotopic composition of U and Pb was measured by MC-ICP-MS on Mn-rich solutions (up to 100 mg/L) without and with chromatographic separation. The values for the 207/206 and 208/206 ratios have been determined with precisions of up to 50 ppm and those of 206/204, 207/204 and 208/204 – up to 200 ppm. The values for the 234/238 ratios have been determined with precisions of 0.4–1%. The results of the separated and unseparated solutions were shown to be equal within the error. Thus there is no significant matrix effect while measuring U and Pb in Mn rich solution using the MC-ICP-MS.The isotopic composition of Pb and U support the distinction between the two types of Mn nodules. Type A nodules have a wide range of 206Pb/204Pb ratios (18.278–19.776), and an almost constant ratio of 208Pb/204Pb. In contrast, type B nodules have almost constant 206Pb/204Pb ratios and a wide range of 208Pb/204Pb ratios (37.986–38.079). Type A nodules form a linear array on a 207Pb/204Pb vs 206Pb/204Pb diagram, while type B nodules form a tight group characterized by lower Pb isotope ratios that slightly deviate from the type A array. The 234U/238U ratio differs between the two types of nodules; type A nodules exhibit a uniform and close to equilibrium 234U/238U ratio while type B nodules show a wide range of 234U/238U ratios above and below the equilibrium value. The isotopic composition of Pb in type A nodules might reflect Pb contributions from plutonic rock weathering, exposed at the time of deposition or later, to the Cambrian sea. These nodules have remained unaffected by processes that occurred since the Cambrian. The higher 208Pb/204Pb values of type B indicate that these nodules were formed from a Th-enriched solution probably during epigenetic processes which occurred also during the last 1 Ma.Thus the two isotopic systems of U and Pb can record formation, leaching and redeposition of Mn ores.  相似文献   

12.
《Applied Geochemistry》1998,13(3):403-413
Lead concentration and isotopic composition of prehistoric (middle and latest Jomon era, 2000–4500 BP, n=6), historic (Edo era, 130–400 BP, n=10), and contemporary (died in 1987–88, n=15) Japanese bones, and deciduous teeth from contemporary Japanese children born during 1985–88 (n=17) were analyzed by inductively coupled plasma mass spectrometry. Lead concentration was lowest in Jomon bones and was higher in rural Edo, contemporary, and urban Edo, in that order. Elevated Pb concentration in historic Edo people, as reported previously, was reconfirmed. The average isotopic ratios (207Pb/206Pb and 208Pb/206Pb) in excavated (prehistoric and historic) bones, contemporary bones, and deciduous teeth were different from each other. The contemporary bones had the least radiogenic composition (mean 207Pb/206Pb: 0.879; mean 208Pb/206Pb: 2.126) while the excavated bones the most (0.848; 2.098), and teeth intermediate (0.866; 2.111). The comparison with the literature data of isotopic compositions of environmental samples showed that the isotopic composition of the excavated bones was within the range of Japanese ores, rocks and soils, indicating the absence of foreign Pb sources in preindustrialized Japan. That of the contemporary bones was closer to the average gasoline Pb, the use of which had been banned in the late 1970s, than to the Pb in airborne particulate matter or refuse incineration ash of 1980s. The average Pb isotopic ratios in the deciduous teeth was close to the isotopic ratios of Pb in airborne particulate matter and refuse incineration ash. These data indicated that the contemporary Japanese population was exposed to foreign Pb which had different isotopic composition from domestic Pb. Exposure to Pb of foreign origin was particularly evidently recorded in people born before the leaded gasoline ban. The history of human Pb contamination in Japan is discussed based on the present results and other previously published data.  相似文献   

