Two high resolution terrestrial records of atmospheric Pb deposition from New Brunswick, Canada, and Loch Laxford, Scotland

Environmental archives like peat deposits allow for the reconstruction of both naturally and anthropogenically forced changes in the biogeochemical cycle of Pb as well as the quantification of past and present atmospheric Pb pollution. However, records of atmospheric Pb deposition from pre-industrial times are lacking.In a publication by Weiss et al. [Weiss, D., Shotyk, W., Boyle, E.A., Kramers, J.D., Appleby, P.G., Cheburkin, A.K., Comparative study of the temporal evolution of atmospheric lead deposition in Scotland and eastern Canada using blanket peat bogs. Sci Total Environ 2002;292:7-18]. Pb isotopes data measured by Q-ICP-MS and TIMS, concentration and enrichment data was presented for sites in eastern Canada (PeW1) and northwestern Scotland (LL7c), dating to 1586 A.D and 715 A.D., respectively. Here these same cores are re-analysed for Pb isotopes by MC-ICP-MS thereby acquiring ²⁰⁴Pb data and improving on the original data in terms of resolution and temporal coverage. Significant differences were found between the Q-ICP-MS/TIMS and MC-ICP-MS measurements, particularly at PeW1. These discrepancies are attributed to the problematic presence of organic matter during sample preparation and analysis complicated by the heterogeneity of the organic compounds that survived sample preparation steps. The precision and accuracy of Pb isotopes in complex matrices like peat is not always well estimated by industrial standards like NIST-SRM 981 Pb.Lead pollution histories at each site were constructed using the MC-ICP-MS data. The entire LL7c record is likely subject to anthropogenic additions. Contributions from local mining were detected in Medieval times. Later, coal use and mining in Scotland, Wales and England became important. After industrialization (ca. 1885 A.D.) contributions from Broken Hill type ores and hence, leaded petrol, dominate atmospheric Pb signatures right up to modern times. At PeW1 anthropogenic impacts are first distinguishable in the late 17th century with the mining and use of local coal. After industrialization (ca. 1810 A.D.), coal and petrol are the main Pb sources. A comprehensive estimate of the natural atmospheric background ²⁰⁶Pb/²⁰⁷Pb signature in eastern Canadian aerosols is made with a value of ~ 1.19.     

Temporal trends of pollution Pb and other metals in east-central Baffin Island inferred from lake sediment geochemistry

Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20° latitude, showed great variability with respect to Pb concentration and stable isotopic Pb ratios, with little apparent latitudinal trend. To constrain the temporal evolution of regional Pb pollution, a well-dated core from one of the sites, Lake CF8 on east-central Baffin Island, was analyzed geochemically at high stratigraphic resolution. A pronounced decrease in the ²⁰⁶Pb/²⁰⁷Pb ratio occurs in sediments deposited between 1923 and the mid-1970s, likely reflecting alkyl-Pb additives derived from the combustion of fossil fuels at a global scale. A two-component mixing model indicates that 17-26% of the Pb in the labile fraction of sediments deposited in Lake CF8 between 2001 and 2005 is from anthropogenic input. A Pb-Pb co-isotopic plot (²⁰⁶Pb/²⁰⁷Pb vs.²⁰⁸Pb/²⁰⁶Pb ratios) of the Lake CF8 time series data indicates multiple possible sources of industrial Pb pollution. Despite widespread reductions in industrial Pb emissions since the 1970s, there is no evidence for attendant reductions of pollution Pb at Lake CF8. Enhanced scavenging from increased primary production as well as changing precipitation rates as climate warms may represent important factors that modulate Pb deposition to Lake CF8, and Arctic lakes elsewhere.     

