Pb Deposition Rates Research Articles

Spatial and temporal trends in winter deposition of Pb, Be, Cu and Zn in selected mountain areas of Central Europe

Atmospheric depositions of trace metals have been the focus of attention because of their potential toxicity to living organisms. In this paper, winter deposition rates of Pb, Be, Cu and Zn collected from 2009 to 2011 at 10 mountain-top localities in the border area of the Czech Republic were compared and summarized. Across the sites there were up to 7–8fold differences in Pb, Be and Zn deposition rates, and up to threefold differences in their Cu deposition rates. In all cases, rime contained higher amounts of Pb, Be, Cu and Zn compared to snow. More than 92 % of Pb, Cu and Zn occured in soluble (bioavailable) form, whereas only 34 % of Be was in soluble form. Recent trace metal concentrations in precipitation considerably decrease compared to those measured during the period of the highest atmospheric emissions in the 1980s. The industrial region in the northeast of the Czech Republic experienced moderate levels of Pb air pollution, while atmospheric Pb inputs in the rest of the country as well as overall inputs of Cu, Zn and Be were low, representing a low threat to human and ecosystem health. Between-site differences made it possible to classify sites into three categories according to their level of pollution load. A previously-mentioned north-south pollution gradient between the industrial north and rural south of the country was not observed. Sites in the northwest and in the south were among those with the lowest pollution loads. On the other hand, sites in the northeast were the most polluted due to their location near the industrial regions of southern Silesia (Poland) and Ostrava.

Anthropogenic, detritic and atmospheric soil-derived sources of lead in an alpine poor fen in northeast China

Ombrotrophic bogs are faithful archive of atmospheric metal deposition, but the potential for fens to reconstruct environmental change is often underestimated. In this study, some new data on the Pb depositional history in northeast China were provided using two 210Pb-dated peat sequences from a poor fen in the Fenghuang Mountain of Heilongjiang province. Anthropogenic, detritic and atmospheric soil sources were discriminated using a two-step sequential digestion (weak acid leaching to liberate mobile Pb which is often regarded as anthropogenic Pb, especially for recent samples) and a ratio of unsupported 210Pb and supported 210Pb with the logic of that the 214Pb mainly represents the residual detritus (constant throughout the core) and the unsupported 210Pb arises from atmospheric fallout. A higher 210Pb/214Pb suggests more contributions from atmospheric deposition to the Pb content in the peat, and a ratio of 10 was defined to indicate the boundary between detritic input and atmospheric deposition. The detritic Pb was estimated to be 10–13 mg·kg−1, the anthropogenic Pb ranged from 10–80 mg·kg−1, and the atmospheric soil-derived Pb ranged from < 5 mg·kg−1 to 30 mg·kg−1. The history of anthropogenic Pb pollution over the last 150 years was reconstructed, and the calculated Pb deposition rate (AR Pb) ranged from 5 to 56 mg·m−2·yr−1. Using Ti as a reliable reference, the enrichment factor of Pb (EF Pb) relative to the upper continental crust was calculated. Both AR Pb and EF Pb increased with time, especially after the foundation of the People’s Republic of China. This is consistent with increasing industrialization and coal burning in the last 60 years in northeast China. The present record of anthropogenic Pb deposition was consistent with the previous reports and an increasing trend of environmental pollution due to anthropogenic activities, in contrasts to Europe and North America which have experienced a major environmental cleanup. For the first time, this work estimates atmospheric Pb deposition via a minerotrophic peat core in China. This will enhance the use of peat archives for studies of environmental change.

Quantifying an early signature of the industrial revolution from lead concentrations and isotopes in soils of Pennsylvania, USA

