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1.
More than 30 epiphytic lichens, collected in Agadir (Morroco) and along a 150-km transect from the Atlantic Ocean eastward, were analyzed for their metal content and lead isotopic composition. This dataset was used to evaluate atmospheric metal contamination and the impact of the city on the surrounding area. The concentrations of Cu, Pb, and Zn (average ± 1 SD) were 20.9 ± 15.2 μg g−1, 13.8 ± 9.0 μg g−1, and 56.6 ± 26.6 μg g−1, respectively, with the highest values observed in lichens collected within the urban area. The 206Pb/207Pb and 208Pb/207Pb ratios in the lichens varied from 1.146 to 1.186 and from 2.423 to 2.460, respectively. Alkyllead-gasoline sold in Morocco by the major petrol companies gave isotopic ratios of 206Pb/207Pb = 1.076–1.081 and 208Pb/207Pb = 2.348–2.360. These new, homogeneous values for gasoline-derived lead improve and update the scarce isotopic database of potential lead sources in Morocco, and may be of great value to future environmental surveys on the presence of lead in natural reservoirs, where it persists over time (e.g., soils and sediments). The interest of normalizing metal concentrations in lichens to concentrations of a lithogenic element is demonstrated by the consistency of the results thus obtained with lead isotopic ratios. Leaded gasoline contributed less than 50% of the total amount of lead accumulated in lichens, even in areas subject to high vehicular traffic. This strongly suggests that the recent banishment of leaded gasoline in Morocco will not trigger a drastic improvement in air quality, at least in Agadir.  相似文献   

2.
Current and past industrial pollution leaves many traces in the environment, in particular along rivers in industrial and urban areas. The isotopic analysis of the lead found in soils and tree rings offers a kind of environmental archive for presenting a portrait of the pollutant distribution in the environment in both spatial and temporal terms. This study is an attempt to identify and compare the source of contamination found in soils and tree rings located along two rivers affected by pollution over several years. Specifically, the focus is on the pattern of lead concentrations and lead isotopic signatures (206Pb/207Pb, 208Pb/206Pb, and 206Pb/204Pb) detected in soils and tree rings located on polluted floodplains. The concentration of Pb in overbank sediments does not rise with the increasing distance downstream from the point source (mining area), suggesting that significant fluvial transport of the pollutant particles over 80 km is involved. For the soil profiles, Pb concentration levels range between 12.32 and 149.13 mg/kg, with the highest concentrations found at the base of the profiles (>1 m). For the lead isotope ratios in the soil profiles, the values obtained range from 0.851 to 0.872 (206Pb/207Pb), 2.081 to 2.111 (208Pb/206Pb), and 0.547 to 0.562 (206Pb/204Pb). The tree ring analysis of red ash (Fraxinus pennsylvanica Marsh.) shows average lead concentrations of 0.63 μg/g, and the lead values of all the tree specimens range between 0.03 and 11.38 μg/g. Pb concentrations varied greatly between the specimens in selected sites and lead isotope ratios in the tree rings showed a strong variability in the time series, particularly from 1945 to 1970. The greater number of variations in the lead concentration rates and isotopic ratios suggest that many more events associated with pollution and contamination have in fact occurred in this area. The study demonstrates the utility of combining stable isotope analyses (soils and tree rings) to examine the source and dispersion of contaminant Pb in fluvial systems by providing reliable and robust indicators for the detection of environmental changes on a local and regional scale.  相似文献   