A lead isotopic study of the human bioaccessibility of lead in urban soils from Glasgow, Scotland

The human bioaccessibility of lead (Pb) in Pb-contaminated soils from the Glasgow area was determined by the Unified Bioaccessibility Research Group of Europe (BARGE) Method (UBM), an in vitro physiologically based extraction scheme that mimics the chemical environment of the human gastrointestinal system and contains both stomach and intestine compartments. For 27 soils ranging in total Pb concentration from 126 to 2160 mg kg^− 1 (median 539 mg kg^− 1), bioaccessibility as determined by the ‘stomach’ simulation (pH ~ 1.5) was 46-1580 mg kg^− 1, equivalent to 23-77% (mean 52%) of soil total Pb concentration. The corresponding bioaccessibility data for the ‘stomach + intestine’ simulation (pH ~ 6.3) were 6-623 mg kg^− 1 and 2-42% (mean 22%) of soil Pb concentration. The soil ²⁰⁶Pb/²⁰⁷Pb ratios ranged from 1.057 to 1.175. Three-isotope plots of ²⁰⁸Pb/²⁰⁶Pb against ²⁰⁶Pb/²⁰⁷Pb demonstrated that ²⁰⁶Pb/²⁰⁷Pb ratios were intermediate between values for source end-member extremes of imported Australian Pb ore (1.04) - used in the manufacture of alkyl Pb compounds (1.06-1.10) formerly added to petrol - and indigenous Pb ores/coal (1.17-1.19). The ²⁰⁶Pb/²⁰⁷Pb ratios of the UBM ‘stomach’ extracts were similar (< 0.01 difference) to those of the soil for 26 of the 27 samples (r = 0.993, p < 0.001) and lower in 24 of them. A slight preference for lower ²⁰⁶Pb/²⁰⁷Pb ratio was discernible in the UBM. However, the source of Pb appeared to be less important in determining the extent of UBM-bioaccessible Pb than the overall soil total Pb concentration and the soil phases with which the Pb was associated. The significant phases identified in a subset of samples were carbonates, manganese oxides, iron-aluminium oxyhydroxides and clays.     

A comparison of the isotopic composition of lead in rainwater, surface vegetation and tree bark at the long-term monitoring site, Glensaugh, Scotland, in 2007

The lead concentrations and isotopic ratios (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁷Pb) of 31 rainwater (September 2006-December 2007) and 11 surface vegetation (moss, lichen, heather) samples (October 2007) from the rural upland catchment of Glensaugh in northeast Scotland and of nine bark samples (October 2007) from trees, predominantly Scots pine, in or near Glensaugh were determined. The mean ²⁰⁶Pb/²⁰⁷Pb ratios for rainwater in 2006 and 2007 were similar to those previously determined for 2000 to 2003 at Glensaugh, yielding an average mean annual value of 1.151 ± 0.005 (± 1 SD) for the period from 2000, when an outright ban on leaded petrol came into force in the UK, to 2007. The mean ²⁰⁶Pb/²⁰⁷Pb ratio (1.146 ± 0.004; n = 7) for surface vegetation near the top (430-450 m) of the catchment was not significantly different (Student's t test) from that of rainwater (1.148 ± 0.017; n = 24) collected over the 12-month period prior to vegetation sampling, but both were significantly different, at the 0.1% (i.e. p < 0.001) and 1% (p < 0.01) level, respectively, from the corresponding mean value (1.134 ± 0.006; n = 9) for the outermost layer of tree bark. When considered in conjunction with similar direct evidence for 2002 and indirect evidence (e.g. grass, atmospheric particulates, dated peat) for recent decades in the Glensaugh area, these findings confirm that the lead isotopic composition of surface vegetation, including that of suitably located moss, reflects that of the atmosphere while that of the outermost layer of Scots pine bark is affected by non-contemporaneous lead. The nature and relative extent of the different contributory sources of lead to the current UK atmosphere in the era of unleaded petrol, however, are presently not well characterised on the basis of lead isotopic measurements.     

