Atmospheric Deposition Data Research Articles

Trend analysis of atmospheric deposition data: A comparison of statistical approaches

Numerical simulation was used to compare the most used trend analysis techniques on data series of ionic concentrations in atmospheric deposition. The Seasonal Kendall Test (SKT) showed the highest power, which increased in particular when using original weekly data instead of pooling together the samples in monthly or yearly volume-weighted averages. The simulation also showed that differences in power among tests and pooling intervals would be negligible for data series longer than about 12 years.We tested these results using data from a network of bulk deposition samplers at nine forest sites in Italy, for which data have been available since 1998. These sites were selected in different forests, ranging from arid Mediterranean evergreen oak forest to rainy Alpine beech or spruce forests. The results showed relevant differences as regards the number of significant trends detected using different techniques and different data pooling, even for 13-year data series.The use of minimum–maximum autocorrelation factor analysis allowed a better interpretation of the data, showing the main trend shapes among stations and variables.

Does spatial auto-correlation call for a revision of latest heavy metal and nitrogen deposition maps?

Abstract Background Within the framework of the Convention on Long-range Transboundary Air Pollution atmospheric depositions of heavy metals and nitrogen as well as critical loads/levels exceedances are mapped yearly with a spatial resolution of 50 km by 50 km. The maps rely on emission data and are calculated by use of atmospheric modelling techniques. For validation, EMEP monitoring data collected at up to 70 sites across Europe are used. This spatially sparse coverage gave reason to test if the chemical and physical relations between atmospheric depositions and their accumulation in mosses collected at up to 7000 sites throughout Europe can be quantified in terms of statistical correlations which, if proven, could be used to calculate deposition maps with a higher spatial resolution. Indeed, combining EMEP maps on atmospheric depositions of cadmium, lead and nitrogen and the related maps of their concentrations in mosses by use of a Regression Kriging approach yielded deposition maps with a spatial resolution of 5 km by 5 km. Since spatial auto-correlation can make testing of statistical inference too liberal, the investigation at hand was to validate the 5 km by 5 km deposition maps by analysing if spatial auto-correlation of both EMEP deposition data and moss data impacted on the significance of their statistical correlation and, thus, the validity of the deposition maps. To this end, two hypotheses were tested: 1. The data on deposition and concentrations in mosses of heavy metals and nitrogen are not spatially auto-correlated significantly. 2. The correlations between the deposition and moss data lack statistical significance due to spatial autocorrelation. Results As already published, the regression models corroborated significant correlations between the concentrations of heavy metals and nitrogen in atmospheric depositions on the one hand and respective concentrations in mosses on the other hand. This investigation proved that atmospheric deposition and bioaccumulation data are spatially auto-correlated significantly in terms of Moran’s I values and, thus, hypothesis 1 could be rejected. Accordingly, the degrees of freedom were reduced. Nevertheless, the results of the calculations regarding the reduced degrees of freedom indicate that the statistical relations between atmospheric depositions and bioaccumulations remained statistically significant so that hypothesis 2 could be rejected, too. Conclusions The positive auto-correlation in data on atmospheric deposition and bioaccumulation does not call for a revision of the 5 km by 5 km deposition maps published in recent papers. Therefore we can conclude that the European moss monitoring yields data that support the validation of modelling and mapping of atmospheric depositions of heavy metals and nitrogen at a high spatial resolution compared to the 50 km x 50 km EMEP maps.

Cosmogenic 7Be: Atmospheric Concentration and Deposition in Japan

Interactions between cosmic rays and atmospheric components produce various nuclear fragments. Cosmogenic 7Be distributes uniformly in the atmosphere which covers all over the earth. Thus, the vertical and horizontal transport of 7Be in the stratosphere as well as troposphere will work as an effective tracer with half life of 53.3 days. Many studies have been conducted on 7Be atmospheric concentration and deposition onto the ground. Generally, the atmospheric 7Be concentration and the 7Be deposition show seasonal and yearly variations which are controlled by solar activity, cosmic ray intensity, atmospheric circulation and other mechanisms such as “washout” and “rainout”. This paper presents atmospheric 7Be concentration and 7Be deposition data obtained by the authors as well as other investigators. The variations of atmospheric 7Be concentration and 7Be deposition and their influential factors are also reviewed.