3.
Lead (Pb) pollution in and around Ulaanbaatar is of national concern, given that the Mongolian capital is home to nearly half of the country’s entire population. By comparison, Mongolian countryside is a pristine environment because of its sparse population and low industrial activity. The concentration of Pb in urban soils (average of 39.1 mg kg–1) was twice the values found (average 18.6 mg kg–1) in background territories (i.e., Mongolian rural sites). Furthermore, Pb contamination was examined by using Pb stable isotopic composition, and covariance of Pb isotopic ratios showed two groups between rural and urban soils as pristine and disturbed sites. The 206Pb/207Pb ratio, the most prominent fingerprint for Pb pollution, was 1.163–1.185 for the urban whereas values for rural soils (1.186–1.207) were analogue to the regional Pb isotopic signatures. Local coal sources and their combustion products, one of the potential Pb pollution sources in Ulaanbaatar, have significant radiogenic properties in terms of Pb isotopic composition and revealed an average of 1.25 for 206Pb/207Pb and 19.551 for 206Pb/204Pb ratios. Thus, contributions from coal firing activity to Pb pollution lower than it was assumed, and smaller range of these values measured in urban soils may be attributed to the mixing of less radiogenic Pb as a constituent of the leaded gasolines.  相似文献   

4.

Purpose

The heavy metal lead (Pb) is toxic to living organisms. Forest soils are important sinks for heavy metals generated by human activities. The forest at Dinghushan of southern China has experienced long-term exposure to atmospheric pollutants from the Pearl River Delta (PRD). The objectives of this research were (a) to determine the vertical and temporal distribution of Pb in the forest soil at Dinghushan, (b) to determine whether dilute acid extraction could be used to identify anthropogenic sources of Pb in forest soil, and (c) to determine the main anthropogenic contributors to soil Pb.

Materials and methods

Lead concentrations and isotopes were measured in two sets of forest soil samples. One set consisted of archived samples from 0 to 20 cm depth collected annually from 1997 to 2010. The other set was collected throughout three profiles sampled at 5-cm intervals to the bedrock (85 cm depth) in 2011. The soil samples were air-dried, ground, and passed through a 100-mesh polyethylene sieve. Lead in the samples was digested with concentrated acid (HNO3?+?HClO4, 4:1?v/v) or extracted with dilute acid (1 M HCl with a soil/solution ratio of 1:10) and was measured with an inductively coupled plasma mass spectrometer.

Results and discussion

Concentrations of Pb obtained both by total digestion and dilute acid extraction decreased with soil depth in the profile samples and increased over time in the archived ones. Soils at 0–20 cm depth had Pb concentrations of more than twice of the local soil background value. In all soil samples, the 206/207Pb ratios was lower and the 206/204Pb, 207/204Pb, and 208/204Pb ratios were higher with the dilute acid extraction than with the strong-acid digestion, indicating that dilute acid extraction could be used to distinguish between anthropogenic and geogenic Pb. Comparison of the Pb isotope ratios in the samples with those in the main pollutants from the PRD indicated that coal combustion and industrial emission were the main contributors to the forest soil Pb at Dinghushan.

Conclusions

The forest soil (0–20 cm depth) at Dinghushan was contaminated by Pb. Dilute acid extraction could be used to identify anthropogenic Pb sources. From 1997 to 2010, the main contributors of anthropogenic Pb to the forest soil at Dinghushan were coal combustion and industrial emission. Measures that control Pb emission from coal combustion and industrial activity, changes in coal consumption, and re-adjustments of industry development in the PRD should reduce Pb contamination of forest soil.  相似文献   

5.
The isotopic composition of lead pollution in the environment provides information as to the source of emission. The 206Pb/207Pb ratio for Canadian industrial emissions (1.153±0.005) is significantly less than U.S. industrial emissions (1.213±0.008) making it possible to determine the relative contributions of emissions from both countries within Eastern North America by means of a simple isotopic mixing model. Profundal sediments in lakes chronicle contaminant inputs and are therefore useful monitors of environmental pollution. Surface sediment from 32 sediment cores across Quebec and Ontario, Canada were analyzed for 206Pb/207Pb to ascertain the relative proportions of Pb emission from Canada and the U.S.A. Data show that U.S. contributions to the total lead burden in surficial sediments across much of southern Quebec and Ontario are often in excess of 50%. Local sources were particularly important in the Eastern Township region of Quebec which lies 200 km south east of the city of Montreal. The results are discussed in relation to the major sources of industrial lead emissions in North America.  相似文献   