Arsenic,Sb and Bi contamination of soils,plants, waters and sediments in the vicinity of the Dalsung Cu-W mine in Korea

The diagnosis of lead poisoning in horses living on farmland in the vicinity of a battery recycling plant was based on clinical signs as well as on laboratory findings. Chemical analysis of six surface soils (0-15 cm) and herbage samples taken at different distances to the recycling plant showed very high total lead levels in the closest sites to the facility and a clear decrease with distance. Total lead levels in soil samples ranged from 127 to 5657 mg kg(-1), with more than 70% of lead extractable by EDTA in the most polluted soils. Lead levels in the aerial part of herbage samples were in the range of 113-4741 mg kg(-1). A water washing pre-treatment of the vegetal samples considerably diminished the concentration of lead, suggesting that airborne lead particles from the facility emissions were fixed on the shoots. The analysis of samples taken from six dead horses showed lead concentrations, expressed as mg kg(-1) (d.w.), as follows: blood: 0.20-0.89; liver: 2.5-15; kidney: 1.70-6.75. Lead intake levels, estimated according to the ingestion rate of Grammineae forage, illustrates that the apported lead through the ingestion of vegetation growing in the closest sites to the recycling plant was approximately 99.5 mg Pb/kg body weight/day surpassing the fatal dosage for horses of 2.4 mg Pb/kg body weight/day reported by Hammond and Aronson, Ann NY Acad Sci, 1964; 111: 595-611.     

Influence of temporal variations in water chemistry on the Pb isotopic composition of rainbow trout (Oncorhynchus mykiss)

Field and laboratory investigations were undertaken to determine (1) the relations between discharge, Pb concentration, and the Pb isotopic composition of the dissolved load in Richland Creek, western North Carolina, and (2) the potential influence of varying Pb water chemistry on the Pb isotopic abundances in liver and bone tissues of rainbow trout (Oncorhynchus mykiss). Stream waters were characterized by relatively low Pb concentrations during periods of base flow exceeding 10 days in length. Moreover, greater than 65% of the Pb was derived from orchard soils located upstream of the monitoring site which are contaminated by lead arsenate. During small to moderate floods, the dissolved load exhibited Pb concentrations more than twice as high as those measured during base flow, but the contribution of Pb from lead arsenate was relatively low and varied directly with discharge. In contrast to smaller events, Pb from lead arsenate in an 8- to 10-year (overbank) event in May 2003 was minimal during peak flow conditions, suggesting that discharge-source relations are dependent on flood magnitude. The hydrologic and geochemical data demonstrate that aquatic biota in Richland Creek are subjected to short-term variations in Pb concentrations and Pb isotopic abundances within the dissolved load ranging from a few hours to few a weeks. Laboratory studies demonstrated that when rainbow trout were exposed to elevated Pb concentrations with a distinct isotopic fingerprint, the bone and liver rapidly acquire isotopic ratios similar to that of the water. Following exposure, bone retains Pb from the contaminant source for a period of months, while the liver excreted approximately 50% of the accumulated Pb within a few days and nearly all of the Pb within a few weeks. Differences in the rates of excretion resulted in contrasting isotopic ratios between the tissues. It seems plausible, then, that previously observed differences between the isotopic composition of bone and liver in rainbow trout from Richland Creek are related to their short-term exposure to Pb from soils contaminated with Pb arsenate that result from fluctuating hydrologic conditions. If these trends prove to be common in other contaminated aquatic environments, it may be possible to use the Pb isotopic composition of bone as an indicator of the long-term exposure to Pb and the liver as a biomarker for short-term Pb exposures.     

Using the Mallard to biomonitor heavy metal contamination of wetlands in north-western Poland

Contents of iron, zinc, copper, manganese, nickel, lead and cadmium were determined in the brain, pectoral muscle, kidney, liver and bones of the Mallard (Anas platyrhynchos), a cosmopolitan, herbivorous duck species. Both immature (im; in the first year of life) and older (adult, ad) ducks were studied. The birds originated from wetlands in two areas in north-western Poland, one located in the S?ońsk waterfowl reserve (n = 32 im + 24 ad) and the other near the city of Szczecin (n = 21 im + 21 ad). There were numerous significant age-dependent differences in the metal contents of the organs of the Mallards obtained from near Szczecin (Sz) and/or S?ońsk (S). Copper contents in the brain (Sz and S), muscles (Sz) and kidneys (Sz) as well as cadmium contents in the liver (Sz, S), kidneys (Sz, S) and muscles (S) were observed to increase with age. Between-area differences in metal contents of individual organs were recorded as well. The S Mallard showed higher contents of iron and copper (in muscles, liver and kidneys), zinc (in liver and kidneys) and cadmium (in muscles, liver and kidneys), while the Sz ducks revealed higher contents of manganese and lead (in brain and bones). The differences observed may be related to the habitat specificity: the Sl?ońsk reserve is periodically flooded by the River Odra (Oder) waters that carry pollutants from a copper mining area 250 km away. On the other hand, the mid-field ponds near Szczecin are affected by pollutants, including those that are manganese-rich, generated by agriculture and traffic.     