Atmospheric Mg2+ wet deposition within the continental United States and implications for soil inorganic carbon sequestration

Little is known about atmospheric magnesium ion (Mg2+) wet deposition in relation to soil inorganic carbon sequestration. Understanding the conversion of carbon dioxide (CO2) or organic carbon to a form having a long residence time within the soil (e.g., dolomite, magnesian calcite) will greatly benefit agriculture, industry, and society on a global scale. This preliminary study was conducted to analyze atmospheric Mg2+ wet deposition within the continental United States (U.S.) and to rank the twelve major soil orders in terms of average annual atmospheric Mg2+ wet deposition. The total average annual Mg2+ wet deposition for each soil order was estimated with geographic information systems (GIS) using the following data layers: (1) atmospheric Mg2+ wet deposition data layers covering the continental U.S. for a 10-yr period (1994–2003) and (2) a soil order data layer derived from a national soils database. A map of average annual Mg2+ wet deposition for 1994–2003 reveals that the highest deposition (0.75–1.41 kg ha-1) occurred in Oregon, Washington, parts of California, and the coastal areas of East Coast states due to magnesium enrichment of atmospheric deposition from sea salt. The Midwestern region of the U.S. received about 0.25–0.75 kg ha-1 Mg2+ wet deposition annually, which was associated with loess derived soils, occurrence of dust storms and possibly fertilization. The soil orders receiving the highest average annual atmospheric Mg2+ wet deposition from 1994 to 2003 were: (1) Mollisols (3.7×107 kg), (2) Alfisols (3.6×107 kg) and (3) Ultisols (2.8×107 kg). In terms of potential soil carbon sequestration, the average annual atmospheric Mg2+ wet deposition was equivalent to formation of the following theoretical amounts of dolomite: (1) Mollisols (2.8 × 108 kg of CaMg(CO3)2), (2) Alfisols (2.7 × 108 kg of CaMg(CO3)2) and (3) Ultisols (2.1 × 108 kg of CaMg(CO3)2). The soil orders receiving the lowest average annual atmospheric Mg2+ wet deposition were: (1) Andisols (3.3 × 106 kg), (2) Histosols (3.4 × 106 kg) and (3) Vertisols (5.0 × 106 kg). The methods proposed here to estimate soil inorganic carbon sequestration potential from atmospheric wet deposition data can be useful for preliminary carbon accounting on a global scale.

Contribution of agricultural liming to riverine bicarbonate export and CO2 sequestration in the Ohio River basin

Chemical weathering of silicates and carbonates is essential in the global cycles of many elements, including carbon. Chemical weathering affects regional and global carbon budgets through the export of bicarbonate, much of which can originate from the atmosphere. Agricultural practices may accelerate chemical weathering from the Mississippi River basin directly or indirectly. Here we investigated one of the direct effects of agricultural practices, liming, on stream bicarbonate export and the carbon budget of agricultural systems. Using geographic information systems (GIS) layers extracted from various sources such as USGS National Land Cover Data set, U.S. Census of Agriculture data, USGS water data, NADP atmospheric acid deposition data, and NASS‐USDA crop production data, we estimated the contributions of liming inputs on both the riverine bicarbonate export and atmospheric CO2 sequestration for a subset of agricultural and forested watersheds within the Ohio River basin. Liming rates have slightly decreased from 23.6 to 19.4 g CaCO3 m−2 cropland yr−1 from 1954–1970 to 1971–1987 in six highly agricultural watersheds. The largest decrease was observed in watersheds located in the state of Ohio while a slight increase was observed in watersheds located in the state of Illinois where agricultural practices are the most intense. An average of 21.1 and 22.4 g CaCO3 m−2 yr−1 were applied to the two most highly agricultural watersheds (91% agricultural in 1992) located in the state of Illinois during 1954–1970 and 1971–1987, respectively. Using a calcium mass balance, we estimated that 29% of the total riverine bicarbonate export from the two most agricultural watersheds was by liming and thus liming is important to the cation/anion balance and buffering capacity of streams. The on‐site net atmospheric C sequestration by liming from the two most agricultural watersheds was estimated to be 0.95 g C m−2 yr−1. However, considering 0.85 g C m−2 yr−1 is estimated to be released as CO2 during the production, transport, and spreading of lime, liming as a C sequestration strategy is not attractive.