6.
A multi-media monitoring field investigation, which included atmospheric, road sediment and soil samples, was carried out at two highway study sites to identify past and present Pb sources. Past Pb anthropogenic sources such as paint and leaded gasoline were linked to significant Pb accumulation in roadside soils at both sites through Pb isotopic analyses. This was achieved by identifying the distinct Pb isotopic composition in older versus newer Pb accumulation at different depths across the soil profile. Older Pb accumulations exhibited lower 206Pb/207Pb isotopic ratios, consistent with Canadian Pb-bearing ores, whereas newer Pb accumulations reflected a mixture of the 206Pb/207Pb ratios of road sediment samples, with the Pb isotopic signature of uncontaminated soil. Isotopic analyses were also helpful in identifying road sediment as an important current source of Pb in roadside soils, by comparing the isotopic signatures derived from road sediment and atmospheric dustfall. The known association of Pb with anthropogenic sources was used to indirectly relate other metals (Cu, Mn, Zn) to the same source by the Enrichment Ratio method. Significant positive correlations at the 90–95% confidence level were found between Cu, Zn and Pb Enrichment Ratios in roadside and dust deposition samples. Weaker correlations were found between Mn and Pb, at the highway study site with the least amount of traffic. However, correlations between these two metals were significant at the 90% confidence level for the busier highway site highlighting Mn potential anthropogenic source. An isotopic tracer study is suggested to further investigate the process of Mn redistribution in the environment due to exhaust fuel emissions. More research is needed regarding the potential impact from using a Mn-based fuel additive.  相似文献   

7.
Isotope ratios of Pb may provide the opportunity to determine the contribution of Pb from a point source to Pb concentrations in soil. Our objective was to quantify the contribution of anthropogenic Pb to total Pb and chemical Pb fractions in contaminated soil profiles with the help of 206Pb/207Pb isotope ratios. We sampled 5 forest and 5 arable Cambisols along a transect from a Cu smelter and determined Pb concentrations and 206Pb/207Pb isotope ratios in total digests of all horizons and in 7 chemical fractions of the A horizons. In the organic layer under forest, Pb concentrations decreased from 2155 mg kg—1 at 1.1 km distance from the smelter to 402 mg kg—1 at 8 km distance; in the Ap horizons, it decreased from 126 to 72 mg kg—1. In the total digests, 206Pb/207Pb isotope ratios could be explained by simple mixing of smelter‐ and background‐Pb as indicated by the correlation between the inverse of the Pb concentration and the 206Pb/207Pb ratio (r = 0.93). The mean proportion of smelter‐Pb in soil horizons decreased with depth from 87% (Oi) to 21% (C) under forest and from 64% (A) to 30% (B) in the arable soils. The smelter‐Pb proportions in the B horizons ranged from 6 to 66% and were independent of the distance from the smelter indicating variable leaching rates. The 206Pb/207Pb ratios in the chemical fractions could not be explained by a simple mixing model. Thus, the 206Pb/207Pb ratios may be used to determine the contribution of anthropogenic Pb in total digests but not in chemical Pb fractions.  相似文献   

8.
The composition of tree rings and soils was studied at several locations affected by smelting and transportation in the vicinity of Kitwe (Copperbelt, Zambia). The contents of cobalt (Co), copper (Cu), manganese (Mn), and lead (Pb) and the 206Pb/207Pb isotope ratios in the tree rings were interpreted in relation to potential sources of contamination such as smelter production, acidification of the environment, soil composition, raw material processing, and atmospheric suspended particulate matter (SPM). The highest Co contents in the tree rings correspond to maximum ore production in the mid-1970s. Acidification through SO2 emissions is documented in the increased Mn contents from the mid-1980s. The isotopic composition of the tree rings of the studied tree species varies in the interval 1.16?C1.34 and the youngest parts of all the studied trees exhibit a low 206Pb/207Pb ratio (<1.17). The soil isotope composition varies in the range 206Pb/207Pb?=?1.18?C1.35. The Pb isotope composition in the soils and tree rings was formed by a combination of lithogenic Pb (206Pb/207Pb????1.3), Pb in processed ores (206Pb/207Pb????1.2), and SPM (automobile) Pb (206Pb/207Pb??1.1). As the soils in the distant region have high 206Pb/207Pb ratios (>1.3) in the whole profile and simultaneously the youngest parts of the tree rings of tree species growing in this soil have a low 206Pb/207Pb ratio (<1.17), it can be assumed that the Pb in the youngest parts of the tree species is derived from absorption of SPM Pb through the bark rather than root uptake. The absence of Pb with a low 206Pb/207Pb ratio in soils in the distant area is probably affected by fires in the herbaceous and bush undergrowth and plant litter, which prevents Pb from biomass from entering the soil and mobilize it back into the atmosphere.  相似文献   