Mass balance for polycyclic aromatic hydrocarbons in the urban watershed of Le Havre (France): transport and fate of PAHs from the atmosphere to the outlet

Polycyclic aromatic hydrocarbon (PAH) concentrations have been monitored simultaneously in ambient air, bulk atmospheric deposition and runoff waters during one year in a small urban watershed of the Seine river basin (France). PAH fluxes from the atmosphere to the outlet of the urban watershed have been calculated to establish a mass balance for PAHs. PAH flux in runoff waters was 5.2 kg km(-2) yr(-1) while PAH atmospheric deposition was 0.21 kg km(-2) yr(-1). The comparison between atmospheric input and output by runoff has shown the importance of street deposits that appeared to be the most important source of PAHs for surface waters in urban areas. PAH profiles in the various compartments showed the fate of PAHs in the air-water system: proportion of carcinogenic PAHs was more important in runoff waters (35%) than in bulk atmospheric deposition (22%) and air (6%).     

Characterisation of atmospheric deposition as a source of contaminants in urban rainwater tanks

To characterise atmospheric input of chemical contaminants to urban rainwater tanks, bulk deposition (wet + dry deposition) was collected at sixteen sites in Brisbane, Queensland, Australia on a monthly basis during April 2007-March 2008 (N = 175). Water from rainwater tanks (22 sites, 26 tanks) was also sampled concurrently. The deposition/tank water was analysed for metals, soluble anions and selected samples were additionally analysed for PAHs, pesticides, phenols, organic & inorganic carbon. Flux (mg/m²/d) of total solids mass was found to correlate with average daily rainfall (R² = 0.49) indicating the dominance of the wet deposition contribution to total solids mass. On average 97% of the total mass of analysed components was accounted for by Cl⁻ (25.0%), Na (22.6%), organic carbon (20.5%), NO₃⁻ (10.5%), SO₄²⁻ (9.8%), inorganic carbon (5.7%), PO₄³⁻ (1.6%) and NO₂⁻ (1.5%). For other minor elements the average flux from highest to lowest was in the order of Fe > Al > Zn > Mn > Sr > Pb > Ba > Cu > Se. There was a significant effect of location on flux of K, Sb, Sn, Li, Mn, Fe, Cu, Zn, Ba, Pb and SO₄²⁻ but not other metals or anions. Overall the water quality resulting from the deposition (wet + dry) was good but 10.3%, 1.7% and 17.7% of samples had concentrations of Pb, Cd and Fe respectively greater than the Australian Drinking Water Guidelines (ADWG). This generally occurred in the drier months. In comparison 14.2% and 6.1% of tank samples had total Pb and Zn concentrations exceeding the guidelines. The cumulative mean concentration of lead in deposition was on average only 1/4 of that in tank water over the year at a site with high concentrations of Pb in tank water. This is an indication that deposition from the atmosphere is not the major contributor to high lead concentrations in urban rainwater tanks in a city with reasonable air quality, though it is still a significant portion.     

Childhood lead exposure and uptake in teeth in the Cleveland area during the era of leaded gasoline