Retention of Inorganic Nitrogen by Epiphytic Bryophytes in a Tropical Montane Forest1

ABSTRACTWe developed and evaluated a model of the canopy of a tropical montane forest at Monteverde, Costa Rica, to estimate inorganic nitrogen (N) retention by epiphytes from atmospheric deposition. We first estimated net retention of inorganic N by samples of epiphytic bryophytes, epiphyte assemblages, vascular epiphyte foliage, and host tree foliage that we exposed to cloud water and precipitation solutions. Results were then scaled up to the ecosystem level using a multilayered model of the canopy derived from measurements of forest structure and epiphyte mass. The model was driven with hourly meteorological and event‐based atmospheric deposition data, and model predictions were evaluated against measurements of throughfall collected at the site. Model predictions were similar to field measurements for both event‐based and annual hydrologic and inorganic N fluxes in throughfall. Simulation of individual events indicated that epiphytic bryophytes and epiphyte assemblages retained 33–67 percent of the inorganic N deposited in cloud water and precipitation. On an annual basis, the model predicted that epiphytic components retained 3.4 kg N ha/yr, equivalent to 50 percent of the inorganic N in atmospheric deposition (6.8 kg N ha/yr). Our results indicate that epiphytic bryophytes play a major role in N retention and cycling in this canopy by transforming highly mobile inorganic N (ca. 50% of atmospheric deposition is NO−3) to less mobile (exchangeable NH+4) and recalcitrant forms in biomass and remaining litter and humus.

Sources, distribution and variability of hydrocarbons and metals in atmospheric deposition in an urban area (Paris, France)

Total atmospheric deposition, i.e., both wet and dry deposition, was sampled during 11 months in the “Ile-de-France” region, France. Monthly fluxes of aliphatic hydrocarbons (AHs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) were studied at three representative sites (two urbanised and one semiurban). A combination of spatial and temporal variability of total fluxes and pollutant fingerprints allows a better understanding of atmospheric pollutant dynamics over this region. In the whole studied area, aggregated total atmospheric fluxes of AHs, PAHs and HMs range from 19 to 33 mg m −2 y −1, 99 to 161 μg m −2 y −1 and 48 to 103 mg m −2 y −1, respectively. The highest values are observed in Paris centre, reflecting the importance of the urban centre as a source of pollutants, with a decline in many atmospheric deposits when moving away from urban areas. The seasonal distribution of these pollutants suggests the impact of residential heating on urban atmospheric deposition of hydrocarbons and the increase of dust loads containing HMs during summer. The qualitative study performed on atmospheric deposition data highlights the main sources of pollutants. Aliphatic fingerprints suggest a marked contribution of biogenic inputs to aliphatic contamination in the whole Ile-de-France region and slight petroleum inputs in urban areas. Aromatic fingerprints, characterised by the great predominance of phenanthrene, fluoranthene and pyrene, associated with some specific ratio values, suggest the mixture of petrogenic and pyrolytic contaminations of atmospheric deposition in the whole “Ile-de-France” region. HM distribution shows the presence of anthropogenic sources of Al and Fe in this area and the stationary sources (incinerators and plants) as a significant source of Si, S and Sb in the urban atmosphere. Moreover, a pollutant mix phenomenon, occurring in such an urban atmosphere, shows a significant influence on atmospheric deposition at the semiurban site.