9.
Lead and its isotope ratios (IRs) in 83 Italian wines from 42 different administrative provinces produced on laboratory scale in 2000 were measured by inductively coupled plasma mass spectrometry. Lead had a median of 19.0 microg/L, ranging from 10.0 up to 149 microg/L and was higher in the samples from northwestern Italy. The values of the IRs were (mean +/- standard deviation) 1.171 +/- 0.011 for (206)Pb/(207)Pb, 2.071 +/- 0.017 for (208)Pb/(206)Pb, 2.425 +/- 0.014 for (208)Pb/(207)Pb, 17.84 +/- 0.32 for (206)Pb/(204)Pb, 15.24 +/- 0.31 for (207)Pb/(204)Pb, and 37.31 +/- 0.52 for (208)Pb/(204)Pb. These ratios agree with those in the literature for several European regions. (206)Pb/(207)Pb distinguished the northwestern from the northeastern and southern Italian wines, and the southern samples were distinguishable only from the northwestern ones. (208)Pb/(206)Pb distinguished the northwestern from the southern Italian samples. Nevertheless, the lead IRs do not seem to be a very effective tool for the origin authentication of wines from different Italian regions.  相似文献   

10.

Purpose

The metal concentrations and Pb isotopic composition in sediments and plants from the Xiangjiang River, China, were investigated to understand the contamination and potential toxicity of metals in sediments; to determine the accumulation and distribution of metals in plant tissues; and to trace the possible pollution source of Pb in sediments and plants.

Materials and methods

Sediments and plants were collected from 43 sampling sites in the study region. After sediments were air-dried and passed through a 63-??m sieve, they were acid-digested and DTPA-extracted for determination of total and bioavailable metals. The plants were separated into roots, leaves, and stems; dried; cut into pieces; and digested with HNO3?CH2O2. Metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) and Pb isotopic composition were analyzed by inductively coupled plasma-mass spectrometry.

Results and discussion

Maximum As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in sediments were 47.18, 55.81, 129.5, 161.6, 160.4, 430.7, and 1,098.8?mg?kg?1, respectively. The bioavailable fractions of As, Cd, Cu, Pb, and Zn had significant linear relationship with their corresponding total contents in sediments while no significant relationship was observed between bioavailable and total contents of Cr and Ni. In general, plant tissues showed higher As, Cd, Cu, Pb, and Zn concentrations and lower Cr and Ni concentrations compared with sediments. The 206Pb/207Pb ratios decreased in the order of total > bioavailable > stems ?? leaves > roots. A strong linear correlation was observed between the 208Pb/206Pb and 206Pb/207Pb ratios of the plant tissues, sediments, and the possible pollution sources of Pb in the Xiangjiang River.