13.
Lead isotope analyses of galena from five ore deposits and six prospects in the Aysén region of southern Chile are reported. Most of the deposits are either low sulfidation epithermal gold–silver veins or skarn and manto deposits; the majority are either suspected to be, or dated as, Late Jurassic to mid-Cretaceous. Galena lead isotope data for most of the deposits from southern Chile cluster near the “orogene” within a “plumbotectonic” model framework. Average values (206Pb/204Pb=18.53, 207Pb/204Pb=15.63, and 208Pb/204Pb=38.50) are near Jurassic to Cretaceous model ages on the “orogene” curve of Zartman and Doe (1981) and the second-stage curve of Stacey and Kramers (1975) on a 206Pb/204Pb versus 207Pb/204Pb plot. These model ages are compatible with absolute ages as currently known. The elongate trends in the general cluster indicate mainly an orogenic model fit, suggesting variable mixing of lead from different sources, mainly model upper crust and lesser model mantle and lower crust reservoirs. Galena lead associated with one deposit (El Faldeo) is relatively radiogenic, and lies near a Jurassic age on the “upper crustal” curve of Zartman and Doe (1981), which is compatible with the Ar/Ar age of the deposit. Galena lead isotope clusters define three main groups of deposits. These three groups appear to be related to three mineralizing events, dated by K–Ar and Ar/Ar, in the Late Jurassic (group 3), and in the Early and mid-Cretaceous (groups 1 and 2 respectively). Averages for group 1, the northern group including El Toqui and Katerfeld, are 206Pb/204Pb=18.51, 207Pb/204Pb=15.62, 208Pb/204Pb=38.48. Averages for group 2, the southern group with Fachinal and Mina Silva, are 206Pb/204Pb = 18.56, 207Pb/204Pb=15.63, 208Pb/204Pb=38.52. Averages for group 3, the southernmost group with the El Faldeo, Lago Chacabuco and Lago Cochrane prospects, are 206Pb/204Pb=18.83, 207Pb/204Pb=15.65, 208Pb/204Pb=38.63. The Cretaceous deposits (groups 1 and 2) contain orogene-type lead that becomes increasingly radiogenic southward. Lead from the Late Jurassic deposits (group 3) appears to reflect mixing of orogene lead with highly radiogenic lead. The observed linear array of lead in group 3 probably reflects mixing of orogene lead with highly radiogenic lead, which was likely extracted by selective leaching of mineralizing hydrothermal solutions from the metamorphic basement. Received: 10 July 1999 / Accepted: 15 July 2000  相似文献   

14.
Lead concentrations and isotopic composition of sediment samples collected from three sites within the Lebanese coastal zones were measured: at Akkar, Dora and Selaata. Akkar is located far from any direct source of contamination, while Dora and Selaata receive urban and industrial wastes, respectively. Low Pb concentrations (6–16 μg g−1) were detected in the Akkar sediments, and high concentrations of Pb (70–101 μg g−1) were detected in the Dora sediments. Measuring stable isotope ratios of Pb makes it possible to identify the principal sources of Pb in the Akkar sediments as Pb emitted from gasoline combustion and Pb originating from natural sources. On the other hand, Pb stable isotopic ratios in Dora sediments indicate that they are more highly influenced by anthropogenic sources. Isotopic Pb ratios in the Selaata deposits, where Pb concentrations range between 5 and 35 μg g−1, have an exceptional radiogenic signature for marine sediments 1.25 < 206Pb/207Pb < 1.6 and 0.5 < 206Pb/208Pb < 0.67, which shows the impact of the phosphogypsum discharged by Selaata’s chemical plant. Isotopic Pb analysis applied to EDTA extracts, to test the mobility of Pb, shows that that this mobility is high (>60%) after 24 h of extraction, and that the extracted Pb is less radiogenic than the residual Pb.  相似文献   

15.
若尔盖高原牧场处于中国偏远洁净高海拔地区,大气沉降是污染物主要来源途径之一。由于季风的影响,污染源的辨析较为困难。本文通过多点大气气溶胶不同季节同时采样方式,利用热电离固体同位素质谱仪可有效校正质谱分析中同位素分馏效应的优点,对若尔盖地区土壤和大气气溶胶的铅同位素比值进行精确分析,并结合季风特征对该地区污染物的来源进行解析。结果表明:土壤的208Pb/204Pb比值变化范围为38.79059±0.00194~38.94461±0.00135,206Pb/207Pb为1.18551±0.00002~1.19362±0.00002;大气气溶胶的208Pb/204Pb比值变化范围为37.49571±0.00117~38.48980±0.00105,206Pb/207Pb为1.12894±0.00001~1.16734±0.00001。该地区土壤铅同位素的特征是放射成因铅高,来自于自身天然存在的岩石矿物,与大气污染关系不大;大气气溶胶的铅同位素组成与土壤差异较大,显示为多元混合模式,受到了天然物质和人类活动来源的混合影响,机动车尾气及来自北部(兰州)和西北部(青海、新疆、哈萨克斯坦、俄罗斯)的大气远程运移是若尔盖大气气溶胶及污染物质的主要来源。  相似文献   