Empirical evidence for the low- and high-NOx photochemical regimes of sulfate and nitrate formation

The formation of sulfate and nitrate in eastern North America is chemically linked to the abundance of oxidants and therefore to the emissions of nitrogen oxides (NOx). Depending on conditions, NOx reacts under either of two distinct photochemical regimes, defined by the types and levels of radical production. In the low-NOx regime (typical of summer), nitrogen dioxide (NO2) is readily consumed during nitric acid formation, leaving an excess of radicals that recombine to form peroxides and a highly oxidizing state favorable to sulfate formation. On the other hand, under high-NOx conditions (as in winter), the oxidizing capacity of the atmosphere is reduced because the NO2 rapidly combines with and thereby depletes hydroxyl radicals, producing nitric acid, but few peroxides. The distinction between these two chemical regimes is crucial for interpreting atmospheric deposition data because it determines whether sulfate or nitrate is the dominant acidifying component. Evidence for these regimes is gained from seasonal observations of sulfate and nitrate in rain samples collected at several sites of the National Atmospheric Deposition Program (NADP). A simple modeling exercise elucidates the processes by which sulfate and nitrate are formed under the high- and low-NOx states.

Precision of atmospheric dry deposition data from the Clean Air Status and Trends Network

A collocated, dry deposition sampling program was begun in January 1987 by the US Environmental Protection Agency to provide ongoing estimates of the overall precision of dry deposition and supporting data entering the Clean Air Status and Trends Network (CASTNet) archive. Duplicate sets of dry deposition sampling instruments were installed adjacent to existing instruments and have been operated for various periods at 11 collocated field sites. All sampling and operations were performed using standard CASTNet procedures. The current study documents the bias-corrected precision of CASTNet data based on collocated measurements made at paired sampling sites representative of sites across the network. These precision estimates include the variability for all operations from sampling to data storage in the archive. Precision estimates are provided for hourly, instrumental ozone (O 3) concentration and meteorological measurements, hourly model estimates of deposition velocity ( V d) from collocated measurements of model inputs, hourly O 3 deposition estimates, weekly filter pack determinations of selected atmospheric chemical species, and weekly estimates of V d and deposition for each monitored filter pack chemical species and O 3. Estimates of variability of weekly pollutant concentrations, expressed as coefficients of variation, depend on chemical species: NO 3 −∼8.1%; HNO 3∼6.4%; SO 2∼4.3%; NH 4 +∼3.7%; SO 4 2−∼2.3%; and O 3∼1.3%. Precision of estimates of weekly V d from collocated measurements of model inputs also depends on the chemical species: aerosols ∼2.8%; HNO 3∼2.6%; SO 2∼3.0%; and O 3∼2.0%. Corresponding precision of weekly deposition estimates are: NO 3 −∼8.6%; HNO 3 −∼5.2%; SO 2∼5.6%; NH 4 +∼3.9%; SO 4 2−∼3.5%; and O 3∼3.3%. Precision of weekly concentration, V d estimates, and deposition estimates are comparable in magnitude and slightly smaller than the corresponding hourly values. Annual precision estimates, although uncertain due to their small sample size in the current study, are consistent with the corresponding weekly values.

Deterioration of atlantic soft water macrophyte communities by acidification, eutrophication and alkalinisation

This review presents an overview of the most important succession patterns and underlying processes associated with the deterioration of soft water macrophyte communities in atlantic and boreo-atlantic regions. As acidification, eutrophication and alkalinisation are the dominant processes, this paper will focus on the successional changes caused by these processes. Observed differences in the succession between soft waters in different areas in Europe are discussed. Most attention has been given to vegetation changes related to acidification, as most research has been carried out on this topic. In acidifying formerly slightly calcareous aquatic systems, a transition takes place from isoetid and other soft water plant communities to vegetation dominated by submerged Sphagnum mosses and Juncus bulbosus forma fluitans. Regional surveys show that this transition is not very common in acidified lakes in Norway, Finland, Canada, and North America. However, the opposite seems to be true for some southern Swedish lakes, some Scottish lakes, lakes in the West European lowlands (The Netherlands and Germany) and also recently for some southern Norwegian lakes. The calcium bicarbonate content of the sediment seems to be an important explanatory variable, as well as the availability and form of inorganic nitrogen. In West European lakes, isoetids disappear during the acidification process. Elsewhere, although Sphagnum mosses and J. bulbosus develop, isoetids continue to coexist. In this paper, it is hypothesized that the succession seen in soft waters outside the West European lowlands has not yet reached the final stage in which isoetids disappear. Thus, the most dramatic deterioration of soft water macrophyte communities has occurred in the West European lowlands, where the number of isoetid sites has decreased dramatically. The West European systems are substantially smaller and shallower than those elsewhere. The morphology of soft water systems is important in determining the way eutrophication becomes manifest. In larger and deeper systems, planktonic algal growth causes a higher turbidity, whilst in smaller and shallower systems lemnids and ricciellids may expand. For a better understanding of the successional differences between soft waters on an interregional scale, further research and cooperation is needed, in which vegetation, physico-chemical and atmospheric deposition data are integrated.