Conclusions

As, Cd, Cu, Pb, and Zn demonstrated higher contamination levels in sediments and plants compared with Cr and Ni. Cd had highest potential ecological risk. The Pb from anthropogenic sources with low 206Pb/207Pb ratios was preferentially associated with the bioavailable fractions in sediments and accumulated in roots. The Pb in plant tissues is mainly derived from the Pb in sediment and is taken up through the sediment-to-root pathway.  相似文献   

11.
The content of Pb, Cd, Mn, K, Ca, Mg and 206Pb/207Pb isotope ratios in spruce tree rings (Picea abies) and peat cores from the Brdy Hills area (10 km W of the Pb smelter) were compared with those in spruce tree rings in the vicinity of the Pb smelter. Maximum Pb content in tree rings (up to 60 mg kg?1 Pb) corresponds to a peak of metallurgical production in the mid 1970s and highest smelter emissions in the early 1970s. The Pb concentration curves obtained from peat deposit profiles closely correlate with the Pb concentrations in tree rings at both sampling sites. The small differences between the individual tree cores, with the identical general trend, may be attributed to the difference in distance from the smelter and the altitude of each sampling site. Similar behaviour to Pb can be observed for Cd and Ca. Lead isotope composition in tree rings (206Pb/207Pb ~1.143–1.174) is controlled mainly by the smelter emissions (206Pb/207Pb ~1.16–1.17), with the exception of the youngest segments from the more distant locality from the smelter, which yield isotopic signatures corresponding to car-emission Pb (206Pb/207Pb ~1.143–1.150). Higher content of Mn, Mg and Ca in tree rings corresponding to the 1970s and 1980s may be related to soil chemistry changes caused by acid deposition. In addition, an increase in K, Mg (and in some cases also Mn) in the youngest part of wood cores corresponds to the physiological processes in sapwood, and may be influenced by a decrease in Pb in organic soil horizons, which limited the cycling of basic inorganic nutrients.  相似文献   

12.
Brännvall  M.-L.  Bindler  R.  Emteryd  O.  Nilsson  M.  Renberg  I. 《Water, air, and soil pollution》1997,100(3-4):243-252
We compare lead concentration and stable lead isotope analyses from three peat bog and three lake sediment records in Sweden. Radiocarbon dated stratigraphies give evidence that trends in the concentration of Pb in the peat and sediment cores are very similar, and follow the general outline of historical global Pb production over several thousand years. Due to the large difference in the 206Pb/207Pb ratio between Sweden, about 1.5, and continental Europe (excluding Fennoscandia), ≤1.2, it is possible to distinguish external sources of Pb to Sweden. In the lake sediments, profiles of 206Pb/207Pb ratio mirror the Pb concentration until 1000 AD; increasing concentration is accompanied by decreasing ratios. After 1000 AD the ratio varies little at about 1.2 in sediments, because of the near total dominance of pollutant Pb. There is a further decline in the Pb ratio to about 1.14 in this century as a result of the addition of alkyl-Pb in petrol. The Pb concentration profiles in the peat match the lakes, but the isotope profiles do not. During the fen-to-bog transition there is a rapid decline in the 206Pb/207Pb ratio from >1.3 to about 1.2, and the ratio continues to decline to the present. We hypothesise that this is because externally-derived Pb from long-range transport of soil dust and atmospheric pollution has always been more important in the ombrotrophic peat than in lakes, which have a greater influx of catchment-derived Pb.  相似文献   

13.
The spatial extent of metal contamination caused by small-scale ore veins is increased by periglacial solifluction. Our objectives were (1) to examine the spatial distribution of Pb in cover beds that migrated over Pb ore veins, (2) to calculate the transport distance of ore-derived Pb, and (3) to determine controls on the transport distance.We examined six transects (320-775 m long) in the Rhenish Slate Mountains in West Germany. The transects included four west-exposed and two east-exposed slopes with inclinations between 2-20°. All transects were forest-covered and located at 280-450 m above sea level. Soils were Dystric Cambisols and Stagnic Luvisols. Samples of 120 B horizons developed in the sediments of the last ice age (Wuerm) were analyzed for total Pb concentrations and partly also 206Pb/207Pb ratios. The Pb concentrations ranged from 20 to 135 mg kg− 1. The spatial Pb distribution suggested that 14 (out of 18) sampling points showing local Pb concentration maxima contained Pb from ore veins upslope. With a two-end-member-mixing model using 206Pb/207Pb isotope ratios of the ore (206Pb/207Pb ratio: 1.1828) as one end member and of the native substrate (a mixture of slate and loess; 206Pb/207Pb ratio: 1.2254 ± 0.0072) as the other we confirmed that the 14 Pb peaks originated from the ore, because they contained 76-100% of ore-derived Pb. By the use of a geographic information system, the transport distance of this Pb was determined to range between 30 and 110 m. Silt concentrations (Pearson r = − 0.69) and the relief curvature (Cramér's V = 0.60) were major controls on the transport distance. Our study demonstrates that Pb ore veins can increase native soil Pb concentrations in soil derived from the periglacial drift of the last ice age (Wuerm) up to a distance of more than 100 m.  相似文献   