Childhood uptake of lead from exposure to atmospheric leaded gasoline in the United States has been studied using mainly blood lead levels. Since reliable blood lead techniques were used only after the peak use of leaded gasoline, the prior exposure history is unclear. The well-documented decline in blood lead levels after the mid-1970s could represent the continuation of a historic steady decline in exposure from many sources. Alternatively, the post-1970s decline might represent the declining phase of a unimodal rise and fall corresponding closely to usage of leaded gasoline. To assess these possibilities, lead concentration and 207Pb/206Pb isotope ratios were measured in the enamel of permanent molar teeth formed between 1936 and 1993 in mainly African-American donors who grew up in the Cleveland area. Tooth enamel preserves the lead concentration and isotope ratio that prevails during tooth formation. Historical trends in enamel lead concentration were significantly correlated with surrogates of atmospheric lead exposure: lead in sediments of two dated Lake Erie cores, and lead consumed in gasoline. About two-thirds of the total lead uptake into enamel in this period was attributable to leaded gasoline, and the remainder to other sources (e.g. paint). Enamel 207Pb/206Pb isotope ratios were similar to those of one lake sediment. Multivariate analysis revealed significant correlation in neighborhoods with higher levels of traffic, and including lake sediment data, accounted for 53% of the variation in enamel lead levels. Enamel lead concentration was highly correlated with reported African-American childhood blood levels. The extrapolated peak level of 48 μg/dL (range 40 to 63) is associated with clinical and behavioral impairments, which may have implications for adults who were children during the peak gasoline lead exposure. In sum, leaded gasoline emission was the predominant source of lead exposure of African-American Cleveland children during the latter two-thirds of the 20th century.     

Anthropogenic impacts in North Poland over the last 1300 years — A record of Pb, Zn, Cu, Ni and S in an ombrotrophic peat bog

Lead pollution history over Northern Poland was reconstructed for the last ca. 1300 years using the elemental and Pb isotope geochemistry of a dated Polish peat bog. The data show that Polish Pb-Zn ores and coal were the main sources of Pb, other heavy metals and S over Northern Poland up until the industrial revolution. After review of the potential mobility of each element, most of the historical interpretation was based on Pb and Pb isotopes, the other chemical elements (Zn, Cu, Ni, S) being considered secondary indicators of pollution. During the last century, leaded gasoline also contributed to anthropogenic Pb pollution over Poland. Coal and Pb-Zn ores, however, remained important sources of pollution in Eastern European countries during the last 50 years, as demonstrated by a high ²⁰⁶Pb/²⁰⁷Pb ratio (1.153) relative to that of Western Europe (ca. 1.10). The Pb data for the last century were also in good agreement with modelled Pb inventories over Poland and the Baltic region.     

Seasonal and diel distributions of denitrifying and bacterial communities in a hypersaline microbial mat (Camargue, France)

Changes in spatio-temporal distribution of bacterial and denitrifying communities were qualitatively studied in a microbial mat from Camargue (France). During a diel and a seasonal cycle, patterns of 16S rRNA and nitrite reductase genes (nirS and nirK) were compared by denaturing gradient gel electrophoresis (DGGE). Statistical analysis of DGGE profiles showed a significant seasonal shift in the community structure of the nirS-containing bacteria with a winter superficial population that extended in summer, whereas the nirK-containing bacteria seemed more affected by vertical gradients rather than by month-to month-changes. Denitrifying activities remained stable during these sampling times. The bacterial community at the surface of the mat also changed according to season, but appeared stable over a day. Finally, during a diel cycle nirK populations were localized in zones with large fluctuations of environmental parameters (oxygen, pH, and sulfur levels) while nirS populations seemed more restricted to the permanent anoxic layer of the microbial mat.     

Particle deposition fluxes of BDE-209, PAHs, DDTs and chlordane in the Pearl River Delta, South China

Year-round bulk air deposition samples were collected at 15 sites in the Pearl River Delta (PRD) on a bimonthly basis from Dec 2003 to Nov 2004, and the particle-phase deposition of BDE-209, PAHs, DDTs and chlordane was measured. The annual deposition fluxes of BDE-209, total PAHs (15 compounds), total DDT (sum of p,p′-DDE, p,p′-DDD, p,p′-DDT, and o,p′-DDT ), and chlordane (sum of trans-chlordane and cis-chlordane) varied from 32.6 to 1970 μg m^− 2 yr^− 1, 22 to 290 μg m^− 2 yr^− 1, 0.8 to 11 μg m^− 2 yr^− 1, and 0.25 to 1.9 μg m^− 2 yr^− 1, respectively. Spatial variations were higher in the centre of the PRD and lower at the coastal sites for all compounds. The seasonal variations of deposition were found to be compound-dependent, influenced by a number of factors, such as the timing of source input, temperature, and precipitation etc. In particular, source input time affected the deposition fluxes of BDE-209 and high-weight PAHs, while temperature-dependent gas-particle partitioning was a key factor for DDT and light-weight PAH deposition. During the whole sampling period, the atmospheric deposition of BDE-209, ΣPAHs, ΣDDTs, and chlordane onto Hong Kong reached about 93, 86, 2.1 and 2.1 kg yr^− 1, respectively, and onto the PRD reached about 13,400, 2950, 82, and 63 kg yr^− 1. By comparing the calculated total air deposition with the burden in the soils, the half residual time of BDE-209 in soils was estimated to be 3 years.     