Evaluating Critical Soil Acidification Loads and Exceedances for a Deciduous Forest at the Turkey Lakes Watershed

Critical soil acidification loads (CL) and related exceedances, base cation leaching, N leaching, and forest biomass growth were evaluated for a well-studied deciduous forest site within the Turkey Lake Watershed (TLW). The assessment was done by way of steady-state mass balance considerations of primary inputs for N, Ca, Mg, and K. Critical soil acidification rates were found to be high at TLW. These rates amounted to about 900 or 1400 eq/(ha yr) depending on the forest harvesting regime (selective harvest or maintainence of old-growth condition, respectively). The TLW soil substrate (till derived from basaltic bedrock) appeared to weather well, thereby buffering against natural and anthropogenic soil acidification. As a consequence, soil acidification exceedances were estimated to be relatively low for both the selective harvest and old-growth scenarios. In comparing overall S and N input/output data (atmospheric deposition data vs soil leaching losses), we found that the TLW site was essentially near or at S and N saturation. We also found that atmospheric deposition and soil leaching rates have been declining since about 1980. The figures for CL and exceedance varied to some extent depending on the quality of input data and related uncertainties. Estimated exceedances were increased when dry- as well as wet-deposition rates were considered. They varied depending on the yearly sulfate/nitrate/base-cation mix, and the definition of “acceptable acid leaching.” In addition, they were dependent on whether the forest was considered old growth or not.

ATMOSPHERIC DEPOSITION AND RUNOFF OF MERCURY AND TRACE METAL IN AN URBAN WATERSHED

Non-point and diffuse sources can be the most significant sources of pollutants in a watershed. Atmospheric deposition in its three forms (ambient, dry, and wet) has often been neglected and thus was not included in watershed approach for water resources management. Often regulatory frameworks for water resources protection have not taken into account atmospheric deposition because little or no data is available. The project undertaken is new and unique in its scope and approach to monitor and measure pollutants in atmospheric deposition and its impact on storm water quality within a river watershed. Specialized sampling equipment and ultra-clean analytical methodology were employed to quantify the concentrations or masses in ambient air, precipitation, and runoff for twelve trace metals. These metals include mercury (Hg), cadmium (Cd), antimony (Sb), aluminum (Al), arsenic (As), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn). Meteorological parameters including wind speed, wind direction, temperature, and relative humidity were also measured. This study represents the most complete set of atmospheric concentration and deposition data for trace metals and mercury in an urban watershed at this time. Additionally, this is the first time that mercury together with other trace elements in dry deposition and runoff has been measured in a study of this length. The results of this study provide both the critical information and valuable study approaches to monitor trace metal deposition in urban watersheds.

Factor analysis of atmospheric trace-element deposition data in the netherlands obtained by moss monitoring

Monte Carlo-Assisted Factor Analysis has been applied to a data set of trace element concentrations in samples of the moss species Pleurozium schreberi, collected in 1992 from 66 locations in the Netherlands. A Monte Carlo approach was used to give more insight in the uncertainties and significance levels of the factor analysis results. Using a selection of 23 elements, factor analysis enabled the identification of 8 significant pollution source types. Two source types were assumed to be related to the influence of foliar leaching from higher plants. The remaining source types were found to correspond with the major source types obtained in earlier biomonitoring surveys in the Netherlands using lichen and bark, i.e. crustal material, sea aerosol and various types of industrial pollution sources, associated with metallurgical industries, refuse incineration and oil combustion or processing of oil products. The contribution of the industrial pollution sources appeared to have decreased between 1987 and 1992.