Abstract During the early industrial revolution, mining and smelting of ores and coal combustion released significant amounts of lead (Pb) into the atmosphere. While many researchers have documented high Pb concentrations in topsoils due to gasoline combustion between 1940s and 1980s, little work has focused on the extent of Pb and other heavy metal deposition into soils during the early industrial period. Here, we report Pb, cadmium (Cd), and zinc (Zn) concentrations and Pb isotope ratios of soils, sediments, parent bedrock, and waters collected from a small, currently pristine watershed (Shale Hills Critical Zone Observatory) in Pennsylvania (United States of America). Our results show that Pb in the soil comprises an addition profile, i.e. more Pb is present in the soil than is present in the equivalent parent bedrock. All three investigated soil profiles at Shale Hills on the same hillslope have Pb inventories (∼400–600 μg cm−2) attributed to atmospheric deposition. Cd and Zn concentrations in these soils show similar addition profiles due to atmospheric deposition. Based on Pb isotopic ratios, the most likely source of the added Pb is coal burning and ore smelting during local iron production in the early 19th century, roughly coincident with the construction of the U.S. transcontinental railroad. Mass balance and diffusive transport modeling were used to quantify Pb deposition rates and redistribution. These model results are consistent with the hypothesis that from ∼1850s to 1920s, coal burning and ore smelting in local iron blasting furnaces significantly increased the local Pb emissions so that Pb deposition rates in soils were in the range of 6–10 μg cm−2 yr−1. These values are comparable to Pb deposition rates found in other areas with early and intensive industrial activities (e.g. since the ∼1860s in Australia). Our new Pb, Cd, and Zn concentrations and Pb isotope results, in combination with the previously observed manganese (Mn) enrichment at Shale Hills, document that early industrial point sources contaminated local soils with metals that remain even today in topsoils with large sorption capacities. Where these metals are retained, their depth profiles provide a mean to infer the history of metal additions and redistributions.

Reconstruction of historical atmospheric Pb using Dutch urban lake sediments: A Pb isotope study

Lake sediments provide a record of atmospheric Pb deposition and changes in Pb isotope composition. To our knowledge, such an approach has not previously been performed in The Netherlands or linked to national air monitoring data. Results are presented for Pb content and isotope composition of 137Cs dated lake sediments from 2 Dutch urban lakes. Between 1942 and 2002A.D. anthropogenic atmospheric Pb deposition rates in the two lakes varied from 12±2 to 69±16μgcm−2year−1. The rise and fall of leaded gasoline is clearly reflected in the reconstructed atmospheric Pb deposition rates. After the ban on leaded gasoline, late 1970s/early 1980s, atmospheric Pb deposition rates decreased rapidly in the two urban lakes and the relative contributions of other anthropogenic Pb sources — incinerator ash (industrial Pb) and coal/galena — increased sharply. Atmospheric Pb deposition rates inferred from the lake record a clear relationship with nearby measured annual mean air Pb concentrations. Based on this relationship it was estimated that air Pb concentrations between 1942 and 2002A.D. varied between 5 and 293ng/m3.

Spatial distribution of lead in the surface layers of mountain forest soils, an example from the Karkonosze National Park, Poland

Total concentrations and pools of Pb in the surface layers of mountain soils in the Karkonosze National Park are presented and discussed in relation to site altitudes and soil properties. Soil samples were collected from a forest floor and from the depths of 0–10cm and 10–20cm in 372 monitoring sites situated in a forested zone of the Park. Particularly high concentrations of Pb (24–200mg∙kg−1, most often over 100mg∙kg−1), potentially hazardous for soil biota, were found in forest litter. The concentrations of Pb in soil layers 0–10cm and 10–20cm were in the ranges 19–248 and 4–196mg∙kg−1, respectively. Pb distribution indicated very high spatial variability, confirmed by geostatistical analysis. Calculated pools of Pb varied in a broad range: 0.16–26.6g∙m−2 (mean: 6.20g∙m−2), and correlated strongly with the stocks of organic matter, both being significantly higher in the lowest altitudinal zone (500–750ma.s.l.) compared to the highest zone (1250–1380ma.s.l.). Nevertheless, there was no simple correlation of Pb pools vs. altitude. The largest pools of Pb are stored in the layer 0–10cm. The pools of accumulated Pb determined in this study are much higher than those assessed on the basis of available data on former and present Pb deposition rates. These findings may be assigned to a seeder–feeder effect and horizontal transport of pollutants. The highest amounts of Pb were identified in three distinct areas (hot spots), in particular in the vicinities of mountain passes, which may be explained by meteorological factors as well as by the influence of local pollution.