Seasonality of diffusive exchange of polychlorinated biphenyls and hexachlorobenzene across the air-sea interface of Kaohsiung Harbor, Taiwan

Gaseous and dissolved concentrations of polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) were measured in the ambient air and water of Kaohsiung Harbor lagoon, Taiwan, from December 2003 to January 2005. During the rainy season (April to September), gaseous PCB and HCB concentrations were low due to both scavenging by precipitation and dilution by prevailing southwesterly winds blown from the atmosphere of the South China Sea. In contrast, trace precipitation and prevailing northeasterly winds during the dry season (October to March) resulted in higher gaseous PCB and HCB concentrations. Instantaneous air-water exchange fluxes of PCB homologues and HCB were calculated from 22 pairs of air and water samples from Kaohsiung Harbor lagoon. All net fluxes of PCB homologues and HCB in this study are from water to air (net volatilization). The highest net volatile flux observed was + 172 ng m^− 2 day^− 1 (dichlorobiphenyls) in December, 2003 due to the high wind speed and high dissolved concentration. The PCB homologues and HCB fluxes were significantly governed by dissolved concentrations in Kaohsiung Harbor lagoon. For low molecular weight PCBs (LMW PCBs), their fluxes were also significantly correlated with wind speed. The net PCB and HCB fluxes suggest that the annual sums of 69 PCBs and HCB measured in this study were mainly volatile (57.4 × 10³ and 28.3 × 10³ ng m^− 2 yr^− 1, respectively) and estimated yearly, 1.5 kg and 0.76 kg of PCBs and HCB were emitted from the harbor lagoon surface waters to the ambient atmosphere. The average tPCB flux in this study was about one-tenth of tPCB fluxes seen in New York Harbor and in the Delaware River, which are reported to be greatly impacted by PCBs.     

Regional lead isotope study of a polluted river catchment: River Wear, Northern England, UK

High precision, lead isotope analyses of archived stream sediments from the River Wear catchment, northeast England (1986-88), provide evidence for three main sources of anthropogenic lead pollution; lead mining, industrial lead emissions and leaded petrol. In the upper catchment, pollution is totally controlled and dominated by large lead discharges from historic mining centres in the North Pennine Orefield (²⁰⁸Pb/²⁰⁶Pb, ²⁰⁷Pb/²⁰⁶Pb ratios range from 2.0744-2.0954 and 0.8413-0.8554 respectively). In the lower catchment, co-extensive with the Durham Coalfield and areas of high population density, pollution levels are lower and regionally more uniform. Isotope ratios are systematically higher than in the upper catchment (²⁰⁸Pb/²⁰⁶Pb, ²⁰⁷Pb/²⁰⁶Pb ratios range from 2.0856-2.1397 and 0.8554-0.8896 respectively) and far exceed values determined for the geogenic regional background. Here, the pollution is characterised by the atmospheric deposition of industrial lead and petrol lead. Lead derived from the combustion of coal, although present, is masked by the other two sources. Recent sediments from the main channel of the River Wear are isotopically indistinguishable from older, low order stream sediments of the North Pennine Orefield, indicating that contamination of the river by lead mining waste (up to several 1000 mg/kg Pb at some locations) continues to pose an environmental problem; a pattern that can be traced all the way to the tidal reach. Using within-catchment isotope variation and sediment lead concentrations, estimates can be made of the discharges from discrete mines or groups of mines to the overall level of lead pollution in the River Wear. As well as providing information pertinent to source apportionment and on-going catchment remediation measures, the database is a valuable resource for epidemiologists concerned with the health risks posed by environmental lead.     