A risk assessment of sulphur deficiency in cereals using soil and atmospheric deposition data

Abstract. A qualitative model was used to assess the risk of S deficiency in cereals in Britain. A risk index was generated for each of 6301 soil data points by considering the inputs of S from atmospheric deposition, the content of soil organic matter, and factors influencing the potential leaching of sulphate, i.e. soil type, texture, pH and annual rainfall. The results show that currently 11% of the British land area is at high risk of S deficiency, and a further 22% at medium risk. The high risk areas are in south‐east Scotland, the Scottish Borders, East Anglia, the Welsh Borders and south‐west England. These agree well with the distribution of reported incidences of S deficiency in cereals. If the UK target for reduction in SO2 emissions by the year 2003 is met, the model predicts that the high and medium risk areas will increase to 23 and 27%, respectively. Thus, agricultural use of S‐containing fertilizers is likely to increase in importance in the near future.

The precision of wet atmospheric deposition data from national atmospheric deposition program/national trends network sites determined with collocated samplers

Abstract A collocated, wet-deposition sampler program has been operated since October 1988 by the U.S. Geological Survey to estimate the overall sampling precision of wet atmospheric deposition data collected at selected sites in the National Atmospheric Deposition Program and National Trends Network (NADP/NTN). A duplicate set of wet-deposition sampling instruments was installed adjacent to existing sampling instruments at four different NADP/NTN sites for each year of the study. Wet-deposition samples from collocated sites were collected and analysed using standard NADP/NTN procedures. Laboratory analyses included determinations of pH, specific conductance, and concentrations of major cations and anions. The estimates of precision included all variability in the data-collection system, from the point of sample collection through storage in the NADP, /NTN database. Sampling precision was determined from the absolute value of differences in the analytical results for the paired samples in terms of median relative and absolute difference. The median relative difference for Mg 2+ , Na + , K 4 + and NH concentration and deposition was quite variable between sites and exceeded 10% at most sites. Relative error for analytes whose concentrations typically approached laboratory method detection limits were greater than for analytes that did not typically approach detection limits. The median relative difference for S0 4 2− and NO 3 − concentration, specific conductance, and sample volume at all sites was less than 7%. Precision for H + concentration and deposition ranged from less than 10% at sites with typically high levels of H + concentration to greater than 30% at sites with low H + concentration. Median difference for analyte concentration and deposition was typically 1.5-2-times greater for samples collected during the winter than during other seasons at two northern sites. Likewise, the median relative difference in sample volume for winter samples was more than double the annual median relative difference at the two northern sites. Bias accounted for less than 25% of the collocated variability in analyte concentration and deposition from weekly collocated precipitation samples at most sites.

Hydrologic control of sulfate mobility in a forested watershed

Five years of atmospheric wet sulfate deposition and stream sulfate export data were evaluated to determine the fate and mobility of sulfate in a forested watershed in central Pennsylvania. Sulfate concentrations in stream water were inversely related to sulfate concentrations in precipitation. Sulfate export from this watershed exceeded wet deposition by approximately 20% in 4 out of the 5 years studied, indicating an additional source of sulfate, possibly dry deposition. The average sulfate export from this watershed during February through May was 69.8% of the total annual export. The fact that sulfate export during this 4‐month period could not result from wet deposition during this period suggests that atmospherically deposited sulfate is temporarily stored on the watershed and that the release of this stored sulfate is controlled strongly by the hydrologic responsiveness of the watershed. Analysis of both monthly and storm flow sulfate export/input data supports these conclusions and suggests that the release of stored sulfate can be described by the variable source area concept. The results also suggest that the sulfate adsorption capacity of the soils on this watershed has been satisfied and that a steady state condition exists between atmospheric sulfate inputs and export. Because hydrologic conditions appear to significantly control sulfate export, multiple years of record are required when using the watershed mass balance technique to estimate dry deposition or determine the status of sulfate adsorption on a basin. It is recommended that at least 3–5 years of input/export data be used when using this technique.