Recent atmospheric lead deposition recorded in an ombrotrophic peat bog of Great Hinggan Mountains, Northeast China, from 210Pb and 137Cs dating

Radioactive markers are useful in dating lead deposition patterns from industrialization in peat archive. Peat cores were collected in an ombrotrophic peat bog in the Great Hinggan Mountains in Northeast China in September 2008 and dated using 210Pb and 137Cs radiometric techniques. The mosses in both cores were examined systematically for dry bulk density, water and ash content. Lead also was measured using atomic emission spectroscopy with inductively coupled plasma (ICP-AES). Both patterned peat profiles were preserved well without evident anthropogenic disturbance. Unsupported 210Pb and 137Cs decreased with the depth in both of the two sample cores. The 210Pb chronologies were established using the constant rate of supply model (CRS) and are in good agreement with the 137Cs time marker. Recent atmospheric 210Pb flux in Great Hinggan Mountains peat bog was estimated to be 337 Bq m −2 y −1, which is consistent with published data for the region. Lead deposition rate in this region was also derived from these two peat cores and ranged from 24.6 to 55.8 mg m −2 y −1 with a range of Pb concentration of 14–262 μg g −1. The Pb deposition patterns were consistent with increasing industrialization over the last 135–170 y, with a peak of production and coal burning in the last 50 y in Northeast China. This work presents a first estimation of atmospheric Pb deposition rate in peatlands in China and suggests an increasing trend of environmental pollution due to anthropogenic contaminants in the atmosphere. More attention should be paid to current local pollution problems, and society should take actions to seek a balance between economic development and environmental protection.

Past atmospheric Pb deposition in Lake Qinghai, northeastern Tibetan Plateau

Two short sediment cores were recovered from sub-basins of Lake Qinghai, China and were analyzed for concentrations of Pb and 16 other elements to determine historic, regional atmospheric Pb deposition on the Tibetan Plateau. Core chronologies, dating back to the eighteenth century, were established using activities of 210Pb and 137Cs. The 17 elements were divided into three principal components. Variations in concentrations of PC1 elements (Al, Cr, Cu, Fe, K, Mn, Ni, and Ti) demonstrate different patterns between the two cores, and are attributed to different sediment sources in the two sub-basins. PC2 elements (Ba, Ca, Na, and Sr) may be associated with the degree of catchment weathering and/or water chemistry. Four elements (Pb, Zn, P, and Co) are related to both PC1 and PC2, and reflect a mixture of natural and anthropogenic sources. The PC3 element is Mg in the north sub-basin, and is perhaps related to aragonite precipitation and/or increased farming. Elevated Pb concentrations in uppermost sediments of both cores signify a recent regional/global increase in anthropogenic Pb release into the environment. After subtracting lithogenic Pb, derived from rock weathering and/or dust and normalized to the background immobile element Ti, results suggest that excess, anthropogenic Pb is transferred to the lake and its sediments predominantly via the atmosphere. This anthropogenic atmospheric Pb is comparable in magnitude and displays similar variation patterns in the two cores, reflecting regional atmospheric deposition and local erosion. The average anthropogenic Pb deposition rate in Lake Qinghai since the 1960s has been ~12.2 ± 3.5 mg/m2/a, comparable with atmospheric Pb fluxes reported for sites elsewhere in the northern hemisphere.

Comparison of PbZr1−xTixO3 thin films deposited on different substrates by liquid delivery metal organic chemical vapor deposition

In the paper, PbZr1−xTixO3 (PZT) thin films were prepared on different substrates including 8 and 4 in. silicon, Pt, Ir, and IrO2/Ir substrates by liquid delivery metal organic chemical vapor deposition. Through optimizing the preparation condition, the better film uniformity of thickness, composition, and temperature was achieved. The thickness uniformity of PZT films on 8 in. substrate was about ±3.24%. The deposition rate of Pb (15.8 nm/min) and Ti (17.9 nm/min) were much faster than that of Zr (2.5 nm/min). The growth temperature of PZT film was 570–630 °C depending on the substrate used. The growth rate of PZT films deposited on Si (30–35 nm/min) was faster than that on metal substrate. The substrate has a great effect on the ferroelectric properties of PZT films. PZT film growing on Ir was much uniform and denser than that on Pt, highlighting the good microstructure achieved. PZT films based on Ir substrate showed excellent ferroelectric properties. At the applied voltage of 5 V, the remanent polarization (2Pr) and coercive field (Ec) values of Ir/IrO2/PZT/IrO2/Ir capacitors were about 36 μC/cm2 and 50 kV/cm, respectively.

