Contrasting controls on arsenic and lead budgets for a degraded peatland catchment in Northern England

Atmospheric deposition of trace metals and metalloids from anthropogenic sources has led to the contamination of many European peatlands. To assess the fate and behaviour of previously deposited arsenic and lead, we constructed catchment-scale mass budgets for a degraded peatland in Northern England. Our results show a large net export of both lead and arsenic via runoff (282 ± 21.3 gPb ha(-1) y(-1) and 60.4 ± 10.5 gAs ha(-1) y(-1)), but contrasting controls on this release. Suspended particulates account for the majority of lead export, whereas the aqueous phase dominates arsenic export. Lead release is driven by geomorphological processes and is a primary effect of erosion. Arsenic release is driven by the formation of a redox-dynamic zone in the peat associated with water table drawdown, a secondary effect of gully erosion. Degradation of peatland environments by natural and anthropogenic processes has the potential to release the accumulated pool of legacy contaminants to surface waters.     

Lead concentrations in soil, sediment and clam samples from the Pungo River peatland area of North Carolina, USA

Lead (Pb) concentrations were measured in samples of peat soils, sediments and clams (Rangia cuneata) collected from the Pungo River region of coastal North Carolina. In peat soils, mean Pb concentrations (dry weight +/- 1 SD) were significantly higher (p<0.05) in surface samples (12.8microg g(-1)+/-7.6) than in samples from depths of 20 cm (2.7microg g(-1)+/-2.7) or 1 m (3.6microg g(-1)+/-3.6). Mean Pb concentrations in surface sediments from canals draining peatlands and from the Pungo River which receives this drainage ranged from 0.1microg g(-1)+/-0.1 to 7.0microg g(-1)+/-0.6. These Pb concentrations are similar to values reported in other studies for areas considered uncontaminated. Fractionation analysis revealed that the majority of the Pb in the peat and sediment samples was associated with the residual fraction, with lesser amounts in the organically-bound fraction, and generally negligible amounts in the water-soluble fraction. These results indicate that the bulk of the Pb in the soils and sediments of this area is relatively immobile and non-bioavailabe. This is supported by the relatively low concentrations of Pb (0.2-0.5 microg g(-1), dry weight) observed in soft tissues of R. cuneata collected from the Pungo River.     

The dynamics of dissolved nitrogen in a blanket peat dominated catchment

Precipitation, soil solution and drainage water were collected from a blanket peat catchment at Moor House National Nature Reserve in the Northern Pennine Uplands, UK, an area of moderately high N deposition. Two tributaries of the main stream were also sampled. Between 1993 and 1995 samples were analysed for NH4+ and NO3- and for part of the period for organic N. Inputs of N in precipitation exceeded outputs in stream water. Organic N represented a small proportion of N inputs while inputs of inorganic N averaged 10.2 kg ha(-1) a(-1). Soil solution from 10 cm depth in the peat was dominated by organic N whereas at 50 cm NH4+ slightly exceeded organic N. NO3- was rarely detected at either depth except during a period of exceptionally warm and dry weather in 1995. Output fluxes in stream water of organic N (5.7 to 6.5 kg ha(-1) a(-1)) were much greater than those of inorganic N (0.6 to 2.2 kg ha(-1) a(-1)). Inorganic N in streams was predominantly NO3- except in the smallest stream which had the largest concentrations of NH4+. This suggests that N transformations, particularly nitrification, may be taking place in the mineral soils adjacent to the streams or within the stream channel of the larger catchment.     

Lead and cadmium in indoor air and the urban environment

The present study was conducted to find potential terrestrial biomonitors for heavy metals in indoor air in an urban environment. TSP, PM(10), and PM(2.5) were collected in three retirement facilities in the urban area of Vienna. In addition, particulate matter and soil, vegetation, and isopods (Porcellio scaber L.) were collected in the adjacent garden areas. Aerosols were sampled with a low-volume air sampler. The sampled materials were wet ashed and total lead and cadmium contents were determined. Water-soluble heavy metal concentrations were measured in aqueous extracts from air exposed filters, soil, and vegetation. Lead and cadmium were analyzed by graphite furnace AAS. Lead contents in the vegetation were inferred from water-soluble lead in soils. Lead in isopods generally reflected the contents in vegetation. Cadmium in plants probably derived from soil solutions as well as from atmospheric input. Isopods reflected the total cadmium contents in soils. Particulate matter was dominated by PM(2.5), both with respect to mass concentrations and to heavy metal contents. The indoor aerosol was found to be influenced by human activity, indoor sources, and outdoor particles. Relationships between indoor airborne heavy metals and the contents in vegetation (lead and cadmium: positive) and isopods (lead: negative) were identified to have the potential for biomonitoring indoor air quality.     