Health risk assessment of heavy metal exposure to street dust in the zinc smelting district, Northeast of China

Heavy metal contamination in the street dust due to metal smelting in the industrial district of Huludao city was investigated. Spatial distribution of Hg, Pb, Cd, Zn and Cu in the street dust was elucidated. Meanwhile, noncancer effect and cancer effect of children and adults due to exposure to the street dust were estimated. The maximum Hg, Pb, Cd, Zn and Cu contents in the street dust are 5.212, 3903, 726.2, 79,869, and 1532 mg kg^− 1, and respectively 141, 181, 6724, 1257 and 77.4 times as high as the background values in soil. The trends for Hg, Pb, Cd, Zn and Cu are similar with higher concentrations trending Huludao zinc plant (HZP). The exponential equation fits quite well for the variations of Pb, Cd, Zn and Cu contents with distance from the pollution sources, but not for Hg. The biggest contribution to street dust is atmospheric deposition due to metal smelting, but traffic density makes slight contribution to heavy metal contamination. According to the calculation on Hazard Index (HI), in the case of noncancer effect, the ingestion of dust particles of children and adults in Huludao city appears to be the route of exposure to street dust that results in a higher risk for heavy metals, followed by dermal contact. The inhalation of resuspended particles through the mouth and nose is almost negligible. The inhalation of Hg vapour as the fourth exposure pathway to street dust is accounting for the main exposure. Children are experiencing the potential health risk due to HI for Pb larger than safe level (1) and Cd close to 1. Besides, cancer risk of Cd due to inhalation exposure is low.     

Evaluating the sources and fate of anthropogenic dissolved inorganic nitrogen (DIN) in two contrasting North Sea estuaries

Nitrogen isotope ratios (delta(15)N) were used to help elucidate the sources and fate of ammonium (NH(4)(+)) and nitrate (NO(3)(-)) in two northeastern English estuaries. The dominant feature of NH(4)(+) in the heavily urbanised Tyne estuary was a plume arising from a single point source; a large sewage works. Although NH(4)(+) concentrations (ranging from 30-150 microM) near the sewage outfall varied considerably between surveys, the sewage-derived delta(15)N-NH(4)(+) signature was remarkably constant (+10.6+/-0.5 per thousand) and could be tracked across the estuary. As indirectly supported by (15)N-depleted delta(15)N-NO(3)(-) values observed close to the mouth of the Tyne, this sewage-derived NH(4)(+) was thought to initiate lower estuarine and coastal zone nitrification. In the more rural Tweed, NH(4)(+) concentrations were low (<7 microM) compared to those in the Tyne and delta(15)N-NH(4)(+) values were consistent with mixing between riverine and marine sources. The dominant form of dissolved inorganic nitrogen (DIN) in the Tweed was agricultural soil-derived NO(3)(-). A decrease in riverine NO(3)(-) flux during the summer coinciding with an increase in delta(15)N-NO(3)(-) values was mainly attributed to enhanced watershed nutrient processing. In the Tyne, where agricultural inputs are less important compared to the Tweed, light delta(15)N-NO(3)(-) (ca. 0 per thousand) detected in the estuary during one winter survey pointed to a larger contribution from precipitation-derived NO(3)(-) during high river discharge. Regardless of the dominant sources, in both estuaries most of the variability in DIN concentrations and delta(15)N values was explained by simple end-member mixing models, implying very little estuarine processing.     