FABRICATION AND PROPERTIES OF METAL-PZT-METAL CAPACITORS BY LIQUID DELIVERY MOCVD

ABSTRACT Pb(Zr1−x,Tix)O3(PZT) thin films were prepared on 8-inch and 4-inch Pt or Ir-electroded Si wafers by liquid delivery metal-organic chemical vapor deposition (LD-MOCVD) using cocktail sources of Pb, Zr and Ti. The processing conditions were optimized in order to obtain high-performance PZT films. The thickness uniformity of PZT films on 8-inch substrate was about ± 3.24%. The deposition rate of Pb (15.8 nm/min) and Ti (17.9 nm/min) deposited on Si substrate were faster than that of Zr (2.5 nm/min). The growth temperature of PZT film was adjusted to 570–630°C depending on the substrates used. The properties of metal/PZT/metal capacitors were also studied. The PZT films based on Pt substrate showed no good ferroelectric properties. By contrast, the ferroelectric properties of Ir/IrO2/PZT/IrO2/Ir capacitors were excellent. At an applied voltage of 5 V, the remanent polarization (Pr) and coercive field (Ec) values were about 36 μ C/cm2 and 50 kV/cm, respectively.

Comment on “The biosphere: A homogeniser of Pb-isotope signals” by C. Reimann, B. Flem, A. Arnoldussen, P. Englmaier, T.E. Finne, F. Koller and Ø. Nordgulen

Reimann et al. (2008) recently published a study on Pb-isotope signature along a 120 km long transect cutting the city of Oslo. Based on concentration but also isotope data, they misinterpret Pb concentration of the biosphere in rural places and explain these large enrichments of Pb as being due to natural processes. The study ignores numerous previous studies either on local, regional or global scales (see reviews by Shotyk and Le Roux, 2005 and Callender, 2003, and references therein), which clearly demonstrate that anthropogenic Pb emitted in the atmosphere from different sources (leaded gasoline, coal burning, metallurgy, etc.) was and is dispersed worldwide. The study also ignores work on Norway by the Steinnes and colleagues group (Harmens et al., 2008, Steinnes et al., 2005a, Steinnes et al., 2005b and Aberg et al., 2004), and measurements and modelling by the EMEP network (www.emep.int/, EMEP, 2005). The study also neglects numerous works on preanthropogenic Pb deposition rate and isotopic signature using continental archives of atmospheric deposition like peat bogs (Shotyk et al., 1998, Klaminder et al., 2003, Kylander et al., 2005 and Le Roux et al., 2005). These studies have shown that preanthropogenic Pb atmospheric deposition rate and its Pb isotopic signature is regionally defined, but also that those signals are negligible compared to past 2 ka and recent Pb atmospheric fluxes (Table 1).

Mercury deposition/accumulation rates in the vicinity of a lead smelter as recorded by a peat deposit

Mercury (Hg) concentration profiles and historical accumulation rates were determined in three 210Pb-dated cores from a peat deposit in the vicinity of a lead (Pb) smelter at Příbram, Czech Republic. The Hg concentrations in peat samples ranged from 66 to 701 μg kg −1. Cumulative Hg inventories from each core (for the past ∼150 yr) varied by a factor of 1.4 (13.6–18.5 mg Hg m −2), indicating variations of net Hg accumulation rate within the peat deposit. Historical changes in vegetation cover (leading to variable interception by trees) are probably responsible for this variation in space and time. The uncorrected Hg accumulation rates peaked between the 1960s and 1980s (up to 226 μg m −2 yr −1). Recent findings show that Hg records from peat tend to overestimate historical levels of Hg deposition. Therefore we used the mass loss compensation factor (MLCF) to normalize Hg accumulation rates. These corrected Hg accumulation rates were significantly lower (maximum 129 μg m −2 yr −1) and better corresponded to changes in historical smelter emissions, which were highest in the 1960s. The agreement between the corrected Hg accumulation rates in the uppermost peat sections (2–38 μg m −2 yr −1) and biomonitoring of atmospheric deposition by mosses in several recent years (4.7–34.4 μg m −2 yr −1) shows the usefulness of MLCF application on Hg accumulation in peat archives. However, the MLCF correction was unsuitable for Pb. The recent Pb deposition rates obtained by an independent biomonitoring study using mosses (0.5–127 mg m −2 yr −1) were better correlated with net Pb accumulation rates recorded in peat (7–145 mg m −2 yr −1) than with corrected rates obtained by the MLCF approach (1–28 mg m −2 yr −1).