Comparative impacts of forest harvest and acid precipitation on soil and streamwater acidity

Annual H+ budgets were calculated for a catchment with a 65-year-old spruce-fir forest, and for an adjacent catchment at three years after a whole-tree harvest. In the harvested catchment sinks for H+ due to weathering and mineralization reactions were 85% greater, and sources of H+ due to biomass uptake were 60% greater than in the undisturbed catchment. There was an overall net consumption of 550 eq H+ ha(-1) year(-1) at year 3 after harvest compared to a net generation of 520 eq H+ ha(-1) year(-1) for the 65-year-old forest. Soil pH increased by 0.2-0.4 units soon after harvest, but there was little change in pH of streamwater from the harvested watershed. The whole-tree harvest resulted in a total production of about 30,000 eq H+ ha(-1) due to biomass removal. In contrast, wet and dry deposition at rates measured in this study could add more than 50,000 eq H+ ha(-1) in the 65-year period before the next harvest. Reducing the intensity of harvest may lessen long-term impacts of these sources of H+ on acidification of soils and streams.     

Scale-dependent spatial variability in peatland lead pollution in the southern Pennines, UK

Increasingly, within-site and regional comparisons of peatland lead pollution have been undertaken using the inventory approach. The peatlands of the Peak District, southern Pennines, UK, have received significant atmospheric inputs of lead over the last few hundred years. A multi-core study at three peatland sites in the Peak District demonstrates significant within-site spatial variability in industrial lead pollution. Stochastic simulations reveal that 15 peat cores are required to calculate reliable lead inventories at the within-site and within-region scale for this highly polluted area of the southern Pennines. Within-site variability in lead pollution is dominant at the within-region scale. The study demonstrates that significant errors may be associated with peatland lead inventories at sites where only a single peat core has been used to calculate an inventory. Meaningful comparisons of lead inventories at the regional or global scale can only be made if the within-site variability of lead pollution has been quantified reliably.     

Dioxins, PCBs, and HCB in soil and peat profiles from a pristine boreal catchment

The aim of this study was to explore how atmospherically derived soil pollution is affected by environmental processes at two typical boreal catchment landscape type settings: wetlands and forested areas. Measurements of hydrophobic organic compounds (HOCs) in forest soil and peat from an oligotrophic mire at various depths were performed at a remote boreal catchment in northern Sweden. HOCs in peat were evenly distributed throughout the body of the mire while levels of HOCs in the forest soil increased with increased amount of organic matter. Evaluation of HOC composition by principal component analysis (PCA) showed distinct differences between surface soils and deeper soil and peat samples. This was attributed to vertical transport, degradation and/or shifting sources over time. The calculated net vertical transport differed between surface layers (0.3%) and deeper soils (8.0%), suggesting that vertical transport conditions and processes differ in the deeper layers compared to the surface layers.     

Storage and distribution of trace metals and spheroidal carbonaceous particles (SCPs) from atmospheric deposition in the catchment peats of Lochnagar, Scotland.

Lochnagar is a remote mountain lake to the south-east of the Cairngorm region in Scotland. Its catchment receives anthropogenic trace metals solely from atmospheric deposition. Ten peat cores were taken from the catchment and analysis confirmed that they have been contaminated by trace metals. The peats have an high affinity for trace metals and this results in metal accumulation in the surface peat layers. The formation of trace metal sulphides may also reduce remobilisation. In this way, trace metals derived from atmospheric deposition have been scavenged and accumulated. In contaminated peat layers, 77.4% Hg, 89.6% Pb, 93.4% Cu, 72.4% Zn and 86.5% Cd of the total stored are from anthropogenic sources. The accumulated trace metals in the peats can potentially influence the lake system through erosion. Spheroidal carbonaceous particle (SCP) profiles were used to date the peat cores. By referring to the SCP profiles in the peats and comparing these with the trace metal profiles in the lake sediments, the mobility of trace metals in the catchment peats is confirmed.     