16.
《Chemical Geology》2004,203(1-2):75-90
The lead isotopic composition of river sediments is reported in the present work for the Earth's major river basins, from old cratonic to young orogenic areas and from subarctic to tropical climates. Sediment samples from these large river basins provide a useful tool to calculate the average upper crustal composition because they are large-scale integrated samples of the weathering products of the present-day Upper Continental Crust (UCC). Two different and complementary calculations were done to estimate the average lead isotopic composition of the UCC. The first, based on the flux weighted average of particulate lead delivered by the rivers, gave values of 19.07, 15.74 and 39.35 for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios, respectively. To avoid over-estimating the contribution of orogenic areas, which produces a bias (because the flux of particulate lead depends strongly on the physical erosion rate), a second calculation was done by averaging with drainage areas of each river basin. This gave values of 18.93, 15.71 and 39.03 for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios, respectively. These direct calculations of the lead isotopic composition of the UCC are similar and are in agreement with previous estimates made using an indirect approach.  相似文献   

17.
Qingdong Zeng    Jianming Liu    Zuolun Zhang    Changshun Jia    Changming Yu    Jie Ye    Hongtao Liu 《Resource Geology》2009,59(2):170-180
The Baiyinnuoer deposit (32.74 Mt ore with grades of 5.44% Zn, 2.02% Pb and 31.36 g t?1 Ag), the largest Zn‐Pb‐Ag deposit in northern China, is hosted by crystalline limestone and slate of the Early Permian Huanggangliang Formation. Detailed cross‐section mapping indicates stratigraphic and fold structural controls on the mineralization. The Zn‐Pb‐Ag mineralization is hosted predominantly by skarn, which occurs as bedding‐parallel lens that pinch out at the margins of the main economic zone. Three skarn stages are identified at the deposit: (i) garnet‐clinopyroxene; (ii) sulfides; and (iii) carbonate‐epidote. Lead isotopic compositions were determined for galena and sphalerite of the ores, whole rock samples of the Yanshanian granite and granodiorite, Permian marble and tuff, and Jurassic volcanic and subvolcanic rocks in and around the Baiyinnuoer area in order to discuss the sources of ore‐forming materials and the relationship between the ore formation and these whole rocks. Galena and sphalerite of the Baiyinnuoer ore have uniform isotopic ratios (206Pb/204Pb, 18.267–18.369; 207Pb/204Pb, 15.506–15.624; 208Pb/204Pb, 38.078–38.394) consistent with the granite and granodiorite (206Pb/204Pb, 18.252–18.346; 207Pb/204Pb, 15.504–15.560; 208Pb/204Pb, 38.141–38.320), whereas the ratios for Jurassic volcanic and subvolcanic rocks are variable and radiogenic (206Pb/204Pb, 18.468–18.614; 207Pb/204Pb, 15.521–15.557; 208Pb/204Pb, 38.304–38.375). These results indicate that the mineralization was not related to the Jurassic volcanism, but to the Yanshanian magmatism. The Permian strata may have a slight contribution to the mineralization. All features show that the Baiyinnuoer deposit is related to the Yanshanian granitic magmatism, and can be classified as a zinc‐lead‐silver skarn deposit.  相似文献   