Annual atmospheric deposition of 16 elements in eight catchments of the central Barents region

Snowpack and rainwater samples were used to calculate total yearly deposition rates for Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mo, Ni, Pb, S, Sb, Sr and V in eight catchments located within the Barents region, in Finland, Norway and Russia. Water-soluble (<0.45 μm) deposition and particulate (>0.45 μm) deposition were determined separately on snowpack samples representative of winter 1993/1994. Filtered rainwater sampled during the summer months of 1994 was used to obtain monthly water-soluble deposition data. The snow data were used to calculate the characteristic parameters of dispersion of the pollutants, which are constant for any given industrial source. To obtain these parameters, the element ratio of water-soluble to particulate deposition was expressed as a function of distance from pollution source. This function can then be used to calculate total (water-soluble+particulate) summer deposition data from the water-soluble deposition data collected. Yearly deposition estimates (in kg/km²) obtained for the area range from 0.05 to 0.4 for Cd, 0.02–60 for Co, 0.14–5.2 for Cr, 0.5–494 for Cu, 0.2–845 for Ni and 125–1500 for S, depending on location (remote vs. industrial).     

Reduction of fecal indicator bacteria (FIB) in the Ballona Wetlands saltwater marsh (Los Angeles County, California, USA) with implications for restoration actions

A benefit of wetland preservation and restoration is the ecosystem service of improving water quality, typically assessed based on bacterial loading. The Ballona Wetlands, a degraded salt marsh of approximately 100 ac located on the southern border of Marina Del Rey (Los Angeles County, California, USA) are currently the focus of publicly funded restoration planning. The wetlands receive tidal water, usually contaminated with fecal indicator bacteria (FIB: total and fecal coliforms, Escherichia coli, enterococci) from the adjacent Ballona Creek and Estuary. During the summer of 2007, two 24-h studies were conducted to determine FIB tidal dynamics within the wetland. Measurements of water flow and mean FIB concentrations (n = 3) were measured every 1.5 h to determine total FIB load estimates. FIB loading rates (MPN/s) were greatest during flood tides as water entered the wetlands, and then again during spring tide conditions when sediments were resuspended during swifter spring ebb flows. During daylight hours, the wetland acted as a sink for these bacteria as loads diminished, presumably by sunlight and other processes. Conversely, during late afternoon and night, the wetlands shifted to being a source as excess FIB departed on ebb flows. Therefore, the wetlands act as both a source and sink for FIB depending on tidal conditions and exposure to sunlight. Future restoration actions would result in a tradeoff - increased tidal channels offer a greater surface area for FIB inactivation, but also would result in a greater volume of FIB-contaminated resuspended sediments carried out of the wetlands on stronger ebb flows. As levels of FIB in Ballona Creek and Estuary diminish through recently established regulatory actions, the wetlands could shift into a greater sink for FIB.     

Model testing of radioactive contamination by Sr, Cs and Pu of water and bottom sediments in the Techa River (Southern Urals, Russia)

This paper presents results of testing models for the radioactive contamination of river water and bottom sediments by ⁹⁰Sr, ¹³⁷Cs and ^239,240Pu. The scenario for the model testing was based on data from the Techa River (Southern Urals, Russia), which was contaminated as a result of discharges of liquid radioactive waste into the river. The endpoints of the scenario were model predictions of the activity concentrations of ⁹⁰Sr, ¹³⁷Cs and ^239,240Pu in water and bottom sediments along the Techa River in 1996. Calculations for the Techa scenario were performed by six participant teams from France (model CASTEAUR), Italy (model MARTE), Russia (models TRANSFER-2, CASSANDRA, GIDRO-W) and Ukraine (model RIVTOX), all using different models. As a whole, the radionuclide predictions for ⁹⁰Sr in water for all considered models, ¹³⁷Cs for MARTE and TRANSFER-2, and ^239,240Pu for TRANSFER-2 and CASSANDRA can be considered sufficiently reliable, whereas the prediction for sediments should be considered cautiously. At the same time the CASTEAUR and RIVTOX models estimate the activity concentrations of ¹³⁷Cs and ^239,240Pu in water more reliably than in bottom sediments. The models MARTE (^239,240Pu) and CASSANDRA (¹³⁷Cs) evaluated the activity concentrations of radionuclides in sediments with about the same agreement with observations as for water. For ⁹⁰Sr and ¹³⁷Cs the agreement between empirical data and model predictions was good, but not for all the observations of ^239,240Pu in the river water-bottom sediment system. The modelling of ^239,240Pu distribution proved difficult because, in contrast to ¹³⁷Cs and ⁹⁰Sr, most of models have not been previously tested or validated for plutonium.