Chemical fractionation of copper, lead and zinc in ombrotrophic peat

Measurement of operationally defined chemical fractions in ombrotrophic peat samples provides information not obtained by total metal extractions. Examination of such sequential data permits interpretation of process dynamics. Results for copper, lead and zinc chemical fractionation of peat profiles from Ringinglow Bog, near Sheffield, Great Britain, are reported and discussed. Lead and zinc share similar patterns of partitioning. A considerable proportion of these records is in a form predisposed to transformation and mobilisation. In contrast, much of the copper is comparatively immobile, it being associated with the more chemically intractable fractions. The results suggest that peat copper deposition records may be used for reconstruction of pollution history. The use of lead and zinc records for these purposes is problematic.     

Organotin compounds in precipitation, fog and soils of a forested ecosystem in Germany

Organotin compounds (OTC) are highly toxic pollutants and have been mostly investigated so far in aquatic systems and sediments. The concentrations and fluxes of different organotin compounds, including methyl-, butyl-, and octyltin species in precipitation and fog were investigated in a forested catchment in NE Bavaria, Germany. Contents, along with the vertical distribution and storages in two upland and two wetland soils were determined. During the 1-year monitoring, the OTC concentrations in bulk deposition, throughfall and fog ranged from 1 ng Sn l(-1) to several ten ng Sn l(-1), but never over 200 ng Sn l(-1). The OTC concentrations in fog were generally higher than in throughfall and bulk deposition. Mono-substituted species were the dominant Sn species in precipitation (up to 190 ng Sn l(-1)) equaling a flux of up to 70 mg Sn ha(-1) a(-1). In upland soils, OTC contents peaked in the forest floor (up to 30 ng Sn g(-1)) and decreased sharply with the depth. In wetland soils, OTC had slightly higher contents in the upper horizons. The dominance of mono-substituted species in precipitation is well reflected in the contents and storages of OTC in both upland and wetland soils. The ratios of OTC soil storages to the annual throughfall flux ranged from 20 to 600 years. These high ratios are probably due to high stability and low mobility of OTC in soils. No evidence was found for methylation of tin in the wetland soils. In comparison with sediments, concentrations and contents of organotin in forest soils are considerably lower, and the dominant species are less toxic. It is concluded that forested soils may act as sinks for OTC deposited from the atmosphere.     

Greenhouse gas emissions from Canadian peat extraction, 1990-2000: a life-cycle analysis

This study uses life-cycle analysis to examine the net greenhouse gas (GHG) emissions from the Canadian peat industry for the period 1990-2000. GHG exchange is estimated for land-use change, peat extraction and processing, transport to market, and the in situ decomposition of extracted peat. The estimates, based on an additive GHG accounting model, show that the peat extraction life cycle emitted 0.54 x 10(6) t of GHG in 1990, increasing to 0.89 x 10(6) t in 2000 (expressed as CO2 equivalents using a 100-y time horizon). Peat decomposition associated with end use was the largest source of GHGs, comprising 71% of total emissions during this 11-y period. Land use change resulted in a switch of the peatlands from a GHG sink to a source and contributed an additional 15%. Peat transportation was responsible for 10% of total GHG emissions, and extraction and processing contributed 4%. It would take approximately 2000 y to restore the carbon pool to its original size if peatland restoration is successful and the cutover peatland once again becomes a net carbon sink.     

Source-pathway-receptor investigation of the fate of trace elements derived from shotgun pellets discharged in terrestrial ecosystems managed for game shooting

Spent shotgun pellets may contaminate terrestrial ecosystems. We examined the fate of elements originating from shotgun pellets in pasture and woodland ecosystems. Two source-receptor pathways: i) soil-soil pore water-plant and ii) whole earthworm/worm gut contents - washed and unwashed small mammal hair were investigated. Concentrations of Pb and associated contaminants were higher in soils from shot areas than controls. Arsenic and lead concentrations were positively correlated in soils, soil pore water and associated biota. Element concentrations in biota were below statutory levels in all locations. Bioavailability of lead to small mammals, based on concentrations in washed body hair was low. Lead movement from soil water to higher trophic levels was minor compared to lead adsorbed onto body surfaces. Lead was concentrated in earthworm gut and some plants. Results indicate that managed game shooting presents minimal risk in terms of element transfer to soils and their associated biota.     