Atmospheric deposition of heavy metals (Cu, Zn, Cd and Pb) in Varanasi City, India

Rapid growth in urbanization and industrialization in developing countries may significantly contribute in heavy metal contamination of vegetables through atmospheric depositions. In the present study, an assessment was made to investigate the spatial and seasonal variations in deposition rates of heavy metals and its contribution to contamination of palak (Beta vulgaris). Samples of bulk atmospheric deposits and Beta vulgaris for analysis of Cu, Zn, Cd and Pb were collected from different sampling locations differing in traffic density and land use patterns. The results showed that the sampling locations situated in industrial or commercial areas with heavy traffic load showed significantly elevated levels of Cu, Zn and Cd deposition rate as compared to those situated in residential areas with low traffic load. The deposition rates of Cu, Zn and Cd were significantly higher in summer and winter as compared to rainy season, however, Pb deposition rate was significantly higher in rainy and summer seasons as compared to winter season. Atmospheric depositions have significantly elevated the levels of heavy metals in B. vulgaris collected during evening as compared to those collected in morning hours. The study further showed that local population has maximum exposure to Cd contamination through consumption of B. vulgaris. The present study clearly points out the urban and industrial activities of a city have potential to elevate the levels of heavy metals in the atmospheric deposits, which may consequently contaminate the food chain and thus posing health risk to the local population.

Growth of ternary PbTiOx films in a combination of binary oxide atomic layer depositions

Ternary PbTiOx films were deposited at 240°C on Pt-covered Si substrates using a combination of liquid injection atomic layer depositions of binary TiOx and PbO films. Ti(OC3H7)2(C11H19O2)2 [Ti(Oi−Pr)2(DPM)2] and Pb(C11H19O2)2 [Pb(DPM)2] dissolved in ethylcyclohexane and H2O were used as source materials. The deposition rates of Pb and Ti were enhanced in the ternary process compared to their binary processes under comparable deposition conditions. The Pb∕Ti ratio of PbTiOx films saturated with an increase in Ti precursor input, while it continued to increase with an increasing Pb precursor input. The self-regulated growth nature of the Pb–O layer in the binary film growth was lost in the mixed PbTiOx process as a result of interaction with the predeposited Ti–O layer. It was confirmed that for the PbTiOx film to grow on Pt substrates, an initial incubation period is required. Both Pb–O and Ti–O layers shared a common incubation period of up to ten sequences. The incubation period was shortened by increasing the input of Pb precursor. It was independent of the input of the Ti precursor and the order of precursor supply. This variable incubation period was considered as a potential key issue for growing stoichiometric and uniform multicomponent films over three-dimensional (3D) structures. The order of precursor supply affected the effective deposition rate after the incubation period. A sequence starting with a Ti precursor injection showed a higher growth rate than a sequence that started with a Pb precursor supply. A PbTiOx film was deposited on a 3D substrate precoated with an Ir layer to demonstrate the uniformity in film thickness and cation composition. Although the present PbTiOx process does not have an ideal wide-process window in the cation composition, the PbTiOx film showed uniform coverage and the distribution of cation composition over the hole structure was within ±10%.

Liquid-Injection Atomic Layer Deposition of TiOx and Pb–Ti–O Films

Pb–Ti–O films were prepared by liquid-injection atomic layer deposition (ALD) using as oxygen source after evaluating Ti precursors with different β-diketonate type ligands, and , dissolved in ethylcyclohexane. For both Ti precursors, the apparent thermal activation energy of the deposition rate of films increased at a deposition temperature of about , and the deposition rate of films grown at saturated against the volume of injected Ti precursors. was selected for the subsequent Pb–Ti–O film deposition because of its high precursor efficiency and the low temperature dependence of the deposition rate. Pb–Ti–O films were prepared using and at deposition temperatures of 240 and . The deposition rates of Pb and Ti in the Pb–Ti–O process were higher than those in binary PbO and processes under the same deposition conditions. The deposition rate of Pb in the Pb–Ti–O process showed a linear increase in response to the injected Pb precursor volume, which was different from the saturated deposition rate of the PbO process. The interface chemistry between the precursors and predeposited cation layers has critical impact on the self-regulated growth mechanism in the multicomponent oxide ALD.