Polychlorinated biphenyls in dated sediments of Milwaukee Harbour, Wisconsin, USA

A sediment core from Milwaukee Harbour was dated by the Pb-210 and Cs-137 methods and analysed for polychlorinated biphenyls (PCBs). The mass sedimentation rate of 1·10 g cm −2 year −1 was significantly higher than for Lake Michigan. The Cs-137 inventory of 162·9 dpm cm −2 was 11·7 times higher than that calculated from atmospheric deposition data. There was a significant degree of PCB pollution in the sediments, as evidenced by the fact that the PCB flux was 596 times higher than the average atmospheric input to Lake Michigan. The vertical distribution of PCBs in the relatively undisturbed core followed the available national sales records (1957–1974) remarkably well. In addition, there was a sharp drop in layers from the late 1970s which would be expected in view of the recent curtailment of PCB usage and production. Relatively high levels of Aroclor 1254 point to local electrical component manufacturers. Several users of hydraulic fluids and lubricants containing PCBs have probably also contributed to the increased levels in the harbour sediments.

Atmospheric fluxes and marsh‐soil inventories of 7Be and 210Pb

The atmospheric flux of 7Be over a 2‐year period at a coastal site (Norfolk, Virginia) and at an inland site (Oak Ridge, Tennessee) typically supports inventories ranging from 1.0 to 2.0 pCi/cm2 (1 pCi = 0.037 Bq), with the highest inventories generally occurring in the spring and the lowest occurring in the fall. The calculated average daily fluxes required to support these inventories range from 0.013 to 0.026 pCi cm−2 d−1. Despite the different production‐source terms for 7Be and 210Pb, there is a high degree of correlation between their measured total monthly deposition reflecting the importance of washout in removing both radionuclides from the atmosphere. Beryllium 7 inventories in soil and vegetated marsh cores compare favorably with inventories calculated from the atmospheric deposition data. Lead 210 inventories in soil and vegetated marsh cores may be enriched (by 20–30%) in relation to inventories calculated from its depositional flux to bucket samplers. Possible explanations for this enrichment are that above‐ground vegetation is more efficient at collecting dry aerosols (containing short‐lived radon daughters) than buckets or that foliage is an effective trap for particles containing sorbed 210Pb which may be eroded from unvegetated surfaces by wind or water. The vertical distribution and inventory of both 7Be and 210Pb in marsh cores are affected by the presence of vegetation and the location of the groundwater table.

Records and sources of metal pollutants in a dated Loch Lomond sediment core

Lead, zinc, copper, chromium, arsenic and cadmium were measured in a sediment core from southern Loch Lomond for which 210Pb dating indicated a sedimentation rate of 22±2 mg/cm 2/yr corresponding to a mean accumulation rate of 0.36 mm/yr. While copper and chromium were enriched to only a minor extent, the lead, zinc, arsenic and cadmium concentrations were markedly enhanced in upper sections. Increasing anthropogenic input associated with industrial activity centred on Glasgow seems responsible for the vertical distribution of lead, zinc and cadmium but a high 0–1 cm level of arsenic (474 μg/g), strongly correlated with enhanced iron content in the surface oxidising layer of sediment, appears attributable to post-depositional diagenetic mobilisation and upward migration in the reducing zone of the sediment column. Leaching, using CH 3CO 2H/NH 2OH·HCl, released over 90% and 80% of the common metal pollutants, lead and zinc, from surface sediment. Onset of an approximately tenfold increase in lead and zinc concentrations above “background” levels of 13±2 μg/g and 47±13 μg/g to upper section levels of 140–170 μg/g and 450–460 μg/g respectively was placed at late-18th century, in accord with the records of the commencement of significant industrial activity in the Glasgow area. Current anthropogenic fluxes (μg/cm 2 /yr) of lead (2.51±0.34) and zinc (8.84±1.20) to the sediment are in agreement with recent atmospheric deposition data for the adjoining Clyde Sea Area. The general concordance between anthropogenic metal fluxes to Loch Lomond sediment and atmospheric deposition fluxes endorses the potential usefulness of Loch Lomond sediment data to the resolution of pollution sources in the adjoining sea lochs and firth of the Clyde Sea Area, illustrated here through consideration of the comparative distribution of chromium in relation to its historical use.