Microbiological characterization of the biological treatment of aircraft paint stripping wastewater

Leaching rates of the herbicide dichlorprop [(+/--2-(2,4-dichlorophenoxy)propanoic acid] and nitrate were measured together in field lysimeters containing undisturbed clay and peat soils. The purpose of the study was to investigate the leaching pattern of the two solutes in structured soils under different precipitation regimes. Spring barley (Hordeum distichum L.) was sown on each monolith and fertilized with 100 kg N ha(-1). Dichlorprop was applied at a rate of 1.6 kg active ingredient (a.i.) ha(-1). Each soil type received supplemental irrigation at two levels ('average' and 'worst-case'), giving total water inputs (irrigation and precipitation) of 664 and 749 mm year(-1), respectively. The larger water input approximately doubled the nitrate loads, from, on average, 11.6 to 21.8 kg N ha(-1) year(-1) in the clay soil and from 37.6 to 65.4 kg N ha(-1) year(-1) in the peat soil. In contrast, dichlorprop leaching was reduced by more than one order of magnitude when the water input was increased, from average amounts of 3.22 to 0.26 g a.i. ha(-1) during an S-month period in the clay and from 28.9 to 2.67 g a.i. ha(-1) in the peat. This leaching pattern of dichlorprop was explained in terms of preferential flow. The dried-out topsoil of 'average' watered monoliths may have allowed water flow in cracks, thus moving some of the herbicide rapidly through the topsoil to the subsoil. Once the compound reached the subsoil, degradation rates would be reduced and the herbicide residues would be stored for later leaching. Nitrate was presumably more evenly distributed in the soil matrix; therefore, water rapidly moving through macropores would not carry significant amounts of nitrate. In contrast, leaching would occur more evenly through the soil matrix, causing larger nitrate loads in the 'worst-case' watered monoliths. These results show that wet years may constitute a worst case scenario in terms of nitrate leaching, but not pesticide leaching, if macropore flow exerts a significant influence on leaching.     

Speciation and origin of particulate copper in runoff water from a Mediterranean vineyard catchment

Fungicide treatments have led to large copper contents of the topsoils of most vineyards. This paper examines the contamination of surface waters by copper in a Mediterranean wine-growing catchment. Its aims were to characterise the forms of copper associated with suspended matter during a heavy autumn storm event and to identify which soils contribute the most to the copper exports. A mixing model involving three reservoirs, corresponding to three soil-landscape units (plateau, terraces and footslope-depression system) and two tracers (reducible iron content and dolomite/calcite ratio) was used to estimate the contribution of each reservoir to erosion during a storm flow. The average copper concentration of the suspended matter was 245 mg kg(-1), of which 1% was exchangeable, 4% acid-soluble, 10% oxidizable, 23% reducible and 63% residual. The soils of the plateau of the catchment (chromic luvisols and haplic calcisols-FAO soil classification) were the source of 42% of copper exports but represented only 27% of the total catchment area.     

Lead sorption in calcareous soils

The sorption of lead by three soils that differed in texture and calcium carbonate content was studied at three different temperatures. Lead sorption was found to conform to both Freundlich and Langmuir isotherms. Soil adsorption maxima were derived from the reciprocal of the slope obtained by a least-squares fit of Langmuir plots for each soil. The highest adsorption capacity was exhibited by CaCO(3)-rich soil (773.55 mmol Pb kg(-1)). Raising the temperature from 298 K to 308 and 318 K increased the sorption capacity of all of the soils.     

Occurrence of Eleven Metals in Airborne Participates and in Surficial Materials

The amounts of eleven metals in urban airborne particulate matter samples collected in the United States from 1965 to 1974 (urban and nonurban) are described in two frames of reference: 1) concentration per unit volume of air; and 2) relative abundance in the collected particulate matter compared with surficial materials (subsurface soils) of the continental U. S. If it may be assumed that airborne particulates of solely natural origin would contain these metals in proportions similar to those in uncontaminated subsurface soils, then instances of metals whose proportions in actual particulate samples exceed soil sample proportions may reasonably be ascribed to the influence of human activity. Lead and, tentatively, cadmium exhibit general and significant enrichment in airborne particulate matter above their natural abundances in U. S. soils. Vanadium exhibits enrichment primarily in the northeastern U. S. The enrichment of copper has been traced to contamination from the sampler's own motor. Beryllium, chromium, cobalt, iron, manganese, nickel, and titanium appear to occur in airborne particulates in proportions comparable with those to be expected in natural aeolian dusts.     