Analysis of the Saharan dust regional transport

The Balkan Peninsula is situated in the impact zone of Saharan dust storms. The case of Saharan dust transport to Belgrade in the period of 14–17 April 1994 is analyzed using the Eta model for synoptic and meso scale processes. Air back trajectories are calculated at six model levels from 434 up to 5129 m with horizontal grid resolutions of 1°×1° and 10′×10′. Following cyclonic circulation the dust was picked up from North Africa, and transported over Mediterranean. Simultaneously, according to the analysis of the three lowest trajectories, transport of trace metals from Macedonia and southern Serbia by the Koshava wind might be dominant in the observed episode. Turbulent flow enhanced the coagulation process of initially clean dust particles with particles containing Pb and Cd. The coagulation and scavenging processes below and in clouds increased deposition rates of Pb and Cd in Belgrade in the course of wet removal, and consequently trough resuspension processes. Dry deposition samples contained characteristic particles up to 30 µm in diameter with Fe content of 11 to 15 atomic% and significant ratio Si/Fe of 3 to 5, determined for selected single particles by the SEM/EDX method. Following dry and wet deposition of Cd and Pb, a residual effect of dustfall is noticed throughout the vegetational period.

Isotopic trends and background fluxes of atmospheric lead in northern Europe: Analyses of three ombrotrophic bogs from south Sweden

Knowledge about the natural atmospheric background deposition rate of lead (Pb) prior to anthropogenic pollution is critical in the understanding of present‐day pollution and for establishing realistic goals for the reduction of atmospheric Pb. We utilize stable Pb isotopes (206Pb and 207Pb) in radiocarbon‐dated peat cores from three ombrotrophic bogs from south Sweden, to calculate fluxes and to survey atmospheric Pb trends prior 3500 BP (the so far known onset of large‐scale anthropogenic pollution). The estimated atmospheric Pb deposition rate was between 1 and 10 μg Pb m2 yr−1 between 5900 and 3700 calendar years BP, which is 100 to 1000 times lower than present‐day deposition rates. The majority of the samples older than 3500 calendar years BP had 206Pb/207Pb ratios ≤1.20, which is significantly lower than unpolluted Swedish mineral soils (206Pb/207Pb &gt; 1.30), suggesting that even the natural atmospheric deposition of Pb was dominated by long‐range transport, rather than local inputs from soil dust. Low 206Pb/207Pb ratios (1.16–1.18) of several samples indicate that this distant transport originated at least partly from early pollution sources. A possible climatic connection with the observed Pb deposition trends is suggested.

Accumulation of trace elements on the surface soil around the Trail smelter, British Columbia, Canada

The quantities of six elements (As, Cd, Cu, Hg, Pb, and Zn) were determined in surface soil from 21 stations around the zinc–lead smelter in Trail, British Columbia, Canada. The flux of elements into a unit of soil was then calculated by extrapolating aerial deposition monitoring data obtained from flat square moss bags, which act as traps for airborne particles/elements. The net increase in the quantity of elements in a 10 cm deep by 1 hectare soil unit over a 3-month time interval was estimated as 0.02, 0.65, 0.07, 0.29, 0.22, and 0.65% for As, Cd, Cu, Hg, Pb, and Zn, respectively. The results of this study can be used for elemental inventory of soil in the Trail area and to predict the long-term degree of accumulation of trace elements in the soil. The significant correlation between the deposition rate of Pb, Zn, Cd, and Cu as registered by moss monitoring stations and the quantity of these elements in surface soil indicate the possible effect of airborne material on the geochemistry of the soils in the study area. In contrast, the poor correlation for Hg and As indicates that the variations of these elements in soil samples are likely related to soil chemistry rather than atmospheric deposition. This demonstrates the importance of monitoring for atmospheric deposition of elements since soil is not always a good indicator of the spatial influence of a point source in the study area.