14.
Soils in urban areas are often artificially formed and preserved as cultural layers in which soil materials are mixed with artifacts. The vertical change of soil properties denotes the historical change of human activities, and therefore, urban soil can be considered as a record of history of urban development. We studied a deep profile of urban soil (600 cm) in Nanjing, China, by intensively sampling at every 5 cm. Soil samples were analyzed for lead content. Charcoal from several layers was found and was dated using 14C to recognize archaeological cultural layers that might be formed in different Chinese dynasties. Pb isotope ratios were determined by thermal ionization mass spectrometry (TIMS) technology. The study found that artificial deposition, i.e., the formation of cultural layer started about 1700 years ago and lasted until recently. All cultural layers above the original loess were heavily contaminated by Pb with total content varying from 100 mg kg− 1 to more than 2000 mg kg− 1. There were several historical periods in which Pb content peaked, indicating significant contamination by human activities, such as ancient ore smelting for various purposes and use of Pb-containing materials for handicraft manufacture. Various Pb isotope ratios of the cultural layers differed substantially from that of the original undisturbed loess in the deepest position. 206Pb/207Pb value decreased gradually from the bottom layer to top layer, although with occasional exceptions, indicating a long-lasting mixing of extraneous sources of Pb during the entire history since ca. 300 A.D. In comparison with the isotope ratios of lead ores of different sources and that of aerosols, it was illustrated that the source of Pb in cultural layers might come from lead ores of southern China in the earlier dynasties, while Pb from north China might have contributed to the Pb source in the more recent years, suggested by the lowering of 206Pb/207Pb ratio in the near-surface cultural layers. However, the impact of petrol burning on cultural layers was basically excluded, considering the relatively short history of petroleum use in this area.  相似文献   

15.
Soils frequently develop from mixtures of different parent materials. We quantified the contributions of different parent materials to the substrate for recent soil development using trace metal concentrations and Pb isotope ratios as input data for end‐member mixing analyses (EMMAs). We examined six transects (320–775 m) at two sites in the Rhenish Slate Mountains. Soil types ranged from acid Cambisols to stagnic Luvisols developed from periglacial cover‐beds. Sixteen O, 11 A, 120 B and 10 C horizons were analysed for total trace metal concentrations and partly also 206Pb:207Pb ratios. Most metal concentrations in the B horizons were in the background range, except for Pb, which partly had elevated concentrations of up to 135 mg kg−1. The depth distribution of metal concentrations and 206Pb:207Pb ratios suggested that metals deposited from the atmosphere had hardly reached the B horizons. A principal component analysis (PCA) of the trace element concentrations in the 120 B horizons identified four main metal sources of the B horizons, which we interpreted as bedrock (slate), loess, Laacher See tephra (LST) resulting from the last volcanic eruption in the Eifel mountains and ore veins. The slate was characterized by Cr and Zn, the loess by Zr, the LST by Nb and the ore veins by Pb. Based on EMMAs with four end‐members using two different sets of tracers (Set 1: concentration ratios of Zr:Cr, Nb:Cr, Pb:Cr, Set 2: Zr:Zn, Nb:Zn, and Pb:Zn), slate, loess and LST contributed, on average, 39–40, 22–24 and 37–38%, respectively, at Site 1 and 19–21, 53–63 and 18–26%, respectively, at Site 2. In contrast, the ore contribution was consistently estimated at 0%. An additional EMMA with two end‐members based on the 206Pb:207Pb ratios estimated the contribution of the ore at 0.02%. We conclude that EMMAs based on trace element concentrations and isotope ratios provide a tool for determining the contribution of different parent materials to the substrate from which soils develop, at least at a small regional scale and if an appropriate tracer that distinguishes all the considered substrates is found.  相似文献   