A Modular Approach to A Microcomputer Monitoring System

Abstract

Under a cooperative agreement with the U.S. Environmental Protection Agency's (USEPA) Superfund Innovative Technology Evaluation (SITE) Emerging Technology Program, COGNIS, Inc. conducted bench-scale studies on the COGNIS TERRAMET® Lead Extraction Process. The process leaches, or extracts, lead from contaminated soil and consists of a lead leaching stage followed by recovery of the dissolved lead from the leachant. Prior to treatment, the soil is characterized, the type and extent of lead contamination is identified, and the soil is pretreated by physical separation methods to facilitate the extraction process. The physical pretreatment, for example, may include particle size separation to allow separate leaching of the sand and fines fractions and removal of larger lead particles by density separation techniques. As part of the SITE Program, COGNIS investigated seven different lead-contaminated soil samples in small bench-scale batch studies and three soils in larger bench-scale continuous-treatment studies. This bench-scale work led to the design, construction, and operation of a full-scale treatment plant by COGNIS at the Twin Cities Army Ammunition Plant (TCAAP), New Brighton, MN where lead and seven other heavy metals were extracted and recovered from over 20,000 tons of treated soil to meet cleanup criteria.     

National-scale estimation of changes in soil carbon stocks on agricultural lands

Average annual net change in soil carbon stocks under past and current management is needed as part of national reporting of greenhouse gas emissions and to evaluate the potential for soils as sinks to mitigate increasing atmospheric CO2. We estimated net soil C stock changes for US agricultural soils during the period from 1982 to 1997 using the IPCC (Intergovernmental Panel on Climate Change) method for greenhouse gas inventories. Land use data from the NRI (National Resources Inventory; USDA-NRCS) were used as input along with ancillary data sets on climate, soils, and agricultural management. Our results show that, overall, changes in land use and agricultural management have resulted in a net gain of 21.2 MMT C year(-1) in US agricultural soils during this period. Cropped lands account for 15.1 MMT C year(-1), while grazing land soil C increased 6.1 MMT C year(-1). The land use and management changes that have contributed the most to increasing soil C during this period are (1) adoption of conservation tillage practices on cropland, (2) enrollment of cropland in the Conservation Reserve Program, and (3) cropping intensification that has resulted in reduced use of bare fallow.     

Effect of recent climate change on Arctic Pb pollution: a comparative study of historical records in lake and peat sediments

Historical changes of anthropogenic Pb pollution were reconstructed based on Pb concentrations and isotope ratios in lake and peat sediment profiles from Ny-?lesund of Arctic. The calculated excess Pb isotope ratios showed that Pb pollution largely came from west Europe and Russia. The peat profile clearly reflected the historical changes of atmospheric deposition of anthropogenic Pb into Ny-?lesund, and the result showed that anthropogenic Pb peaked at 1960s-1970s, and thereafter a significant recovery was observed by a rapid increase of (206)Pb/(207)Pb ratios and a remarkable decrease in anthropogenic Pb contents. In contrast to the peat record, the longer lake record showed relatively high anthropogenic Pb contents and a persistent decrease of (206)Pb/(207)Pb ratios within the uppermost samples, suggesting that climate-sensitive processes such as catchment erosion and meltwater runoff might have influenced the recent change of Pb pollution record in the High Arctic lake sediments.     

Distribution of chromium, cadmium, nickel and lead in agricultural soils collected from Kazanli-Mersin, Turkey

This study reports total levels of chromium, cadmium, nickel and lead in the agricultural land adjacent a factory producing chromate compounds in Kazanli-Mersin. Surface soil samples were collected from fields around the factory as well as from fields farther away to measure contamination due to aerial transportation and deposition of dust produced in the industrial process. Heavy metals in soil were extracted using wet digestion, and concentrations were measured by atomic absorption spectrophotometry. The concentrations were compared with Turkish maximum allowable concentration values. The metal concentrations averaged 80, 0.14, 228 and 431mg1kg^-1 for chromium, cadmium, nickel and lead, respectively. Soil samples contaminated with chromium were mainly found 500–20001m from the factory and decreased with increasing distance from the factory. Elevated chromium and nickel concentrations were determined in the soils around the factory, especially to the northwest (prevailing wind) and west. Lead concentrations exceeded the limit in only roadside soils (4000 and 50001m to the west), but tended to increase in the vicinity of industrial activity (especially in the west, the northwest and the north). The cadmium concentration did not exceed the limit and was within the normal range for soils.