200 Years of Pb Deposition throughout the Czech Republic: Patterns and Sources

Historical rates of Pb deposition were determined over the past 150−200 years for eight sites throughout the Czech Republic using 210Pb-dated, Sphagnum-derived peat cores. Maximum historical Pb deposition was greater at sites in the northern and western parts of the Czech Republic than at sites in the southern part of the Czech Republic (peak values averaging 57, 21, and 16 mg m-2 yr-1, respectively). Lead deposition patterns generally reflect increasing industrialization over the past 100−200 years, especially in the post-World War II era. For seven of the eight sites, maximum Pb deposition occurred between 1965 and 1992, corresponding to a period of peak production and burning of lignite coal. A decrease in Pb deposition rates since 1975−1980 was evident in seven of the sites. The most recent Pb deposition rates (1992), estimated from the uppermost peat core sections, averaged 32, 11, and 7 mg m-2 yr-1 for the northern, western, and southern sites, respectively, are higher than current Pb deposition in the eastern United States of 4 mg m-2 yr-1. Lead deposition rates prior to Czech industrialization, estimated from the deepest dateable peat core sections, averaged 8, 5, and 1 mg m-2 yr-1 for the northern, western, and southern sites, respectively. Using acid-insoluble ash concentrations in peat and peat magnetic susceptibility determinations, we were able to identify past periods of elevated Pb deposition related to local mining of Pb-containing ore deposits at three of the sites and periods of elevated Pb deposition from fossil fuel combustion at five of the sites. Without stable Pb isotopic determinations, the importance of leaded gasoline-derived Pb could not be determined.

Determination of regional influences on the deposition of Pb, Cd and H + ion in a network of rain samplers

In order to determine the wet deposition rates of Pb, Cd and acid constituents, represented by pH, in industrial, urban, rural and maritime areas in Germany since 1979, a network of precipitation samplers has been established. Sampler positions are described and classified geographically and assumptions on pollutant sources effective at the sampler positions are made. These geographical expectations are verified by statistical analyses. Discriminant analysis of the total average values of the wet deposition rates regarding the complete network, permitted the classifications of industry, town and country for the sampler locations. The industry group is characterized by high wet deposition rates of Pb and Cd, the town group by enhanced wet deposition rates of acid constituents, whilst the country group in comparison with the town group showed altogether lower wet deposition rates for Pb, Cd and acid constituents. Factor analysis of the local time series of pollutant wet deposition rates including the precipitation rate shows the direct influence of strong pollutant sources at a number of sampler positions, especially for locations in the industry group. The town and country groups are characterized by non-individual wet depositions, depending preferentially on general local atmospheric conditions.

Equilibrium line and mean annual mass balance of Finsterwalderbreen, Spitsbergen, determined by in situ and laboratory gamma-ray measurements of nuclear test deposits

In order to determine the equilibrium line (EL) and the annual net mass balance over the accumulation area of Finsterwalderbreen, Spitsbergen, Svalbard (by detection of the 1962–63 radioactive peak from the 1961–62 atmospheric nuclear tests), we collected 14 ice cores, at elevations of 445–730 m, in the springs of 1994 and 1995. The corresponding samples were melted and filtered for laboratory gamma spectrometry. In the accumulation area, the 1962–63 radioactive layer is found well below the surface. The mean annual accumulation is not invariably related to altitude. The EL, averaged to 545 in a.s.l., leads to an accumulation area ratio of 0.3 and indicates a strong negative balance. The 584 Bq m−2 mean137 Cs deposition rate (1954–74 nuclear tests) for eight ice cores in the accumulation area is nearly twice the 340 Bq m−2 mean Svalbard value obtained from six other glaciers (at time of deposition). An in situ gamma-ray detector was lowered down each borehole, and137 Cs levels were recorded. The counting rate is proportional to the apparent deposition rate and the specific activity. The laboratory measurements perfectly match the in situ determinations. In the ablation area, a dust layer and the associated nuclear test deposits are concentrated close to the bare ice surface of the glacier, under the winter snow layer and present maximum 137 Cs and 210 Pb contents. The dust layer acts like a filter for radioactive materials removed from the glacier and its basin by melting and water flow. The original specific activities and deposition rates at a given location are enhanced by adsorption of additional radioactivity on the dust particles. A linear relationship exists between 137 Cs and 210 Pb deposition rates. This process is almost constant for all studied ice cores. The apparent 137 Cs deposition rate for seven ice cores in the ablation area is 465 Bq m−2 (at date of measurement: 1 July 1995).