18.
A peat core from an ombrotrophic bog documents the isotopic evolution of atmospheric Pb in central Ontario since AD 1804 ± 53 (210Pb dating). Despite the introduction of unleaded gasoline in the mid-1970’s, the ratio 206Pb/207Pb in atmospheric deposition has not increased as expected, but rather continues to decline. In fact, snowpack sampling (2005 and 2009) and rainwater samples (2008) show that the isotopic composition of atmospheric Pb today is often far less radiogenic than the gasoline lead that had been used in Canada in the past. The peat, snow, and rainwater data presented here are consistent with the Pb isotope data for aerosols collected in Dorset in 1984 and 1986 which were traced by Sturges and Barrie (1989) to emissions from the Noranda smelter in northern Quèbec, Canada’s largest single source of atmospheric Pb. Understanding atmospheric Pb deposition in central Ontario, therefore, requires not only consideration of natural sources and past contributions from leaded gasoline, but also emissions from metal smelting and refining.Lead in the streams which enter Kawagama Lake today (206Pb/207Pb = 1.16 − 1.19) represents a mixture between the natural values (1.191 − 1.201 estimated using pre-industrial lake sediments) and the values found in the humus layer of the surrounding forest soils (206Pb/207Pb = 1.15 − 1.19). In the lake itself, however, Pb is much less radiogenic (206Pb/207Pb as low as 1.09) than in the streams, with the dissolved fraction less radiogenic than particulate material. The evolution of Pb isotope ratios within the watershed apparently reflects preferential removal by sedimentation of comparatively dense, radiogenic, terrestrial particles (derived from the mineral fraction of soils) from the humus particles with lower ratios of 206Pb/207Pb (because of atmospheric Pb contamination). Despite the contemporary enrichments of Pb in rain and snow, concentrations of dissolved Pb in the lake are extremely low (sometimes below 10 ng/l), with Pb concentrations and Pb/Sc ratios approaching “natural” values because of efficient binding to particles, and their subsequent removal in the watershed.  相似文献   

19.
To discriminate possible anthropogenic and lithogenic sources of Pb in Lower Silesia (SW Poland), the Pb isotope composition was investigated in a spectrum of rocks and anthropogenic materials as well as within 10 soil profiles. Silicate rocks in Lower Silesia have 206Pb/207Pb ratios that vary from 1.17 for serpentinites to 1.38 for gneisses, and this variability is reflected in the isotope composition of the mineral soil horizons. The Pb isotope composition of coals, ores and anthropogenic materials (slags and fly ashes) is rather uniform, with 206Pb/207Pb ratios ranging from 1.17 to 1.18. Similar ratios were observed in ore and coal samples from Upper Silesia. The O soil horizons also have uniform 206Pb/207Pb ratios of 1.17–1.18 and the heterogeneity of the 206Pb/207Pb ratios increases with depth in the soil profiles. Five soils, with varying Pb concentrations, analysed far from contamination centres, show consistent, approximately 2-fold enrichment in Pb concentration from the C to A horizons, which is consistent with natural re-distribution of Pb within the profiles. The increase in the Pb concentration is accompanied by a decrease in 206Pb/207Pb ratios, also attributed to natural Pb isotope fractionation. Four soil profiles from industrial areas show variable enrichments in Pb concentrations and these are attributed to anthropogenic input from air-borne pollutants or even slag particles at smelting sites. The implication is that a lithogenic Pb source can deviate from the basement rock composition, and detailed isotope characteristics of the geological background and natural enrichments in soils are often needed to determine the lithogenic/anthropogenic proportions of Pb in soils.  相似文献   

20.
Abstract: The Dajing Cu‐polymetallic ore deposit in Linxi county, Inner Mongolia Autonomous Region, China, is economically a valuable Cu–Sn–Ag–Zn–Pb deposit in the southern section of the Da Hinggan metallogenic province. For the analyzed 23 samples of sulfide minerals, including chalcopyrite, pyrite, sphalerite and galena, the δ34S values range from –1.8 to +3.8 % with an average of +0.65 %. The narrow distributions of the δ34S values with +1 % peak value, including the published data, and the δ13C values around –5 % indicate that the sulfur and carbon of the hydrothermal fluids are derived from a hypomagmatic source, and exclude the possibility that the hosted strata, i.e., the Upper Permian Linxi Formation, provided certain amounts of sulfur and carbon. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of sulfide ores range respectively within 18.257‐18.368, 15.476‐15.609, and 37.916‐38.355 with the model ages of 122–209 Ma. The black shale, however, contains higher radiogenic lead with the 206Pb/204Pb ratios of 18.473‐20.156, differing from the ores. However, the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of the ore, basaltic porphyrite and feldspar leads are similar, and lie on the same lines in the diagrams of 208Pb/204Pb vs. 206Pb/204Pb and 207Pb/204Pb vs. 206Pb/204Pb. The fact that these mixing lines are composed of the two end members, the mantle and orogenic belt, strongly supports that all the metallogenic elements were carried by the hypomagma mixing the matters of the mantle and orogenic belt prior to the Mesozoic. Therefore, the Dajing ore deposit is a typical mag–matic–hydrothermal vein type ore deposit associated with subvolcanic rocks.  相似文献   

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