16.
Farmer  J.G.  Mackenzie  A.B.  Sugden  C.L.  Edgar  P.J.  Eades  L.J. 《Water, air, and soil pollution》1997,100(3-4):253-270
The concentrations, inventories, fluxes and isotopic composition of Pb in four 210Pb-dated cores from the raised Flanders Moss peat bog are compared with corresponding data for two sediment cores from Loch Lomond, also in central Scotland. Although the inventories and fluxes of Pb revealed by the peat record for the past few hundred years are generally lower, the isotopic records are in good agreement, confirming a prevailing 206Pb/207Pb ratio of 1.17 for anthropogenic ("industrial") Pb in the atmosphere prior to the introduction of leaded petrol in the 1920s. The 206Pb-depleted nature of the latter has resulted in a decline of about -0.04 to -0.05 in the 206Pb/207Pb ratio of deposited Pb for both peat and lake sediments. Despite the time-resolution limitations of the peat record, car exhaust emissions of Pb appear to have contributed 35-50% over the past 20 years, 15-30% over the past 75 years, but no more than 27% overall to the peat Pb burden. The finding that 67-85% of anthropogenic Pb in the peat was apparently deposited post-1900 compared with 51% for the Loch Lomond sediments could be due to geographical variations in atmospheric deposition of Pb, other additional inputs to the sediments, or perhaps to some post-depositional loss of Pb from peat, although the integrity of the 206Pb/207Pb record does argue against any significant vertical mobility of Pb in peat.  相似文献   

17.
Seventy-five samples of six soil profiles from forests on different substrates plus one next to a motorway were analyzed for the variation of Pb concentration and isotopic composition with depth. A substantial fraction of the anthropogenic Pb (peak concentrations between 74 and 300 ppm) is still stored in the organic top soil, and seldom penetrates deeper than 20–30 cm. In (208Pb/206Pb) vs. (207Pb/206Pb)-diagrams the Pb in the uppermost layers of the profiles plots on an excellent correlation line (R = 0.99) indicating essentially a two-component mixing system. Values for the dust on Scottish plants, Norwegian and Swiss bogs as well as for aerosols collected over the North Atlantic (data from the literature) plot on the same correlation line showing that the Pb was deposited from a continent-wide mixing system with two apparent end members: The radiogenic one is similar to geogenic Pb and could consist of contributions from certain European ore deposits and from different soil components (e.g. silicates and Fe-oxides), power plants and cement factories. The less radiogenic component must contain or consist of Pb from Proterozoic or even Archaic ore deposits. However, the sources of this Pb remain somewhat elusive. In any case, this isotopic pattern is so consistent all over Europe that the correlation line may serve as a line of reference for quasi normal or European Standard Lead Pollution (ESLP). The gasoline derived Pb in the soils is swamped by Pb of other provenances.  相似文献   

18.

Purpose

Frequent mining activities and higher background values in soil have led to the contamination of the sediments of some rivers in southwest China by several metals and arsenic (As). This study combined multivariate analysis with geochemical approaches to differentiate mining activity from other sources, which may aid to evaluate the effectiveness of reducing mining release.

Materials and methods

Sixteen sediment samples were collected along the Yuan River, China. The total concentrations of lead (Pb), zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), mercury (Hg), and As were measured by inductively coupled plasma-atomic emission spectrometer (ICP-AES). The Pb isotopic composition was measured using a thermal ionization mass spectrometer (TIMES). Both geochemical approaches and multivariate statistical analysis were used to identify the sources of these metals. The fractionation of Pb was determined through a Community Bureau of Reference (BCR) sequential extraction procedure to aid the identification of the sources.

Results and discussion

The concentrations and enrichment factors (EFs) of Pb, Zn, Cu, Cd, and As in the middle reach of the river were higher than those at the other sites, indicating anthropogenic sources. The factor analysis (FA) extracted “mining and smelting,” “mixture of anthropogenic and natural,” and “natural” factors. The Pb isotope composition of metal ores was similar (206Pb/207Pb?<?1.190 and 208Pb/206Pb?>?2.023) to that found in the sediments in the middle reach, indicating anthropogenic sources of mining activities. Compared with the narrow ranges of the δ34S ratios in the bedrock (+8.5 to +9.3?‰) and the metal ores (?1.4 to +1.9?‰), the sediment samples presented a relatively wide range of δ34S ratios from ?2.6 to +9.2?‰ with a mean of +2.6?‰, which suggests a mixed composition. The BCR sequential extraction procedure revealed that the proportion of the extractable fraction in the sediments in the middle reach was higher than that in other sites, suggesting anthropogenic sources as the cause of contamination in the study area.

Conclusions

Lead, Zn, Cu, Cd, Cr, Hg, and As are mainly derived from natural materials in the upstream region. In the middle reach, these elements are the result of anthropogenic activities, particularly activities associated with the mining industry. In the downstream region, the origin of these elements is considered to be a mixture of anthropogenic and natural sources. In addition to geochemical approaches and multivariate statistical analysis, the BCR sequential extraction method is an effective procedure for the identification of the anthropogenic sources of sediment-associated metals.  相似文献   

19.
Stable Pb isotope ratios were used to trace thesources and pathways of Pb between the atmosphere,surficial sediment fractions, the white water-lilyNymphaea odorata, and waters collected at 26littoral sites in 23 Ontario lakes in summer 1993,three years after alkyl Pb additives were finallyeliminated from Canadian gasoline. Based onsimilarities of isotopic composition, the exchange ofPb between lakewater and sediment 'carbonate', andsubsequently between 'carbonate', 'oxide' and othersediment fractions, was the most likely water-sedimentpathway of Pb movement. pH controlled Pb fractionationwithin surficial sediments, with the 'organic' poolcomprising 80–97% of total Pb in most acidic lakesand 15–60% in alkaline lakes. About 28% of the Pb inN. odorata shoots was accumulated directly fromwater, whereas there was no evidence of root uptake ofPb from sediments. The Pb in plant tissues wasisotopically homogeneous and dissimilar to thevariable composition exhibited in ambient waters andsediments. Plant Pb isotopes strongly resembled thehistorical Canadian atmospheric (alkyl Pb) signature.A possible explanation is that, like essential tracemetals, historically-accumulated Pb was highlyconserved during the annual growth cycle of thislong-lived, clonal macrophyte, being storedover-winter in underground rhizomes and recycled intospring growth. Given the low rate of 'new' Pb uptake,historical alkyl Pb may continue to dominate planttissues for some time, even though it was notdetectable in littoral waters and sediments.  相似文献   

20.
The objective of this study was to develop a technique for determining the country of origin of rice in the Japanese market. The rice samples included a total of 350 products grown in Japan (n = 200), the United States (n = 50), China (n = 50), and Thailand (n = 50). In this study, (87)Sr/(86)Sr and Pb isotope ((204)Pb, (206)Pb, (207)Pb, and (208)Pb) ratios and multielement concentrations (Al, Fe, Co, Ni, Cu, Rb, Sr, and Ba) were determined by high-resolution inductively coupled plasma mass spectrometry. By combining three chemometric techniques based on different principles and determination criteria, the countries of origin of rice were determined. The predictions made by 10-fold cross-validation were around 97% accurate. The presented method demonstrated the effectiveness of determining the geographic origin of an agricultural product by combining several chemometric techniques using heavy element isotope ratios and multielement concentrations.  相似文献   

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